TY  - JOUR
A1  - Schober, Lars
A1  - Löhmannsröben, Hans-Gerd
T1  - Determination of optical parameters for light penetration in particulate materials and soils with diffuse reflectance (DR) spectroscopy
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Löhmannsröben, Hans-Gerd
T1  - In situ Laser-induced fluorescence (LIF) analysis pf petroleum product-contaminared soil samples
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Haitzer, Markus
A1  - Löhmannsröben, Hans-Gerd
A1  - Steinberg, Christian E. W.
A1  - Zimmermann, Ute
T1  - In vivo laser-induced fluorescence detection of pyrene in nematodes and determination of pyrene binding constants for humic substances by fluorescences quenching and bioaccumulation experiments
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Schael, Frank
A1  - Reich, Oliver
A1  - Löhmannsröben, Hans-Gerd
T1  - Near infrared diode laser spectroscopy of organic compounds in turbid aqueous solutions
N2  - Diffuse reflectance measurements and photon migration studies with near infrared (NIR) diode lasers were employed to elucidate experimental methods for determining absorption and scattering coefficients and species concentrations in highly scattering solutions. Applicability of theoretical approaches were established by investigating model systems with absorbing (e.g. ink, malachite green) and scattering (e.g. milk powder, caolinit) species in aqueous solution. While diffuse reflectance measurements practically requires calibration procedures, photon migration studies allow quantitative determination of absorption and scattering coefficients of turbid solutions consistent with absorptions coefficients obtained from Lambert-Beer's law. Furthermore, NIR absorption spectra of water, chlorinated hydrocarbons (chloroform, 1,2-dichloroethane, trichloroethene) and of various sugars ($alpha$-D-glucose, sucrose, maltose) are discussed. Spectral variations of NIR water absorption with temperature and solvents are exammined. Exemplary, NIR diode laser detection of water in acetone/water mixtures is performed.
Y1  - 2000
SN  - 0-9528666-1-7
ER  - 
TY  - JOUR
A1  - Dosche, Carsten
A1  - Löhmannsröben, Hans-Gerd
A1  - Bieser, A.
A1  - Dosa, P. I.
A1  - Han, S.
A1  - Iwamoto, M.
A1  - Schleifenbaum, A.
A1  - Vollhardt, K. Peter C.
T1  - Photophysical properties of [N]phenylenes
Y1  - 2002
ER  - 
TY  - JOUR
A1  - Engelhard, Sonja
A1  - Löhmannsröben, Hans-Gerd
A1  - Schael, Frank
T1  - Quantifying ethanol content of beer using interpretive near-infrared spectroscopy
N2  - On the basis of absorption measurements in the near-infrared (NIR) spectral range, a new method for the quantification of the ethanol content of beer is presented. Instead of the multivariate calibration models most commonly employed in NIR spectroscopic works, we use interpretive difference spectroscopy: Two wavelengths are selected according to the assignment of the absorption bands of the main substances of content of beer in the NIR region, and the difference between the absorbances at these wavelengths is used for ethanol quantification. Absorption spectra of the dominating beer ingredients are discussed and the calibration procedure with ethanol/water mixtures is shown. Robustness against the carbohydrate content of beer samples was demonstrated by analyzing solutions of ethanol and maltose in water. Validation of the method was performed with various beer samples with an ethanol concentration range between 0.5 and 7.7 vol %. The pertinent advantage of the procedure developed in this work is the indication that the results are independent from seasonal variations of the ingredients, which is of high interest for products with natural ingredients such as beer
Y1  - 2004
SN  - 0003-7028
ER  - 
TY  - JOUR
A1  - Dosche, Carsten
A1  - Kumke, Michael Uwe
A1  - Löhmannsröben, Hans-Gerd
A1  - Ariese, Freek
A1  - Bader, Arjen N.
A1  - Gooijer, Cees
A1  - Miljanic, Ognjen S.
A1  - Iwamoto, M.
A1  - Vollhardt, K. Peter C.
A1  - Puchta, Ralph
A1  - Hommes, N. J. R. V.
T1  - Deuteration effects on the vibronic structure of the fluorescence spectra and the internal conversion rates of triangular [4]phenylene
N2  - Deuteration effects on the vibronic structure of the emission and excitation spectra of triangular [ 4] phenylene (D-3h [4]phenylene) were studied using laser-excited Shpol'skii spectroscopy (LESS) in an octane matrix at 4.2 K. For correct assignment of the vibrational modes, the experimental results were compared with calculated frequencies (B3LYP/6-31G*). CH vibrations were identified by their characteristic isotopic shifts in the spectra of deuterated triangular [4]phenylenes. Two CC stretching modes, at 100 cm(-1) and 1176 cm(-1), suitable as probes for bond strength changes in the excited state, were identified. The isotope effect on the internal conversion rates of triangular [4] phenylene was evaluated from measurements of temperature dependent lifetime. Isotope dependency and the magnitude of the internal conversion rates indicate that internal conversion in triangular [4] phenylene is most likely induced by CH vibrations. The results obtained by LESS and lifetime measurements were compared with PM3 PECI calculations of the excited state structure. The theoretical results and the relation between ground and excited state vibration energies of the 1176 cm(-1) probe vibration indicate a reduction of bond alternation of the central cyclohexatriene ring in the excited state
Y1  - 2004
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Horner, G.
A1  - Lau, Steffen
A1  - Kantor, Z.
A1  - Löhmannsröben, Hans-Gerd
T1  - Isotope selective analysis of CO2 with tunable diode laser (TDL) spectroscopy in the NIR
N2  - The performance of a home-built tunable diode laser (TDL) spectrometer, aimed at multi-line detection of carbon dioxide, has been evaluated and optimized. In the regime of the (3001)(III) <-- (000) band of (CO2)-C-12 around 1.6 mum, the dominating isotope species (CO2)-C-12, (CO2)-C-13, and (COO)-C-12-O-18-O-16 were detected simultaneously without interference by water vapor. Detection limits in the range of few ppmv were obtained for each species utilizing wavelength modulation (WM) spectroscopy with balanced detection in a long-path absorption cell set-up. High sensitivity in conjunction with high precision-typically +/-1% and +/-6% for 3% and 0.7% of CO2, respectively-renders this experimental approach a promising analytical concept for isotope-ratio determination of carbon dioxide in soil and breath gas. For a moderate (CO2)-C-12 line, the pressure dependence of the line profile was characterized in detail, to account for pressure effects on sensitive measurements
Y1  - 2004
SN  - 0003-2654
ER  - 
TY  - JOUR
A1  - Hildebrandt, Niko
A1  - Charbonniere, Loïc J.
A1  - Beck, Michael
A1  - Ziessel, Raymond F.
A1  - Löhmannsröben, Hans-Gerd
T1  - Quantum dots as efficient energy acceptors in a time-resolved fluoroimmunoassay
Y1  - 2005
SN  - 1433-7851
ER  - 
TY  - JOUR
A1  - Löhmannsröben, Hans-Gerd
T1  - Laser-induced fluorescence (LIF) spectroscopy and laser-based ion mobility (IM) spectrometry for in-situ analysis of contaminated soils
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Löhmannsröben, Hans-Gerd
A1  - Lau, Steffen
T1  - Isotope selectivity in environmental monitoring : NIR diode laser spectroscopy for isotope-selective sensing of soil-respired carbon dioxide
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Lemke, Matthias
A1  - Fernandez-Trujillo, R.
A1  - Löhmannsröben, Hans-Gerd
T1  - In-situ LIF analysis of biological and petroleum-based hydraulic oils on soil
N2  - Absorption and fluorescence properties of 4 hydraulic oils ( 3 biological and 1 petroleum-based) were investigated. In-situ LIF (laser-induced fluorescence) analysis of the oils on a brown sandy loam soil was performed. With calibration, quantitative detection was achieved. Estimated limits of detection were below ca. 500 mg/kg for the petroleum-based oil and ca. 2000 mg/kg for one biological oil. A semi-quantitative classification scheme is proposed for monitoring of the biological oils. This approach was applied to investigate the migration of a biological oil in soil- containing compartments, namely a soil column and a soil bed
Y1  - 2005
SN  - 1424-8220
ER  - 
TY  - JOUR
A1  - Beitz, Toralf
A1  - Laudien, Robert
A1  - Löhmannsröben, Hans-Gerd
A1  - Kallies, Bernd
T1  - Ion mobility spectrometric investigation of aromatic cations in the gas phase
N2  - In this work, ion mobility (IM) spectra of more than 50 aromatic compounds were recorded with a laser-based IM spectrometer at atmospheric pressure. IM spectra of PAH in the laser desorption experiment show a high complexity resulting from the occurrence of monomeric, dimeric, and oligomeric cluster ions. The mobilities of all compounds were determined in helium as drift gas. This allows the calculation of the diffusion cross sections (Omega(calc)) on the basis of the exact hard sphere scattering model and their comparison with the experimentally determined diffusion cross sections (Omega(exp)). Extended Omega(exp)/Omega(calc) and Omega(exp/)mass correlations were performed in order to gain insight into conformational properties of cationic alkyl benzenes and internal rotation of phenyl rings in aromatic ions. This is demonstrated with some examples, such as the evaluation of the dihedral angle of the ions of 9,10- diphenylanthracene, o- and m-terphenyl, and 1,2,3- and 1,3,5-triphenylbenzene. Furthermore, sandwich and T-structures of dimeric PAH cations are discussed. The analysis was extended to oligomeric ions with up to nine monomer units. Experimental evidence is presented suggesting the formation of pi-stacks with a transition toward modified pi-stacks with increasing cluster size. The distance between monomeric units in dimeric and oligomeric ions was obtained
Y1  - 2006
UR  - http://pubs.acs.org/journal/jpcafh
U6  - https://doi.org/10.1021/Jp055335n
SN  - 1089-5639
ER  - 
TY  - JOUR
A1  - Kumke, Michael Uwe
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Trowitzsch-Kienast, Wolfram
A1  - Löhmannsröben, Hans-Gerd
T1  - Spectroscopic characterization of the artificial siderophore pyridinochelin
Y1  - 2006
UR  - http://www.znaturforsch.com/c.htm
SN  - 0939-5075
ER  - 
TY  - JOUR
A1  - Engelhard, Sonja
A1  - Kumke, Michael Uwe
A1  - Löhmannsröben, Hans-Gerd
T1  - Examples of the application of optical process and quality sensing (OPQS) to beer brewing and polyurethane foaming processes
N2  - Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near- infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O-2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant
Y1  - 2006
UR  - http://www.springerlink.com/content/100417
U6  - https://doi.org/10.1007/s00216-005-3364-4
SN  - 1618-2642
ER  - 
TY  - JOUR
A1  - Dosche, Carsten
A1  - Mickler, Wulfhard
A1  - Löhmannsröben, Hans-Gerd
A1  - Agenet, Nicolas
A1  - Vollhardt, K. Peter C.
T1  - Photoinduced electron transfer in [N]phenylenes
N2  - First studies of electron transfer in [N]phenylenes were performed in bimolecular quenching reactions of angular [3]- and triangular [4]phenylene with various electron acceptors. The relation between the quenching rate constants k(q) and the free energy change of the electron transfer (Delta G(CS)(0)) could be described by the Rehm- Weller equation. From the experimental results, a reorganization energy lambda of 0.7 eV was derived. Intramolecular electron transfer reactions were studied in an [N]phenylene bichomophore and a corresponding reference compound. Fluorescence lifetime and quantum yield of the bichromophor display a characteristic dependence on the solvent polarity, whereas the corresponding values of the reference compound remain constant. From the results, a nearly isoenergonic charge separation process can be determined. As the triplet quantum yield is nearly independent of the polarity, charge recombination leads to the population of the triplet state.
Y1  - 2007
UR  - http://www.sciencedirect.com/science/journal/10106030
U6  - https://doi.org/10.1016/j.jphotochem.2006.12.038
SN  - 1010-6030
ER  - 
TY  - JOUR
A1  - Roth, Martin M.
A1  - Löhmannsröben, Hans-Gerd
A1  - Kelz, A.
A1  - Kumke, Michael Uwe
T1  - innoFSPEC : fiber optical spectroscopy and sensing
Y1  - 2008
SN  - 978-0-819-47228-1
ER  - 
TY  - JOUR
A1  - Laudien, Robert
A1  - Riebe, Daniel
A1  - Beitz, Toralf
A1  - Löhmannsröben, Hans-Gerd
T1  - Detection of explosive related nitroaromatic compounds (ERNC) by laser-based ion mobility spectrometry
Y1  - 2008
SN  - 978-0-8194-7348-6
ER  - 
TY  - JOUR
A1  - Geißler, Daniel
A1  - Butlin, Nathaniel G.
A1  - Hill, Diana
A1  - Löhmannsröben, Hans-Gerd
A1  - Hildebrandt, Niko
T1  - Multiplexed diagnostics and spectroscopic ruler applications with terbium to quantum dots FRET
Y1  - 2008
SN  - 1605-7422
ER  - 
TY  - JOUR
A1  - Hille, Carsten
A1  - Berg, Maik
A1  - Bressel, Lena
A1  - Munzke, Dorit
A1  - Primus, Philipp
A1  - Löhmannsröben, Hans-Gerd
A1  - Dosche, Carsten
T1  - Time-domain fluorescence lifetime imaging for intracellular pH sensing in living tissues
N2  - pH sensing in living cells represents one of the most prominent topics in biochemistry and physiology. In this study we performed one-photon and two-photon time-domain fluorescence lifetime imaging with a laser-scanning microscope using the time-correlated single-photon counting technique for imaging intracellular pH levels. The suitability of different commercial fluorescence dyes for lifetime-based pH sensing is discussed on the basis of in vitro as well of in situ measurements. Although the tested dyes are suitable for intensity-based ratiometric measurements, for lifetime- based techniques in the time-domain so far only BCECF seems to meet the requirements of reliable intracellular pH recordings in living cells.
Y1  - 2008
U6  - https://doi.org/10.1007/s00216-008-2147-0
ER  - 
TY  - JOUR
A1  - Jelicic, Aleksandra
A1  - Garcia, Nuria
A1  - Löhmannsröben, Hans-Gerd
A1  - Beuermann, Sabine
T1  - Prediction of the ionic liquid influence on propagation rate coefficients in methyl methacrylate radical polymerizations based on Kamlet-Taft solvatochromic parameters
Y1  - 2009
UR  - http://pubs.acs.org/journal/mamobx?cookieSet=1
U6  - https://doi.org/10.1021/ma9017907
SN  - 0024-9297
ER  - 
TY  - JOUR
A1  - Hille, Carsten
A1  - Lahn, Mattes
A1  - Löhmannsröben, Hans-Gerd
A1  - Dosche, Carsten
T1  - Two-photon fluorescence lifetime imaging of intracellular chloride in cockroach salivary glands
Y1  - 2009
UR  - http://www.rsc.org/Publishing/Journals/pp/index.asp
U6  - https://doi.org/10.1039/B813797H
SN  - 1474-905X
ER  - 
TY  - JOUR
A1  - Kumke, Michael Uwe
A1  - Löhmannsröben, Hans-Gerd
T1  - Introduction to fluorescence spectroscopy
Y1  - 2009
ER  - 
TY  - JOUR
A1  - Geißler, Daniel
A1  - Charbonnière, Loïc J.
A1  - Ziessel, Raymond F.
A1  - Löhmannsröben, Hans-Gerd
T1  - Quantum dots as FRET acceptors for highly sensitive multiplexing immunoassays
Y1  - 2009
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Mickler, Wulfhard
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Klamroth, Tillmann
A1  - Löhmannsröben, Hans-Gerd
A1  - Saalfrank, Peter
A1  - Holdt, Hans-Jürgen
T1  - Systematic investigation of photoinduced electron transfer controlled by internal charge transfer and its consequences for selective PdCl2 coordination
N2  - Fluoroionophores of fluorophore-spacer-receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorophore probes 1-13 consist of a fluorophore group, in alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1-3) revealed, dominant through-space pathway for oxidative photoinduced electron transfer (PET) in CH2-bridged dithiomaleonitrile fluoroionophores. Second. fluorescent probes 4-9 containing two anthracene or pyrene fragments connected through CH2 bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (E-Ox) through electron-withdrawing or -donating groups on the anthracene moiety regulates file thermodynamic driving force for oxidative PET (Delta G(PET)) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (Phi(f)), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl2 were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10-13 were synthesized.
Y1  - 2010
UR  - http://onlinelibrary.wiley.com/doi/10.1002/chem.200902281/pdf
U6  - https://doi.org/10.1002/chem.200902281
SN  - 0947-6539
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Mickler, Wulfhard
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Klamroth, Tillmann
A1  - Löhmannsröben, Hans-Gerd
A1  - Saalfrank, Peter
A1  - Holdt, Hans-Jürgen
T1  - Systematic investigation of photoinduced electron transfer controlled by internal charge transfer and its consequences for selective PdCl2 coordination
N2  - Fluoroionophores of fluorophore-spacer-receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorescent probes 1-13 consist of a fluorophore group, an alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1-3) revealed a dominant through-space pathway for oxidative photoinduced electron transfer (PET) in CH2-bridged dithiomaleonitrile fluoroionophores. Second, fluorescent probes 4-9 containing two anthracene or pyrene fragments connected through CH2 bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (EOx) through electron-withdrawing or -donating groups on the anthracene moiety regulates the thermodynamic driving force for oxidative PET (GPET) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (f), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl2 were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10-13 were synthesized.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/journal/26293/home
SN  - 0947-6539
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Klamroth, Tillmann
A1  - Löhmannsröben, Hans-Gerd
A1  - Saalfrank, Peter
A1  - Cleve, Ernst
A1  - Buschmann, Hans-Jürgen
A1  - Holdt, Hans-Jürgen
T1  - Combination of a CT modulated PET and an intramolecular excimer formation to quantify PdCl2 by large fluorescence enhancement
N2  - The [6.6](9,10)anthracenophane 1 (Scheme 1) is a selective fluoroionophore for the detection of PdCl2 with a large fluorescence enhancement factor (I/I-0 > 250).
Y1  - 2010
UR  - http://pubs.rsc.org/en/content/articlehtml/2010/cc/b919973j
U6  - https://doi.org/10.1039/B919973j
SN  - 1359-7345
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Klamroth, Tillmann
A1  - Löhmannsröben, Hans-Gerd
A1  - Saalfrank, Peter
A1  - Cleve, Ernst
A1  - Buschmann, Hans-Jürgen
A1  - Holdt, Hans-Jürgen
T1  - Combination of a CT modulated PET and an intramolecular excimer formation to quantify PdCl2 by large fluorescence enhancement
Y1  - 2010
UR  - http://www.rsc.org/ej/CC/2010/b919973j.pdf
SN  - 1359-7345
ER  - 
TY  - JOUR
A1  - Bland-Hawthorn, Joss
A1  - Ellis, S. C.
A1  - Leon-Saval, S. G.
A1  - Haynes, R.
A1  - Roth, Martin M.
A1  - Löhmannsröben, Hans-Gerd
A1  - Horton, A. J.
A1  - Cuby, J. -G.
A1  - Birks, T. A.
A1  - Lawrence, J. S.
A1  - Gillingham, P.
A1  - Ryder, S. D.
A1  - Trinh, C.
T1  - A complex multi-notch astronomical filter to suppress the bright infrared sky
JF  - Nature Communications
N2  - A long-standing and profound problem in astronomy is the difficulty in obtaining deep near-infrared observations due to the extreme brightness and variability of the night sky at these wavelengths. A solution to this problem is crucial if we are to obtain the deepest possible observations of the early Universe, as redshifted starlight from distant galaxies appears at these wavelengths. The atmospheric emission between 1,000 and 1,800 nm arises almost entirely from a forest of extremely bright, very narrow hydroxyl emission lines that varies on timescales of minutes. The astronomical community has long envisaged the prospect of selectively removing these lines, while retaining high throughput between them. Here we demonstrate such a filter for the first time, presenting results from the first on-sky tests. Its use on current 8 m telescopes and future 30 m telescopes will open up many new research avenues in the years to come.
Y1  - 2011
U6  - https://doi.org/10.1038/ncomms1584
SN  - 2041-1723
VL  - 2
IS  - 50
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Riebe, Daniel
A1  - Zühlke, Martin
A1  - Zenichowski, Karl
A1  - Beitz, Toralf
A1  - Dosche, Carsten
A1  - Löhmannsröben, Hans-Gerd
T1  - Characterization of rhodamine 6G release in electrospray ionization by means of spatially resolved fluorescence spectroscopy
JF  - Zeitschrift für physikalische Chemie : international journal of research in physical chemistry and chemical physics
N2  - In the present work, the density distribution of rhodamine 6G ions (R6G) in the gas phase and the droplets of an electrospray plume was studied by spatial and spectral imaging. The intention is to contribute to the fundamental understanding of the release mechanism of gaseous R6G in the electrospray ionization (ESI) process. Furthermore, the influence of ESI-parameters on the release efficiency of R6G, e. g. solvent flow, R6G and salt concentration were examined via direct fluorescence imaging of R6G. A solvent-shift of the fluorescence maximum,lambda(max) = 555 nm in methanolic solution and lambda(max) = 505 nm in gas phase, allows the discrimination between solvated and gaseous R6G. Two experimental setups were used for our measurements. In the first experiment, the R6G fluorescence and the light scattered from the spray plume were imaged in two spatial dimensions using a tunable wavelength filter. The second experiment was designed for obtaining 1-dimensional spatially resolved emission spectra of the spray. Here, the intensity distribution of solvated and gaseous R6G as well as scattered light (lambda = 355 nm) were measured simultaneously.
 The results show the distribution of gaseous R6G in the plane, orthogonal to the ESI capillary, decreasing slightly towards the spray center and showing maxima at the cone margins. The distribution of gaseous R6G confirms the preferred release of gaseous ions from nano-droplets, indicating the ion evaporation model (IEM) to be the dominating release mechanism. Up to now, only a few fluorescence spectra of ionic compounds in the gas phase were published because the measurement of emission spectra of mass-selected ions in an ion trap is experimentally challenging. The fluorescence spectrum of gaseous lucigenin at atmospheric pressure is reported for the first time. This spectrum of lucigenin in the gas phase exhibits a blue shift of about Delta lambda = 10 nm in comparison to the corresponding spectrum in methanol.
KW  - Fluorescence
KW  - Electrospray Ionization
KW  - Rhodamine 6G
KW  - Gaseous Ions
KW  - Lucigenin
Y1  - 2011
U6  - https://doi.org/10.1524/zpch.2011.0149
SN  - 0942-9352
VL  - 225
IS  - 9-10
SP  - 1055
EP  - 1072
PB  - De Gruyter Oldenbourg
CY  - München
ER  - 
TY  - JOUR
A1  - Cywinski, Piotr J.
A1  - Moro, Artur J.
A1  - Ritschel, Thomas
A1  - Hildebrandt, Niko
A1  - Löhmannsröben, Hans-Gerd
T1  - Sensitive and selective fluorescence detection of guanosine nucleotides by nanoparticles conjugated with a naphthyridine receptor
JF  - Analytical & bioanalytical chemistry
N2  - Novel fluorescent nanosensors, based on a naphthyridine receptor, have been developed for the detection of guanosine nucleotides, and both their sensitivity and selectivity to various nucleotides were evaluated. The nanosensors were constructed from polystyrene nanoparticles functionalized by (N-(7-((3-aminophenyl) ethynyl)-1,8-naphthyridin- 2-yl) acetamide) via carbodiimide ester activation. We show that this naphthyridine nanosensor binds guanosine nucleotides preferentially over adenine, cytosine, and thymidine nucleotides. Upon interaction with nucleotides, the fluorescence of the nanosensor is gradually quenched yielding Stern-Volmer constants in the range of 2.1 to 35.9mM(-1). For all the studied quenchers, limits of detection (LOD) and tolerance levels for the nanosensors were also determined. The lowest (3 sigma) LOD was found for guanosine 3',5'-cyclic monophosphate (cGMP) and it was as low as 150 ng/ml. In addition, we demonstrated that the spatial arrangement of bound analytes on the nanosensors' surfaces is what is responsible for their selectivity to different guanosine nucleotides. We found a correlation between the changes of the fluorescence signal and the number of phosphate groups of a nucleotide. Results of molecular modeling and zeta-potential measurements confirm that the arrangement of analytes on the surface provides for the selectivity of the nanosensors. These fluorescent nanosensors have the potential to be applied in multi-analyte, array-based detection platforms, as well as in multiplexed microfluidic systems.
KW  - Naphthyridine receptor
KW  - cGMP
KW  - Base pairing
KW  - Nucleotide nanosensor
KW  - Fluorescence spectroscopy
Y1  - 2011
U6  - https://doi.org/10.1007/s00216-010-4420-2
SN  - 1618-2642
VL  - 399
IS  - 3
SP  - 1215
EP  - 1222
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Zakrevskyy, Y.
A1  - Ritschel, T.
A1  - Dosche, C.
A1  - Löhmannsröben, Hans-Gerd
T1  - Quantitative calibration - and reference-free wavelength modulation spectroscopy
JF  - Infrared physics & technology
N2  - A unified model for quantitative description of harmonic spectra of gases obtained by wavelength modulation spectroscopy (WMS) technique is presented. In the model, both intensity modulation (IM) and frequency modulation (FM) of the laser emission are taken into account using minimum number of parameters. For the first time, the static behavior of a laser is described as a limiting case of its dynamic response. Laser and its driver are considered as a single device converting applied bias to laser emission. This allows application of the model to any type of laser and the introduced parameters can be assigned to the corresponding laser and/or driver properties. The approach was tested using a distributed feedback (DFB) laser spectrometer. Correctness of the proposed model is justified by very good agreement between the measured and modeled/fitted spectra, which allowed evaluation of the setup performance and assessment of modulation parameters of the DFB laser. An algorithm to minimize the time of numerical calculation of harmonic spectra using numerically approximated Voigt lineshape function was developed. Absolute values of the absorption line parameters (line strength and line width) were obtained from a single calibration- and reference-free spectrum scan with accuracy better than 0.1%.
KW  - Wavelength modulation gas spectroscopy
KW  - Diode laser
KW  - Isotope detection
Y1  - 2012
U6  - https://doi.org/10.1016/j.infrared.2011.12.001
SN  - 1350-4495
VL  - 55
IS  - 2-3
SP  - 183
EP  - 190
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Ellis, S. C.
A1  - Bland-Hawthorn, Joss
A1  - Lawrence, J.
A1  - Horton, A. J.
A1  - Trinh, C.
A1  - Leon-Saval, S. G.
A1  - Shortridge, K.
A1  - Bryant, J.
A1  - Case, S.
A1  - Colless, M.
A1  - Couch, W.
A1  - Freeman, K.
A1  - Gers, L.
A1  - Glazebrook, K.
A1  - Haynes, R.
A1  - Lee, S.
A1  - Löhmannsröben, Hans-Gerd
A1  - O'Byrne, J.
A1  - Miziarski, S.
A1  - Roth, M.
A1  - Schmidt, B.
A1  - Tinney, C. G.
A1  - Zheng, J.
T1  - Suppression of the near-infrared OH night-sky lines with fibre Bragg gratings - first results
JF  - Monthly notices of the Royal Astronomical Society
N2  - The background noise between 1 and 1.8 ?mu m in ground-based instruments is dominated by atmospheric emission from hydroxyl molecules. We have built and commissioned a new instrument, the Gemini Near-infrared OH Suppression Integral Field Unit (IFU) System (GNOSIS), which suppresses 103 OH doublets between 1.47 and 1.7?mu m by a factor of 1000 with a resolving power of 10?000. We present the first results from the commissioning of GNOSIS using the IRIS2 spectrograph at the Anglo-Australian Telescope. We present measurements of sensitivity, background and throughput. The combined throughput of the GNOSIS fore-optics, grating unit and relay optics is 36?per cent, but this could be improved to 46?per cent with a more optimal design. We measure strong suppression of the OH lines, confirming that OH suppression with fibre Bragg gratings will be a powerful technology for low-resolution spectroscopy. The integrated OH suppressed background between 1.5 and 1.7 mu m is reduced by a factor of 9 compared to a control spectrum using the same system without suppression. The potential of low-resolution OH-suppressed spectroscopy is illustrated with example observations of Seyfert galaxies and a low-mass star. The GNOSIS background is dominated by detector dark current below 1.67 mu m and by thermal emission above 1.67 mu m. After subtracting these, we detect an unidentified residual interline component of 860 +/- 210 photons s-1 m-2?arcsec-2?mu m-1, comparable to previous measurements. This component is equally bright in the suppressed and control spectra. We have investigated the possible source of the interline component, but were unable to discriminate between a possible instrumental artefact and intrinsic atmospheric emission. Resolving the source of this emission is crucial for the design of fully optimized OH suppression spectrographs. The next-generation OH suppression spectrograph will be focused on resolving the source of the interline component, taking advantage of better optimization for a fibre Bragg grating feed incorporating refinements of design based on our findings from GNOSIS. We quantify the necessary improvements for an optimal OH suppressing fibre spectrograph design.
KW  - atmospheric effects
KW  - instrumentation: miscellaneous
KW  - infrared: general
Y1  - 2012
U6  - https://doi.org/10.1111/j.1365-2966.2012.21602.x
SN  - 0035-8711
VL  - 425
IS  - 3
SP  - 1682
EP  - 1695
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Ast, Cindy
A1  - Schmälzlin, Elmar
A1  - Löhmannsröben, Hans-Gerd
A1  - van Dongen, Joost T.
T1  - Optical oxygen micro- and nanosensors for plant applications
JF  - Sensors
N2  - Pioneered by Clark's microelectrode more than half a century ago, there has been substantial interest in developing new, miniaturized optical methods to detect molecular oxygen inside cells. While extensively used for animal tissue measurements, applications of intracellular optical oxygen biosensors are still scarce in plant science. A critical aspect is the strong autofluorescence of the green plant tissue that interferes with optical signals of commonly used oxygen probes. A recently developed dual-frequency phase modulation technique can overcome this limitation, offering new perspectives for plant research. This review gives an overview on the latest optical sensing techniques and methods based on phosphorescence quenching in diverse tissues and discusses the potential pitfalls for applications in plants. The most promising oxygen sensitive probes are reviewed plus different oxygen sensing structures ranging from micro-optodes to soluble nanoparticles. Moreover, the applicability of using heterologously expressed oxygen binding proteins and fluorescent proteins to determine changes in the cellular oxygen concentration are discussed as potential non-invasive cellular oxygen reporters.
KW  - oxygen sensor
KW  - biosensors
KW  - microsensors
KW  - nanosensors
KW  - endogenous sensor proteins
KW  - dual-frequency phase-modulation
KW  - phosphorescence quenching
KW  - plant science
Y1  - 2012
U6  - https://doi.org/10.3390/s120607015
SN  - 1424-8220
VL  - 12
IS  - 6
SP  - 7015
EP  - 7032
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Geissler, Daniel
A1  - Stufler, Stefan
A1  - Löhmannsröben, Hans-Gerd
A1  - Hildebrandt, Niko
T1  - Six-color time-resolved forster resonance energy transfer for ultrasensitive multiplexed biosensing
JF  - Journal of the American Chemical Society
N2  - Simultaneous monitoring of multiple molecular interactions and multiplexed detection of several diagnostic biomarkers at very low concentrations have become important issues in advanced biological and chemical sensing. Here we present an optically multiplexed six-color Forster resonance energy transfer (FRET) biosensor for simultaneous monitoring of five different individual binding events. We combined simultaneous FRET from one Tb complex to five different organic dyes measured in a filter-based time-resolved detection format with a sophisticated spectral crosstalk correction, which results in very efficient background suppression. The advantages and robustness of the multiplexed FRET sensor were exemplified by analyzing a 15-component lung cancer immunoassay involving 10 different antibodies and five different tumor markers in a single 50 mu L human serum sample. The multiplexed biosensor offers clinically relevant detection limits in the low picomolar (ng/mL) concentration range for all five markers, thus providing an effective early screening tool for lung cancer with the possibility of distinguishing small-cell from non-small-cell lung carcinoma. This novel technology will open new doors for multiple biomarker diagnostics as well as multiplexed real-time imaging and spectroscopy.
Y1  - 2013
U6  - https://doi.org/10.1021/ja310317n
SN  - 0002-7863
VL  - 135
IS  - 3
SP  - 1102
EP  - 1109
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Harma, Harri
A1  - Pihlasalo, Sari
A1  - Cywinski, Piotr J.
A1  - Mikkonen, Piia
A1  - Hammann, Tommy
A1  - Löhmannsröben, Hans-Gerd
A1  - Hanninen, Pekka
T1  - Protein quantification using resonance energy transfer between donor nanoparticles and acceptor quantum dots
JF  - Analytical chemistry
N2  - A homogeneous time-resolved luminescence resonance energy transfer (TR-LRET) assay has been developed to quantify proteins. The competitive assay is based on resonance energy transfer (RET) between two luminescent nanosized particles. Polystyrene nanoparticles loaded with Eu3+ chelates (EuNPs) act as donors, while protein-coated quantum dots (QDs), either CdSe/ZnS emitting at 655 nm (QD655-strep) or CdSeTe/ZnS with emission wavelength at 705 nm (QD705-strep), are acceptors. In the absence of analyte protein, in our case bovine serum albumin (BSA), the protein-coated QDs bind nonspecifically to the EuNPs, leading to RET. In the presence of analyte proteins, the binding of the QDs to the EuNPs is prevented and the RET signal decreases. RET from the EuNPs to the QDs was confirmed and characterized with steady-state and time-resolved luminescence spectroscopy. In accordance with the Forster theory, the approximate average donor acceptor distance is around 15 nm at RET efficiencies, equal to 15% for QD655 and 13% for QD705 acceptor, respectively. The limits of detection are below 10 ng of BSA with less than a 10% average coefficient of variation. The assay sensitivity is improved, when compared to the most sensitive commercial methods. The presented mix-and-measure method has potential to be implemented into routine protein quantification in biological laboratories.
Y1  - 2013
U6  - https://doi.org/10.1021/ac303586n
SN  - 0003-2700
VL  - 85
IS  - 5
SP  - 2921
EP  - 2926
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Eich, Susanne
A1  - Schmälzlin, Elmar
A1  - Löhmannsröben, Hans-Gerd
T1  - Distributed fiber optical sensing of Oxygen with optical time domain reflectometry
JF  - Sensors
N2  - In many biological and environmental applications spatially resolved sensing of molecular oxygen is desirable. A powerful tool for distributed measurements is optical time domain reflectometry (OTDR) which is often used in the field of telecommunications. We combine this technique with a novel optical oxygen sensor dye, triangular-[4] phenylene (TP), immobilized in a polymer matrix. The TP luminescence decay time is 86 ns. The short decay time of the sensor dye is suitable to achieve a spatial resolution of some meters. In this paper we present the development and characterization of a reflectometer in the UV range of the electromagnetic spectrum as well as optical oxygen sensing with different fiber arrangements.
KW  - OTDR
KW  - optical sensing
KW  - molecular oxygen
KW  - triangular-[4] phenylene
Y1  - 2013
U6  - https://doi.org/10.3390/s130607170
SN  - 1424-8220
VL  - 13
IS  - 6
SP  - 7170
EP  - 7183
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Brendler, Christian
A1  - Riebe, Daniel
A1  - Ritschel, Thomas
A1  - Beitz, Toralf
A1  - Löhmannsröben, Hans-Gerd
T1  - Investigation of neuroleptics and other aromatic compounds by laser-based ion mobility mass spectrometry
JF  - Analytical & bioanalytical chemistry
N2  - Laser-based ion mobility (IM) spectrometry was used for the detection of neuroleptics and PAH. A gas chromatograph was connected to the IM spectrometer in order to investigate compounds with low vapour pressure. The substances were ionized by resonant two-photon ionization at the wavelengths lambda = 213 and 266 nm and pulse energies between 50 and 300 mu J. Ion mobilities, linear ranges, limits of detection and response factors are reported. Limits of detection for the substances are in the range of 1-50 fmol. Additionally, the mechanism of laser ionization at atmospheric pressure was investigated. First, the primary product ions were determined by a laser-based time-of-flight mass spectrometer with effusive sample introduction. Then, a combination of a laser-based IM spectrometer and an ion trap mass spectrometer was developed and characterized to elucidate secondary ion-molecule reactions that can occur at atmospheric pressure. Some substances, namely naphthalene, anthracene, promazine and thioridazine, could be detected as primary ions (radical cations), while other substances, in particular acridine, phenothiazine and chlorprothixene, are detected as secondary ions (protonated molecules). The results are interpreted on the basis of quantum chemical calculations, and an ionization mechanism is proposed.
KW  - Ion mobility spectrometry
KW  - Mass spectrometry
KW  - Gas chromatography
KW  - Laser ionization
KW  - REMPI
KW  - Neuroleptics
Y1  - 2013
U6  - https://doi.org/10.1007/s00216-012-6654-7
SN  - 1618-2642
VL  - 405
IS  - 22
SP  - 7019
EP  - 7029
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Riebe, Daniel
A1  - Laudien, Robert
A1  - Brendler, Christian
A1  - Beitz, Toralf
A1  - Löhmannsröben, Hans-Gerd
T1  - Laser ionization of H2S and ion-molecule reactions of H3S+ in laser-based ion mobility spectrometry and drift cell time-of-flight mass spectrometry
JF  - Analytical & bioanalytical chemistry
N2  - The detection of hydrogen sulfide (H2S) by 2 + 1 resonance-enhanced multi-photon ionization (REMPI) and the application of H2S as a laser dopant for the detection of polar compounds in laser ion mobility (IM) spectrometry at atmospheric pressure were investigated. Underlying ionization mechanisms were elucidated by additional studies employing a drift cell interfaced to a time-of-flight mass spectrometer. Depending on the pressure, the primary ions H2S+, HS+, S+, and secondary ions, such as H3S+, were observed. The 2 + 1 REMPI spectrum of H2S near lambda = 302.5 nm was recorded at atmospheric pressure. Furthermore, the limit of detection and the linear range were established. In the second part of the work, H2S was investigated as an H2O analogous laser dopant for the ionization of polar substances by proton transfer. H2S exhibits a proton affinity (PA) similar to that of H2O, but a significantly lower ionization energy facilitating laser ionization. Ion-molecule reactions (IMR) of H3S+ with a variety of polar substances with PA between 754.6 and 841.6 kJ/mol were investigated. Representatives of different compound classes, including alcohols, ketones, esters, and nitroaromatics were analyzed. The IM spectra resulting from IMR of H3S+ and H3O+ with these substances are similar in structure, i.e., protonated monomer and dimer ion peaks are found depending on the analyte concentration.
KW  - Ion mobility spectrometry
KW  - Mass spectrometry
KW  - REMPI
KW  - Hydrogen sulfide
KW  - Proton transfer reaction
Y1  - 2013
U6  - https://doi.org/10.1007/s00216-013-7186-5
SN  - 1618-2642
VL  - 405
IS  - 22
SP  - 7031
EP  - 7039
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Cywinski, Piotr J.
A1  - Nono, Katia Nchimi
A1  - Charbonniere, Loic J.
A1  - Hammann, Tommy
A1  - Löhmannsröben, Hans-Gerd
T1  - Photophysical evaluation of a new functional terbium complex in FRET-based time-resolved homogenous fluoroassays
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - A new functional luminescent lanthanide complex (LLC) has been synthesized with terbium as a central lanthanide ion and biotin as a functional moiety. Unlike in typical lanthanide complexes assembled via carboxylic moieties, in the presented complex, four phosphate groups are chelating the central lanthanide ion. This special chemical assembly enhances the complex stability in phosphate buffers conventionally used in biochemistry. The complex synthesis strategy and photophysical properties are described as well as the performance in time-resolved Forster Resonance Energy Transfer (FRET) assays. In those assays, this biotin-LLC transferred energy either to acceptor organic dyes (Cy5 or AF680) labelled on streptavidin or to quantum dots (QD655 or QD705) surfacefunctionalised with streptavidins. The permanent spatial donor-acceptor proximity is assured through strong and stable biotin-streptavidin binding. The energy transfer is evidenced from the quenching observed in donor emission and from a decrease in donor luminescence decay, both associated with simultaneous increase in acceptor intensity and in the decay time. The dye-based assays are realised in TRIS and in PBS, whereas QD-based systems are studied in borate buffer. The delayed emission analysis allows for quantifying the recognition process and for auto-fluorescence-free detection, which is particularly relevant for application in bioanalysis. In accordance with Forster theory, Forsterradii (R0) were found to be around 60 angstrom for organic dyes and around 105 angstrom for QDs. The FRET efficiency (Z) reached 80% and 25% for dye and QD acceptors, respectively. Physical donor-acceptor distances (r) have been determined in the range 45-60 angstrom for organic dye acceptors, while for acceptor QDs between 120 angstrom and 145 angstrom. This newly synthesised biotin-LLC extends the class of highly sensitive analytical tools to be applied in the bioanalytical methods such as time-resolved fluoroimmunoassays (TR-FIA), luminescent imaging and biosensing.
Y1  - 2014
U6  - https://doi.org/10.1039/c3cp54883j
SN  - 1463-9076
SN  - 1463-9084
VL  - 16
IS  - 13
SP  - 6060
EP  - 6067
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Cywinski, Piotr J.
A1  - Hammann, Tommy
A1  - Huehn, Dominik
A1  - Parak, Wolfgang J.
A1  - Hildebrandt, Niko
A1  - Löhmannsröben, Hans-Gerd
T1  - Europium-quantum dot nanobioconjugates as luminescent probes for time-gated biosensing
JF  - Journal of biomedical optics
N2  - Nanobioconjugates have been synthesized using cadmium selenide quantum dots (QDs), europium complexes (EuCs), and biotin. In those conjugates, long-lived photoluminescence (PL) is provided by the europium complexes, which efficiently transfer energy via Forster resonance energy transfer (FRET) to the QDs in close spatial proximity. As a result, the conjugates have a PL emission spectrum characteristic for QDs combined with the long PL decay time characteristic for EuCs. The nanobioconjugates synthesis strategy and photo-physical properties are described as well as their performance in a time-resolved streptavidin-biotin PL assay. In order to prepare the QD-EuC-biotin conjugates, first an amphiphilic polymer has been functionalized with the EuC and biotin. Then, the polymer has been brought onto the surface of the QDs (either QD655 or QD705) to provide functionality and to make the QDs water dispersible. Due to a short distance between EuC and QD, an efficient FRET can be observed. Additionally, the QD-EuC-biotin conjugates' functionality has been demonstrated in a PL assay yielding good signal discrimination, both from autofluorescence and directly excited QDs. These newly designed QD-EuC-biotin conjugates expand the class of highly sensitive tools for bioanalytical optical detection methods for diagnostic and imaging applications. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)
KW  - quantum dots
KW  - europium complex
KW  - amphiphilic polymer assembly
KW  - nanobioconjugate
KW  - biosensor
KW  - time-resolved fluorescence
Y1  - 2014
U6  - https://doi.org/10.1117/1.JBO.19.10.101506
SN  - 1083-3668
SN  - 1560-2281
VL  - 19
IS  - 10
PB  - SPIE
CY  - Bellingham
ER  - 
TY  - JOUR
A1  - Cywinski, Piotr J.
A1  - Moro, Artur J.
A1  - Löhmannsröben, Hans-Gerd
T1  - Cyclic GMP recognition using ratiometric QD-fluorophore conjugate nanosensors
JF  - Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics
KW  - Quantum dots
KW  - Naphthyridines
KW  - Cyclic GMP
KW  - Base pairing
KW  - Fluorescent nanoconjugate
KW  - Nanosensor
Y1  - 2014
U6  - https://doi.org/10.1016/j.bios.2013.09.002
SN  - 0956-5663
SN  - 1873-4235
VL  - 52
SP  - 288
EP  - 292
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Riebe, Daniel
A1  - Beitz, Toralf
A1  - Dosche, Carsten
A1  - Löhmannsröben, Hans-Gerd
A1  - Raab, Volker
A1  - Raab, Corinna
A1  - Unverzagt, Matthias
T1  - High-resolution spectrometer using combined dispersive and interferometric wavelength separation for raman and laser-induced Breakdown Spectroscopy (LIBS)
JF  - Applied spectroscopy : an international journal of spectroscopy ; official publication of the Society for Applied Spectroscopy
N2  - In this paper the concept of a compact high-resolution spectrometer based on the combination of dispersive and interferometric elements is presented. Dispersive elements are used to spectrally resolve the light in one direction with coarse resolution (Delta lambda < 0.5 nm), while perpendicular to that direction an etalon provides high spectral resolution (Delta lambda < 50 pm). This concept for two-dimensional spectroscopy has been implemented for the wavelength range lambda = 350-650 nm. Appropriate algorithms for reconstructing spectra from the two-dimensional raw data and for wavelength calibration were established in an analysis software. Potential applications for this new spectrometer are Raman and laser-induced breakdown spectroscopy (LIBS). Resolutions down to 28 pm (routinely 54 pm) could be realized for these applications.
KW  - Raman spectroscopy
KW  - Laser-induced breakdown spectroscopy
KW  - LIBS
KW  - Fabry-Perot etalon
KW  - High-resolution spectrometer
Y1  - 2014
U6  - https://doi.org/10.1366/13-07426
SN  - 0003-7028
SN  - 1943-3530
VL  - 68
IS  - 9
SP  - 1030
EP  - 1038
PB  - Society for Applied Spectroscopy
CY  - Frederick
ER  - 
TY  - JOUR
A1  - Schirmack, Janosch
A1  - Boehm, Michael
A1  - Brauer, Chris
A1  - Löhmannsröben, Hans-Gerd
A1  - de Vera, Jean-Pierre Paul
A1  - Moehlmann, Diedrich
A1  - Wagner, Dirk
T1  - Laser spectroscopic real time measurements of methanogenic activity under simulated Martian subsurface analog conditions
JF  - Planetary and space science
N2  - On Earth, chemolithoautothrophic and anaerobic microorganisms such as methanogenic archaea are regarded as model organisms for possible subsurface life on Mars. For this reason, the methanogenic strain Methanosarcina soligelidi (formerly called Methanosarcina spec. SMA-21), isolated from permafrost-affected soil in northeast Siberia, has been tested under Martian thermo-physical conditions. In previous studies under simulated Martian conditions, high survival rates of these microorganisms were observed. In our study we present a method to measure methane production as a first attempt to study metabolic activity of methanogenic archaea during simulated conditions approaching conditions of Mars-like environments. To determine methanogenic activity, a measurement technique which is capable to measure the produced methane concentration with high precision and with high temporal resolution is needed. Although there are several methods to detect methane, only a few fulfill all the needed requirements to work within simulated extraterrestrial environments. We have chosen laser spectroscopy, which is a non-destructive technique that measures the methane concentration without sample taking and also can be run continuously. In our simulation, we detected methane production at temperatures down to -5 degrees C, which would be found on Mars either temporarily in the shallow subsurface or continually in the deep subsurface. The pressure of 50 kPa which we used in our experiments, corresponds to the expected pressure in the Martian near subsurface. Our new device proved to be fully functional and the results indicate that the possible existence of methanogenic archaea in Martian subsurface habitats cannot be ruled out. (C) 2013 Published by Elsevier Ltd.
KW  - Mars
KW  - Methanogens
KW  - Methane
KW  - Sub-zero temperature (Celsius)
KW  - Wavelength modulation spectroscopy (laser spectroscopy)
Y1  - 2014
U6  - https://doi.org/10.1016/j.pss.2013.08.019
SN  - 0032-0633
VL  - 98
SP  - 198
EP  - 204
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Zakrevskyy, Yuriy
A1  - Cywinski, Piotr
A1  - Cywinska, Magdalena
A1  - Paasche, Jens
A1  - Lomadze, Nino
A1  - Reich, Oliver
A1  - Löhmannsröben, Hans-Gerd
A1  - Santer, Svetlana
T1  - Interaction of photosensitive surfactant with DNA and poly acrylic acid
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
Y1  - 2014
U6  - https://doi.org/10.1063/1.4862679
SN  - 0021-9606
SN  - 1089-7690
VL  - 140
IS  - 4
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Salffner, Katharina
A1  - Boehm, Michael
A1  - Reich, Oliver
A1  - Löhmannsröben, Hans-Gerd
T1  - A broadband cavity ring-down spectrometer based on an incoherent near infrared light source
JF  - Applied physics : B, Lasers and optics
Y1  - 2014
U6  - https://doi.org/10.1007/s00340-014-5762-9
SN  - 0946-2171
SN  - 1432-0649
VL  - 116
IS  - 4
SP  - 785
EP  - 792
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Cywinski, Piotr J.
A1  - Olejko, Lydia
A1  - Löhmannsröben, Hans-Gerd
T1  - A time-resolved luminescent competitive assay to detect L-selectin using aptamers as recognition elements
JF  - Analytica chimica acta : an international journal devoted to all branches of analytical chemistry
N2  - L-selectin is a protein with potential importance for numerous diseases and clinical disorders. In this paper, we present a new aptamer-based luminescent assay developed to detect L-selectin. The sensing system working principle is based on Forster Resonance Energy Transfer (FRET) from a donor terbium complex (TbC) to an acceptor cyanine dye (Cy5). In the present approach, the biotinylated aptamer is combined with Cy5-labelled streptavidin (Cy5-Strep) to yield an aptamer-based acceptor construct (Apta-Cy5-Strep), while L-selectin is conjugated using luminescent TbC. Upon aptamer binding to the TbC-labelled L-selectin (L-selectin-TbC), permanent donor-acceptor proximity is established which allows for radiationless energy transfer to occur. However, when unlabelled L-selectin is added, it competes with the L-selectin-TbC and the FRET signal decreases as the L-selectin concentration increases. FRET from the TbC to Cy5 was observed with time-gated time-resolved luminescence spectroscopy. A significant change in the corrected luminescence signal was observed in the dynamic range of 10 -500 ng/mL L-selectin, the concentration range relevant for accelerated cognitive decline of Alzheimer's disease, with a limit of detection (LOD) equal to 10 ng/mL. The aptasensor-based assay is homogeneous and can be realized within one hour. Therefore, this method has the potential to become an alternative to tedious heterogeneous analytical methods, e.g. based on enzyme-linked immunosorbent assay (ELISA). (C) 2015 Elsevier B.V. All rights reserved.
KW  - Aptamer
KW  - FRET
KW  - L-selectin
KW  - Luminescence spectroscopy
KW  - Fluoroassay
KW  - Lanthanide
Y1  - 2015
U6  - https://doi.org/10.1016/j.aca.2015.06.045
SN  - 0003-2670
SN  - 1873-4324
VL  - 887
SP  - 209
EP  - 215
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Zühlke, Martin
A1  - Riebe, Daniel
A1  - Beitz, Toralf
A1  - Löhmannsröben, Hans-Gerd
A1  - Zenichowski, Karl
A1  - Diener, Marc
A1  - Linscheid, Michael W.
T1  - An electrospray ionization-ion mobility spectrometer as detector for high-performance liquid chromatography
JF  - European journal of mass spectrometry
N2  - The application of electrospray ionization (ESI) ion mobility (IM) spectrometry on the detection end of a high-performance liquid chromatograph has been a subject of study for some time. So far, this method has been limited to low flow rates or has required splitting of the liquid flow. This work presents a novel concept of an ESI source facilitating the stable operation of the spectrometer at flow rates between 10 mu L min(-1) and 1500 mu L min(-1) without flow splitting, advancing the T-cylinder design developed by Kurnin and co-workers. Flow rates eight times faster than previously reported were achieved because of a more efficient dispersion of the liquid at increased electrospray voltages combined with nebulization by a sheath gas. Imaging revealed the spray operation to be in a rotationally symmetric multijet-mode. The novel ESI-IM spectrometer tolerates high water contents (<= 90%) and electrolyte concentrations up to 10 mM, meeting another condition required of high-performance liquid chromatography (HPLC) detectors. Limits of detection of 50 nM for promazine in the positive mode and 1 mu M for 1,3-dinitrobenzene in the negative mode were established. Three mixtures of reduced complexity (five surfactants, four neuroleptics, and two isomers) were separated in the millisecond regime in stand-alone operation of the spectrometer. Separations of two more complex mixtures (five neuroleptics and 13 pesticides) demonstrate the application of the spectrometer as an HPLC detector. The examples illustrate the advantages of the spectrometer over the established diode array detector, in terms of additional IM separation of substances not fully separated in the retention time domain as well as identification of substances based on their characteristic IMs.
KW  - ESI
KW  - IMS
KW  - HPLC
KW  - spray imaging
KW  - neuroleptics
KW  - pesticides
KW  - surfactants
Y1  - 2015
U6  - https://doi.org/10.1255/ejms.1367
SN  - 1469-0667
SN  - 1751-6838
VL  - 21
IS  - 3
SP  - 391
EP  - 402
PB  - WeltTrends
CY  - Sussex
ER  - 
TY  - JOUR
A1  - Morgner, Frank
A1  - Lecointre, Alexandre
A1  - Charbonniere, Loic J.
A1  - Löhmannsröben, Hans-Gerd
T1  - Detecting free hemoglobin in blood plasma and serum with luminescent terbium complexes
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - Hemolysis, the rupturing of red blood cells, can result from numerous medical conditions (in vivo) or occur after collecting blood specimen or extracting plasma and serum out of whole blood (in vitro). In clinical laboratory practice, hemolysis can be a serious problem due to its potential to bias detection of various analytes or biomarkers. Here we present the first "mix-and-measure' method to assess the degree of hemolysis in biosamples using luminescence spectroscopy. Luminescent terbium complexes (LTC) were studied in the presence of free hemoglobin (Hb) as indicators for hemolysis in TRIS-buffer, and in fresh human plasma with absorption, excitation and emission measurements. Our findings indicate dynamic as well as resonance energy transfer (FRET) between the LTC and the porphyrin ligand of hemoglobin. This transfer leads to a decrease in luminescence intensity and decay time even at nanomolar hemoglobin concentrations either in buffer or plasma. Luminescent terbium complexes are very sensitive to free hemoglobin in buffer and blood plasma. Due to the instant change in luminescence properties of the LTC in presence of Hb it is possible to access the concentration of hemoglobin via spectroscopic methods without incubation time or further treatment of the sample thus enabling a rapid and sensitive detection of hemolysis in clinical diagnostics.
Y1  - 2015
U6  - https://doi.org/10.1039/c4cp04206a
SN  - 1463-9076
SN  - 1463-9084
VL  - 17
IS  - 3
SP  - 1740
EP  - 1745
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Villatoro, José Andrés
A1  - Zühlke, Martin
A1  - Riebe, Daniel
A1  - Riedel, Jens
A1  - Beitz, Toralf
A1  - Löhmannsröben, Hans-Gerd
T1  - IR-MALDI ion mobility spectrometry
JF  - Analytical and bioanalytical chemistry : a merger of Fresenius' journal of analytical chemistry and Analusis
N2  - The novel combination of infrared matrix-assisted laser dispersion and ionization (IR-MALDI) with ion mobility (IM) spectrometry makes it possible to investigate biomolecules in their natural environment, liquid water. As an alternative to an ESI source, the IR-MALDI source was implemented in an in-house-developed ion mobility (IM) spectrometer. The release of ions directly from an aqueous solution is based on a phase explosion, induced by the absorption of an IR laser pulse (lambda = 2.94 mu m, 6 ns pulse width), which disperses the liquid as nano- and micro-droplets. The prerequisites for the application of IR-MALDI-IM spectrometry as an analytical method are narrow analyte ion signal peaks for a high spectrometer resolution. This can only be achieved by improving the desolvation of ions. One way to full desolvation is to give the cluster ions sufficient time to desolvate. Two methods for achieving this are studied: the implementation of an additional drift tube, as in ESI-IM-spectrometry, and the delayed extraction of the ions. As a result of this optimization procedure, limits of detection between 5 nM and 2.5 mu M as well as linear dynamic ranges of 2-3 orders of magnitude were obtained for a number of substances. The ability of this method to analyze simple mixtures is illustrated by the separation of two different surfactant mixtures.
KW  - Ion mobility spectrometry
KW  - IR-MALDI
KW  - Laser
Y1  - 2016
U6  - https://doi.org/10.1007/s00216-016-9739-x
SN  - 1618-2642
SN  - 1618-2650
VL  - 408
SP  - 6259
EP  - 6268
PB  - Springer
CY  - Heidelberg
ER  -