@article{AstSchwarzeMuelleretal.2013, author = {Ast, Sandra and Schwarze, Thomas and M{\"u}ller, Holger and Sukhanov, Aleksey and Michaelis, Stefanie and Wegener, Joachim and Wolfbeis, Otto S. and K{\"o}rzd{\"o}rfer, Thomas and D{\"u}rkop, Axel and Holdt, Hans-J{\"u}rgen}, title = {A highly K+-Selective Phenylaza-[18]crown-6-Lariat-Ether-Based Fluoroionophore and its application in the sensing of K+ Ions with an optical sensor film and in cells}, series = {Chemistry - a European journal}, volume = {19}, journal = {Chemistry - a European journal}, number = {44}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201302350}, pages = {14911 -- 14917}, year = {2013}, abstract = {Herein, we report the synthesis of two phenylaza-[18]crown-6 lariat ethers with a coumarin fluorophore (1 and 2) and we reveal that compound 1 is an excellent probe for K+ ions under simulated physiological conditions. The presence of a 2-methoxyethoxy lariat group at the ortho position of the anilino moiety is crucial to the substantially increased stability of compounds 1 and 2 over their lariat-free phenylaza-[18] crown-6 ether analogues. Probe 1 shows a high K+/Na+ selectivity and a 2.5-fold fluorescence enhancement was observed in the presence of 100 mm K+ ions. A fluorescent membrane sensor, which was prepared by incorporating probe 1 into a hydrogel, showed a fully reversible response, a response time of 150 s, and a signal change of 7.8\% per 1 mm K+ within the range 1-10 mm K+. The membrane was easily fabricated (only a single sensing layer on a solid polyester support), yet no leaching was observed. Moreover, compound 1 rapidly permeated into cells, was cytocompatible, and was suitable for the fluorescent imaging of K+ ions on both the extracellular and intracellular levels.}, language = {en} } @article{SchwarzeGarzTeuchneretal.2014, author = {Schwarze, Thomas and Garz, Andreas and Teuchner, Klaus and Menzel, Ralf and Holdt, Hans-J{\"u}rgen}, title = {Two-photon probes for metal ions based on phenylaza[18]crown-6 ethers and 1,2,3-triazoles as pi-linkers}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {15}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {12}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201402232}, pages = {2436 -- 2439}, year = {2014}, language = {en} } @article{SchwarzeRiemerEidneretal.2015, author = {Schwarze, Thomas and Riemer, Janine and Eidner, Sascha and Holdt, Hans-J{\"u}rgen}, title = {A Highly K+-Selective Two-Photon Fluorescent Probe}, series = {Chemistry - a European journal}, volume = {21}, journal = {Chemistry - a European journal}, number = {32}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201501473}, pages = {11306 -- 11310}, year = {2015}, abstract = {A highly K+-selective two-photon fluorescent probe for the in vitro monitoring of physiological K+ levels in the range of 1-100 mM is reported. The two-photon excited fluorescence (TPEF) probe shows a fluorescence enhancement (FE) by a factor of about three in the presence of 160 mM K+, independently of one-photon (OP, 430 nm) or two-photon (TP, 860 nm) excitation and comparable K+-induced FEs in the presence of competitive Na+ ions. The estimated dissociation constant (K-d) values in Na+-free solutions (K-d(OP)=(28 +/- 5) mM and K-d(TP)=(36 +/- 6) mM) and in combined K+/Na+ solutions (K-d(OP)=(38 +/- 8) mM and K-d(TP)=(46 +/- 25) mM) reflecting the high K+/Na+ selectivity of the fluorescent probe. The TP absorption cross-section (sigma(2PA)) of the TPEF probe+160 mMK(+) is 26 GM at 860 nm. Therefore, the TPEF probe is a suitable tool for the in vitro determination of K+.}, language = {en} } @article{NazirMeilingCywinskietal.2015, author = {Nazir, Rashid and Meiling, Till Thomas and Cywinski, Piotr J. and Gryko, Daniel T.}, title = {Synthesis and Optical Properties of alpha,beta-Unsaturated Ketones Bearing a Benzofuran Moiety}, series = {Asian journal of organic chemistry : an ACES journal}, volume = {4}, journal = {Asian journal of organic chemistry : an ACES journal}, number = {9}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2193-5807}, doi = {10.1002/ajoc.201500242}, pages = {929 -- 935}, year = {2015}, abstract = {Five pi-expanded alpha,beta-unsaturated ketones have been prepared from a strongly electron-rich benzofuran derivative via Knoevenagel reaction and aldol condensation. The incorporation of two 6-didodecylaminobenzofuran-2-yl groups at the periphery of D-pi-A and D-pi-A-pi-D molecules resulted in dyes with excellent solubility in the majority of organic solvents. In contrast to the majority of alpha,beta-unsaturated ketones, these dyes emit relatively strongly in the red region with a fluorescence quantum yield up to 40\%. They also display strong solvatofluorochromism with emission shifting from 570 nm in toluene to 670 nm in CHCl3. Depending on the chemical structure, they two-photon cross-sections (sigma(2)) are up to 1700 GM (1 GM=10(50) cm(4)s photon(-1)).}, language = {en} } @article{SchwarzeSchneiderRiemeretal.2016, author = {Schwarze, Thomas and Schneider, Radu and Riemer, Janine and Holdt, Hans-J{\"u}rgen}, title = {A Highly K+-Selective Fluorescent Probe - Tuning the K+-Complex Stability and the K+/Na+ Selectivity by Varying the Lariat-Alkoxy Unit of a Phenylaza[18]crown-6 Ionophore}, series = {Chemistry : an Asian journal ; an ACES journal}, volume = {11}, journal = {Chemistry : an Asian journal ; an ACES journal}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1861-4728}, doi = {10.1002/asia.201500956}, pages = {241 -- 247}, year = {2016}, abstract = {A desirable goal is to synthesize easily accessible and highly K+/Na+-selective fluoroionophores to monitor physiological K+ levels in vitro and in vivo. Therefore, highly K+/Na+-selective ionophores have to be developed. Herein, we obtained in a sequence of only four synthetic steps a set of K+-responsive fluorescent probes 4, 5 and 6. In a systematic study, we investigated the influence of the alkoxy substitution in ortho position of the aniline moiety in -conjugated aniline-1,2,3-triazole-coumarin-fluoroionophores 4, 5 and 6 [R=MeO (4), EtO (5) and iPrO (6)] towards the K+-complex stability and K+/Na+ selectivity. The highest K+-complex stability showed fluoroionophore 4 with a dissociation constant K-d of 19mm, but the K-d value increases to 31mm in combined K+/Na+ solutions, indicating a poor K+/Na+ selectivity. By contrast, 6 showed even in the presence of competitive Na+ ions equal K-d values (K-d(K+)=45mm and K-d(K+/Na+)=45mm) and equal K+-induced fluorescence enhancement factors (FEFs=2.3). Thus, the fluorescent probe 6 showed an outstanding K+/Na+ selectivity and is a suitable fluorescent tool to measure physiological K+ levels in the range of 10-80mm in vitro. Further, the isopropoxy-substituted N-phenylaza[18]crown-6 ionophore in 6 is a highly K+-selective building block with a feasible synthetic route.}, language = {en} } @article{SchwarzeMuellerSchmidtetal.2017, author = {Schwarze, Thomas and Mueller, Holger and Schmidt, Darya and Riemer, Janine and Holdt, Hans-J{\"u}rgen}, title = {Design of Na+-Selective Fluorescent Probes: A Systematic Study of the Na+-Complex Stability and the Na+/K+ Selectivity in Acetonitrile and Water}, series = {Chemistry - a European journal}, volume = {23}, journal = {Chemistry - a European journal}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201605986}, pages = {7255 -- 7263}, year = {2017}, abstract = {There is a tremendous demand for highly Na+-selective fluoroionophores to monitor the top analyte Na+ in life science. Here, we report a systematic route to develop highly Na+/K+ selective fluorescent probes. Thus, we synthesized a set of fluoroionophores 1, 3, 4, 5, 8 and 9 (see Scheme 1) to investigate the Na+/K+ selectivity and Na(+-)complex stability in CH3CN and H2O. These Na+-probes bear different 15-crown-5 moieties to bind Na+ stronger than K+. In the set of the diethylaminocoumarin-substituted fluoroionophores 1-5, the following trend of fluorescence quenching 1 > 3 > 2 > 4 > 5 in CH3CN was observed. Therefore, the flexibility of the aza-15-crown-5 moieties in 1-4 determines the conjugation of the nitrogen lone pair with the aromatic ring. As a consequence, 1 showed in CH3CN the highest Na+-induced fluorescence enhancement (FE) by a factor of 46.5 and a weaker K+ induced FE of 3.7. The Na+-complex stability of 1-4 in CH3CN is enhanced in the following order of 2 > 4 > 3 > 1, assuming that the O-atom of the methoxy group in the ortho-position, as shown in 2, strengthened the Na+-complex formation. Furthermore, we found for the N( o-methoxyphenyl) aza-15-crown-5 substituted fluoroionophores 2, 8 and 9 in H2O, an enhanced Na+-complex stability in the following order 8 > 2 > 9 and an increased Na+/K+ selectivity in the reverse order 9 > 2 > 8. Notably, the Na+-induced FE of 8 (FEF = 10.9), 2 (FEF = 5.0) and 9 (FEF = 2.0) showed a similar trend associated with a decreased K+-induced FE [8 (FEF = 2.7) > 2 (FEF = 1.5) > 9 (FEF = 1.1)]. Here, the Na+-complex stability and Na+/K+ selectivity is also influenced by the fluorophore moiety. Thus, fluorescent probe 8 (K-d = 48 mm) allows high-contrast, sensitive, and selective Na+ measurements over extracellular K+ levels. A higher Na+/K+ selectivity showed fluorescent probe 9, but also a higher Kd value of 223 mm. Therefore, 9 is a suitable tool to measure Na+ concentrations up to 300 mm at a fluorescence emission of 614 nm.}, language = {en} } @article{SchwarzeRiemerHoldt2018, author = {Schwarze, Thomas and Riemer, Janine and Holdt, Hans-J{\"u}rgen}, title = {A Ratiometric Fluorescent Probe for K+ in Water Based on a Phenylaza-18-Crown-6 Lariat Ether}, series = {Chemistry - a European journal}, volume = {24}, journal = {Chemistry - a European journal}, number = {40}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201802306}, pages = {10116 -- 10121}, year = {2018}, abstract = {This work presents two molecular fluorescent probes 1 and 2 for the selective determination of physiologically relevant K+ levels in water based on a highly K+/Na+ selective building block, the o-(2-methoxyethoxy)phenylaza-18-crown-6 lariat ether unit. Fluorescent probe 1 showed a high K+-induced fluorescence enhancement (FE) by a factor of 7.7 of the anthracenic emission and a dissociation constant (K-d) value of 38mm in water. Further, for 2+K+, we observed a dual emission behavior at 405 and 505nm. K+ increases the fluorescence intensity of 2 at 405nm by a factor of approximately 4.6 and K+ decreases the fluorescence intensity at 505nm by a factor of about 4.8. Fluorescent probe 2+K+ exhibited a K-d value of approximately 8mm in Na+-free solutions and in combined K+/Na+ solution a similar K-d value of about 9mm was found, reflecting the high K+/Na+ selectivity of 2 in water. Therefore, 2 is a promising fluorescent tool to measure ratiometrically and selectively physiologically relevant K+ levels.}, language = {en} } @article{BroekerRoskeVallerianietal.2019, author = {Broeker, Nina K. and Roske, Yvette and Valleriani, Angelo and Stephan, Mareike Sophia and Andres, Dorothee and Koetz, Joachim and Heinemann, Udo and Barbirz, Stefanie}, title = {Time-resolved DNA release from an O-antigen-specific Salmonella bacteriophage with a contractile tail}, series = {The journal of biological chemistry}, volume = {294}, journal = {The journal of biological chemistry}, number = {31}, publisher = {American Society for Biochemistry and Molecular Biology}, address = {Bethesda}, issn = {1083-351X}, doi = {10.1074/jbc.RA119.008133}, pages = {11751 -- 11761}, year = {2019}, abstract = {Myoviruses, bacteriophages with T4-like architecture, must contract their tails prior to DNA release. However, quantitative kinetic data on myovirus particle opening are lacking, although they are promising tools in bacteriophage-based antimicrobial strategies directed against Gram-negative hosts. For the first time, we show time-resolved DNA ejection from a bacteriophage with a contractile tail, the multi-O-antigen-specific Salmonella myovirus Det7. DNA release from Det7 was triggered by lipopolysaccharide (LPS) O-antigen receptors and notably slower than in noncontractile-tailed siphoviruses. Det7 showed two individual kinetic steps for tail contraction and particle opening. Our in vitro studies showed that highly specialized tailspike proteins (TSPs) are necessary to attach the particle to LPS. A P22-like TSP confers specificity for the Salmonella Typhimurium O-antigen. Moreover, crystal structure analysis at 1.63 angstrom resolution confirmed that Det7 recognized the Salmonella Anatum O-antigen via an E15-like TSP, DettilonTSP. DNA ejection triggered by LPS from either host showed similar velocities, so particle opening is thus a process independent of O-antigen composition and the recognizing TSP. In Det7, at permissive temperatures TSPs mediate O-antigen cleavage and couple cell surface binding with DNA ejection, but no irreversible adsorption occurred at low temperatures. This finding was in contrast to short-tailed Salmonella podoviruses, illustrating that tailed phages use common particle-opening mechanisms but have specialized into different infection niches.}, language = {en} } @misc{BeisnerGrossartGasol2019, author = {Beisner, Beatrix E. and Grossart, Hans-Peter and Gasol, Josep M.}, title = {A guide to methods for estimating phago-mixotrophy in nanophytoplankton}, series = {Journal of plankton research}, volume = {41}, journal = {Journal of plankton research}, number = {2}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0142-7873}, doi = {10.1093/plankt/fbz008}, pages = {77 -- 89}, year = {2019}, abstract = {Growing attention to phytoplankton mixotrophy as a trophic strategy has led to significant revisions of traditional pelagic food web models and ecosystem functioning. Although some empirical estimates of mixotrophy do exist, a much broader set of in situ measurements are required to (i) identify which organisms are acting as mixotrophs in real time and to (ii) assess the contribution of their heterotrophy to biogeochemical cycling. Estimates are needed through time and across space to evaluate which environmental conditions or habitats favour mixotrophy: conditions still largely unknown. We review methodologies currently available to plankton ecologists to undertake estimates of plankton mixotrophy, in particular nanophytoplankton phago-mixotrophy. Methods are based largely on fluorescent or isotopic tracers, but also take advantage of genomics to identify phylotypes and function. We also suggest novel methods on the cusp of use for phago-mixotrophy assessment, including single-cell measurements improving our capacity to estimate mixotrophic activity and rates in wild plankton communities down to the single-cell level. Future methods will benefit from advances in nanotechnology, micromanipulation and microscopy combined with stable isotope and genomic methodologies. Improved estimates of mixotrophy will enable more reliable models to predict changes in food web structure and biogeochemical flows in a rapidly changing world.}, language = {en} } @article{SchwarzeRiemer2020, author = {Schwarze, Thomas and Riemer, Janine}, title = {Highly K+ selective probes with fluorescence emission wavelengths higher than 500 nm in water}, series = {ChemistrySelect}, volume = {5}, journal = {ChemistrySelect}, number = {42}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2365-6549}, doi = {10.1002/slct.202003785}, pages = {13174 -- 13178}, year = {2020}, abstract = {Herein, we report on the synthesis of highly K+/Na+ selective fluorescent probes in a feasible number of synthetic steps. These K+ selective fluorescent probes, so called fluoroionophores, 1 and 2 consists of different highly K+/Na+ selective building blocks the alkoxy-substituted N-phenylaza-18-crown-6 lariat ethers (ionophores) and "green" (cf. coumarin unit in 1) or "red" (cf. nile red unit in 2) fluorescent moieties (fluorophores). The fluorescent probes 1 and 2 show K+ induced fluorescence enhancement factors of 4.1 for 1 and 1.9 for 2 and dissociation constants for the corresponding K+ complexes of 43 mM (1+K+) and 18 mM (2+K+) in buffered aqueous solution. The fluorescence signal of 1 and 2 is changed by less than 5 \% by pH values in the range of 6.8 to 8.8. Thus, 1 and 2 are capable fluorescent tools to determine extracellular K+ levels by fluorescence enhancements at wavelengths higher than 500 nm.}, language = {en} }