@article{Schwarze2021,
  author    = {Schwarze, Thomas},
  title     = {Determination of Pd2+ by fluorescence enhancement caused by an off-switching of an energy- and an electron transfer},
  series = {ChemistrySelect},
  volume    = {6},
  journal   = {ChemistrySelect},
  number    = {3},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {2365-6549},
  doi       = {10.1002/slct.202003975},
  pages     = {318 -- 322},
  year      = {2021},
  abstract  = {In this paper, we introduce a fluorescent dye 1, which is able to detect selectively Pd2+ by a clear fluorescence enhancement (FE) in THF. In the presence of eight Pd2+ equivalents, we observed a fluorescence enhancement factor (FEF) of 28.3. The high Pd2+ induced FEF can be explained by an off switching of multiple quenching processes within 1 by Pd2+. In the free dye 1 a photoinduced electron transfer (PET) and energy transfer (ET) takes place and quenches the anthracenic fluorescence. The coordination of eight Pd2+ units by the alkylthio-substituted porphyrazine receptor suppresses the PET and ET quenching process and the anthracenic fluorescence is switched on.},
  language  = {en}
}
@article{SchwarzeKellingSperlichetal.2021,
  author    = {Schwarze, Thomas and Kelling, Alexandra and Sperlich, Eric and Holdt, Hans-J{\"u}rgen},
  title     = {Influence of regioisomerism in 9-anthracenyl-substituted dithiodicyanoethene derivatives on photoinduced electron transfer controlled by intramolecular charge transfer},
  series = {ChemPhotoChem},
  volume    = {5},
  journal   = {ChemPhotoChem},
  number    = {10},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {2367-0932},
  doi       = {10.1002/cptc.202100070},
  pages     = {911 -- 914},
  year      = {2021},
  abstract  = {In this paper, we report on the fluorescence behaviour of three regioisomers which consist of two 9-anthracenyl fluorophores and of differently substituted dithiodicyanoethene moieties. These isomeric fluorescent probes show different quantum yields (phi(f)). In these probes, an oxidative photoinduced electron transfer (PET) from the excited 9-anthracenyl fluorophore to the dithiodicyanoethene unit quenches the fluorescence. This quenching process is accelerated by an intramolecular charge transfer (ICT) of the push-pull pi-electron system of the dithiodicyanoethene group. The acceleration of the PET depends on the strength of the ICT unit. The higher the dipole moment of the ICT unit, the stronger the observed fluorescence quenching. To the best of our knowledge, this is the first report of a regioisomeric influence on an oxidative PET by an ICT.},
  language  = {en}
}
@article{SchwarzeMertensMuelleretal.2017,
  author    = {Schwarze, Thomas and Mertens, Monique and Mueller, Peter and Riemer, Janine and Wessig, Pablo and Holdt, Hans-J{\"u}rgen},
  title     = {Highly K+-Selective Fluorescent Probes for Lifetime Sensing of K+ in Living Cells},
  series = {Chemistry - a European journal},
  volume    = {23},
  journal   = {Chemistry - a European journal},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0947-6539},
  doi       = {10.1002/chem.201704368},
  pages     = {17186 -- 17190},
  year      = {2017},
  abstract  = {The new K+-selective fluorescent probes 1 and 2 were obtained by Cu-I-catalyzed 1,3-dipolar azide alkyne cycloaddition (CuAAC) reactions of an alkyne-substituted [1,3]dioxolo[4,5-f][1,3]benzodioxole (DBD) ester fluorophore with azido-functionalized N-phenylaza-18-crown-6 ether and N-(o-isopropoxy) phenylaza-18-crown-6 ether, respectively. Probes 1 and 2 allow the detection of K+ in the presence of Na+ in water by fluorescence enhancement (2.2 for 1 at 2000mm K+ and 2.5 for 2 at 160mm K+). Fluorescence lifetime measurements in the absence and presence of K+ revealed bi-exponential decay kinetics with similar lifetimes, however with different proportions changing the averaged fluorescence decay times ((f(av))). For 1 a decrease of (f(av)) from 12.4 to 9.3ns and for 2 an increase from 17.8 to 21.8ns was observed. Variation of the substituent in ortho position of the aniline unit of the N-phenylaza-18-crown-6 host permits the modulation of the K-d value for a certain K+ concentration. For example, substitution of H in 1 by the isopropoxy group (2) decreased the K-d value from >300mm to 10mm. 2 was chosen for studying the efflux of K+ from human red blood cells (RBC). Upon addition of the Ca2+ ionophor ionomycin to a RBC suspension in a buffer containing Ca2+, the fluorescence of 2 slightly rose within 10min, however, after 120min a significant increase was observed.},
  language  = {en}
}
@article{LoewBogdanoffHerrmannetal.2006,
  author    = {Loew, Noya and Bogdanoff, Peter and Herrmann, Iris and Wollenberger, Ursula and Scheller, Frieder W. and Katterle, Martin},
  title     = {Influence of modifications on the efficiency of pyrolysed CoTMPP as electrode material for horseradish peroxidase and the reduction of hydrogen peroxide},
  series = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis},
  volume    = {18},
  journal   = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis},
  number    = {23},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1040-0397},
  doi       = {10.1002/elan.200603664},
  pages     = {2324 -- 2330},
  year      = {2006},
  abstract  = {A tailor-made horseradish peroxidase (HRP) bulk composite electrode was developed on the basis of pyrolyzed cobalt tetramethoxyphenylporphyrin (CoTMPP) by modifying pore size and surface area of the porous carbon material through varying amounts of iron oxalate and sulfur prior to pyrolyzation. The materials were used to immobilize horseradish peroxidase (HRP). These electrodes were characterized in terms of their efficiency to reduce hydrogen peroxide. The heterogeneous electron transfer rate constants of different materials were determined with the rotating disk electrode method and a k(S) (401 +/- 61 s(-1)) exceeding previously reported values for native HRP was found.},
  language  = {en}
}
@article{PengUteschYarmanetal.2015,
  author    = {Peng, Lei and Utesch, Tillmann and Yarman, Aysu and Jeoung, Jae-Hun and Steinborn, Silke and Dobbek, Holger and Mroginski, Maria Andrea and Tanne, Johannes and Wollenberger, Ursula and Scheller, Frieder W.},
  title     = {Surface-Tuned Electron Transfer and Electrocatalysis of Hexameric Tyrosine-Coordinated Heme Protein},
  series = {Chemistry - a European journal},
  volume    = {21},
  journal   = {Chemistry - a European journal},
  number    = {20},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0947-6539},
  doi       = {10.1002/chem.201405932},
  pages     = {7596 -- 7602},
  year      = {2015},
  abstract  = {Molecular modeling, electrochemical methods, and quartz crystal microbalance were used to characterize immobilized hexameric tyrosine-coordinated heme protein (HTHP) on bare carbon or on gold electrodes modified with positively and negatively charged self-assembled monolayers (SAMs), respectively. HTHP binds to the positively charged surface but no direct electron transfer (DET) is found due to the long distance of the active sites from the electrode surfaces. At carboxyl-terminated surfaces, the neutrally charged bottom of HTHP can bind to the SAM. For this "disc" orientation all six hemes are close to the electrode and their direct electron transfer should be efficient. HTHP on all negatively charged SAMs showed a quasi-reversible redox behavior with rate constant k(s) values between 0.93 and 2.86 s(-1) and apparent formal potentials E-app(0)' between -131.1 and -249.1 mV. On the MUA/MU-modified electrode, the maximum surface concentration corresponds to a complete monolayer of the hexameric HTHP in the disc orientation. HTHP electrostatically immobilized on negatively charged SAMs shows electrocatalysis of peroxide reduction and enzymatic oxidation of NADH.},
  language  = {en}
}
@article{KielbSezerKatzetal.2015,
  author    = {Kielb, Patrycja and Sezer, Murat and Katz, Sagie and Lopez, Francesca and Schulz, Christopher and Gorton, Lo and Ludwig, Roland and Wollenberger, Ursula and Zebger, Ingo and Weidinger, Inez M.},
  title     = {Spectroscopic Observation of Calcium-Induced Reorientation of Cellobiose Dehydrogenase Immobilized on Electrodes and its Effect on Electrocatalytic Activity},
  series = {ChemPhysChem : a European journal of chemical physics and physical chemistry},
  volume    = {16},
  journal   = {ChemPhysChem : a European journal of chemical physics and physical chemistry},
  number    = {9},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1439-4235},
  doi       = {10.1002/cphc.201500112},
  pages     = {1960 -- 1968},
  year      = {2015},
  abstract  = {Cellobiose dehydrogenase catalyzes the oxidation of various carbohydrates and is considered as a possible anode catalyst in biofuel cells. It has been shown that the catalytic performance of this enzyme immobilized on electrodes can be increased by presence of calcium ions. To get insight into the Ca2+-induced changes in the immobilized enzyme we employ surface-enhanced vibrational (SERR and SEIRA) spectroscopy together with electrochemistry. Upon addition of Ca2+ ions electrochemical measurements show a shift of the catalytic turnover signal to more negative potentials while SERR measurements reveal an offset between the potential of heme reduction and catalytic current. Comparing SERR and SEIRA data we propose that binding of Ca2+ to the heme induces protein reorientation in a way that the electron transfer pathway of the catalytic FAD center to the electrode can bypass the heme cofactor, resulting in catalytic activity at more negative potentials.},
  language  = {en}
}
@misc{AstFischerMuelleretal.2013,
  author    = {Ast, Sandra and Fischer, Tobias and M{\"u}ller, Holger and Mickler, Wulfhard and Schwichtenberg, Mathias and Rurack, Knut and Holdt, Hans-J{\"u}rgen},
  title     = {Integration of the 1,2,3-Triazole "Click" Motif as a potent signalling element in metal ion responsive fluorescent probes},
  series = {Chemistry - a European journal},
  volume    = {19},
  journal   = {Chemistry - a European journal},
  number    = {9},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0947-6539},
  doi       = {10.1002/chem.201201575},
  pages     = {2990 -- 3005},
  year      = {2013},
  abstract  = {In a systematic approach we synthesized a new series of fluorescent probes incorporating donoracceptor (D-A) substituted 1,2,3-triazoles as conjugative -linkers between the alkali metal ion receptor N-phenylaza-[18]crown-6 and different fluorophoric groups with different electron-acceptor properties (4-naphthalimide, meso-phenyl-BODIPY and 9-anthracene) and investigated their performance in organic and aqueous environments (physiological conditions). In the charge-transfer (CT) type probes 1, 2 and 7, the fluorescence is almost completely quenched by intramolecular CT (ICT) processes involving charge-separated states. In the presence of Na+ and K+ ICT is interrupted, which resulted in a lighting-up of the fluorescence in acetonitrile. Among the investigated fluoroionophores, compound 7, which contains a 9-anthracenyl moiety as the electron-accepting fluorophore, is the only probe which retains light-up features in water and works as a highly K+/Na+-selective probe under simulated physiological conditions. Virtually decoupled BODIPY-based 6 and photoinduced electron transfer (PET) type probes 35, where the 10-substituted anthracen-9-yl fluorophores are connected to the 1,2,3-triazole through a methylene spacer, show strong ion-induced fluorescence enhancement in acetonitrile, but not under physiological conditions. Electrochemical studies and theoretical calculations were used to assess and support the underlying mechanisms for the new ICT and PET 1,2,3-triazole fluoroionophores.},
  language  = {en}
}
@article{WawrzinekZiomkowskaHeuvelingetal.2013,
  author    = {Wawrzinek, Robert and Ziomkowska, Joanna and Heuveling, Johanna and Mertens, Monique and Herrmann, Andreas and Schneider, Erwin and Wessig, Pablo},
  title     = {DBD Dyes as Fluorescence Lifetime Probes to Study Conformational Changes in Proteins},
  series = {CHEMISTRY-A EUROPEAN JOURNAL},
  volume    = {19},
  journal   = {CHEMISTRY-A EUROPEAN JOURNAL},
  number    = {51},
  publisher = {WILEY-V C H VERLAG GMBH},
  address   = {WEINHEIM},
  issn      = {0947-6539},
  doi       = {10.1002/chem.201302368},
  pages     = {17349 -- 17357},
  year      = {2013},
  abstract  = {Previously, [1,3]dioxolo[4,5-f][1,3]benzodioxole (DBD)-based fluorophores used as highly sensitive fluorescence lifetime probes reporting on their microenvironmental polarity have been described. Now, a new generation of DBD dyes has been developed. Although they are still sensitive to polarity, in contrast to the former DBD dyes, they have extraordinary spectroscopic properties even in aqueous surroundings. They are characterized by long fluorescence lifetimes (10-20ns), large Stokes shifts (approximate to 100nm), high photostabilities, and high quantum yields (>0.56). Here, the spectroscopic properties and synthesis of functionalized derivatives for labeling biological targets are described. Furthermore, thio-reactive maleimido derivatives of both DBD generations show strong intramolecular fluorescence quenching. This mechanism has been investigated and is found to undergo a photoelectron transfer (PET) process. After reaction with a thiol group, this fluorescence quenching is prevented, indicating successful bonding. Being sensitive to their environmental polarity, these compounds have been used as powerful fluorescence lifetime probes for the investigation of conformational changes in the maltose ATP-binding cassette transporter through fluorescence lifetime spectroscopy. The differing tendencies of the fluorescence lifetime change for both DBD dye generations promote their combination as a powerful toolkit for studying microenvironments in proteins.},
  language  = {en}
}