Publications
Publications from 2025
Monitoring copper ions in C. elegans using porphyrin phosphonic acids
Patrik Tholen, Ann-Kathrin Weishaupt, Franz-Josef Schmitt, Tim Müller, Jonas Fabrizi, Tuong VM Nguyen, Claudia Keil, Maria Maares, Lutz Schomburg, Hajo Haase, Yunus Zorlu, Jens Beckmann, Julia Bornhorst, Gündog Yücesan
Communications Materials, 6, 1, p. 228 (2025)
Herein we report a charge-assisted hydrogen bonded organic framework (HOF) built with an extended tethered phosphonic acid namely 5,10,15,20-Tetra-(4’-yl-[1’,1”-biphenyl]−4”phosphonic acid) porphyrin (p-H8-TBPPA) and phenyl phosphonic acid (PPA). Metal responsive fluorescent properties of the linker p-H8-TBPPA with biologically significant transition metal ions (Zn2+, Cu2+, Ni2+, Co2+, Fe2+, Mn2+) and heavy metal ions (Hg2+, Pb2+, Cd2+) is further characterized. p-H8-TBPPA shows distinct fluorescence responses for each metal ion with very specific decreases in intensity for the different analytes, and the strong turn off fluorescence of p-H8-TBPPA in presence of copper is used to monitor copper ion homeostasis in C. elegans. p-H8-TBPPA is also found to be non-toxic for Caco-2 cells and C. elegans at concentrations required for fluorescence measurements. These findings establish p-H8-TBPPA as …
Fructosylglycine assembles into melanoidin with more glycine than glucose while heating
GF Mohsin, AI Hornemann, FJ Schmitt
European Food Research and Technology, p. 1-14 (2025)
In this study, melanoidins formed from fructosylglycine and heated mixtures of glycine and glucose were analyzed and compared using spectroscopic techniques including UV/Vis, FTIR, EPR, NMR, as well as elemental analysis (EA). EA revealed that melanoidin formed from fructosylglycine incorporates a higher proportion of glycine compared to melanoidin produced through the direct reaction of glycine and glucose upon heating. FTIR spectra identified carbonyl or carboxyl groups with distinct bands at ~ 1749–1759 cm⁻¹, contributing to the extended π-electron system observed at 170–200 ppm in NMR spectra. EPR measurements demonstrated a higher abundance of unpaired electrons in fructosylglycine-derived melanoidin. The UV/Vis, FTIR, and NMR data indicated that the backbones of fructosylglycine-derived melanoidins contain a greater number of conjugated π bonds. Therefore, we conclude that the …
Fluorescence Lifetime Tomography
Fabian Rieder, Karl Otto Dirk Schnelle, Jan Laufer, Franz-Josef Schmitt
European Conference on Biomedical Optics, p. W3A. 24 (2025)
Time-resolved fluorescence tomography enables precise spatial differentiation of fluorophores with overlapping spectra. Using a scanning system, we acquired decay kinetics from a sample phantom filled with acridine orange and fluorescein, revealing distinct lifetime contrasts.
The Fluorescence Yield of Red pH Sensitive Proteins is Mainly
Determined by Stability and Internal Water Contact of the
Chromophore
Franz-Josef Schmitt, Amna Shah Mehmood, Hoang Trong Phan, Christian Tüting, Fabian Rieder, Alina-Sophie Henneberger, Farzin Ghane Golmohamadi, Panagiotis L Kastritis, Jan Laufer
European Conference on Biomedical Optics, p. W3A. 12 (2025)
The different pH dependence of the time resolved fluorescence spectra in two red-shifted fluorescent proteins, mCardinal and mNeptune are explained by differences in internal water contact and H-bonds between chromophore and the surrounding residues.
High Fluorescence of Phytochromes Does Not Require Chromophore Protonation
Franz-Josef Schmitt, Sagie Katz, Hoang Trong Phan, Fabian Rieder, Jan Laufer, Peter Hildebrandt
European Conference on Biomedical Optics, p. W3A. 11 (2025)
Two single-domain phytochromes, miRFP670nano3 and miRFP718nano, contain biliverdins deprotonated at one of the inner pyrrole rings, which is unusual for tetrapyrroles in proteins. The rates of proton exchange most probable determine the fluorescence quantum yields.
Probing the photophysical properties of fluorescent proteins
using photoacoustic pump-probe spectroscopy and imaging
Farzin Ghane Golmohamadi, Amna Mehmood, Hoang Trong Phan, Franz-Josef Schmitt, Jan Laufer
Photoacoustics, 44, p. 100738 (2025)
Pump-probe excitation of fluorophores has been shown to overcome the limitations of conventional multiwavelength imaging and linear unmixing approaches by providing fluorophore-specific contrast whilst eliminating the dominant background signal of endogenous chromophores. In this study, methods for generating pump-probe signals and images are investigated that rely on changing 1) the pump wavelength whilst keeping the probe wavelength fixed, 2) the probe wavelength whilst keeping the pump wavelength fixed, and 3) the time delay between the pump and probe pulse. Time-resolved PA signals were generated in purified solutions of genetically expressed red fluorescent proteins Katushka, mNeptune, and mCardinal in a cuvette. Spectra of the difference signal amplitude were found to correlate with the absorption and emission spectra. The difference signal plotted as a function of time delay also …