2020/08/19 by Ioanna A. Gorbunova, Gorbunova, Ioanna A., Maxim E. Sasin +10
Biochemistry, Genetics and Molecular Biology · Chemistry · Physics and Astronomy · #Analytical Chemistry (journal) #Atomic physics #Chemical Physics (physics.chem-ph) #Chemistry #Excitation #Excited state #FOS: Physical sciences #Fluorescence #Fluorescence anisotropy #Laser-Matter Interactions and Applications #Molecular physics #Molecule #Photochemistry and Electron Transfer Studies #Photosynthetic Processes and Mechanisms #Physics #Relaxation (psychology) #Rotational diffusion #Spectroscopy and Quantum Chemical Studies #physics.chem-ph
paper · pdf · doi:10.48550/arxiv.2008.08686
published in arXiv (Cornell University) (Cornell University) · 58 pages, 12 figures
arxiv created 2020/08/19 · openalex publication_date 2020/08/19 · arxiv updated 2020/08/21 · openalex created_date 2022/07/26 · openalex updated_date 2026/08/06
The dynamics of polarized fluorescence in NADH at 460 nm under two-photon\nexcitation at 720 nm by femtosecond laser pulses in water-methanol solutions\nhas been studied experimentally and theoretically as a function of methanol\nconcentration. A number of fluorescence parameters have been determined from\nexperiment by means of the global fit procedure and then compared with the\nresults reported by other authors. A comprehensive analysis of experimental\nerrors was made. The interpretation of the experimental results obtained was\nsupported by ab initio calculations of the structure of NADH and NMNH in\nvarious solutions. An explanation of the heterogeneity in the measured decay\ntimes in NADH and NMNH has been suggested based on the influence of the\ninternal molecular electric field in the nicotinamide ring on non-radiative\ndecay rates. We suggest that different charge distributions in the cis and\ntrans configurations result in different internal electrostatic field\ndistributions that lead to the decay time heterogeneity. A slight but\nnoticeable rise of the decay times tau1 and \τ2 with methanol concentration\nwas observed and treated as a minor effect of a non-radiative relaxation\nslowing due to the decrease of solution polarity. The analysis of the\nrotational diffusion time taur as a function of methanol concentration on the\nbasis of the Stokes-Einstein-Debye equation allowed for determination of\nrelative concentrations of the folded and unfolded NADH conformations in\nsolutions. The analysis of the fluorescence anisotropy parameters and parameter\nOmega determined from experiment allowed for determination of the two-photon\nexcitation tensor components and suggested the existence of two excitation\nchannels with comparable intensities.\n