New Aspects of the Structure of d-Amino Acid Oxidase from Porcine Kidney in Solution: Molecular Dynamics Simulation and Photoinduced Electron Transfer

Mammalian d-amino acid oxidase (DAAO) plays an important role for d-serine metabolism in the brain and regulation of glutamatergic neurotransmission. In the present work, the structures in solution obtained by the methods of molecular dynamic simulation (MDS) and analyses of photoinduced electron transfer (ET) from aromatic amino acids to the excited isoalloxazine (Iso*) are described based upon our recent works, comparing among DAAO dimer, monomer, DAAO-benzoate (DAOB) complex dimer and monomer. The fluorescence lifetimes of DAAO and DAOB in the time domain of picoseconds and femtoseconds are used for the ET analyses as experimental data. The ET parameters (static dielectric constants near isoalloxazine (Iso), standard free energy gap (SFEG) between the photoproducts and reactants), ET rates, and related physical quantities (solvent reorganization energy, net electrostatic energy between the photoproducts and ionic groups in the proteins), in addition to MDS structures, are used to compare the protein structures. The structure of the DAOB dimer in solution obtained by MDS is substantially different from the crystal structure, and the structures of the two subunits are not equivalent in solution. The ET rates and related physical quantities also differ between the two subunits

Fluorescence kinetics of flavin adenine dinucleotide in different microenvironments

Fluorescence kinetics of flavin adenine dinucleotide was measured in a wide time and spectral range in different media, affecting its intra- end extramolecular interactions, and analyzed by a new method based on compressed sensing

Coherent ultrafast torsional motion and isomerization of a biomimetic dipolar photoswitch

Femtosecond fluorescence up-conversion, UV-Vis and IR transient absorption spectroscopy are used to study the photo-isomerization dynamics of a new type of zwitterionic photoswitch based on a N-alkylated indanylidene pyrroline Schiff base framework (ZW-NAIP). The system is biomimetic, as it mimics the photophysics of retinal, in coupling excited state charge translocation and isomerization. While the fluorescence lifetime is 140 fs, excited state absorption persists over 230 fs in the form of a vibrational wavepacket according to twisting of the isomerizing double bond. After a short "dark'' time window in the UV-visible spectra, which we associate with the passage through a conical intersection (CI), the wavepacket appears on the ground state potential energy surface, as evidenced by the transient mid-IR data. This allows for a precise timing of the photoreaction all the way from the initial Franck-Condon region, through the CI and into both ground state isomers, until incoherent vibrational relaxation dominates the dynamics. The photo-reaction dynamics remarkably follow those observed for retinal in rhodopsin, with the additional benefit that in ZW-NAIP the conformational change reverses the zwitterion dipole moment direction. Last, the pronounced low-frequency coherences make these molecules ideal systems for investigating wavepacket dynamics in the vicinity of a CI and for coherent control experiments

The stacked flavin adenine dinucleotide conformation in water is fluorescent on picosecond timescale.

The fluorescence upconversion technique has been applied to examine the picosecond fluorescence decay kinetics of flavin adenine dinucleotide (FAD) in aqueous solution. In the observation range of 30 ps three fluorescent lifetimes can be distinguished. The shortest-lived component (similar to1 ps) arises from water relaxation around the excited flavin. The 9-ps component originates from the intramolecular complex between flavin and adenine, whereas the nanosecond decay is attributed to the unstacked form of FAD. The spectra of the three forms are derived from global analysis of decay curves at different emission wavelengths and time regimes using a triple exponential function. It is assumed that the amplitude belonging to the nanosecond fluorescence component reflects the steady-state fluorescence spectrum. Fluorescence anisotropy to its maximum value of 0.4 is instantaneously created. (C) 2003 Elsevier B.V. All rights reserved