Artificial neural network modification of simulation-based fitting: application to a protein-lipid system

Simulation-based fitting has been applied to data analysis and parameter determination of complex experimental systems in many areas of chemistry and biophysics. However, this method is limited because of the time costs of the calculations. In this paper it is proposed to approximate and substitute a simulation model by an artificial neural network during the fitting procedure. Such a substitution significantly speeds up the parameter determination. This approach is tested on a model of fluorescence resonance energy transfer (FRET) within a system of site-directed fluorescence labeled M13 major coat protein mutants incorporated into a lipid bilayer. It is demonstrated that in our case the application of a trained artificial neural network for the substitution of the simulation model results in a significant gain in computing time by a factor of 5 x 10(4). Moreover, an artificial neural network produces a smooth approximation of the noisy results of a stochastic simulation.     

Study of the Zn-porphyrin structure by fluorescence spectroscopy methods

Results of investigation of the optical properties of zinc complexes of mesotetraphenylporphyrin and monopyridyltriphenylporphyrin in impurity-free organic solvent are presented. Analyses of absorption and emission spectra and fluoresence decay kinetics in terms of both a sum of exponentials and using simulation of energy-transformation processes in a tetramer-type Zn-porphyrin complex compound are carried out. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 549–552, July–August, 1999.     

Electronic Spectra and Fluorescence Polarization Kinetics of Thin Zn-Porphyrin Films

The photophysical properties of thin films of Zn-monopyridyltriphenylporphyrin (Zn(4-Py)TrPP) obtained by the method of centrifugation on a quartz film substrate have been investigated. The results of the analysis of the measured excitation and luminescence spectra and also of the kinetic curves of fluorescence depolarization, as they decay, of the Zn(4-Py)TrPP films permit the conclusion that Zn-meso-monopyridylporphyrins self-organize into aggregates. The symmetric closed tetramer ([Zn(4-Py)TrPP]₄) seems to be the most probable aggregate of Zn-meso-monopyridylporphyrins.     

Excited-state properties of water-soluble porphyrin dimers

The excited-state properties of heterodimers oftetra(4-carboxyphenyl)porphyrin (TPPC) and tetra(N-methylpyridyl) porphyrin (TMPyP) are studied by absorption and emission spectroscopy, EPR and zero-field ODMR. The excited singlet and triplet states of dimers formed by pairing H₂TPPC with H₂TMPyP or ZnTMPyP are localized on H₂TPPC. The dimers formed by pairing H₂TPPC with CuTMPyP and H₂TMPyP with ZnTPPC or CuTPPC are non-fluorescent due to intramolecular electron transfer.