Application of the differential evolution for simulation of the linear optical response of photosynthetic pigments

Abstract

For many applications the Differential Evolution (DE) algorithm had proved to be a very efficient tool for getting the best solution especially when the problem has hundreds of free parameters to optimize. This study aims to expend the list of DE successful scientific applications and to use the DE method for photosynthetic pigments optical response modeling. Chlorophyll (Chl) and bacteriochlorophyll (BChl) are the main pigment molecules of the photosynthetic light-harvesting complexes. These complexes are responsible for photon absorption and sequential transport of energy to the photosynthetic reaction center where the charge separation occurs. The DE routines were adopted to perform the fitting of Chl and Bchl Qy band absorption and fluorescence spectra measured in dimethyl ether. To simulate these spectra the stochastic Brownian oscillator model with 49 vibronic modes for Chl and 60 modes for BChl has been applied. By using the artificially calculated spectra, 10 strategies were tested with different settings of the scaling factor (F) and crossover parameter (Cr) before to fit the real experimental data. Once the proper strategy and settings, which give the fastest convergence, were found, the set of parameters representing the electron–phonon coupling (Huang–Rhys factors) and the lowest frequency modes were calculated. These parameters can be used for modeling of the light-harvesting complex nonlinear optical response.