RESONANCE RAMAN-SPECTRA OF SELECTED PTERIN MOLECULES - GENETIC ALGORITHMS APPROACH TO FORCE-FIELD SCALING

The resonance Raman spectra of the pterin group molecules lumazine and isoxanthopterin are presented for the first time and their in-plane n ormal modes analysis is performed. The semiempirical AM1 force fields of the molecules were scaled using a novel computational approach to t he determination of scale factors. The problem of force field scaling was conceived as a multiparameter optimization task and the adaptive o ptimization technique Genetic Algorithms (GA) was applied to solve it. The approach permits, owing to the power of GA, the automatic constru ction of the most reasonable assignment of the calculated normal mode wavenumbers to the experimental bands. Simultaneously, the scale facto r values are tuned during the optimization procedure, minimizing the r oot mean square deviation between the experimental and calculated harm onic normal mode wavenumbers. It was found that the GA-based scaling p rocedure is efficient enough to recover the principal vibrational mode s. (C) 1998 John Wiley & Sons, Ltd.