The room temperature absorption bandshape for the Q transition region of chlorophyll a is calculated using the vibrational frequency modes and Franck-Condon (FC) factors obtained by line-narrowing spectroscopies of chlorophyll a in a glassy (Rebane and Avarmaa, Chem. Phys. 1982; 68:191-200) and in a native environment (Gillie et al., J. Phys. Chem. 1989; 93:1620-1627) at low temperatures. The calculated bandshapes; are compared with the absorption spectra of chlorophyll a measured in two different solvents and with that obtained in vivo by a mutational analysis of a chlorophyll-protein complex. It is demonstrated that the measured distributions of FC factors can account for the absorption bandshape of chlorophyll a in a hexacoordinated state, whereas, when pentacoordinated, reduced FC coupling for vibrational frequencies in the range 540-850 cm(-1) occurs. The FC factor distribution for pentacoordinated chlorophyll also describes the native chlorophyll a spectrum but, in this case, either a low-frequency mode (v < 200 cm(-1)) must be added or else the 262-cm(1) mode must increase in coupling by about one order of magnitude to describe the skewness of the main absorption bandshape.
The calculated in vitro and in vivo chlorophyll a absorption bandshape / G. Zucchelli, R.C. Jennings, F.M. Garlaschi, G. Cinque, R. Bassi, O. Cremonesi. - In: BIOPHYSICAL JOURNAL. - ISSN 0006-3495. - 82:1(2002), pp. 378-390. [10.1016/S0006-3495(02)75402-7]
The calculated in vitro and in vivo chlorophyll a absorption bandshape
R.C. Jennings;F.M. Garlaschi;
2002
Abstract
The room temperature absorption bandshape for the Q transition region of chlorophyll a is calculated using the vibrational frequency modes and Franck-Condon (FC) factors obtained by line-narrowing spectroscopies of chlorophyll a in a glassy (Rebane and Avarmaa, Chem. Phys. 1982; 68:191-200) and in a native environment (Gillie et al., J. Phys. Chem. 1989; 93:1620-1627) at low temperatures. The calculated bandshapes; are compared with the absorption spectra of chlorophyll a measured in two different solvents and with that obtained in vivo by a mutational analysis of a chlorophyll-protein complex. It is demonstrated that the measured distributions of FC factors can account for the absorption bandshape of chlorophyll a in a hexacoordinated state, whereas, when pentacoordinated, reduced FC coupling for vibrational frequencies in the range 540-850 cm(-1) occurs. The FC factor distribution for pentacoordinated chlorophyll also describes the native chlorophyll a spectrum but, in this case, either a low-frequency mode (v < 200 cm(-1)) must be added or else the 262-cm(1) mode must increase in coupling by about one order of magnitude to describe the skewness of the main absorption bandshape.Pubblicazioni consigliate
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