The calculated in vitro and in vivo chlorophyll a absorption bandshape.
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 (nu < 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.
Zucchelli
Giuseppe
G
Centro Consiglio Nazionale delle Ricerche, Biologia Cellulare e Molecolare Piante, Dipartimento di Biologia, Università degli Studi di Milano, 20133 Milano, Italy. giuseppe.zucchelli@unimi.it
Jennings
Robert C
RC
Garlaschi
Flavio M
FM
Cinque
Gianfelice
G
Bassi
Roberto
R
Cremonesi
Oliviero
O
D002734:Chlorophyll / Q000737:chemistry*; D000077194:Chlorophyll A; D008962:Models, Theoretical; D013053:Spectrophotometry; D013816:Thermodynamics; D014732:Vibration
D002734:Chlorophyll; D000077194:Chlorophyll A