期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1975
卷号：72
期号：8
页码：2873-2876
DOI：10.1073/pnas.72.8.2873
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The relative donor properties of the three carbonyl groups of chlorophyll a have been studied theoretically by a series of ab initio molecular fragment, floating spherical Gaussian orbital, self-consistent field calculations on ethyl chlorophyllide a and experimentally through a 13C magnetic resonance study on chlorophyll a. The approximate ground state electronic wavefunction of ethyl chlorophyllide a was perturbed by monopole and dipole point charges whose signs, magnitudes, and positions were chosen to mimic the coulombic interactions associated with carbonyl coordination to Mg. Because the polarizability of the ring V keto carbonyl binding site is substantially greater than that for the ester carbonyl binding sites, the ring V keto binding site binds with smallest binding energy for weak perturbations and with largest binding energy for strong perturbations. A comparison of 13C magnetic resonance chemical shifts in chlorophyll a monomer and dimer provides new experimental evidence that the donor-acceptor interactions that bind the chlorophyll dimer together involve a substantial participation by the ring V keto carbonyl and minimal participation by the two ester carbonyl groups, and thus are in agreement with conclusions derived from the ab initio calculations.
