Abstract
Bacteriopheophytin is a key component in the mechanism by which photosynthetic bacteria transduce solar energy into chemical form. The structure of methyl bacteriopheophorbide a, a bacteriopheophytin derivative, has been determined by three-dimensional x-ray diffraction. The compound crystallizes in space group P1 in a unit cell containing a molecule of methyl bacteriopheophorbide and a benzene molecule of crystallization, with lattice constants a = 7.2502 (8) A, b = 8.1070 (9) A, c = 17.224 (5) A, ..cap alpha.. = 90.80 (2)/sup 0/, ..beta.. ..-->.. = 94.17 (2)/sup 0/, and ..gamma.. = 110.38 (1)/sup 0/. The structure has been refined with isotropic thermal parameters on F by full-matrix least squares to R/sub F/ = 0.110, based on 860 reflections. The molecules associate in chains via ..pi..-..pi.. interactions with ring I of one molecule overlapping ring III of its neighbor with a vertical separation of 3.6 A. The one-dimensional chains form two-dimensional layers without the intervention of the hydrogen bonding by water molecules previously reported for chlorophyllides. This work represents the first crystallographic determination of a bacteriochlorin and confirms the canonical structures and relative orientations of the five chiral centers of bacteriochlorophyll a derivatives.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
