Structural characterization of artificial self-assembling porphyrins that mimic the natural chlorosomal bacteriochlorophylls c, d, and e.
We report two crystal structures of a synthetic porphyrin molecule which was programmed for self-assembly. The same groups which ensure that bacteriochlorophylls c, d, and e can self-assemble into the chlorosomal nanorods, the photosynthetic antenna system of some green bacteria, have been engineered into desired positions of the tetrapyrrolic macrocycle. In the case of the 5,15-meso-substituted anchoring groups, depending upon the concentration, by using the same crystallization solvents, either a tetragonal or a layered structure of porphyrin stacks were encountered. Surprisingly, pi-pi interactions combined with extensive dispersive interactions, which also encompass cyclohexane, one of the crystallization solvents, win over putative hydrogen bonding. We are aware that our compounds differ considerably from the natural bacteriochlorophylls, but based upon our findings, we now question the hydrogen-bonding network, previously proposed to organize stacks of bacteriochlorophylls. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS) on various isomeric compounds support our challenge of current models for the chlorosomal antenna as these show structures, astonishingly similar to those of chlorosomes.
Balaban
Teodor Silviu
TS
Forschungszentrum Karlsruhe, Institute for Nanotechnology, Postfach 3640, 76021 Karlsruhe, Germany. silviu.balaban@int.fzk.de
Linke-Schaetzel
Myriam
M
Bhise
Anil D
AD
Vanthuyne
Nicolas
N
Roussel
Christian
C
Anson
Christopher E
CE
Buth
Gernot
G
Eichhöfer
Andreas
A
Foster
Keir
K
Garab
Gyözö
G
Gliemann
Hartmut
H
Goddard
Richard
R
Javorfi
Tamas
T
Powell
Annie K
AK
Rösner
Harald
H
Schimmel
Thomas
T
D001426:Bacterial Proteins / Q000737:chemistry* / Q000648:ultrastructure; D001429:Bacteriochlorophylls / Q000737:chemistry*; D002876:Chromosomes, Bacterial / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D018360:Crystallography, X-Ray; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry*; D013057:Spectrum Analysis
D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D011166:Porphyrins; C120930:bacteriochlorophyll e; C002084:bacteriochlorophyll c; C459779:bacteriochlorophyll d