title: Structural characterization of artificial self-assembling porphyrins that mimic the natural chlorosomal bacteriochlorophylls c, d, and e.
abstract: 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.
authors.affiliation: Forschungszentrum Karlsruhe, Institute for Nanotechnology, Postfach 3640, 76021 Karlsruhe, Germany. silviu.balaban@int.fzk.de
authors.forename: Teodor Silviu
authors.initials: TS
authors.lastname: Balaban
authors.forename: Myriam
authors.initials: M
authors.lastname: Linke-Schaetzel
authors.forename: Anil D
authors.initials: AD
authors.lastname: Bhise
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vanthuyne
authors.forename: Christian
authors.initials: C
authors.lastname: Roussel
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Anson
authors.forename: Gernot
authors.initials: G
authors.lastname: Buth
authors.forename: Andreas
authors.initials: A
authors.lastname: Eichhöfer
authors.forename: Keir
authors.initials: K
authors.lastname: Foster
authors.forename: Gyözö
authors.initials: G
authors.lastname: Garab
authors.forename: Hartmut
authors.initials: H
authors.lastname: Gliemann
authors.forename: Richard
authors.initials: R
authors.lastname: Goddard
authors.forename: Tamas
authors.initials: T
authors.lastname: Javorfi
authors.forename: Annie K
authors.initials: AK
authors.lastname: Powell
authors.forename: Harald
authors.initials: H
authors.lastname: Rösner
authors.forename: Thomas
authors.initials: T
authors.lastname: Schimmel
mesh_terms: 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
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D011166:Porphyrins; C120930:bacteriochlorophyll e; C002084:bacteriochlorophyll c; C459779:bacteriochlorophyll d