Photosynthesis Research

, Volume 121, Issue 1, pp 49–60

Statistical considerations on the formation of circular photosynthetic light-harvesting complexes from Rhodopseudomonas palustris

Regular Paper


Depending on growth conditions, some species of purple photosynthetic bacteria contain peripheral light-harvesting (LH2) complexes that are heterogeneous owing to the presence of different protomers (containing different αβ-apoproteins). Recent spectroscopic studies of Rhodopseudomonas palustris grown under low-light conditions suggest the presence of a C3-symmetric LH2 nonamer comprised of two distinct protomers. The software program Cyclaplex, which enables generation and data-mining of virtual libraries of molecular rings formed upon combinatorial reactions, has been used to delineate the possible number and type of distinct nonamers as a function of numbers of distinct protomers. The yield of the C3-symmetric nonamer from two protomers (A and B in varying ratios) has been studied under the following conditions: (1) statistical, (2) enriched (preclusion of the B-B sequence), and (3) seeded (pre-formation of an A-B-A block). The yield of C3-symmetric nonamer is at most 0.98 % under statistical conditions versus 5.6 % under enriched conditions, and can be dominant under conditions of pre-seeding with an A-B-A block. In summary, the formation of any one specific nonamer even from only two protomers is unlikely on statistical grounds but must stem from enhanced free energy of formation or a directed assembly process by as-yet unknown factors.


Bacterial photosynthesis Light-harvesting Heterogeneous Oligomer Diversity Simulation Self-assembly 



Light-harvesting complex 2

Bchl a

Bacteriochlorophyll a



Supplementary material

11120_2014_9975_MOESM1_ESM.pdf (68 kb)
Supplementary material 1 (PDF 68 kb)

Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  1. 1.Department of ChemistryNorth Carolina State UniversityRaleighUSA
  2. 2.Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life SciencesUniversity of GlasgowGlasgowUK

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