Related Experiment Video
Updated: May 11, 2026

Isolation and Characterization of Intact Phycobilisome in Cyanobacteria
Published on: November 10, 2021
Conformational flexibility of phycocyanobilin: an AM1 semiempirical study
A H Göller1, D Strehlow, G Hermann
1Institut für Physikalische Chemie, Friedrich-Schiller-Universität Jena, Jena, Germany.
Abstract:
Semiempirical AM1 studies on phycocyanobilin, the most abundant chromophore in the light-harvesting phycobiliproteins and a suitable model of the phytochrome chromophore, have been carried out. For the all-Z isomer, the structures and energies of all possible conformers, which arise from rotation about the single bonds of the exocyclic methine bridges, were calculated. In addition, the rotational barriers between the different conformers were deduced from the computed energy hypersurfaces. The cyclic helical SSS conformation is the most stable structure. Other minimum-energy structures with well-separated local minima on the energy hypersurface are the partially extended ASS and SAS conformations, although the conformational situation is characterized by a high degree of kinetic flexibility. The energy of the different conformers is mainly governed by intramolecular hydrogen bonding and steric repulsion of the substituents at the tetrapyrrolic backbone. It is very likely that the energetically most favorable conformers, SSS, ASS, and SAS, correspond with the three ground-state conformers of phycocyanobilin detected in previous time-resolved absorption studies.
More Related Videos
Related Concept Videos
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
UV–Vis Spectroscopy of Conjugated Systems
One of the factors influencing λmax is the extent of conjugation in the...
Noncovalent Attractions in Biomolecules
Four types of noncovalent interactions are hydrogen bonds, van der Waals forces, ionic bonds, and hydrophobic interactions.
Hydrogen bonding results from the electrostatic attraction of a hydrogen atom covalently bonded to a strong-electronegative atom like oxygen,...
Conformations of Cyclohexane
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
Gene Families
Occasionally these regions can be adapted to take on new roles within the organism, becoming novel genes...

