The role of the local environment on the structural heterogeneity of carotenoid ß-ionone rings.
Photosynth Res
; 156(1): 3-17, 2023 Apr.
Article
em En
| MEDLINE
| ID: mdl-36063303
ABSTRACT
Our analysis of the X-ray crystal structure of canthaxanthin (CAN) showed that its ketolated ß-ionone rings can adopt two energetically equal, but structurally distinct puckers. Quantum chemistry calculations revealed that the potential energy surface of the ß-ionone ring rotation over the plane of the conjugated π-system in carotenoids depends on the pucker state of the ß-ring. Considering different pucker states and ß-ionone ring rotation, we found six separate local minima on the potential energy surface defining the geometry of the keto-ß-ionone ring-two cis and one trans orientation for each of two pucker states. We observed a small difference in energy and no difference in relative orientation for the cis-minima, but a pronounced difference for the position of trans-minimum in alternative pucker configurations. An energetic advantage of ß-ionone ring rotation from a specific pucker type can reach up to 8 kJ/mol ([Formula see text]). In addition, we performed the simulation of linear absorption of CAN in hexane and in a unit cell of the CAN crystal. The electronic energies of [Formula see text] transition were estimated both for the CAN monomer and in the CAN crystal. The difference between them reached [Formula see text], which roughly corresponds to the energy gap between A and B pucker states predicted by theoretical estimations. Finally, we have discussed the importance of such effects for biological systems whose local environment determines conformational mobility, and optical/functional characteristics of carotenoid.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Carotenoides
/
Norisoprenoides
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
Photosynth Res
Assunto da revista:
METABOLISMO
Ano de publicação:
2023
Tipo de documento:
Article