Related Experiment Video
Updated: Sep 29, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Pheophytin-protein interactions in photosystem II studied by resonance Raman spectroscopy of modified reaction
Marta Germano1, Andy Pascal, Anatoli Ya Shkuropatov
1Huygens Laboratory, Biophysics Department, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands. marta@nat.vu.nl
Abstract:
Soret-excited resonance Raman spectra of two types of pheophytin-exchanged photosystem II RCs are reported. The cofactor composition of the reaction centers was modified by exchanging pheophytin a for 13(1)-deoxo-13(1)-hydroxypheophytin a, yielding one preparation with selective replacement of the photochemically inactive pheophytin (H(B)) and a second one exhibiting total replacement of H(B) and 40% replacement of H(A), the primary electron acceptor. Resonance Raman spectra indicate that the other bound cofactors present are not significantly perturbed by Pheo substitution. The resonance Raman contributions from H(A) and H(B) in the carbonyl stretching region are identified at 1679 and 1675 cm(-)(1), respectively, indicating that both pheophytin molecules in the photosystem II reaction center have hydrogen-bonded keto-carbonyl groups. This conclusion differs from what is observed in the functionally related RCs of purple non-sulfur bacteria, where the keto-carbonyl group of H(B) is not hydrogen bonded, but confirms predictions from models based on protein sequence alignments.
More Related Videos
11:55In Vitro Reconstitution of Light-harvesting Complexes of Plants and Green Algae
Published on: October 10, 2014
08:40Separation of Spinach Thylakoid Protein Complexes by Native Green Gel Electrophoresis and Band Characterization using Time-Correlated Single Photon Counting
Published on: February 14, 2019
Related Concept Videos
The Photochemical Reaction Center
Photosystem II
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Photosystem I
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Photosystems
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
The Antenna Complex
Photoreceptors and Plant Responses to Light