Related Experiment Video
Updated: Aug 9, 2026

A New Approach for the Comparative Analysis of Multiprotein Complexes Based on 15N Metabolic Labeling and Quantitative Mass Spectrometry
Published on: March 13, 2014
Electron transfer in ruthenium-modified spinach plastocyanin mutants
K Sigfridsson1, M Ejdebäck, M Sundahl
1Lundberg Laboratory, Göteborg University and Chalmers University of Technology, Medicinaregatan 9C, Göteborg, S-413 90, Sweden. karl.sigfridsson@nordicsynthesis.se
Abstract:
Four site-directed mutants of spinach plastocyanin, Pc(Leu12His), Pc(Leu15His), Pc(Thr79His), and Pc(Lys81His), have been modified by covalent attachment of a photoactive [Ru(bpy)2(im)]2+ complex at the surface-exposed histidine residues. The Pc-Ru complexes were characterized with optical absorption, CD, and EPR spectroscopy and their spectra were found to be similar to the unmodified proteins except in the case of the Pc(Leu12His) mutant which lost the Cu ion irreversibly during the Ru modification. Electron transfer (ET) within the other Pc-Ru complexes was studied with time-resolved optical spectroscopy, using an external-quencher approach. The fully reduced [Cu(I), Ru(II)] proteins were photoexcited and subsequently oxidized by an external quencher, [Ru(NH3)6]Cl3, forming the [Cu(I), Ru(III)] proteins. This was followed by an internal ET from Cu(I) to Ru(III). The rates of the internal ET reactions exhibit an exponential dependence on metal-to-metal separation, with a decay factor of 1.1 A-1. From a temperature-dependence study of the Ru-modified Pc(Lys81His) protein, a reorganization energy for the Cu-to-Ru ET reaction of 1.2 eV was determined. In this analysis it was found necessary to include an appreciable temperature dependence in the driving force of the ET reaction.
More Related Videos
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
10:46Evaluation of Photosynthetic Efficiency in Photorespiratory Mutants by Chlorophyll Fluorescence Analysis
Published on: December 9, 2022
Related Concept Videos
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...
The Calvin Benson Cycle
The Photochemical Reaction Center
The Z-Scheme of Electron Transport in Photosynthesis
Electron Transport Chain: Complex III and IV
Protein Transport to the Inner Chloroplast Membrane