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A direct approach is offered by femtosecond time-resolved experiments on native and mutant (L168 H [right arrow] F) reaction centers of blastochloris viridis, to study the reaction mechanism and the optimization strategies for the primary steps in the light reaction of bacterial photosynthesis. The experiments focus on a temperature-dependent analysis of reaction rates and an evaluation of the oscillatory contributions.

Heterogenous nucleation on small molecule crystals causes a monoclinic crystal form of bacteriorhodopsin (BR) in which trimers of this membrane protein pack differently than in native purple membranes. Analysis of single crystals by nano-electrospray ionization-mass spectrometry demonstrated a preservation of the purple membrane lipid composition in these BR crystals. The 2.9-[Angstrom] x-ray structure shows a lipid-mediated stabilization of BR trimers where the glycolipid S-TGA-1 binds into the central compartment of BR trimers. The BR trimer/lipid complex provides an example of local membrane thinning as the lipid head-group boundary of the central lipid patch is shifted by 5 [Angstrom] toward the membrane center. Nonbiased electron density maps reveal structural differences to previously reported BR structures, especially for the cytosolic EF loop and the proton exit pathway. The terminal proton release complex now comprises an E194-E204 dyad as a diffuse proton buffer.

Proteins are separated from Rhodobacter (R.) sphaeroides to examine the electron-transfer energetics from the soluble cytochrome (cyt) c2 to the photooxidized reaction center, RC. A study of RCs with site-directed mutations at residue L162 is conducted with wild-type (WT) RC. Regulation of the absence of the absorption band of the photooxidized basic donor P+ and the alpha-band of cytc2 is observed. Intact cells have the same energetics when conditions of high equimolar RC and cytc2 concentrations are observed. None of the mutants show the quick constituent of energetics usually observed in WT.

Rhodobacter (R.) sphaeroides show the presence of the pufL gene with a tyrosine residue 162, which is replaced with phenylalanine, serine, leucine, methionine and glycine, by five site-directed mutants. The R. sphaeroides puf elimination strain PUFdeltaLMX21/3 reveals the mutation and wild-type (WT) genes. Photoheterotrophical competence of all mutants and defects of L162G and L162S is observed by primary characterization. The mutants and WT reveal similar quantities of mutant interaction cores, spectral properties and rates of intraprotein electron transfer and turnover.