In neuronal nitric-oxide synthase (NOS), electron transfer proceeds across domains in a linear sequence from NADPH to flavins to heme, with calmodulin (CaM) triggering the interdomain electron transfer to the heme (Abu-Soud, H. M., and Stuehr, D. J. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 10769-10772). Here, we utilized a neuronal NOS devoid of its bound heme and tetrahydrobiopterin (apo-NOS) ...

Electron transfer from P+QA-QB to form P+QAQB- was measured in Rhodobacter sphaeroides R-26 reaction centers (RCs) where the native primary quinone, ubiquinone-10 (UQA), was replaced by 2-methyl-3-phytyl-1,4-naphthoquinone (MQA). The native secondary quinone, UQ-10, was retained as UQB. The difference spectrum of the semiquinone MQA- minus UQB- absorption is very similar to that of MQ- minus UQ...

We have investigated the nature of the photocurrent generated by Photosystem II (PSII), the water oxidizing enzyme, isolated from Thermosynechococcus elongatus, when immobilized on nanostructured titanium dioxide on an indium tin oxide electrode (TiO2/ITO). We investigated the properties of the photocurrent from PSII when immobilized as a monolayer versus multilayers, in the presence and absenc...

Microorganisms exploit extracellular electron transfer (EET) in growth and information exchange with external environments or with other cells. Every microbial cell is surrounded by extracellular polymeric substances (EPS). Understanding the roles of three-dimensional (3D) EPS in EET is essential in microbiology and microbial exploitation for mineral bio-respiration, pollutant conversion, and b...

1 The spin–boson model is applied to describe the coupling between protein motion and electron transfer for the primary electron transfer in the photosynthetic reaction center of Rps. viridis, a coupling which involves a very large number of degrees of freedom of the protein. For this purpose the relationship between the spectral function J(ω) characterizing the protein motion and the fluctuati...

We present a study of excited-state dynamics of two flavin cofactors: flavin-adenine dinucleotide (FAD) and flavin-mononucleotide (FMN). We used femtosecond mid-R transient absorption spectroscopy to study the effect of FAD conformation on its excited-state behavior. The conformation of FAD was modulated by changing the solvent polarity: in D(2)O, FAD is present predominantly in the "stacked" c...

A novel Raman spectroscopic model for the dinuclear iron site in ribonucleotide reductase and met-hemerythrin, [Fe2(micro-O)(phen)4(H2O)2]4+, 1, (phen = 1,10-phenanthroline) quantitatively oxidizes hydrogen peroxide to dioxygen via an inner-sphere electron transfer pathway. Although 1 deprotonates to form [Fe2(micro-O)(phen)4(H2O)(OH)]3+ (2) and [Fe2(micro-O)(phen)4(OH)2]2+ (3) in aqueous media...

The photoinduced electron transfer between either cationic 5,50-dichloro-3,30,9-triethylthiacarbocyanine (1) or a structurally similar anionic dye (2) and appropriate donors, e.g. ascorbic acid, and acceptors, e.g. methyl viologen, was studied by ns-laser photolysis. In aqueous solution the dyes in the ground state are present as an equilibrated mixture of dimers and monomers, whereas the tripl...