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A device that collects electrical current from photosynthetic organisms or their products. Electron transfer across cellular envelopes and to an electrode links biological reducing power with an external circuit; light absorption alone does not establish that current reaches the electrode.^[ref]

Chris Anthony coauthored the 1964 study of a bacterial methanol dehydrogenase with L. J. Zatman. His own research account explicitly connects his name with the initial-only Anthony–Zatman publications.^[ref]

The experiment measured an optical response associated with electron transfer, using a dye-linked enzyme assay. The paper describes a Unicam SP.500 spectrophotometer and $10\mathrm{mm}$ cuvettes. Establishing the reaction product required separate chemical analysis rather than the optical signal alone.^[ref]

For an original illustration of the optical measurement, assume the Beer-Lambert lawwith absorbance $A=0.20$, liquid path $\ell =1.0\mathrm{cm}$ and a hypothetical molar coefficient $\epsilon =10^4\mathrm{L}\mathrm{mo}{\mathrm{l}}^{-1}\mathrm{c}{\mathrm{m}}^{-1}$. ThenA decrease of $0.05$ absorbance units would correspond to a $5\times 10^{-6}\mathrm{mol}{\mathrm{L}}^{-1}$ decrease of the absorbing species under those assumptions. It does not by itself give the amount of methanol consumed: the chemical identity of the absorber and the coupling stoichiometry must also be known. The coefficient and measurements are invented for this example.

Cyclic voltammetry sweeps an electrode potential forward and then reverses the sweep while recording electric current. The resulting current-potential curve probes electron transfer and chemical reactions coupled to it.

An oxidation peak followed by a reduction peak can indicate that an electrode-generated species survives long enough to react on the return sweep. Changing the scan rate changes the experimental timescale; loss of a return peak can therefore reveal a subsequent reaction, although transport and electrode kinetics must also be considered.

A cytochrome is a protein containing a haem group whose iron can change oxidation state during electron transfer. The surrounding protein tunes the properties of the haem and its interactions with electron donors and acceptors. The name denotes a broad biochemical class, not one unique enzyme or one universal reaction. ^[ref]

For example, cytochrome c is a mobile carrier between respiratory complexes, while cytochrome c oxidase is a larger terminal complex that transfers electrons toward oxygen. Carrying an electron and pumping protons are distinct operations; not every individual cytochrome performs both. Spectral changes accompanying oxidation and reduction make these cofactors experimentally useful reporters of electron-transfer state.

A researcher in statistical mechanics and physical chemistry who developed theory and simulation methods for liquids. His work connects microscopic molecular fluctuations with collective behavior, including the hydrophobic effect, electron transfer and the glass transition. The scientific value of this approach is that the surrounding liquid is an active part of a process: its changing molecular arrangement can determine whether a reaction proceeds or a structure assembles.^[ref]

A sequence of electron transfer, chemical reaction, electron transfer and chemical reaction. Binding reactions can shift reduction potentials and separate reduction from product-release waves.

A fusion protein combines sequences from two or more protein components in one polypeptide chain. The joining can arise through a gene fusion or be engineered for an experiment. Its covalent continuity distinguishes it from a protein complex whose separately made chains associate without becoming one backbone.

A peptide linker can connect the components while allowing some relative motion. For an original size calculation, components of 200 and 300 amino acid residues joined by a 10-residue peptide linker produce a510-residue chain. This arithmetic specifies composition and order; it does not establish that both components retain their original activities.

A structural experiment illustrates both the usefulness and the cost of tethering. Researchers connected adrenodoxin to the cholesterol side-chain cleavage enzyme to capture a normally transient electron-transfer interaction. Crystallizable fusion proteins made with different peptide linkers showed a similar interaction interface. Their catalytic activities were lower than those of the nonfused system, and electron transfer depended on linker length even when substrate affinity was preserved.^[ref]

Tethering can therefore help reveal an interaction without reproducing every property of the freely associating partners. Structural capture, substrate recognition and catalytic turnover remain separate measurements.

Electron transfer through a ligand shared by two metal centres. Bridge formation, electron transfer and bridge cleavage can leave transferred-ligand connectivity in a substitution-inert product.

Nicotinamide, ${\mathrm{C}}_6{\mathrm{H}}_6{\mathrm{N}}_2\mathrm{O}$, is the amide of nicotinic acid, with a pyridine ring bearing a carboxamide group. It is one form of vitamin B3 and supplies the nicotinamide unit of nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate.^[ref]

These coenzymes connect its structure to metabolism: the nicotinamide ring participates in reversible electron transfer between oxidized and reduced forms. Incorporation into a coenzyme is different from the free nicotinamide molecule itself carrying out every associated reaction.^[ref]

The difference between an applied electrode potential and the relevant equilibrium potential. Increasing its magnitude can drive electron transfer toward a mass-transport limit.

The free end of N-bound $\mathrm{Co}-\mathrm{NCS}$ is sulfur. Cr(II) binds there, giving the remote bridge $\mathrm{C}{\mathrm{o}}^{\mathrm{III}}-\mathrm{N}-\mathrm{C}-\mathrm{S}-\mathrm{C}{\mathrm{r}}^{\mathrm{II}}$. Electron transfer and cleavage of the Co-N bond leave S-bound Cr(III), $[\mathrm{Cr}(\mathrm{SCN})(\mathrm{O}{\mathrm{H}}_2{)}_5{]}^{2+}$; labile Co(II) becomes hexaaquacobalt(II).

The much smaller rate constant shows that the efficiency of bridge formation/electron transmission is strongly sensitive to linkage orientation. Efficient donation and coupling in a Co-S-bound precursor need not be reproduced when cobalt is N-bound. Its reduction is still consistent with inner-sphere electron transfer; a slow rate alone is not a criterion for outer-sphere transfer.

These are inner-sphere electron transfer pathways distinguished by where Cr(II) attacks the coordinated thiocyanate. Cr(II) is substitution-labile and can replace an aqua ligand to form a bridged Co(III)/Cr(II) precursor.

In both cases the product Co(II) rapidly loses its ammines to give the hexaaqua ion, whereas substitution-inert Cr(III) retains the bridge-end information. The two chromium linkage isomers are therefore a record of two precursor geometries, rather than evidence that one outer-sphere electron-transfer event somehow selects two arbitrary new ligands afterwards.

Make heterogeneous electron transfer fast relative to delivery of reactant, usually by applying sufficient overpotential so that its surface concentration approaches zero. Use excess supporting electrolyte to suppress migration. For purely diffusional transient transport, suppress uncontrolled convection; for a rotating disk electrode, controlled convection supplies the bulk while diffusion across the thin interfacial boundary layer limits the current. A limiting current that no longer increases with driving potential is the characteristic test; a large current alone is not sufficient.

Event a probes electron transfer between the semiquinone and dianion. Benzoquinone's smaller framework localizes charge and undergoes a greater change in bonding and solvation on this reduction; a larger effective reorganization barrier can make its heterogeneous transfer insufficiently fast for Nernst equilibrium on the $50\mathrm{mV}{\mathrm{s}}^{-1}$ time scale. Anthraquinone's extended framework distributes the added charge and can support the more reversible response seen here.

This is a kinetic interpretation of quasi-reversibility, not a claim that benzoquinone cannot be reduced. Follow-up chemistry or adsorption can also distort peak separation and return-current ratios; scan-rate-dependent measurements would distinguish them from slow electron transfer. A single trace does not uniquely identify the cause.

A peptide linker is a peptide segment connecting protein components within one continuous polypeptide chain. It joins their backbones while allowing relative positioning that depends on the segment's sequence and conformation. The connected regions can be distinct protein domains or components brought together in a fusion protein.

For an original residue-accounting example, components of 180 and 240 amino acid residues joined by a six-residue peptide linker produce a chain of 426 residues. Replacing that connector with an eighteen-residue peptide linker produces 438 residues. The twelve-residue difference specifies a sequence-length change; it does not uniquely determine the end-to-end distance of a polymer chain, binding affinity or catalytic rate.

A structural experiment illustrates why the distinction matters. Researchers tethered adrenodoxin to the cholesterol side-chain cleavage enzyme through different peptide linkers. The resulting crystallizable fusion proteins captured a similar interface, yet their catalytic activities differed from the nonfused comparison, and electron transfer depended on linker length even when substrate affinity was preserved.^[ref]

Linker choice is therefore part of the experiment. Structural capture, substrate recognition and catalytic performance are separate readouts. Success at one of them does not establish that the connector reproduces every property of the freely associating components.

Production of useful molecules using photosynthesis to supply fixed carbon, energy or reducing power. Engineering a Cytochrome P450 at a photosynthetic membrane illustrates how an introduced biosynthetic reaction can draw on light-driven electron transfer.^[ref]

A rotating disk electrode is a flat disk electrode rotated at a controlled angular speed. Rotation drives fluid motion that makes the reactant transport layer reproducible.

For an appropriate diffusion-limited reaction, the limiting electric current varies as the square root of angular speed. Comparing measured current with that transport dependence helps distinguish a mass-transfer limit from slow interfacial electron transfer.

Yaniv Shlosberg coauthored research on electron transfer.^[ref]

Transfer of an electron between chemical species or between a species and an electrode. Its rate depends on driving force, electronic coupling and nuclear/solvent reorganization.