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N Alberding

Publications and source records attributed to N Alberding.

8 recordsLinked to original sources
PubMed1981

Hemerythrin's oxygen-binding reaction studied by laser photolysis.

The dioxygen--iron bond in oxyhemerythrin is shown to be photosensitive. The recombination reaction after photodissociation depends strongly on solvent viscosity. In water (eta = 1 centipoise or 1 x 10(-3) Pa . s) the recombination is monophasic and second-order in solvent oxygen concentration, with a bimolecular rate coefficient of 2.9 x 10(7) M-1 s-1. In a glycerol/water mixture (eta = 180 centipoise) a concentration-dependent geminate recombination process is also seen. This opens a class of proteins to study by flash photolysis.

Animals↗
PubMed1978

Binding of carbon monoxide to isolated hemoglobin chains.

Binding of carbon monoxide to the separated alpha and beta chains of hemoglobin, with and without bound p-mercuribenzoate, has been measured at temperatures from 5 to 340 K for times 2 mus to 1 ks using flash photolysis. All four proteins exhibit three different rebinding processes. The data are interpreted by a model in which the carbon monoxide, moving from the solvent to the binding site at the ferrous heme iron, encounters three barriers. The temperature dependences of the three processes yield activation enthalpies and entropies for the three barriers for all four proteins. Binding at temperatures below about 200 K is nonexponential, implying that the innermost barrier has a distribution of activation enthalpies. The distributions for the four proteins have been determined. At temperatures below 30 K, the CO binding rates approach finite low-temperature limits; binding thus proceeds by quantum-mechanical tunneling. Invoking a simple model, the widths of the innermost barriers are extracted from the measured tunneling rates. The experimental parameters are correlated with structural features of the hemoglobin chains and compared with previously published data on myoglobin and protoheme. A correlation is established between the height of the innermost barrier and the equilibrium CO pressure.

Carbon Monoxide↗
PubMed1978

Fast reactions in carbon monoxide binding to heme proteins.

Using fast flash photolysis, we have measured the binding of CO to carboxymethylated cytochrome c and to heme c octapeptide as a function of temperature (5 degrees-350 degreesK) over an extended time range (100 ns(-1) ks). Experiments used a microsecond dye laser (lambda = 540 nm), and a mode-locked frequency-doubled Nd-glass laser (lambda = 530 nm). At low temperatures (5 degrees-120 degreesK) the rebinding exhibits two components. The slower component (I) is nonexponential in time and has an optical spectrum corresponding to rebiding from an S = 2, CO-free deoxy state. The fast component (I*) is exponential in time with a lifetime shorter than 10 mus and an optical spectrum different from the slow component. In myoglobin and the separated alpha and beta chains of hemoglobin, only process I is visible. The optical absorption spectrum of I* and its time dependence suggest that it may correspond to recombination from an excited state in which the iron has not yet moved out of the heme plane. The temperature dependences of both processes have been measured. Both occur via quantum mechanical tunneling at the lowest temperatures and via over-the-barrier motion at higher temperatures.

Binding Sites↗
PubMed1978

Stochastic theory of ligand migration in biomolecules.

When ligand binding to proteins involves the presence of more than one ligand inside a given biomolecule, linear deterministic rate equations become useless. A stochastic approach, however, permits a treatment of the migration and binding of small molecules to proteins even at high ligand concentrations. An appropriate linear master equation and its analytic solution are given. As an example, the binding of carbon monoxide to myoglobin at partial pressures from 1 to 10(3) bars (0.1 to 100 MPa) is treated.

Binding Sites↗
PubMed1976

Tunneling in ligand binding to heme proteins.

Rebinding of carbon monoxide to the beta chain of hemoglobin after photodissociation by a laser flash is intramolecular below about 200 K. Above 25 K, rebinding occurs via classical over-the-barrier motion; below, quantum-mechanical tunneling dominates. Both are described by an energy spectrum peaked at Epeak=4.0 kilojoules per mole. The barrier width d(E), determined from the energy dependence of the tunneling rate, depends on barrier height, d(E) approximately 0.05 nanometer X (E/Epeak) 1.5.

Carbon Monoxide↗