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Biomedical subjects

R C Prince

Publications and source records attributed to R C Prince.

At least 55 records · Page 3Linked to original sources
PubMed1991

Microbial populations and hydrocarbon biodegradation potentials in fertilized shoreline sediments affected by the T/V Exxon Valdez oil spill.

The effort of clean up the T/V Exxon Valdez oil spill in Prince William Sound, Alaska, included the use of fertilizers to accelerate natural microbial degradation of stranded oil. A program to monitor various environmental parameters associated with this technique took place during the summer of 1990. Microbiological assays for numbers of heterotrophic and oil-degrading microbes and their hydrocarbon mineralization potentials were performed in support of this program. Fertilizer addition resulted in higher hexadecane and phenanthrene mineralization potentials on treated plots than on untreated reference plots. Microbial numbers in treated and reference surface sediments were not significantly different immediately after the first nutrient application in May 1990. However, subsurface sediments from treated plots had higher numbers of hydrocarbon degraders than did reference sediments shortly after treatment. The second application of fertilizer, later in summer, resulted in surface and subsurface increases in numbers of hydrocarbon degraders with respect to reference sediments at two of the three study sites. Elevated mineralization potentials, coupled with increased numbers of hydrocarbon degraders, indicated that natural hydrocarbon biodegradation was enhanced. However, these microbiological measurements alone are not sufficient to determine in situ rates of crude oil biodegradation.

Alaska↗
PubMed1990

Tryptophan radicals.

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Cytochrome-c Peroxidase↗
PubMed1989

E.p.r.-spectroscopic studies on the molybdenum-iron site of nitrogenase from Clostridium pasteurianum.

The e.p.r. spectroscopy of the nitrogenase molybdenum-iron protein from Clostridium pasteurianum was re-investigated. The sharpness of the delta Ms = +/- 3 g'z peak from the +/- 3/2 Kramer's doublet enables the observation and quantification of incompletely resolved hyperfine splittings from the stable magnetic nuclei 95Mo and 57Fe in samples enriched in these isotopes. No couplings to 1H or 17O could be discerned by examination of spectra from samples exchanged into 2H2O and H2(17)O respectively. Simulation of the spectrum from 95Mo-enriched samples yields a hyperfine coupling of 2.9 MHz, and indicates that the earlier electron-nuclear-double-resonance-derived estimate of 8.1 +/- 0.2 MHz is substantially in error.

Binding Sites↗
PubMed1989

Structure of the active site of sulfite oxidase. X-ray absorption spectroscopy of the Mo(IV), Mo(V), and Mo(VI) oxidation states.

The active site of sulfite oxidase has been investigated by X-ray absorption spectroscopy at the molybdenum K-edge at 4 K. We have investigated all three accessible molybdenum oxidation states, Mo(IV), Mo(V), and Mo(VI), allowing comparison with the Mo(V) electron paramagnetic resonance data for the first time. Quantitative analysis of the extended X-ray absorption fine structure indicates that the Mo(VI) oxidation state possesses two terminal oxo (Mo = O) and approximately three thiolate-like (Mo-S-) ligands and is unaffected by changes in pH and chloride concentration. The Mo(IV) and Mo(V) oxidation states, however, each have a single oxo ligand plus one Mo-O- (or Mo-N less than) bond, most probably Mo--OH, and two to three thiolate-like ligands. Both reduced forms appear to gain a single chloride ligand under conditions of low pH and high chloride concentration.

Animals↗
PubMed1989

Paramagnetic centers of carbon monoxide dehydrogenase from aceticlastic Methanosarcina barkeri.

Carbon monoxide dehydrogenase from Methanosarcina barkeri, purified to 95% homogeneity, contains 30 Fe, 2 Ni, 1 Zn, and 1 Cu (per alpha 2 beta 2 enzyme). Core extrusion experiments indicate 6 [4Fe-4S] clusters/tetramer, and electron paramagnetic resonance (epr) spectroscopy detects at least one of these clusters, in the reduced form, with apparent g values of 2.05, 1.94, and 1.90, and Em9.2-390 mV. A second epr signal, also seen in the reduced enzyme, has apparent g values of 2.005, 1.91, and 1.76, and Em9.2-35 mV. Two signals were seen in thionin-oxidized enzyme, one with a line shape suggestive of Cu(II), and the other resembling that of a [3Fe-4S] cluster. The enzymes nonphysiological substrate, CO, caused several spectral changes to the reduced enzyme, most notably a shift of the g = 1.76 feature to g = 1.73.

Aldehyde Oxidoreductases↗
PubMed1989

X-ray-absorption-spectroscopic evidence for a novel iron cluster in hydrogenase II from Clostridium pasteurianum.

Hydrogenase II from Clostridium pasteurianum contains three different iron-sulphur clusters. Two are [4Fe-4S](2+.1+) clusters, whereas the other, which is thought to be the site of interaction with H2 and is known as the 'H cluster', is of unknown structure and possesses unusual spectroscopic properties. Analysis of the iron e.x.a.f.s. spectra shows that the H cluster contains iron co-ordinated mostly to sulphur and possesses 2.8 A (1 A = 0.1 nm) Fe--Fe separations when oxidized and 3.3 A Fe--Fe separations when reduced with H2. The data suggest that the reduced H cluster represents a new structural type of iron-sulphur cluster.

Clostridium↗
PubMed1989

Demonstration that spleen green hemeprotein is identical to granulocyte myeloperoxidase.

The biochemical, spectroscopic, enzymatic, and redox properties of spleen myeloperoxidase, a peroxidase formerly called "spleen green hemeprotein," and granulocyte myeloperoxidase were compared by electrophoresis, amino-terminal amino acid sequences, optical and EPR spectroscopy, steady-state enzyme kinetics, and oxidation-reduction potential. The spleen enzyme exhibits properties indistinguishable from those of the granulocyte enzyme. We conclude that the spleen enzyme is indeed identical to granulocyte myeloperoxidase.

Amino Acid Sequence↗
PubMed1989

The manganese site of the photosynthetic water-splitting enzyme.

As the originator of the oxygen in our atmosphere, the photosynthetic water-splitting enzyme of chloroplasts is vital for aerobic life on the earth. It has a manganese cluster at its active site, but it is poorly understood at the molecular level. Polarized synchrotron radiation was used to examine the x-ray absorption of manganese in oriented chloroplasts. The manganese site, in the "resting" (S1) state, is an asymmetric cluster, which probably contains four manganese atoms, with interatomic separations of 2.7 and 3.3 angstroms; the vector formed by the 3.3-angstrom manganese pair is oriented perpendicular to the membrane plane. Comparisons with model compounds suggest that the cluster contains bridging oxide or hydroxide ligands connecting the manganese atoms, perhaps with carboxylate bridges connecting the 3.3-angstrom manganese pair.

Chloroplasts↗
PubMed1989

The cytochrome bc1 complex of Rhodobacter sphaeroides can restore cytochrome c2-independent photosynthetic growth to a Rhodobacter capsulatus mutant lacking cytochrome bc1.

Plasmids encoding the structural genes for the Rhodobacter capsulatus and Rhodobacter sphaeroides cytochrome (cyt) bc1 complexes were introduced into strains of R. capsulatus lacking the cyt bc1 complex, with and without cyt c2. The R. capsulatus merodiploids contained higher than wild-type levels of cyt bc1 complex, as evidenced by immunological and spectroscopic analyses. On the other hand, the R. sphaeroides-R. capsulatus hybrid merodiploids produced only barely detectable amounts of R. sphaeroides cyt bc1 complex in R. capsulatus. Nonetheless, when they contained cyt c2, they were capable of photosynthetic growth, as judged by the sensitivity of this growth to specific inhibitors of the photochemical reaction center and the cyt bc1 complex, such as atrazine, myxothiazol, and stigmatellin. Interestingly, in the absence of cyt c2, although the R. sphaeroides cyt bc1 complex was able to support the photosynthetic growth of a cyt bc1-less mutant of R. capsulatus in rich medium, it was unable to do so when C4 dicarboxylic acids, such as malate and succinate, were used as the sole carbon source. Even this conditional ability of R. sphaeroides cyt bc1 complex to replace that of R. capsulatus for photosynthetic growth suggests that in the latter species the cyt c2-independent rereduction of the reaction center is not due to a structural property unique to the R. capsulatus cyt bc1 complex. Similarly, the inability of R. sphaeroides to exhibit a similar pathway is not due to some inherent property of its cyt bc1 complex.

Carotenoids↗
PubMed1989

Purification and properties of ferredoxin and rubredoxin from Butyribacterium methylotrophicum.

A ferredoxin and a rubredoxin from Butyribacterium methylotrophicum, which displays a carbonyl-dependent acetyl-coenzyme A synthesis, were purified to electrophoretic homogeneity. The two electron carriers showed absorption spectra similar to those in Clostridium species. The ferredoxin displayed absorption peaks at 280 and 391 nm, while rubredoxin displayed absorption peaks at 279, 382, and 482 nm. Minimum molecular weights calculated from the respective amino acid compositions were 5,727 for ferredoxin and 5,488 for rubredoxin, excluding iron and inorganic sulfur atoms. Both electron carriers were isolated as monomers, according to gel-filtration data. Electron spin resonance analysis revealed that the ferredoxin was a 2[4Fe-4S]-type and that both clusters had a midpoint redox potential value of -410 mV, whereas rubredoxin contained one acid-stable iron and had a redox value of -40 mV. The coupling of these electron carriers to hydrogenase and carbon monoxide dehydrogenase activities was investigated. Rubredoxin showed higher activity towards carbon monoxide dehydrogenase, whereas ferredoxin showed higher activity towards hydrogenase.

Aldehyde Oxidoreductases↗
PubMed1988

The nature of the phosphate complex of sulphite oxidase from electron-paramagnetic-resonance studies.

The phosphate complex of sulphite oxidase in the Mo(V) oxidation state was investigated by e.p.r. spectroscopy. Third-derivative spectra reveal a wealth of structural detail previously unobserved in this spectrum. Most notable is the presence of hyperfine coupling from two inequivalent I = 1/2 nuclei, which we tentatively attribute to two 31P nuclei. Unresolved hyperfine interactions from at least one exchangeable 1H nucleus are also present.

Electron Spin Resonance Spectroscopy↗
PubMed1988

Spectroscopic properties of the hydroxylase of methane monooxygenase.

The hydroxylase component of methane monooxygenase (EC 1.14.13.25), which catalyzes the oxidation of methane to methanol, has been studied by visible, electron spin resonance and X-ray spectroscopies. The enzyme appears to possess a mu-oxo- or mu-hydroxo-bridged binuclear iron site, with no sulfur ligands to the cluster. Each Fe has 4-6 oxygen (or nitrogen) ligands, at an average distance of 1.92 +/- 0.03 A. The Fe-Fe distance is 3.05 +/- 0.05 A. Essentially all of the irons are in the Fe3+ state as the enzyme is prepared, but reduction with N-methylphenazonium methosulfate generates ESR-detectable states that appear to emanate from mixed-valence binuclear sites. One of these, with gav near 1.85, displays typical Curie law microwave saturation behavior, but the other, gav near 1.73, has a very potent method of spin-relaxation. Together they account for approximately 0.6 spins per molecule.

Binding Sites↗
PubMed1988

Tetrodotoxin.

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Animals↗
PubMed1988

Tyrosine radicals.

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Electron Transport↗
PubMed1987

Physiological electron donors to the photochemical reaction center of Rhodobacter capsulatus.

The nature and number of physiological electron donors to the photochemical reaction center of Rhodobacter capsulatus have been probed by deleting the genes for cytochromes c1 and b of the cytochrome bc1 complex, alone or in combination with deletion of the gene for cytochrome c2. Deletion of cytochrome c1 renders the organism incapable of photosynthetic growth, regardless of the presence or absence of cytochrome c2, because in the absence of the bc1 complex there is no cyclic electron transfer, nor any alternative source of electrons to rereduce the photochemically oxidized reaction center. While cytochrome c2 is capable of reducing the reaction center, there appears no alternative route for its rereduction other than the bc1 complex. The deletion of cytochromes c1 and c2 reveals previously unrecognized membrane-bound and soluble high potential c-type cytochromes, with Em7 = +312 mV and Em6.5 = +316 mV, respectively. These cytochromes do not donate electrons to the reaction center, and their roles are unknown.

Bacteria↗