The electron spin echo studies of metalloproteins.
Item
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Title
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The electron spin echo studies of metalloproteins.
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Identifier
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AAI9009746
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identifier
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9009746
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Creator
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Jin, Haiyong.
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Contributor
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Adviser: Hans Thomann
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Date
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1989
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biophysics, General | Chemistry, Physical | Chemistry, Biochemistry
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Abstract
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A systematic method is developed to analyze Electron Spin Echo (ESE) spectra of frozen solution materials. The ESE signal of a frozen solution sample arises from molecules which orient differently with respect to the applied field. The "orientation selectivity" by EPR associates the ESE signal at a given field setting to a distinct subset of molecules. This, together with the dependence of ESE envelope modulation spectra on the field setting, makes it possible to obtain single crystal level information about the molecular structure from a frozen solution sample.;In the ESE spectra of both native and isotopically enriched nitrogenase molybdenum iron protein, nuclear modulation due to at least one nitrogen coordinated to the iron molybdenum cofactor, the protein active site, have been observed. Based on the nuclear quadrupole parameters ({dollar}e\sp2 qQ/h{dollar} = 2.0 MHz, {dollar}\eta{dollar} = 0.65) obtained from numerical analysis, in comparison with existing {dollar}\sp{14}{dollar}N Nuclear Quadrupole Resonance data and recent site-directed mutagenesis studies of the protein, this nitrogen is most likely from the side chain of a histidine, or a glutamine. Furthermore, the significant change of the nitrogen modulation amplitude introduced by the difference in molybdenum isotope enrichment suggests that this nitrogen is likely connected to the FeMoco through coordination to the molybdenum.;In the ESE and EPR studies of the multicopper enzyme nitrous oxide reductase, two types of copper sites are identified: antiferromagnetically coupled (J {dollar}>{dollar} 200 cm{dollar}\sp{lcub}-1{rcub}{dollar}) dimeric sites and unusual Cu(II) sites. The EPR susceptibility arises from these Cu(II) sites and from binuclear mixed valence Cu(I)/Cu(II) half--met sites which are derived from partially reduced dimers. On average, six of the eight copper ions per protein are in the form of the EPR silent binuclear type 3 dimers. The inverse proportionality of EPR activity and biological activity among various forms of the enzyme suggests that the reduction of N{dollar}\sb2{dollar}O may take place at the sites of EPR--silent binuclear dimers. Also, the ESE envelope modulation data of the enzyme provide a direct evidence that the Cu{dollar}\sb{lcub}\rm A{rcub}{dollar} site, which exists in cytochrome c oxidase, is also present in this enzyme.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
