Document Detail

A nuclear magnetic resonance study of the heme environment in beef liver catalase.
MedLine Citation:
PMID:  945745     Owner:  NLM     Status:  MEDLINE    
The effect of high-spin heme iron in beef liver catalase on the longitudinal and transverse proton relaxation rates of the solvent has been used to probe the environment of the paramagnetic center. The longitudinal proton relaxation rates were measured as a function of temperature (5-31 degrees C), frequency (5-100 MHz), and pH. T1p was found to be pH independent in the range 6-11, indicating that no significant difference occurs in the heme surrounding within this pH range. The ligands formate and acetate, which preserve the spin state of the heme iron upon ligation, displace a water molecule from the sixth coordination position. This reaction is pH independent, while the binding measured by optical spectroscopy is pH dependent. The electron methanol and ethanol essentially do not change the proton relaxation rates. The temperature and frequency dependencies indicate that the relaxation times are governed by the electronic relaxation time of the high-spin ferric iron tau s. Tau s, which was found to be frequency independent, could not be determined from the T1p/T2p ratio, but only from the frequency dependence of the longitudinal relaxation rate at low frequencies. The results of the least-squares fit of the data to the theory indicate that there is one iron-bound rapidly exchanging water molecule. For the Fe3+ ion it was determined that tau s = 7 x 10(-11) s.
A Lanir; A Schejter
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Biochemistry     Volume:  15     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  1976 Jun 
Date Detail:
Created Date:  1976-09-25     Completed Date:  1976-09-25     Revised Date:  2003-11-14    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  2590-6     Citation Subset:  IM    
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MeSH Terms
Binding Sites
Heme / analysis
Liver / enzymology*
Magnetic Resonance Spectroscopy
Protein Binding
Protein Conformation
Reg. No./Substance:
14875-96-8/Heme; EC

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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