Linked Life Data

7326244

Source:http://linkedlifedata.com/resource/pubmed/id/7326244

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
26
pubmed:dateCreated
1982-4-22
pubmed:abstractText
Well-defined 1:1 complexes have been formed between apomyoglobin (apoMb) and a number of chlorophyllide derivatives. The chlorophyllides substitute for heme in the pocket of myoglobin. These include magnesium chlorophyllide a, magnesium and zinc pyrochlorophyllide a, zinc pyrochlorophyllide b, zinc pyrochlorophyllide d, zinc pyromesochlorophyllide a, zinc 2-acetyl-2-devinylpyrochlorophyllide a, zinc protopyrochlorophyllide a, and zinc bacteriopyrochlorophyllide a. The effects of the protein on the electronic absorption, circular dichroism (CD), magnetic circular dichroism, and triplet state electron spin resonance spectra and fluorescence lifetimes in solution are compared with appropriate models in organic solvents. With the exception of the CD spectra, the protein causes shifts and intensity changes which are within the range observed for solvent effects. The CD spectra change substantially: the signs of several transitions are entirely reversed in the chlorins, and 3-6-fold intensity increases are observed with zinc bacteriochlorophyllide a. High-field 1H NMR spectra of ring current shifted Val-E11 methyl protons for the series porphyrin-, chlorin-, and bacteriochlorin-apoMb are used to establish the probable absolute orientation of the chromophore in the heme pocket. Doubled peaks in the NMR spectra of certain complexes are shown to arise from interconvertible species. The temperature dependence of the peak intensities and saturation transfer studies show that the species giving rise to the doubled peaks exchange on the time scale of about 1-60 s. Arguments are presented against inversion of the macrocycle in the heme pocket by either an inter- or an intramolecular mechanism as the origin of doubled peaks, and simple two-site exchange is ruled out by the NMR data. We suggest that the data are consistent with the idea that at least two slowly interconverting conformational substrates of the protein are populated, depending sensitively on small changes in rings I and II of the macrocycle and temperature.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
22
pubmed:volume
20
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7546-56
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1981
pubmed:articleTitle
Solution properties of synthetic chlorophyllide--and bacteriochlorophyllide--apomyoglobin complexes.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.