Linked Life Data

8611547

Source:http://linkedlifedata.com/resource/pubmed/id/8611547

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
17
pubmed:dateCreated
1996-6-6
pubmed:abstractText
The cyanide complex of FeIIMb prepared and maintained at temperatures below 0 degrees C is sufficiently stable to permit spectroscopic characterization and allow comparison with free HCN and other ferric and ferrous CN complexes. The visible absorption spectrum of FeIIMb-CN has a split alpha band maxima at 571 and 563 nm, suggesting distortion in the x-y plane of the porphyrin. FeIIMb-CN, like the CO complex, was found to be optically active by circular dichroism. The C-N stretching frequencies for the CN-ferrous complexes are very sensitive to parameters within the heme pocket. The values are as follows: FEIIMb at pH 8, 2057 cm-1 with a shoulder appearing at 2078 cm-1 at pH 5.6; FeIIMp, 2034 cm-1. In contrast, the frequencies for C-N stretch differ little among ferric heme complexes, ranging from 2123 to 2125 cm-1 for myoglobin, hemoglobin, and microperoxidase. These values compare with free HCN (2094 cm-1) or CN- (2080 cm-1). Quantum chemical modeling of the neutral iron-porphyrin complex with imidazole and cyanide and of its anion was used to explain the effects of the cyanide coordination and of iron reduction on the C-N stretching frequencies. The lower nu C-N for FeIIMb-CN relative to the ferric complex is attributed to the appearance of additional electron density on all the anti-bonding CN orbitals. The extra electron density was also used to explain that the band width of C-N stretching mode was greater in the ferrous complexes than in the ferric complex. Finally, the calculation shows that sigma donation weakens the Fe-C bond, in qualitative agreement with the spontaneous dissociation of CN- from FeIIMb at -5 degrees C. The sensitivity of CN complexes of ferrous heme proteins to the heme pocket environment and the ability to correlate spectroscopic parameters with calculated electron density suggest that infrared spectroscopy of the CN ligand is an appropriate tool to study ferrous heme proteins.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
30
pubmed:volume
35
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5562-70
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1996
pubmed:articleTitle
Infrared spectroscopy of the cyanide complex of iron (II) myoglobin and comparison with complexes of microperoxidase and hemoglobin.
pubmed:affiliation
Johnson Research Foundation, Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia 19104, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't