Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1994-2-4
pubmed:abstractText
Phenomena occurring in the heme pocket after photolysis of carbonmonoxymyoglobin (MbCO) below about 100 K are investigated using temperature-derivative spectroscopy of the infrared absorption bands of CO. MbCO exists in three conformations (A substrates) that are distinguished by the stretch bands of the bound CO. We establish connections among the A substates and the substates of the photoproduct (B substates) using Fourier-transform infrared spectroscopy together with kinetic experiments on MbCO solution samples at different pH and on orthorhombic crystals. There is no one-to-one mapping between the A and B substates; in some cases, more than one B substate corresponds to a particular A substate. Rebinding is not simply a reversal of dissociation; transitions between B substates occur before rebinding. We measure the nonequilibrium populations of the B substates after photolysis below 25 K and determine the kinetics of B substate transitions leading to equilibrium. Transitions between B substates occur even at 4 K, whereas those between A substates have only been observed above about 160 K. The transitions between the B substates are nonexponential in time, providing evidence for a distribution of substates. The temperature dependence of the B substate transitions implies that they occur mainly by quantum-mechanical tunneling below 10 K. Taken together, the observations suggest that the transitions between the B substates within the same A substate reflect motions of the CO in the heme pocket and not conformational changes. Geminate rebinding of CO to Mb, monitored in the Soret band, depends on pH. Observation of geminate rebinding to the A substates in the infrared indicates that the pH dependence results from a population shift among the substates and not from a change of the rebinding to an individual A substate.
pubmed:grant
pubmed:commentsCorrections
http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-1191643, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-1409682, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-1548699, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-1557397, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-1749933, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-2018766, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-2018767, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-2207247, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-2765511, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-293700, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-3181161, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-3186739, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-3293595, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-3393531, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-34425, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-3607234, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-3820301, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-3860839, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-460437, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-6264435, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-6578506, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-6942409, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-6954517, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-7118916, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-7138833, http://linkedlifedata.com/resource/pubmed/commentcorrection/8274643-732583
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0006-3495
pubmed:author
pubmed:issnType
Print
pubmed:volume
65
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1496-507
pubmed:dateRevised
2010-9-13
pubmed:meshHeading
pubmed:year
1993
pubmed:articleTitle
Ligand binding to heme proteins: II. Transitions in the heme pocket of myoglobin.
pubmed:affiliation
Department of Physics, University of Illinois at Urbana-Champaign 61801-3080.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.