Linked Life Data

2986133

Source:http://linkedlifedata.com/resource/pubmed/id/2986133

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
9
pubmed:dateCreated
1985-6-20
pubmed:abstractText
The competition between various groups for a proton is studied by ab initio molecular orbital methods. It is found that reorientations of the two groups involved in a H-bond can reverse the equilibrium position of the proton shared between them. Specifically, the carbonyl and hydroxyl groups were modeled by H2CO and HOH. In the H-bond between these two groups, association of the proton with the carbonyl (H2COH...OH2)+ is favored over the hydroxyl (H2CO...HOH2)+ when the latter group is situated along a lone pair of the carbonyl oxygen. However, displacement of the water to the C = O axis between the two carbonyl lone pairs reverses the situation and (H2CO...HOH2)+ is more stable. A similar reversal of stability is observed in the H-bond involving a Schiff base (modeled by CH2NH) and amine (NH3). In one arrangement where the lone pairs of the two groups point toward one another, the proton prefers the Schiff base to the amine--i.e., (H2CHNH...NH3)+ is more stable than (H2CHN...HNH3)+. On the other hand, rotation of the lone pair of the amine away from the Schiff base nitrogen results in proton transfer across to the amine. These shifts in stability correspond to reversal of relative pK of the groups involved. A fundamental principle emerging from the calculations is that ion-dipole electrostatic interactions favor transfer of a proton to the group that is positioned as closely as possible to the negative end of the dipole moment vector of the other. The ideas developed here suggest a number of means by which conformational changes may be utilized to shift protons from residue to residue within a protein molecule such as an enzyme or bacteriorhodopsin.
pubmed:grant
pubmed:commentsCorrections
http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-16592567, http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-16593445, http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-272644, http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-6286619, http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-6287921, http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-6306243, http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-6313293, http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-6955790, http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-6956906, http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-7138840, http://linkedlifedata.com/resource/pubmed/commentcorrection/2986133-7217054
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0027-8424
pubmed:author
pubmed:issnType
Print
pubmed:volume
82
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2741-5
pubmed:dateRevised
2010-9-9
pubmed:meshHeading
pubmed:year
1985
pubmed:articleTitle
Modification of pK values caused by change in H-bond geometry.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't