Linked Life Data

12105903

Source:http://linkedlifedata.com/resource/pubmed/id/12105903

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
28
pubmed:dateCreated
2002-7-10
pubmed:abstractText
Second-order rate constants k(DO) (M(-1) s(-1)) were determined in D(2)O for deprotonation of the N-terminal alpha-amino carbon of glycylglycine and glycylglycylglycine zwitterions, the internal alpha-amino carbon of the glycylglycylglycine anion, and the acetyl methyl group and the alpha-amino carbon of the N-acetylglycine anion and N-acetylglycinamide by deuterioxide ion. The data were used to estimate values of k(HO) (M(-1) s(-1)) for proton transfer from these carbon acids to hydroxide ion in H(2)O. Values of the pK(a) for these carbon acids ranging from 23.9 to 30.8 were obtained by interpolation or extrapolation of good linear correlations between log k(HO) and carbon acid pK(a) established in earlier work for deprotonation of related neutral and cationic alpha-carbonyl carbon acids. The alpha-amino carbon at a N-protonated N-terminus of a peptide or protein is estimated to undergo deprotonation about 130-fold faster than the alpha-amino carbon at the corresponding internal amino acid residue. The value of k(HO) for deprotonation of the N-terminal alpha-amino carbon of the glycylglycylglycine zwitterion (pK(a) = 25.1) is similar to that for deprotonation of the more acidic ketone acetone (pK(a) = 19.3), as a result of a lower Marcus intrinsic barrier to deprotonation of cationic alpha-carbonyl carbon acids. The cationic NH(3)(+) group is generally more strongly electron-withdrawing than the neutral NHAc group, but the alpha-NH(3)(+) and the alpha-NHAc substituents result in very similar decreases in the pK(a) of several alpha-carbonyl carbon acids.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
17
pubmed:volume
124
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
8251-9
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
Formation and stability of peptide enolates in aqueous solution.
pubmed:affiliation
Department of Chemistry, University at Buffalo, SUNY, Buffalo, New York 14260-3000, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't