Linked Life Data

2163670

Source:http://linkedlifedata.com/resource/pubmed/id/2163670

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
20
pubmed:dateCreated
1990-8-16
pubmed:abstractText
Using proton magnetic resonance, we have investigated imino and amino proton exchange in the Z form of the four oligomers d(Cbr8GCGCbr8G), d(CGm5CGCG), d(CG)6, and d(CG)12. In the latter two oligomers, all five exchangeable protons have been assigned. We find that proton acceptors such as NH3 or the basic form of Tris enhance imino proton exchange. The base-pair lifetime can then be obtained by extrapolation of the exchange time to infinite concentration of proton acceptor. For d(CG)6 and d(CG)12, the values are ca. 3.5 ms at 80 degrees C and ca. 130 ms at 35 degrees C. The latter value is about 65 times longer than in the same oligomers in the B form. The activation energy of base-pair opening, 80 kJ/mol, is the same in the Z and the B forms of d(CG)12. At 5 degrees C, the base-pair lifetime is about 3 s, much smaller than the time constant of the Z to B transition, to which it is therefore unrelated. The base-pair dissociation constant at 35 degrees C, 0.5 X 10(-6), is 5 times smaller than for the same oligomers in the B form. In the absence of added catalyst, at pH 7, the exchange time of the imino proton is 30 min at 5 degrees C. That of both cytidine amino protons, assigned by NOE, is about 50 min. The longest proton exchange time, ca. 330 min, is assigned unambiguously to the guanosine amino protons. Thus assigned and interpreted in terms of exchange chemistry rather than structural kinetics, the exchange times do not support earlier models of Z-DNA internal motions.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
22
pubmed:volume
29
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4799-805
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1990
pubmed:articleTitle
Processes of base-pair opening and proton exchange in Z-DNA.
pubmed:affiliation
Groupe de Biophysique, Ecole Polytechnique, Palaiseau, France.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't