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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
2
|
| pubmed:dateCreated |
1988-6-29
|
| pubmed:abstractText |
Using nuclear magnetic resonance line broadening, longitudinal relaxation and magnetization transfer from water, we have measured the imino proton exchange times in the duplex form of the 10-mer d-CGCGATCGCG and in seven other deoxy-duplexes, as a function of the concentration of exchange catalysts, principally ammonia. All exchange times are catalyst dependent. Base-pair lifetimes are obtained by extrapolation to infinite concentration of ammonia. Lifetimes of internal base-pairs are in the range of milliseconds at 35 degrees C and ten times more at 0 degrees C. Lifetimes of neighboring pairs are different, hence base-pairs open one at a time. Lifetimes of d(G.C) are about three times longer than those of d(A.T). The nature of neighbors usually has little effect, but lifetime anomalies that may be related to sequence and/or structure have been observed. In contrast, there is no anomaly in the A.T base-pair lifetimes of d-CGCGA[TA]5TCGCG, a model duplex of poly[d(A-T)].poly[d(A-T)]. The d(A.T) lifetimes are comparable to those of r(A.U) that we reported previously. End effects on base-pair lifetimes are limited to two base-pairs. The low efficiency of exchange catalysts is ascribed to the small dissociation constant of the deoxy base-pairs, and helps to explain why exchange catalysis had been overlooked in the past. This resulted in a hundredfold overestimation of base-pair lifetimes. Cytosine amino proteins have been studied in the duplex of d-CGm5CGCG. Exchange from the closed base-pair is indicated. Hence, the use of an amino exchange rate to evaluate the base-pair dissociation constant would result in erroneous, overestimated values. Catalyzed imino proton exchange is at this time the safest and most powerful, if not the only probe of base-pair kinetics. We propose that the single base-pair opening event characterized here may be the only mode of base-pair disruption, at temperatures well below the melting transition.
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| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Mar
|
| pubmed:issn |
0022-2836
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| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:day |
20
|
| pubmed:volume |
200
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
223-38
|
| pubmed:dateRevised |
2006-11-15
|
| pubmed:meshHeading |
pubmed-meshheading:2836594-Base Composition,
pubmed-meshheading:2836594-Deoxyribonucleotides,
pubmed-meshheading:2836594-Kinetics,
pubmed-meshheading:2836594-Magnetic Resonance Spectroscopy,
pubmed-meshheading:2836594-Protons,
pubmed-meshheading:2836594-Temperature,
pubmed-meshheading:2836594-Thermodynamics
|
| pubmed:year |
1988
|
| pubmed:articleTitle |
Characterization of base-pair opening in deoxynucleotide duplexes using catalyzed exchange of the imino proton.
|
| pubmed:affiliation |
Groupe de Biophysique, Ecole Polytechnique, Palaiseau, France.
|
| pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
|