Document Detail

Physicochemical studies of the d(G3T4G3)*d(G3A4G3).d(C3T4C3) triple helix.
MedLine Citation:
PMID:  7706270     Owner:  NLM     Status:  MEDLINE    
We have targeted the d(G3A4G3).d(C3T4C3) duplex for triplex formation with d(G3T4G3) in the presence of MgCl2. The resulting triple helix, d(G3T4G3)*d(G3-A4G3).d(C3T4C3), is considerably weaker than the related triplex, d(G3A4G3)*d(G3A4G3).d(C3T4C3), and melts in a biphasic manner, with the third strand dissociating at temperatures about 20-30 degrees C below that of the remaining duplex. This is in distinct contrast to the d(G3A4G3)*d(G3A4G3).d(C3T4C3) triplex, which melts in essentially a single transition. Gel electrophoresis under non-denaturing conditions shows the presence of the d(G3T4G3)*d(G3A4G3).d(C3T4C3) triplex as a band of low mobility compared to the duplex or the single strand bands. Binding of the d(G3T4G3) third strand and the purine strand of the duplex can be monitored by imino proton NMR spectra. While these spectra are typically very broad for intermolecular triplexes, the line widths can be dramatically narrowed by the addition of two thymines to both ends of the pyrimidine strand. Thermodynamic analysis of UV melting curves shows that this triplex is considerably less stable than related triplexes formed with the same duplex. The orientation of the third strand was addressed by a combination of fluorescence energy transfer and UV melting experiments. Results from these experiments suggest that, in the unlabeled triplex, the preferred orientation of the third strand is parallel to the purine strand of the duplex.
P V Scaria; S Will; C Levenson; R H Shafer
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  270     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1995 Mar 
Date Detail:
Created Date:  1995-05-10     Completed Date:  1995-05-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  7295-303     Citation Subset:  IM    
Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco 94143, USA.
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MeSH Terms
Base Sequence
Circular Dichroism
Magnesium Chloride
Magnetic Resonance Spectroscopy
Molecular Sequence Data
Nucleic Acid Conformation*
Nucleic Acid Denaturation
Oligodeoxyribonucleotides / chemical synthesis,  chemistry*
Spectrophotometry, Ultraviolet
Reg. No./Substance:
0/Oligodeoxyribonucleotides; 7786-30-3/Magnesium Chloride

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