Thermodynamics of triple helix formation: Spectrophotometric studies on the d(A)10·2d(T)10 and d(C+3T3C+3)·d(G3A4G3)·d(C3T4C3) triple helices

Daniel S. Pilch, Roland Brousseau, Richard H. Shafer

Research output: Contribution to journalArticlepeer-review

122 Scopus citations

Abstract

We have stabilized the d(A)10·2d(T)10 and d(C+3T4C+3)·d(G3A4G3)·d(C3T4C3) triple helices with either NaCl or MgCl2 at pH 5.5. UV mixing curves demonstrate a 1:2 stoichtometry of purine to pyrimidine strands under the appropriate conditions of pH and ionic strength. Circular dichroic tltrations suggest a possible sequence-independent spectral signature for triplex formation. Thermal denaturation profiles indicate the initial loss of the third strand followed by dissociation of the underlying duplex with increasing temperature. Depending on the base sequence and ionic conditions, the binding affinity of the third strand for the duplex at 25°C is two to five orders of magnitude lower than that of the two strands forming the duplex. Thermodynamic parameters for triplex formation were determined for both sequences in the presence of 50 mM MgCl2 and/or 2.0 M NaCl. Hoogsteen base pairs are 0.22 - 0.64 kcal/mole less stable than Watson-Crick base pairs, depending on ionic conditions and base composition. C+·G and T·A Hoogsteen base pairs appear to have similar stability in the presence of Mg2+ ions at low pH.

Original languageEnglish (US)
Pages (from-to)5743-5750
Number of pages8
JournalNucleic acids research
Volume18
Issue number19
DOIs
StatePublished - Oct 11 1990
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Genetics

Fingerprint

Dive into the research topics of 'Thermodynamics of triple helix formation: Spectrophotometric studies on the d(A)10·2d(T)10 and d(C+3T3C+3)·d(G3A4G3)·d(C3T4C3) triple helices'. Together they form a unique fingerprint.

Cite this