Thermal stability of the Z conformation of the hexanucleoside pentaphosphate d(br5CGbr5CGbr5CG): evidence for a conformational transition before melting |
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Authors: | B Hartmann D Genest N T Thuong M Ptak M Leng |
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Institution: | 1. Centre de Biophysique Moléculaire, C.N.R.S., 1A avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France;2. Université d''Orléans, Orléans, France;1. Concordia Institute for Information Systems Engineering (CIISE), Concordia University, Montreal, QC, Canada;2. G-SCOP lab / Grenoble Institute of Technology, Grenoble, France |
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Abstract: | The thermal stability of the hexanucleoside pentaphosphate d(br5CGbr5CGbr5CG) has been studied at two nucleotide concentrations, in the presence of 1 M NaClO4. At low nucleotide concentration (7 X 10(-5) M), circular dichroism experiments show a conformational transition from the Z conformation to another conformation, named X, which is not the B conformation, as the temperature is increased from 0 to 35 degrees C. Between 40 and 65 degrees C, another transition is observed which corresponds to the melting of the X conformation. At higher nucleotide concentration (2 X 10(-3) M), circular dichroism and 31P nuclear magnetic resonance experiments show that at low temperature (br5dC-dG)3 adopts the Z conformation. There are associations between the oligonucleotides which progressively disappear as the temperature increases. In the range 35-60 degrees C a transition from the Z conformation to another conformation is observed. This new conformation is the X conformation detected at low nucleotide concentration. |
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