PubMed Health⌕ Search

Biomedical subjects

S Premilat

Publications and source records attributed to S Premilat.

8 recordsLinked to original sources
PubMed1992

Effect of a mechanical tension on the hydration of DNA in fibres.

Fiber X-ray diffraction and measurement of fibre dimensions yield information about the effects of a mechanical tension on hydration of DNA in fibres. At a given relative humidity, the mechanical tension changes the DNA conformation but does not modify the number of water molecules associated to a nucleotide. The number of water molecules per nucleotide necessary to maintain B form decreases for increasing tensions applied to the DNA fibre. Form transitions can be opposed by mechanical tensions; an energy of 1 Kcal per mole of nucleotide pairs is sufficient to prevent the B to A transition.

DNA↗
PubMed1992

[Experimental method for the definition of intercalation of compounds in DNA].

Intercalation of aromatic compounds into DNA can be appreciated by using, in a complementary way, fibre X-ray diffraction and measurement of variations of the fibre dimensions. The different behaviours resulting from an actual intercalation or an association of small molecules into the DNA grooves can be distinguished by this experimental method which provides significant results for proflavine, ethidium bromide, a platinum compound, 9-aminoacridine and ellipticine.

DNA↗
PubMed1976

[X-ray diffraction study of the binding of Cu2+ and Ag2+ cations to DNA].

An X-ray diffraction study has been undertaken on fibres of two different DNA compositions respectively corresponding to 42 and 72% of (G-C) base percentages. The fibres were prepared after binding of copper or silver ions to the DNA gels. With a relative humidity of 92%, the B-form has been observed for these two DNA molecules in the presence of copper ions or with a low percentage of silver ion binding. When the silver ion percentage is increased, a new form appears. From the comparison between the experimental and calculated intensities one can note that the proposed binding sites for copper involve few modifications in the X-ray patterns. For the silver, the calculated intensities show that the metal atom is near the double helix axis. For low percentages of silver the site between successive guanine bases cannot be distinguished with certainty by intensity analysis.

Animals↗
PubMedDate not supplied

Helical structures of poly(D-L-peptides). A conformational energy analysis.

Conformational energy calculations are reported for a number of possible helical structures of poly(D-L-peptides): the alpha helix, two single-stranded piDL, and five double-stranded pipiDL helices. For a poly(D-alanine-L-alanine) sequence, the energies of the various helices are found to differ by less than 1 kcal/(mol residue). For some helices (especially the piDL ones) two structural variants are predicted. These variants, called "goniomers", are characterized by reversed sequences of conformational angles but have the same screw sense and similar helical parameters. A biological implication of these goniomers is suggested, and their usefulness as a critical test for energy calculations is considered.

Alanine↗