ABSTRACT
The temperature dependence of poly(C) is shown by the infrared spectroscopy to be different for the free polynucleotide and for the polynucleotide in complexes with membranes. The intensity of stretching vibrations of C = 0 bond of poly(C) in the complex appears to be sensitive to the temperature. The intensity of this band is sharply decreased by increasing the temperature. This effect depends upon concentration of Mg2+-cations. Adsorption of poly(I)-poly(C) on the surface of vesicles from phosphatidylcholine results in the increase of the double helix.
Subject(s)
Liposomes/analysis , Phospholipids/analysis , Poly C/analysis , Poly I-C/analysis , Polyribonucleotides/analysis , Hot Temperature , In Vitro Techniques , Molecular Conformation , Nucleic Acid Denaturation , Spectrophotometry, InfraredABSTRACT
IR-spectra of poly-A phosphatidylcholine complexes in D2O were studied. It has been shown that in the absence of Mg2+ the spectrum was a superposition of spectra of poly-A and phosphatidylcholine. Introduction of MgCl2 to the concentration of 0.03 M led to the dramatic decrease of absorbance at 1629 cm-1 characteristic of backbone vibration of adenine. Further increase of the concentration of MgCl2 up to 0.08 M resulted in the additional absorbance maximum at 1627 cm-1. Under a variety of temperatures the position of the maximum did not change. It was assumed that on adding magnesium ions to the "poly-A-lipid" mixture in D2O the components formed a stable complex. At high Mg2+ concentration a partial disarrangement of stacking interactions in poly-A occurred that might be a consequence of the incorporation of nucleic bases into hydrophobic membrane phase.
