Kalorimetricheskoe izuchenie perekhoda spiral'-klubok v DNK pri vzaimodeistvii s ionami Cu2+

Using the method of differential scanning calorimetry, the DNA helix-coil transition was studied in solutions (10(-3) M Na+, 10(-3) M tris HCl, pH 7.0) containing divalent copper ions at relative metal ion concentrations (Mt2+/PDNA) ranging from 0.2 to 20. Dependences of the melting temperature and enthalpy on relative ion concentration were determined. An aggregation of Cu(2+) + DNA complexes in the range of average ion concentration was established. It is shown that the melting enthalpy of "units" increases with copper ion concentration. The data obtained were compared with values determined by UV-spectroscopy. Association constants for Cu2+ binding to DNA were defined by the ligand theory

Precise and millidegree stable temperature control for fluorescence imaging: Application to phase transitions in lipid membranes

We present the design of a custom temperature-controlled chamber suitable for water or oil immersion fluorescence microscopy and its application to phase behavior in lipid bilayer vesicles. The apparatus is self-contained and portable, suitable for multiuser microscopy facilities. It offers a higher temperature resolution and stability than any comparable commercial apparatus, on the order of millidegrees. We demonstrate the utility of the system in the study of miscibility transitions in model membranes. The temperature-dependent phase behavior of model membrane systems that display liquid-ordered (Lo) phase coexistence with the liquid-disordered (Ld) phase is relevant to understanding the existence of heterogeneities in biological cell plasma membranes, ubiquitously termed “lipid rafts.

Vibrational spectroscopic studies of the divalent metal ion effect on DNA structural transitions

Raman spectroscopy is used to study DNA complexes with Cu2+, Mn2+ and Ca2+ ions in 0.001 M NaCl, pH 7.0. The changes observed in the spectra permit us to conclude that all the ions interact both with the DNA phosphate groups and with the nucleic bases, changing the DNA structure. Ca2+ and Mn2+ ions bind to N7 of guanine and adenine only, but Cu2+ ions can probably bind to N7, O6 of guanine and N3 of cytosine as well. The latter type of binding occurs as the base is turning around the glycoside bonds and a G-C pair transition from anti to syn conformation takes place. Besides, at high concentrations of Ca2+ ions a partial B-A transition takes place in DNA

Study of Ca2+, Mn2+and Cu2+ binding to DNA in solution by means of IR spectroscopy

The interaction of Cu2+, Mn2+ and Ca2+ ions with the DNA macromolecule was studied in aqueous solutions at different metal ion concentrations. All these ions interact with both the bases and the phosphate groups of DNA. Cu2+ ions alter the DNA B-conformation at [Cu2+] > 2 × 10−2M. Metal ions binding to DNA induce DNA compactisation. The highly positive cooperativity of this process was shown. The binding constants and parameters of cooperativity of the metal ions binding to DNA were estimated