|کد مقاله||کد نشریه||سال انتشار||مقاله انگلیسی||ترجمه فارسی||نسخه تمام متن|
|5196278||1381378||1999||9 صفحه PDF||سفارش دهید||دانلود کنید|
Polyelectrolyte complexes of calf-thymus DNA and polycations, such as PDADMAC, IONENE, and P4VP were formed and analysed with respect to their thermodynamical stability. The UV-VIS spectrographic melting curves yield two denaturation temperatures, Tm,1 and Tm,2. This is explained as follows: DNA molecules contain two kinds of repeat unit sequences. There are sequences that are not complexed, they denature at Tm,1; the other DNA repeat units are complexed with polycation repeat units, they denature at Tm,2. Thereby, Tm,2 is much larger than Tm,1. That is, polycation binding stabilises calf-thymus DNA. Surprisingly, the absolute value of Tm,1 depends neither on the degree of complexation nor on the polycation type. Tm,1 agrees quite well with the denaturation temperature of the pure, uncomplexed DNA. Also Tm,2 does depend not on the degree of polycation complexation, but on the polycation type. One observes Tm,2(PDADMAC)>Tm,2(P4VP)>Tm,2(IONENE). The probable reason for this series is the polycation molar mass. Tm,2 increases slightly as Mw is increased. While Tm,1 depends on the concentration of the added NaCl-salt, Tm,2 does not. This is explained using the fact that the complexed DNA repeat units are electrically neutral, so that there are no salt/charge interactions. Measurements in aqueous/organic solvent mixtures show that both Tm,1 as well Tm,2 decrease continually as the content of the organic solvent is increased. Very marked is this effect for water/N-methylformamide. At wNMFâ40%, Tm,1 and Tm,2 are nearly half as large as in pure water.
Journal: Polymer - Volume 40, Issue 25, December 1999, Pages 7019-7027