Poly , temperature dependence chemical shifts

The dissociation of the proflavine poly(dA-dT) complex can be followed by monitoring the temperature dependent chemical shift or the line width as demonstrated by shift data on the thymidine CH3-5 resonance (Figure 18A) and width data on the adenosine H-8 resonance (Figure 18B). The proton resonances shift as average peaks during the dissociation of the complex, indicative of fast exchange ( dissociation 10 sec l at the transition midpoint) between the complex and its dissociated components on the NMR time scale. 

Based on the solution property of poly (DMAEMA-co-AAm) in response to temperature, the temperature dependence of equilibrium swelling of poly (DMAEMA-c6>-AAm) gel as a function of chemical composition was observed as shown in Figure 6. The transition temperature of copolymer gel between the shrunken and swollen state was shifted to the lower temperature with increases in AAm content in the gel network. This is attributed to the hydrogen bond in the copolymer gel network and its hydrophobic contribution to the LCST Copolymer II gel was selected as a model polymer network for permeation study because it showed the sharp swelling transition around 34°C. 

H2O solution (6 to 14 ppm) were recorded between 0° and 55°C and the exchangeable protons identified by comparison with the corresponding spectra recorded in 20 solution. The thymidine H-3 imino hydrogen-bonded resonance is observed at 13.0 ppm in the spectrum of poly(dA-dT) at 25.5°C (Figure 1A) and its chemical shift and line width dependence are plotted as a function of temperature in Figures IB and 1C respectively. 

The temperature dependence of the chemical shifts of the base and sugar resonances of poly(dA-dT) in 0.1 M phosphate buffer is plotted in Figure 3. There are upfield and downfield shifts associated with the noncooperative premelting transition between 5 and 55°C while only downfield shifts are observed for most of the base and sugar protons on raising the temperature above 65°C in the noncooperative postmelting transition temperature range. 

The temperature dependence of the chemical shifts of the base resonances in poly(dA-dT) and poly(dA-5brdU) are plotted in Figure 5. These data demonstrate that the adenosine H-8 and H-2 protons exhibit very similar behavior over the entire temperature range and are not perturbed by the substitution on the pyrimidine 5 position. 

Figure 18. The temperature dependence of (A) the thymidine CH.,-5 chemical shift and (B) the adenosine H-8 linewidth in poly(dA-dT) (O), the proflavine polv(dA-dT) complex, Nuc/D 24 (A) and Nuc/D = 8(9) in 1M NaCl, lOmM cacodylate, lOmM EDTA, sH.O, pH 7...

Figure 19. The temperature dependence of the nucleic acid (O) and proflavine (0) chemical shifts between 5.5 and 8.6 ppm for poly(dA-dT) and the Nuc/D = 24 and 8 proflavine poly(dA-dT) complexes in /M NaCl, lOmWl cacodylate, lOmM EDTA, 2 HO between 50° and 100°C. The poly(dA-dT) concentration was fixed at I2.6mM in phosphates and the proflavine concentration was varied to make the different Nuc/D ratio complexes.

Figure 36. The temperature dependence (40° to 100°C) of the sugar H-l chemical shifts of poly(dA-dT) (O) and the netropsin poly(dA-dT) complex, Nuc/D = 50 (9) in 01M cacodylate, 4.4mM EDTA, 2HlO solution...

Figure 39. The temperature dependence of the chemical shifts and linewidths of the base resonances of poIy(dA-dT) (O) and the Nuc/D = 50 netropsin poly-(dA-dT) complex ( J in 0.1 M cacodylate, 4.4mWl EDTA, 2HiO, pH 7.25...

A typical example of these measurements is the mechanical loss factor (for definition, see Section 11). Here a loss maximum for poly (cyclohexyl methacrylate) is observed at — 125°C when the frequency is 10 Hz (Figure 10-26). The maximum is shifted to higher temperatures when the frequency is increased. In addition, the reciprocal loss temperature depends linearly on the logarithm of the frequency (Figure 10-27). Studies on different chemical compounds show that this loss maximum is specific to the cyclohexyl group. The values for both poly(cyclohexyl methacrylate) and poly(cyclohexyl... 

Dipolar spin decoupling has been used to study the numbers of contacts of various types and the free energy of formation of a single mixed contact. Sp6vacek et al. used temperature dependence of chemical shifts in H-n.m.r. spectra to examine the specific interactions in poly(methyl methacrylate) solutions. Cabane has used n.m.r. methods to study aggregation in aqueous polymer detergent systems. Compatibility and phase structure in polymer mix-... 

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