Thermal transconformation

ABSTRACT The principle of electrical spectrography and its measurement system is discussed. The phenomenon of noise in electrolytes and interfaces receives attention. Noise spectrography is found to have applications in some biomolecular systems, viz., DNA helix-to-coil transition, thermal transconformation, and salt-free premelting effects. Noise conductivity emission spectra of collagen solutions gave information on permanent dipole fluctuations and hydrodynamic properties of the system. 

Ionic Atmosphere around DNA and Direct Visualization of the Thermal Transconformation (Helix- Coil Transition)... 

The thermal transconformation or helix- coil transition is followed by an ejection of Na counterions... 

FIGURE 9. Variation of noise resistance Rn of a DNA solution in NaCl 4 x 10 mol/liter, versus the frequency v. , native DNA (chicken erythrocyte at the concentration C = 1 g/liter at 25°C) , the same native DNA at 40°C A, the same DNA after thermal transconformation (sample heated at 80°C) measured at 40°C. 

On the other hand, the increase in noise conductivity with T for temperatures above the T indicates that the number of free ions in solution increases also this phenomenon corresponds to the ejection of a percentage a. of the compensating Na counterions from the phosphate sites, during the thermal transconformation. 

Figure 11 shows the variation of N in two DNA solutions versus the temperature. Before and after the melting point T , we observe two horizontal plateaus before and after the thermal transconformation, N is constant. 

The percentage Axj/ of Na ejected during the thermal transconformation is thus given by... 

A study of the thermal transconformation of DNA has allowed us to follow the evolution of the charge parameter and the length b as functions of the temperature. 

During the thermal transconformation of DNA, the activities of the surrounding ions change. From the ratio of the ionic activities and a, measured for the helix and coil phases, it is possible to deduce the ratio This ratio may be compared directly with the theoretical value proposed by Manning. Table I shows the results thus obtained for the counter-ion sodium. 

Acid A-speotrum of lysozyme is sensitive to ionic strength, does not involve transconformation Intensive studies on thermal- and acid-generated transconforma-tions... 

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