J. Biochem, 1982, Vol. 92, No. 3 623-635
© 1982 Japanese Biochemical Society
research-article |
Salt-Concentration Dependence of Thermal Denaturation of Restriction Fragment DNAs from 
X1741
*Department of Physics, Faculty of Science, The University of Tokyo Hongo, Bunkyo-ku, Tokyo 113
**Biochemistry Division, Saitama Cancer Center Research Institute Ina-machi, Kitaadachi-gun, Saitama 362
3 To whom all correspondence should be addressed.
High-resolution differential melting curves of 
X174 Y1 and Y2 restriction fragment DNAs, for which the base sequences were known, were measured at various sodium ion concentrations ranging from 195 to 2.3 mM. The curves were resolved into component peaks, and the change in the melting temperature, the change in the area, and the change in the breadth of each peak with change in salt concentration were examined. The locations of the melting regions corresponding to the peaks in the melting curves were assigned based on theoretical calculations of melting curves and stability maps. It was found that as the salt concentration was decreased from the high to the intermediate range, the breadths of the peaks on the low-temperature side decreased whereas those on the high-temperature side remained almost constant, and also the separation between the peaks along the temperature axis increased. Changes in the positions of peaks relative to one another were interpreted in terms of the difference in the free energy increase between a loop state and an end-coil state as the salt concentration decreased.
1 This study was partly supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan.
2 Present address: Division of Science of Materials, The Graduate School of Science & Technology, Kobe University, Rokko-dai, Nada-ku, Kobe, Hyogo 657.