Behaviour of DNA-RNase A complex in the presence of formaldehyde
Malinina, L.B.; Kosaganov, I.N.; Lazurkin, I.S.
Molekuliarnaia Biologiia 10(5): 1061-1071
1976
ISSN/ISBN: 0026-8984 PMID: 1053260 Document Number: 100934
A formaldehyde-produced fixation of defects caused by a despiraling action of a protein was studied in the case of DNA [phage T2]-RNase A complex. The concentration of the defects fixed was measured by kinetic formaldehyde method (KF-method). The following processes take place in the complex in the presence of formaldehyde: fixation of defects; unwinding of DNA; and, inactivation of the protein. The rates of all these processes depend on the concentration of formaldehyde, .phi. At formaldehyde concentrations above some critical value .phi.c the protein is inactivated before the defects are fixed. At .phi. < .phi.c the protein inactivation proceeds more slowly than the fixation of defects; at sufficiently low formaldehyde concentration almost no inactivation of protin occurs during the fixation time (20 min). The number of new defects formed during the time of fixation is linear with the formaldehyde concentration in the region where no inactivation of the protein occurs. The initial concentration of defects can be determined through an extrapolation to zero concentration of formaldehdye. On the basis of the data obtained a method is proposed for the evaluation of the number of defects in DNA caused by the despiraling action of proteins. A model is proposed describing the behavior of the complexes of DNA with despiraling proteins in the presence of formaldehyde.