Aspects of specific protein-DNA interaction; multi-mode binding of the oligopeptide antibiotic netropsin to (A.T)-rich DNA segments.

By means of titration viscometry a number of distinct modes could be resolved for the interaction between the antibiotic netropsin and DNA species of 50, 58, and 69 mole + (A+T) below r = 0.04 netropsin molecules bound per DNA phosphate group. The number of corresponding binding sites increases with a high power of the (A+T) content. The apparent association constants are very high (greater than 10(6) M-1, some perhaps greater than 10(6) M-1) and also rather different for most of the binding sites. It is suggested that some of these interaction modes differ in the number of hydrogen bonds formed between donors of the ligand and acceptors of the binding sites. The interaction modes were characterized quantitatively by their (species-independent) changes of DNA contour length and by the percentage of local DNA stiffening.

Simple mathematical deductions in the seroepidemiology of viral infections. II. (Para) myxoviruses (measles, mumps, influenza B), rubella, enteroviruses (polio, coxsackie B), adenoviruses, and mycoplasma pneumoniae.

Large samples of nonselected persons collected in South-West Germany were investigated for the prevalence of serum antibodies to Poliovirus 1-3 and Coxsackievirus B 1-5 (neutralisation test), to Measles, Rubella, and Mumps (hemagglutination inhibition test), Mumps, Influenza B, Adenovirus, and Mycoplasma pneumoniae (complement-fixation test). According to "catalytic models", which compare the infection spread to simple chemical reactions of molecules as self-limiting procedures, a mathematical approximation of the serum surveys was performed. By the use of only two parameters it became possible to calculate the annual attack rates (without regard of age group arrangement and test sensibility), to construct "true" epidemic curves, and to estimate the persistence of humoral immunity in the population investigated for NT and HIT antibodies.