[Protein binding of the macrolide antibiotic turimycin. Methodologic effects on results]

A methodological investigation deals with the binding of the macrolide antibiotic turimycin to bovine serum albumin (BSA) and serum proteins. On this occasion, it is pointed out that, especially when serum is used, the critical evaluation of the analytical method is of the same importance as the utilization of standardized procedures for the quantification of the protein binding in the sense of general comparability. This concerns, for example, the chemistry of the reaction used for detection, the formation of degradation products of the active principle in the serum during the study of the binding and possible repercussions on the chemical determination, the electrolyte content of the sample in the punched hole of the microbiological test plate, losses of activity or synergistic effects of the serum-antibiotic combination during incubation of microbiological test plates after termination of the equilibrium dialysis. The determination of binding constants by means of a competitive fluorescence titration, the chemical analysis of equilibrium dialyses and their parallel assessment with the aid of the agar-diffusion plate test led to results which were not in agreement with each other. Turimycin which is very slightly soluble at pH = 7.4 and fairly soluble at pH = 5.0, is practically not bonded at the lower pH value of BSA and serum proteins (fluorescence titration of BSA: Kb approximately 20; equilibrium dialysis and chemical evaluation). The microbiological determination in serum on the basis of equilibrium dialyses yields higher values for the binding of turimycin.(ABSTRACT TRUNCATED AT 250 WORDS)