ABSORPTION AND FLUORESCENCE ESPECTRA OF POLYENE ANTIBIOTICS IN THE PRESENCE OF HUMAN SERUM ALBUMIN

ROMANINI, DIANA; FARRUGGIA, BEATRIZ; PICO, GUILLREMO

BIOCHEMISTRY AND MOLECULAR BIOLOGY INTERNATIONAL.

ACADEMIC PRESS AUTRALIA

Lugar: Chicago; Año: 1998 vol. 44 p. 595 - 603

1039-9712

Abstract             The alteration in the fluorescence specrta observed for the polyene antibiotics: nystatin and amphotericin B in the presence of human serum albumin is due to a decrease in the polar character of the antibiotics enviroment when this arebound to the protein. Amphotericin B showed two types of binding sites, the first having very high affinity (5.8 107 M-1)and the secondary binding sites whit an affinity one order lowerthan the primary sites.  This secondary binding site was very sensitive  to temperature change. Nystatin yielded only one type of binding sites with an affinity of 1.1 106 M-1. An electrostatic component was found in the binding of both ligands, as well as an important disorder at the protein binding sites. However, the secondary binding site for Anphotericin B  showed  negative entropic change  value, which suggests different mechanim of binding respect to the primary one. Conformational change induced by the temperature in the albumin molecule was detected by nystatin binding. Fatty acids produced an interference in the binding of both antibiotics to albumin