Cephalosporin binding sites to human serum albumin and the relation with the N-B transition of this protein.

The binding of some cephalosporins to human serum albumin was studied using probes for the so-called I, II, bilirubin and fatty acids binding sites. The results showed that cephradine and cefsulodin bind to site II, cefaclor, cefamandole, cefsulodin, cephaloglycin and cefadroxil bind to the bilirubin binding site, while cefaclor does it to the fatty acid binding site. No binding of these cephalosporins to site I of albumin was found. The binding produced a perturbation on the N-B equilibrium of albumin, stabilizing the N conformational form, which suggests that the N form of albumin has more affinity with the cephalosporins than the B form. This finding gives support to the assumption that the binding of cephalosporins to site II, bilirubin and fatty acids binding sites affects the N-B transition of albumin.