[Parameters of binding of fluorescent probe pyrrone red with human serum albumin]

The constant of binding of a new fluorescent probe pyrrone red to human serum albumin (Kb = 4.7.10(5) M-1) and the number of binding sites (N = 2) were determined by the method of double fluorimetric titration at a Fex/Fem intensity ratio of 560/625 nm. The affinity of pyrrone red for albumin was by 20% lower than that of 8-anilinonaphthalenesulfonate and 2.4 times higher than that of another probe K35. Thus, pyrrone red is almost identical to amlinonaphthalenesulfonate in affinity for albumin and can be considered as a long-wavelength "red" analogue of anilinonaphthalenesulfonate.