Evidence of a strong interaction of 2,4-Dichlorophenoxyacetic Acid herbicide with human serum albumin.

ROSSO, S; GONZALES, M; BAGATOLLI, L; DUFFARD, R; FIDELIO, G

LIFE SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 1998 vol. 63 p. 2343 - 2351

0024-3205

The interaction of 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) with human serum albumin @ISA) was studied using fluorescence and differential scanning calorimetry @SC). Fluorescence displacement of 1-anilino-S-naphtalenesulfonate (ANS) bound to HSA was used to evaluate the binding atTmity of 2,4-D to HSA. The binding is associated to a high afXnity site of HSA located in the IIIA subdomain. The association constant &) of the herbicide was about 5 @I’,several times higher than the atlinity found for pharmaceutical compounds, This relatively strong interaction with HSA was evidenced by the increase in HSA protein thermostability induced as consequence of herbicide interaction. 2,4-D induces an increase in the midpoint of thermal denaturation temperature from 60.1 “C in herbicide free solution to 75.6 “C in full ligand saturating condition. The calorimetric enthalpy and the excess heat capacity also increased upon 2,4-D binding. To investigate the possibility of other/s system/s of 2,4-D transport in blood, besides of HSA, the interaction of the herbicide with lipid monolayers was explored. No interaction was detected with any of the lipids tested. The overall results provided evidence that high at&t&y 2,4-D-HSA complex exhibits enhanced thermal stability and that HSA is the unique transport system for 2,4-D in blood.