FLUORESCENCE QUENCHING STUDIES OF THE RAT OVARIAN LH HCG RECEPTOR/

Fluorescence quenching method providing information about the structur e and dynamics of proteins, ligand-protein and protein-lipid interacti ons was used in a study of the rat ovarian LH/hCG receptor. The effici ency of two different quenchers, acrylamide and iodide, was tested. Ac rylamide was significantly more effective in quenching of intrinsic fl uorescence of ovarian membranes than iodide and therefore it was used in all of the following experiments. Both acrylamide and iodide were n ot effective in quenching of membranes labelled with fluorescence prob e 1,6-diphenyl-1,3,5-hexatriene (DPH). In the process of desensitizati on of ovarian LH/hCG receptors the administration to rats of hCG modif ied the quenching rate of protein fluorescence and intrinsic fluoresce nce spectral properties of membranes. Alteration in the quenching of i ntrinsic fluorescence of ovarian membranes was observed after chemical modification of LH/hCG receptors by 2-hydroxy-5-nitrobenzyl bromide ( HNB-Br). The accessibility of tryptophan fluorophores was increased in BNB-Br - treated membranes. Delipidation of the LH/hCG receptor modif ied the quenching of protein fluorescence characteristic for control p roteoliposomes. These results demonstrate that fluorescence quenching technique can be successfully applied in the study of the LH/hCG recep tor.