Interaction between human alpha1-acid glycoprotein (orosomucoid) and 2-p-toluidinylnaphthalene-6-sulfonate.
The interaction between human alpha1-acid glycoprotein (orosomucoid) and the fluorescent probe, 2-p-toluidinylnaphthalene-6-sulfonate (TNS) has been studied. An association constant of 16.7 (+/- 3) x 10(3) M-1 was obtained for the complex at 20 degrees C with a stoichiometry of 1:1. From the effect of temperature on the binding process, the standard enthalpy change for the binding is calculated to be delta H0 = -18 +/- 3 kJ mol-1 and the standard entropy change delta S0 = 19 +/- 12 J K-1 mol-1. The tryptophan fluorescence of the protein can be described by a sum of three exponentials. Upon TNS binding, the average fluorescence lifetime of the protein in the complex changes much less than the fluorescence intensity. The bound TNS is therefore a very efficient acceptor for the protein fluorescence. The TNS bound to orosomucoid present two fluorescence lifetimes 11 and 4.3 ns. The possible origins of the two lifetimes are discussed.
Albani
J
J
Laboratoire de Biophysique Moléculaire, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq.
Vos
R
R
Willaert
K
K
Engelborghs
Y
Y
D005456:Fluorescent Dyes / Q000737:chemistry*; D006801:Humans; D009282:Naphthalenesulfonates / Q000737:chemistry*; D009961:Orosomucoid / Q000737:chemistry*; D013816:Thermodynamics
D005456:Fluorescent Dyes; D009282:Naphthalenesulfonates; D009961:Orosomucoid; C009497:2-(4-toluidino)-6-naphthalenesulfonic acid