ARTICLE NO. CS974948 NOTE Tryptophan, Tryptophan-Leucine, and BSA Adsorption at an Oil-Water Interface rV Å
p(e 1 / e 2 ) 1/2 l(e 1 0 e 2 ) h.
[2]
Adsorption of the amino acid tryptophan, the peptide tryptophan-leucine and the protein bovine serum albumin (BSA) at buffered water-oleyl alcohol interfaces has been studied by ellip-If the adsorbed amount is small, then e is near to either e 1 or e 2 so that h sometry. Tryptophan-leucine solutions showed a systematic becomes change in ellipticity with concentration indicating an adsorption of 0.5 mg/m 2 for a solution concentration of 1 g/L and evidence h Å (e 2 0 e 1 ) e 2
͐ dz (e 0 e 2 ) Å (e 2 0 e 1 )
of saturation at that concentration. BSA showed an adsorption of 0.45 mg/m 2 for a concentration of 3.5 g/L with no sign of saturation. There appeared to be little adsorption of tryptophan at the
Here G e is the total excess of the dielectric constant in the interface region,
interface. ᭧ 1997 Academic Press
which can be directly related to the total excess number of adsorbed molecules per unit area G once the relation between e and concentration c is known. If the change in dielectric constant de varies with concentration as de(c) Å bc, we have G Å G e /b. (When the concentration c is given in mass per unit volume, G has the units of mass per unit area.) Thus the only additional information required in the determination of G is the variation