Recognition of substrates by immobilized albumin membranes prepared from Langmuir-Blodgett and entrapment methods - Response of circular dichroism induced by D- and L-tryptophan

The change in the circular dichroism spectra induced by immersion of the membranes into the aqueous tryptophan solution was measured using the immobilized serum albumin membranes prepared by the Langmuir-Blodgett (LB) method and the entrapment method. The alpha-helix content of the albumin membranes prepared by the LB method was observed to decrease on the immersion of the membranes into 0.01 M D-tryptophan solution, whereas the completely opposite tendency was observed when the albumin membranes prepared from the entrapment method were used. The change in the circular dichroism originates from the conformational change of the immobilized albumin membranes induced by the binding between the albumin and tryptophan on the membranes. It is considered that orientated albumin on the LB film of poly (alpha-amino acid) makes the different conformational responses to the tryptophan binding to the albumin compared to randomly located albumin in the immobilized albumin membranes prepared by the entrapment method, because albumin on the LB film of poly (alpha-amino acid) was observed to be orientated from focal laser scanning microscopic measurements.