Discrimination of chiral probes, N-[4(1-pyrene)butyroyl]-phenylalanine, by binding with proteins in Langmuir monolayers at air/water interface

Owing to its interesting photoelectric properties, pyrene is usually imported into a molecule as a function group. The chiral derivatives of pyrene, N-[4(1-pyrene)butyroyl]-l-phenylalanine (Py-l-Phe) and N-[4(1-pyrene)butyroyl]-d-phenylalanine (Py-d-Phe), are used in the present study in order to clarify structural discrimination and binding sites in protein by interaction with proteins at the air/water interface. For these purposes, surface pressure versus area per molecule (π–A) isotherms of Py-l-Phe and Py-d-Phe on the subphase of distilled water, and those containing lysozyme and bovine serum albumin (BSA) solution were performed and compared, respectively. The π–A isotherms of Py-l-Phe or Py-d-Phe on the subphase containing lysozyme display a plateau like region which indicates a phase transition corresponding to a reorientation of lysozyme molecules at the air/water interface. The shape of π–A isotherms on the subphase containing BSA is different from that of lysozyme, with a pressure increasing gradually with compression. Different from that in aqueous solution, no significant discriminations are illustrated between Py-l-Phe and Py-d-Phe in binding with lysozyme and BSA in monolayer at the air/water interface.