NONLINEAR-OPTICAL ACTIVITY AND BIOMOLECULAR CHIRALITY

Circular-difference response of second-harmonic generation from chiral surfaces is shown to be a sensitive probe of chiral biological sample s. The sensitivity of this nonlinear effect is several orders of magni tude higher than that of linear circular dichroism and is demonstrated using samples of bacteriorhodopsin. This nonlinear optical activity p robes molecular chirality on a more general level than linear techniqu es. Surface specifity of the novel approach can be of considerable imp ortance in the study of biological membranes. Hence, this process has the potential of becoming a new chiro-optical tool in the fields of an alytical (bio)chemistry, surface chemistry, and cell biology.