OBSERVATION OF OPTICAL 2ND-HARMONIC GENERATION IN WET-SPUN FILMS OF NA-DNA

The observation of optical second harmonic generation (SHG) from wet-s pun films of Na-DNA is reported. The SHG signal is stronger at a relat ive humidity of 92% (corresponding to the B conformation of Na-DNA) th an at low humidity of approximately 33% (corresponding to a disordered conformation of Na-DNA). The strength of the SHG signal is also depen dent on the orientation of the incident laser beam polarization with r espect to the DNA helical axes.