I tested DNA structure (5uM dissolved in 50 mM Tris) using JASCO-1500 but found no peak at wavelength 220-350. The results look like a wave shape throughout the wavelength...
Thank you for answering. There are two reasons, one is the low concentration, and another is the set of digital integration time (DIT). I increased the concentration to20 uM and DID to 1 s (was 1 msec). Problem solved.