A system for automatic temperature-programmed recording of circular dichroism and optical rotatory dispersion

The effect of temperature on the circular dichroism (CD) and the optical rotatory dispersion (ORD) of macromolecules, and particularly nucleic acids, provides useful information regarding macromolecular conformation (1–3). Instruments which can perform this function, however, are not commercially available. The dependence of CD upon temperature is usually measured by manual variation of the temperature of a jacketed-cell assembly positioned within the spectropolarimeter. We wish to report a modification of the Beckman T_m Analyzer ¹, which is designed to record temperature-optical density profiles, permitting the use of this instrument in conjunetion with a Durrum-Jasco recording spectropolarimeter ². This assembly provides for automatic recording of CD or ORD versus temperature at wavelengths between 190 and 700 mμ. We recently employed this system in studies of the temperature dependence of CD in DNA-ethidium bromide complexes (4,5).