CD measurement of protein film samples in the vacuum UV region

CD spectroscopy is generally considered an essential tool for the secondary structure analysis of proteins. Marker bands for specific secondary structures are most typically observed in the UV region below 260 nm and as far into the far-UV region as possible. It has been widely reported that CD measurements using synchroton radiation have been used to successfully measure spectra down to around 140 nm. While synchrotron radiation has proven to be a very effective method to measure the CD spectra of protein lm samples in the vacuum UV region, it requires access to a limited number of costly facilities.
As an alternative to synchrotron radiation, the J-1500 CD spectrometer has been improved for measurements in the vacuum UV region. The J-1500’s nitrogen purge efficiency has recently been optimized through computer modelling, the optical system has been enhanced for more light throughput, and new system electronics include digital lock-in technology. These features ensure that CD spectra can be obtained from strongly absorbing and high signal-to-noise (S/N) samples across the spectrum and into the vacuum-UV region. The quality of spectral data obtained, including data obtained at shorter wavelengths, substantially improves the accuracy of protein secondary structure analysis.

This application note illustrates the measurement and analysis of a protein film sample in the vacuum-UV region using the J-1500 CD spectrometer.