Wavelength Calibration Uncertainty in Protein Circular Dichroism Data Bank Spectra.

Algorithms to objectively compare the circular dichroism spectra of biopharmaceuticals, as a measure of consistent higher order structure, are sensitive to errors in spectropolarimeter wavelength calibration. A public database, the Protein Circular Dichroism Data Bank contains 108 unique calibration spectra of -camphor-10-sulphonic acid, mainly collected on synchrotron-based instruments. Deconvolution of these spectra and statistical evaluation of the peaks located near 290 and 190 nm shows significant mean peak wavelength differences between instruments, with data ranges of 1.8 and 2.3 nm. Peak positions and peak height ratios for individual instruments changed significantly through time, and the difference between wavelength maxima was instrument dependent.