Circular dichroism (CD) spectroscopy
Coriolis Pharma is specialized in providing protein structural conformation analysis, including Near-UV and Far-UV circular dichroism (CD) spectroscopy.
Circular dichroism measurements are most commonly used to determine changes in the secondary and tertiary structure of proteins, but can be applied to other bio-molecules as well. The signal obtained from CD measurements (ellipticity) arises from differences in absorption by chiral molecules of left- and right-handed circularly polarized light.
For proteins, Far-UV CD measurements are obtained using circularly polarized light over a wavelength range of about ≤ 200-250 nm. Light absorption in this wavelength range is mainly due to absorption by the peptide bonds. Since each type of secondary structure element (such as α-helix, β-sheet, etc.) has a distinctive spectral CD profile, Far-UV CD is sensitive to changes in the secondary structure. For instance, Far-UV CD measurements can be performed in different solution conditions (pH, excipients, etc…) to determine the effects thereof on the secondary structural content of a given protein.
Near-UV CD measurements are obtained over a wavelength range of about 250-300 nm, where tyrosine, tryptophan and phenylalanine residues, as well as disulfide bridges absorb light and are CD sensitive. Near-UV CD signals largely depend on the relative orientation as well as the local mobility of these residues. Consequently, Near-UV CD measurements can provide information about changes in the tertiary structure of proteins, e.g., as a result of formulation conditions, temperature, storage, etc..
Coriolis Pharma uses a Jasco J-815s circular dichroism spectrometer to obtain Near- and Far-UV CD measurements. The instrument is equipped with a Peltier device capable of heating the sample up to 100°C allowing to determine the melting temperature (Tm) of proteins in different formulations.