Lysozyme and N-acetyl glucosamine interaction probed by Circular Dichroism (CD)

Changes in a protein’s CD spectrum directly reflect the changes in its structure. The absorption derived from the protein’s peptide bonds can be seen below 240 nm of the CD spectrum. Therefore, by measuring the CD spectrum in the far-UV wavelength region, information regarding a protein’s secondary structure can be obtained. On the other hand, absorption due to aromatic amino acid side chain residues are seen in the 210-220 nm wavelength region of the spectrum. There are additional absorption bands at wavelengths beyond 240 nm which do not overlap with the absorption band of the peptide bonds. For this reason, in order to study side chain residues the CD spectrum is usually measured in the wavelength region longer than 240 nm which is known as the near-UV.

In this application note, the interaction between lysozyme and its inhibitor, N-acetyl-(D+)-glucosamine (NAG) was measured in the near-UV region using a J-1500 CD spectrometer and a ATS-530 automatic titrator.