Practice question

Circular dichroism spectroscopy probes chirality of peptide chromophores. In far-ultraviolet range 190-250 nm, peptide bonds in different secondary arrangements exhibit distinct differential absorption of left and right circularly polarized light. Alpha-helices display characteristic double minima near 208 and 222 nm with positive maximum at 192 nm, beta-sheets show single minimum near 218 nm, and random coil shows minimum near 198 nm. X-ray diffraction requires crystals and gives full atomic coordinates, infrared reports bond vibrations, and MALDI provides mass. CD therefore offers rapid solution-state estimation of secondary structure content and folding transitions.