Chemistry
How Circular Dichroism Spectroscopy Reveals Secondary Structure in Peptides
Quick fact
The shape of a protein's far-UV circular dichroism spectrum is like a fingerprint: an alpha-helical protein shows two negative bands at 222 nm and 208 nm and a positive band at 193 nm, while a beta-sheet protein gives a single negative band near 218 nm and a positive band at ~195 nm.
Why this is interesting
You have probably seen a protein's structure as a ribbon diagram, but how do scientists know what that shape is when the protein sits in solution? Circular dichroism spectroscopy can read the secondary structure of a protein without ever seeing an atom.