13. Heme is an achiral molecule that binds to the protein myoglobin. However, a 30 micromolar solution of myoglobin (containing heme) in 5 mM sodium phosphate buffer at pH 7 exhibits a positive circular dichroism signal near 400 nm (where heme absorbs). Since chirality is a requirement for circular dichroism, what is responsible for the CD signal?

The near-UV CD range (>250 nm) of proteins delivers info on the define configuration. The indications found within the 250-300 nm section are because of the engagement, dipole alignment and also the environment of the encircling atmosphere of the essential amino acid, tyrosine, aminoalkanoic acid (or S-S disulfide associations) and essential amino acids. In contrast to far-UV CD, the near-UV CD variation can't be allotted to any specific 3D configuration. Relatively, near-UV CD varieties offer essential info on the character of the prosthetic teams in proteins, e. g., the pigment teams in hemoprotein and cytochrome.