Isoalloxazine is the traditional name of the head group of a
flavin cofactor: small
molecules typically found bound to
enzymes involved in
electron transfer reactions in
metabolism. It looks like this:
H R
| |
H-C-H N N O
\ // \ / \ // \ //
\// \/ \// \//
| || | |
| || | |
/\\ /\ //\ N
/ \\ / \ // \ / \
H-C-H N || H
| ||
H O
The 'R' on the top of the figure varies depending on the flavin in question (see
flavin cofactors for a full description of the possible R-groups.) The extensive
conjugation of the head group is what makes it amenable to the addition/subtraction of electrons or a
hydride. This is a representation of the molecule without any added electrons (i.e. it is in it's
oxidized state.) Electrons or a hydride typically are added to the
nitrogen atom at the bottom of the center ring, forming
reduced flavin species. This nitrogen is in a very unusual environment, as evinced by it's extreme
NMR chemical shift of 350 ppm.