Bio 513: Problem Set #2 - due 2/7/18 1. _has a non-polar side chain and interact

Question

Bio 513: Problem Set #2 - due 2/7/18 1. _has a non-polar side chain and interacts with other aromatic rings. Aromatic rings have a tendency to stack with other aromatic rings. This amino acid does not contain an indole ring. Lone electron pairs in the imidazole R group of this amino acid makes it, like Met, a potential ligand. It is important in binding the iron atoms in hemoglobin. It is The carbons in an amino acid are labeled with Greek letters beginning with the a-carbon and extending out the side chains, B,y,8, . If two or three groups other than hydrogen atoms are attached to the B-caron, the molecule is said to branch at the B-carbon. Two adjacent residues that branch at the B-carbon make the a-helix unstable. By this criterion and should be helix breakers when adjacent. In proteins, under normal physiological conditions (near pH 7),. and _side chains are positively charged.

Explanation / Answer

i) Phenylalanine

Phenylalanine has aromatic side chain as a result it can be involved in stacking interactions with other aromatic side chains.

ii) Histidine

Histidine has an imidazole functional group with two nitrogens. It can act as a potential ligand and occupies the fifth coordination site of iron in hemoglobin.

iii) Valine, isoleucine and valine

These have branching at beta carbon and thus make the alpha helix unstable if present adjacent to each other.

iv) Amino, guanidine and imidazole side chains

Lysine and arginine are almost entirely positively charged at pH=7, but histidine is only partially positively charged.

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