Dynamic of aromatic side chains in proteins
Aromatic side-chains are over represented in the hydrophobic core and in interaction sites. This makes them excellent first hand probes for dynamic processes therein (conformational dynamics).
Symmetric rings of phenylalanine and tyrosine continuously undergo 180° jumps around chi-2, so called ring-flips. They enable measurements of transient protein breathing and interaction strengths of aromatics (aromatic stacking, cation-π).
Tyrosine and histidine exchange protons with their environment. Both are important catalytic residues in acid-base catalysis. Histidine is the most important catalytic amino acid. it exists in protonated charged and in 2 neutral tautomeric forms. By this it can function as a proton shuttle and plays a key role in the hydrogen bond network.
