Dynamics of intramolecular contact formation in polypeptides: distance dependence of quenching rates in a room-temperature glass.
Quenching of the triplet state of tryptophan by cysteine is an important new tool for measuring the rate of forming a specific contact between amino acids in a polypeptide chain. To determine the length scale associated with this contact, tryptophan was embedded in a room-temperature glass containing a high concentration of cysteine. The decay of the triplet population is extended in time, consistent with a rate coefficient that decreases exponentially with distance. Solving the diffusion equation with this distant-dependent rate reproduces the observed bimolecular rates in water and shows that quenching at low viscosities takes place less than or similar to A from van der Waals contact between the tryptophan and cysteine.
Lapidus
L J
LJ
Laboratory of Chemical Physics, Building 5, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Eaton
W A
WA
Hofrichter
J
J
D003545:Cysteine / Q000737:chemistry*; D005898:Glass / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D010777:Photochemistry; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry*; D013696:Temperature; D014364:Tryptophan / Q000737:chemistry*
D011506:Proteins; D014364:Tryptophan; D003545:Cysteine