Articolo in rivista, 1994, ENG

Heterogeneity of protein conformation in solution from the lifetime of tryptophan phosphorescence

Cioni, P. and Gabellieri, E. and Gonnelli, M. and Strambini, G.B.

Istituto di Biofisica, CNR, Via S. Lorenzo 26, 56127 Pisa, Italy

The decay of Trp phosphorescence of proteins in fluid solutions was shown to provide a sensitive tool for probing the conformational homogeneity of these macromolecules in the millisecond to second time scale. Upon examination of 15 single Trp emitting proteins multiexponential decays were observed in 12 cases, a demonstration that the presence of slowly interconverting conformers in solution is more the norm rather than an exception. The amplitude of preexponential terms, from which the conformer equilibrium is derived, was found to be a sensitive function of solvent composition (buffer, pH, ionic strength and glycerol cosolvent), temperature, and complex formation with substrates and cofactors. In many cases, raising the temperature, a point is reached at which the decay becomes practically monoexponential, meaning that conformer interconversion rates have become commensurate with the triplet lifetime. Estimation of activation free energy barriers to interconversion shows that the large values of ?G* are rather similar among polypeptides and that the protein substates involved are sufficiently long-lived to display individual binding/catalytic properties. © 1994.

Biophysical chemistry (Print) 52 (1), pp. 25–34

Keywords

tryptophan, article, phosphorescence, priority journal, protein conformation

CNR authors

Gonnelli Margherita, Gabellieri Edi, Cioni Patrizia

CNR institutes

ID: 259020

Year: 1994

Type: Articolo in rivista

Creation: 2013-09-09 13:04:43.000

Last update: 2016-03-04 11:33:27.000

External IDs

CNR OAI-PMH: oai:it.cnr:prodotti:259020

Scopus: 2-s2.0-0028068112