This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.105.060517v1 88/6/4213    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Cioni, P. Articles by Strambini, G. B. Search for Related Content PubMed PubMed Citation Articles by Cioni, P. Articles by Strambini, G. B.

Effects of Sucrose on the Internal Dynamics of Azurin

Patrizia Cioni ^*, Emilia Bramanti  and Giovanni B. Strambini ^*

^* Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Area della Ricerca di Pisa Via Moruzzi 1, Pisa, Italy; and Istituto per i Processi Chimico Fisici, Consiglio Nazionale delle Ricerche, Area della Ricerca di Pisa Via Moruzzi 1, Pisa, Italy

Correspondence: Address reprint requests to Giovanni B. Strambini, E-mail: g.strambini{at}pi.ibf.cnr.it.

Sucrose is a natural osmolyte accumulated in cells of organisms as they adapt to environmental stresses. In vitro, sucrose increases protein stability and forces partially unfolded structures to refold. Its effects on the native fold structure and dynamics are not fully established. This study, utilizing Trp phosphorescence spectroscopy, examined the influence of molar concentrations of sucrose on the flexibility of metal-free azurin from Pseudomonas aeruginosa. In addition, by means of specific mutants of the test protein, namely I7S, F110S, and C3A/C26A, that altered its thermodynamic stability, its intrinsic flexibility, and the extent of internal hydration, this investigation sought to identify possible correlations between these features of protein structure and the influence of the osmolyte on protein dynamics. Alterations of structural fluctuations were assessed by both the intrinsic phosphorescence lifetime (), which reports on local structure about the triplet probe, and the acrylamide bimolecular quenching rate constant (k_q) that is a measure of the average acrylamide diffusion coefficient through the macromolecule. From the modulation of and k_q across a wide temperature range and up to a concentration of 2M sucrose, it is concluded that sucrose attenuates structural fluctuations principally when macromolecules are internally hydrated and thermally expanded. Preliminary tests with trehalose and xylitol suggest that the effects of sucrose are general of the polyol class of osmolytes.

This article has been cited by other articles:

				P. Cioni Role of Protein Cavities on Unfolding Volume Change and on Internal Dynamics under Pressure Biophys. J., November 1, 2006; 91(9): 3390 - 3396. [Abstract] [Full Text] [PDF]

				E. Gabellieri and G. B. Strambini ANS Fluorescence Detects Widespread Perturbations of Protein Tertiary Structure in Ice Biophys. J., May 1, 2006; 90(9): 3239 - 3245. [Abstract] [Full Text] [PDF]