Does the anesthetic 2,2,2‐trifluoroethanol interact with bovine serum albumin by direct binding or by solvent‐mediated effects? A calorimetric and spectroscopic investigation

Abstract

Thermal unfolding of bovine serum albumin (BSA) has been studied in the presence of 2,2,2-trifluoroethanol (TFE) using high-sensitivity microdifferential scanning calorimetry. Quantitative thermodynamic parameters accompanying the thermal transitions have been evaluated. TFE is observed to be a stabilizer or a destabilizer of the folded state of BSA depending on the pH. CD spectroscopy revealed an increase in the -helical content of BSA and a decrease in the tertiary structure in the presence of increasing molalities of TFE. Isothermal titration calorimetric results do not indicate appreciable binding of the TFE molecules to BSA. TFE quenches the steady-state tryptophan fluorescence of BSA only at higher molalities and there is no effect on the tryptophan fluorescence at lower molalities. The calorimetric and spectroscopic results obtained in this work suggest that solvent-mediated effects dominate the interaction of TFE with BSA and the binding component may be very weak. Since the binding component is very weak, one of the possibilities of anesthetic action of TFE molecules on the actual targets may be through perturbation of the structural and dynamic properties of the lipid bilayer so that the function of crucial but unspecified membrane proteins is affected. C 2005 Wiley Periodicals, Inc. Biopolymers 78: [78][79][80][81][82][83][84][85][86] 2005 This article was originally published online as an accepted preprint. The ''Published Online''date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

HFIP‐induced structures and assemblies of the peptides from the transmembrane domain 4 of membrane protein Nramp1

“…The cross peaks between water and H/H signals (CH, CH 2 , or CH 3 ) can be attributed unambiguously to NOE, while the cross peaks between water and HN might originate from either NOE or exchange. Both NOE and exchange imply that water molecules interact with peptides through direct binding possibly accompanied by water/HN exchange in 40% HFIP-d 2 aqueous solutions and HFIP may function as an indirect mechanism 42,43 to induce the formation of helical structure. Based on this observation, a value of 0.4 was used for 1 (see Materials And Methods).…”

The role of interfacial viscoelasticity in the stabilization of an electrospun jet

“…In solution #2, the protein's native structure is partially altered due to the good solvating properties of the TFE, and the protein chains are stabilized in a so-called partially-unfolded state, as described elsewhere [29][30][31]. Additionally, the TFE prevents inter-molecular interactions between the partially-unfolded protein coils, preventing the formation of an organized lattice in this solution and resulting in a Newtonian flow behavior.…”

About the albumin structure in solution and related electro-spinnability issues

“…Most prominently, at high TFE concentrations, the interactions of the protein hydrophilic regimes with water molecules as well as the associated hydrophobic interactions within the protein are disrupted by TFE [27,[37][38][39]. The bulk effect causes unfolding of the tertiary structure of the proteins while concurrently strengthening some intra-molecular hydrogen bonds involved with secondary structures, such as˛-helixes.…”