Counteraction ability of TMAO toward different denaturing agents

• Published in: Biopolymers Vol. 109; no. 10; pp. e23104 - n/a
• Main Authors: Vigorita, Marilisa, Cozzolino, Serena, Oliva, Rosario, Graziano, Giuseppe, Del Vecchio, Pompea
• Format: Journal Article
• Language: English
• Published: United States 01.08.2018
• Subjects: aqueous solution density; Calorimetry, Differential Scanning; denaturing agents; Hydrogen-Ion Concentration; Methylamines - pharmacology; pKa of TMAO; Protein Denaturation - drug effects; protein stability; Ribonuclease, Pancreatic - chemistry; Solutions; Solvents - chemistry; solvent‐excluded volume effect; Thermodynamics; TMAO counteraction; aqueous solution density; denaturing agents; TMAO counteraction; pKa of TMAO; solvent-excluded volume effect; protein stability
• ISSN: 0006-3525; 1097-0282
• DOI: 10.1002/bip.23104

Differential scanning calorimetry measurements performed on RNase A in aqueous binary solutions containing different concentrations of urea, tetramethylurea, guanidinium chloride, and guanidinium thiocyanate, and in aqueous ternary solutions, containing the same denaturants plus 1 M trimethylamine N‐oxide, TMAO, demonstrate that the latter has a general counteracting ability at pH 7.0, but not at pH 4.0. Experimental data rule out the idea that counteraction originates from direct interactions between TMAO molecules and denaturing agents. A rationalization is provided on the basis of a theoretical approach grounded on the solvent‐excluded volume effect, whose magnitude depends on the density of aqueous solutions.