Effect of pH on protein stabilizing property of betaine

This study investigated the pH dependence of the stabilizing effect of betaine on three different proteins - α-lactalbumin (α-LA), lysozyme and ribonuclease-A (RNase-A). They measured Tm (midpoint of denaturation), ΔHm (denaturational enthalpy change at Tm), ΔCp (constant-pressure heat capacity change) and ΔGDo (denaturational Gibbs energy change at 25 °C) of proteins in the presence of different betaine concentrations.

They found that betaine:

- stabilizes RNase-A at all pH values
- has opposite effects on α-LA and lysozyme at high pH and low pH values
- did not significantly change ΔHm and ΔCp

Singh et al (2009). "Glycine betaine may have opposite effects on protein stability at high and low pH values." Biochim Biophys Acta. Epub