stability Betaine Lysozyme Tm Low pH ΔTm of -0.5 °C at 1 (Singh et al. M pH 3.5 & 0.5 M 2009) pH 3 Betaine α-lactalbumin Tm Low pH ΔTm of -6.6 °C at 1 (Singh et al. M pH 4 2009) Betaine GFP CD to “High” Partial unfolding of (Natalello et monitor concentration 10 secondary al. 2009) protein mM structure and loss structure of tertiary structure TMAO Lysozyme Tm Low pH (below ΔTm of -5.4 °C at 1 (Singh et al. pKa of 4.7) M pH 2.5 2005) TMAO RNase A Tm Low pH (below ΔTm of -4 °C at 1 M (Singh et al. pKa of 4.7) pH 2 2005) TMAO α-lactalbumin Tm Low pH (below ΔTm of -5 °C at 1 M (Singh et al. pKa of 4.7) pH 4 2005) TMAO Prion protein Tm Low pH (below ΔTm of -7 °C at 0.1 (Granata et al. pKa of 4.7) M pH 4 2006) All of the charged amino acids have been shown to destabilise proteins at least under certain conditions (Table 14), although this is unsurprising as they are mostly not naturally present in cells as osmolytes (Table 15). Interestingly glutamate is shown to destabilise IgG despite being used as an osmolyte, although the destabilisation recorded is very small (Falconer et al. 2011).
stability Betaine Lysozyme Tm Low pH ΔTm of -0.5 °C at 1 M pH 3.5 & 0.5 M pH 3 (Singh et al. 2009) Betaine α-lactalbumin Tm Low pH ΔTm of -6.6 °C at 1 M pH 4 (Singh et al. 2009) Betaine GFP CD to monitor protein structure “High” concentration 10 mM Partial unfolding of secondary structure and loss of tertiary structure (Natalello et al. 2009) TMAO Lysozyme Tm Low pH (below pKa of 4.7) ΔTm of -5.4 °C at 1 M pH 2.5 (Singh et al. 2005) TMAO RNase A Tm Low pH (below pKa of 4.7) ΔTm of -4 °C at 1 M pH 2 (Singh et al. 2005) TMAO α-lactalbumin Tm Low pH (below pKa of 4.7) ΔTm of -5 °C at 1 M pH 4 (Singh et al. 2005) TMAO Prion protein Tm Low pH (below pKa of 4.7) ΔTm of -7 °C at 0.1 M pH 4 (Granata et al. 2006) All of the charged amino acids have been shown to destabilise proteins at least under certain conditions (Table 14), although this is unsurprising as they are mostly not naturally present in cells as osmolytes (Table 15). Interestingly glutamate is shown to destabilise IgG despite being used as an osmolyte, although the destabilisation recorded is very small (Falconer et al. 2011).