Guanidinium chloride

Guanidinium chloride or guanidine hydrochloride, usually abbreviated GuHCl and sometimes GdnHCl or GdmCl, is the hydrochloride salt of guanidine. Guanidinium chloride or guanidine hydrochloride, usually abbreviated GuHCl and sometimes GdnHCl or GdmCl, is the hydrochloride salt of guanidine. Guanidinium chloride crystallizes in orthorhombic space group Pbca. The crystal structure consists of a network of guanidinium cations and chloride anions linked by N–H···Cl hydrogen bonds. Guanidinium chloride is a weak acid with a pKa of 13.6. The reason letting it such a weak acid is because of the complete delocalisation of the positive charge through 3 nitrogen atoms (plus a little bit positive charge on carbon). However, some stronger base can deprotonate it, such as sodium hydroxide: C ( NH 2 ) 3 + + OH − ↽ − ⇀ HNC ( NH 2 ) 2 + H 2 O {displaystyle {ce {C(NH2)3+ + OH- <=>> HNC(NH2)2 + H2O}}} The equilibrium is not complete: because the acidity of guanidinium and water is not large (The approximate pKa values: 13.6 vs 15.7). Complete deprotonation should be done with extremely strong bases, such as lithium diisopropylamide. C ( NH 2 ) 3 + Cl − + Li + N ( C 3 H 7 ) 2 − ⟶ HNC ( NH 2 ) 2 + HN ( C 3 H 7 ) 2 + LiCl {displaystyle {ce {C(NH2)3+Cl- + Li+N(C3H7)2- -> HNC(NH2)2 + HN(C3H7)2 + LiCl}}} Guanidinium chloride is a strong chaotrope and one of the strongest denaturants used in physiochemical studies of protein folding. Guanidine Hydrochloride also has the ability to decrease enzyme activity and increase the solubility of hydrophobic molecules. At high concentrations of guanidinium chloride (e.g., 6 M), proteins lose their ordered structure, and they tend to become randomly coiled, i.e. they do not contain any residual structure. However, at concentrations in the millimolar range in vivo, guanidinium chloride has been shown to 'cure' prion positive yeast cells (i.e. cells exhibiting a prion positive phenotype revert to a prion negative phenotype). This is the result of inhibition of the Hsp104 chaperone protein known to play an important role in prion fiber fragmentation and propagation. Petrunkin and Petrunkin (1927, 1928) appear to be the first who studied the binding of GndCl to gelatin and a mixture of thermally denatured protein from brain extract. Greenstein (1938, 1939), however, appears to be the first to discover the high denaturing action of guanidinium halides and thiocyanates in following the liberation of sulfhydryl groups in ovalbumin and few other proteins as a function of salt concentration.