(1) MacDonald, R.J. et al. (1987) Methods Enzymol. 152, 219-227
Isolation of RNA using guanidinium salts.
(2) Cockle, S.A. et al. (1978) J. Biol. Chem. 253, 8019-8026
Resistance of lipophilin, a hydrophobic myelin protein, to denaturation by urea and guanidinium salts.
Guanidine hydrochloride denatures proteins and inhibits nucleases. It is applied at high concentrations for the isolation of non-degraded RNA (e. g. stock solution 7.5 M; ref. 1). β-Mercaptoethanol or DTT increase the denaturing activity of guanidine hydrochloride, since they break intramolecular disulfide bonds. Guanidine thiocyanate acts even stronger than guanidine hydrochloride as a denaturant and is used for ''valuable'' samples/assays. Strongly hydrophobic proteins, like the membrane protein lipophilin will not be denatured by guanidine hydrochloride (2).