Guanidine hydrochloride features

Titration studies of lysozyme have revealed two unique features, both occurring in the carboxyl region of the titration curve. The pertinent data are shown in Table XIV. It is seen (o) that the count of carboxyl groups varies widely from one preparation of lysozyme to another, and (5) that three extra carboxyl groups appear in denaturing solvents such as 8 Af guanidine hydrochloride. 

These features are characteristic of peptide random coil and p-sheet structures, and the magnitude of the positive ellipticity band revealed a significant difference in p-sheet contents between the two toxins. The secondary structures of the two toxins were found to be disrupted by the addition of 5.2 M guanidine hydrochloride at pH 7.4, since the spectra changed to a pattern typical of predominantly random coil structure. It was concluded that co-[d-Ser ]Aga-TK has a significantly higher p-sheet content than co-[l-Ser 6]Aga XK under neutral conditions. 

The adsorption of proteins at fluid interfaces is a key step in the stabilization of numerous food and non-food foams and emulsions.1 Our general goal is to relate the amino acid sequence of proteins to their surface properties, e. g. to the equation of state or other structural and thermodynamic properties. To improve this understanding, the effect of guanidine hydrochloride (Gu HC1) on /1-casein adsorption is evaluated in the framework of the block-copolymer model for the adsorption of this protein. At first the main features of the model are presented, and then the effect of Gu HC1 is interpreted using the previously introduced concepts. 

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