[The internal cavities of pike alpha-parvalbumin probably contain water].

The kinetics of hydrogen exchange of pike a-parvalbumin was investigated using the method of infrared spectroscopy (sensitive to the amide hydrogen atoms in the peptide) and radioisotope method (sensitive to all labile hydrogen atoms). Ultraslow exchangeable hydrogen atoms were found to be substantially less in the first case than in the second one. Taking into account that the internal cavities in the parvalbumin are formed by hydrophobic amino acid residues, devoid of labile hydrogen atoms, it is possible to make the most appropriate assumption, namely, these cavities contain water molecules, hydrogen atoms of which are ultraslow exchangeable.