CHEMICAL-REACTIONS OF BENZYL ISOTHIOCYANATE WITH MYOGLOBIN

The interaction of benzyl isothiocyanate (in concentrations of 2 . 5-2 50 mg benzyl-ITC g(-1) protein) with myoglobin leads to the formation of derivatives which have been characterised in terms of their solubil ity, free epsilon amino groups, content of tryptophan and its quenchin g as well as their molecular properties determined with electrophoreti c and chromatographic methods. The reaction takes place primarily at t he epsilon amino groups of lysine, whose content decreases depending o n the concentration of the benzyl-ITC present. A second possibility is the reaction of the secondary amino group present in tryptophan, whos e concentration also decreases. These reactions increased the electrop horetical mobility during PAGE in the presence of urea, as a result of which the isoelectric points shifted from 7 . 33-7 . 45 to 5 . 13-5 . 6 as shown by means of the isoelectrical focusing technique. The mole cule size (size exclusion chromatography) decreased as a result of inc reased hydrophobicity (RP-HPLC). A slight polymerisation with an incre ase in the content of dimer (38 kDa, SDS-PAGE) was observed. The deriv ative with the highest degree of derivatisation (250 mg benzyl-ITC g(- 1) protein) showed an unexpected behaviour with all its investigated p roperties, which can be explained as a result of structural changes ta king place during the process of derivatisation.