Chemical Derivatives of Peptide Fragments

The conformations and immunochemical activities of chemical derivatives of fragment 377-571, selectively modified at particular amino acid residues, have been studied (Kazim et d., 1977, 1979) with several antisera prepared against the native fragment as well as against BSA and taken at different times after immunization. 

The modification of all four tyrosine residues (Tyr-399, 408,449, and 494) of fragment 377-571 by nitration with tetranitromethane yielded a homogeneous derivative which, by circular dichroism and optical rotatory dispersion measurements, had suffered no conformational alterations. Disulfide availability studies, however, indicated a slight increase in the reducibility of its disulfide bonds. The nitrated derivative behaved in an identical manner to unmodified peptide 377-571 in precipitin reactions with antisera to 377-571, and was also equally as effective in inhibiting the precipitin reaction of BSA with antisera to BSA. Also, with each of the antisera tested in immunoadsorbent studies, the derivative 

Antigen w noic antiserum Effluent Ab eluted Effluent Ab eluted Effluent Ab eluted  

Results represent the average of triplicate analyses which varied 1.5% or less. 

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