Summary
Chemical modification of tryptophan residues in antithrombin III by dimethyl (2-hydroxy-5-nitrobenzyl)
sulfonium bromide (HNBSB) generates products with similar levels of modification (equivalent
to 0.9 mole 2-hydroxy-5-nitrobenzyl [HNB] incorporated/mole of antithrombin III) but
with high or low affinity for heparin-Sepharose. Upon digestion with pancreatic or
neutrophil elastase the low affinity forms generate a product of molecular weight
form (55 kDa) not seen in digests of native antithrombin III or modified forms with
high affinity for heparin. When measured as loss of activity the obserued rate of
digestion of the latter in the absence of heparin was more rapid than that of native
antithrombin III. The differences in digestion are considered to be related to conformation
at differences between the various forms.
