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. Author manuscript; available in PMC: 2010 Feb 9.
Published in final edited form as: Curr Pharm Biotechnol. 2008 Jun;9(3):185. doi: 10.2174/138920108784567344

Table 8.

Effect of Chemical Modification on Affinity of Ribonucleases for RI

Ribonuclease Modification Ribonucleolytic activity Ki or Kd IC50 or phenotype Ref.
C31S BS-RNase or C32S BS-RNase Sulfhydryl group carboxymethylation Not quantitated Reduced affinity for RI Specifically toxic to spermatogenic layers 200
RNase A Carboxyl group amidation with ethylenediamine 1.6% of RNase A Ribonucleolytic activity reduced by 10-fold molar excess of RI 0.17 μM (3T3-SV40) 18
RNase 1 Carboxyl group amidation with ethylenediamine 0.38% of RNase A Ribonucleolytic activity reduced by 10-fold molar excess of RI 0.13 μM for (3T3-SV40) 18
RNase A Carboxyl group amidation with ethylenediamine to Z = +15.6 5% of RNase A 19 nM 0.085 μM (MCF-7) 0.075 μM (3T3-SV40) 48
RNase A Carboxyl group amidation with polyethylenimine (250, 600, 1000, 1800 Da) Not determined “Markedly decreased” affinity for RI” 0.33–3.3 μM (3T3-SV40) 201
RNase A Amino group amidation with PEG (5, 22 kDa) Not determined Not determined Aspermatogenic and anti-tumoral activity 168
RNase A Amino group amidation with PHPMA (classic and star-like) Not determined Not determined Tumor growth inhibited in CD-1 nude mice bearing human tumors 170