Isonitrile derivatives of polyacrylamide as supports for the immobilization of biomolecules

Isonitrile derivatives of crosslinked polyacrylamide beads (Biogell P-100) were prepared by a two-step procedure: a. N-hydroxymethylation (methylolation) of amide groups on the polymer by treatment with formaldehyde; and b. Attachment of side chains, containing isonitrile functional groups by a displacement reaction involving 1-tosyloxy-3-isocyanopropane (p-CH₃-C₆H₄·SO₂·O·(CH₂)₃ NC) and alkoxide ions generated on methylolated polyacrylamide by treatment with a strong base in a polar aprotic solvent. The modified polyacrylamide beads were tested as support for the immobilization of proteins, and low mol wt ligands by four component condensation (4CC) reactions. Trypsin-polyacrylamide acting on N-benzoyl-L-arginine ethylester exhibited nonlinear Michaelis Menten kinetics and distorted pH activity profiles. The kinetic anomalies could be reduced by increasing the concentration of buffer. The data were consistent with a model assuming “buffer facilitated proton transport” in a diffusionally constrained system.