The effects of the water-miscible organic solvents (methanol, ethanol, 1-propanol, 2-propanol, acetonitrile, N,N'-dimethylformamide and tetrahydrofuran) on the stability and catalytic activity of alpha-chymotrypsin (CT) immobilized on Eupergit CM were studied. Enhanced stabilities and activities were observed both as a consequence of immobilization and the presence of organic solvent, which in combination provide long term (at least 24 h) retention of activity, and up to 50-fold increase in 50% (v/v) methanol in buffer. Low quantities (20%, v/v) of acetonitrile not only prevented CT inactivation by autolysis at 20 degrees C but also induced a significant increase in the activity of both free (six-fold) and immobilized (two-fold) CT.

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Here we report the first application of phage display screening in low dielectric media. Two series of phage clones with affinity for alpha-chymotrypsin (CT) were selected from a Ph.D.(TM)-C7C library, using either a buffer or acetonitrile in buffer (50%, v/v). The affinity of lysates, individual clones or selected cyclic peptides for the enzyme was studied by examining their influence on CT activity. Peptides displayed on phage selected in buffer provided significant protection from enzyme autolysis resulting in marked increase in CT activity (>100%). Phage selected in ACN provided some, albeit weak, protection from the detrimental influence on CT from ACN. In conclusion, the results demonstrate the potential for the application of phage display screening protocols to targets in media of low dielectricity.

Phage display screening of a surface-immobilized adenine derivative led to the identification of a heptameric peptide with selectivity for adenine as demonstrated through quartz crystal microbalance (QCM) studies. The peptide demonstrated a concentration dependent affinity for an adeninyl moiety decorated surface (KD of 968 ± 53.3 μM), which highlights the power of piezoelectric sensing in the study of weak interactions.