posted on 2006-11-15, 00:00authored byChang-Cheng You, Sarit S. Agasti, Mrinmoy De, Michael J. Knapp, Vincent M. Rotello
Amino-acid-functionalized gold clusters modulate the catalytic behavior of α-chymotrypsin (ChT)
toward cationic, neutral, and anionic substrates. Kinetic studies reveal that the substrate specificity (kcat/KM) of ChT−nanoparticle complexes increases by ∼3-fold for the cationic substrate but decreases by 95%
for the anionic substrate as compared with that of free ChT, providing enhanced substrate selectivity.
Concurrently, the catalytic constants (kcat) of ChT show slight augmentation for the cationic substrate and
significant attenuation for the anionic substrate in the presence of amino-acid-functionalized nanoparticles.
The amino acid monolayer on the nanoparticle is proposed to control both the capture of substrate by the
active site and release of product through electrostatic interactions, leading to the observed substrate
specificities and catalytic constants.