Electrodetection of Small Molecules by Conformation-Mediated Signal Enhancement.

Electrochemical biosensors allow the rapid, selective, and sensitive transduction of critical biological parameters into measurable signals. However, current electrochemical biosensors often fail to selectively and sensitively detect small molecules because of their small size and low molecular complexity. We have developed an electrochemical biosensing platform that harnesses the analyte-dependent conformational change of highly selective solute-binding proteins to amplify the redox signal generated by analyte binding. Using this platform, we constructed and characterized two biosensors that can sense leucine and glycine, respectively. We show that these biosensors can selectively and sensitively detect their targets over a wide range of concentrations-up to 7 orders of magnitude-and that the selectivity of these sensors can be readily altered by switching the bioreceptor's binding domain. Our work represents a new paradigm for the design of a family of modular electrochemical biosensors, where access to electrode surfaces can be controlled by protein conformational changes.

Biotransformation of ß-keto nitriles to chiral (S)-ß-amino acids using nitrilase and ω-transaminase.

OBJECTIVE: To enzymatically synthesize enantiomerically pure ß-amino acids from ß-keto nitriles using nitrilase and ω-transaminase. RESULTS: An enzyme cascade system was designed where in ß-keto nitriles are initially hydrolyzed to ß-keto acids using nitrilase from Bradyrhizobium japonicum and subsequently ß-keto acids were converted to ß-amino acids using ω-transaminases. Five different ω-transaminases were tested for this cascade reaction, To enhance the yields of ß-amino acids, the concentrations of nitrilase and amino donor were optimized. Using this enzymatic reaction, enantiomerically pure (S)-ß-amino acids (ee > 99%) were generated. As nitrilase is the bottleneck in this reaction, molecular docking analysis was carried out to depict the poor affinity of nitrilase towards ß-keto acids. CONCLUSIONS: A novel enzymatic route to generate enantiomerically pure aromatic (S)-ß-amino acids from ß-keto nitriles is demonstrated for the first time.