Salk Institute -- Science Image (IMAGE) Salk Institute Caption The protein X-ray crystal structure of chalcone isomerase, complexed with a product molecule called (2S)-naringenin, reveals how the active site arginine (labeled as Arg 37) facilitates catalysis of the correct isomer. Credit Salk Institute/ACS Catalysis Usage Restrictions with credit and related coverage. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.