NOTE ON THE BIOSYNTHESIS AND ISOLATION OF 35S-LABELLED BENZYLPENICILLIN

SUMMARY: This appendix describes in the form of laboratory notes a simple and rapid method for producing and isolating 35S-labelled benzyl-penicillin. The process yields 5–15 mg. of the compound virtually free from radioactive contaminants and with a specific activity up to c. 0·2 μ c./unit. Approximately 20% of the ‘carrier-free’ 35S added to the medium is converted into penicillin. This process was evolved as the result of work ancillary to other researches and is not claimed to be original. But as there appears to be no published account which describes in detail the preparation of 35S-penicillin, the information given here may be useful to other workers in the field.