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Protocol for the synthesis of the radiotracer 35S DMSP

Dimethylsulphonioproprionate (DMSP) is one of the most fascinating molecules in the oceans. It is principally an osmolyte or compatible solute and is synthesised by a variety of microalgae and several higher plants. DMSP can be broken down by enzymatic cleavage to produce the climatically active gas, dimethyl sulphide (DMS) and acrylate.

In the surface oceans, bacteria play an important role in determining how much DMSP is converted to DMS and hence, how much DMS has the potential to enter the atmosphere. Bacteria also regulate the flux of DMS from the ocean to the atmosphere by consuming DMS itself. The most sensitive means of quantifying how much DMSP is utilised by bacteria and transformed to DMS, and of quantifying the consumption rates of DMS by bacteria is to use 35S-radiotracer techniques. 35-S DMSP is not available commercially.

We have developed a modification of procedures used by Dr. Andrew Hanson, University of Florida, Gainsville and Dr. Ron Kiene, University of South Alabama to synthesise 35S-DMSP and 35S-DMS to a high purity (>95%), allowing their use as radiotracers of bacterial metabolism. The synthesised radiotracer has been used successfully to determine DMSP and DMS turnover rates by bacterioplankton in the waters of Plymouth Sound, and in the waters off the Iberian Peninsula. The synthesis utilises an amino acid oxidase reaction to convert labelled methionine to methiolpropionate (MTP). MTP is then methylated to DMSP. Purification of the products involves ion exchange purification and HPLC seperation procedures. Typical labelled DMSP- yields from the radiolabelled methionine ranges from 5 to 12%.

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Reported by

Research Laboratory
Plymouth Marine Laboratory
PL1 3DH Plymouth
United Kingdom