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The stability of restriction enzymes as supplied by manufacturers without any modification has been examined. No reduction in activity was observed for three enzymes (HindIII, EcoRI and Tsp509I) held at ambient temperature or 4 degrees C for the period of study (12 months), while activity was observed for up to 12 weeks after storage at 37 degrees C, which was considerably better than following desiccation with trehalose, a recognized preservation technique. A larger trial of 23 different restriction enzymes held at room temperature for one week showed that all enzymes retained significant activity. As a practical demonstration of the usefulness of this finding, enzymes were posted to Africa by conventional mail (cost $1 US) and shown to retain activity upon arrival after three weeks in transit (compared to a cost of $1000 US by cold-chain transportation). Supplying enzymes to third-world markets should now be possible by removing the necessity for cold-chain transport. After arrival, enzymes can simply be stored in a standard domestic refrigerator.

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