Prospects and Conclusion

A pressing need is simplification of the Tetrahymena and other assay methods for folic acid so that an enzymologist, needing to know whether a likely folic acid cofactor is absent or tightly bound, can buy from reliable 

Nutritional dependence on pterinoid antimetabolites is a fascinating phenomenon and part of the problem of resistance to the antifolics in cancer therapy. Law (1958) noted that some strains of mouse leukemia have become dependent on antifolics. Is the explanation like that for Neurospora If one had antifolio-dependent strains of protozoa and bacteria, analysis of their growth requirements might uncover new metabolites, as happened for streptomycin-dependent bacteria. 

The deepest theoretical value of pterinoid studies may come, as noted, from the glimpses afforded of a remarkable self-regulating ( feedback ) system for the synthesis of the folic-B catalysts, in which FA and B12 participate in their own synthesis, catalyze synthesis of portions in each other, and join in the synthesis of building blocks of ribonucleic acid, deoxyribonucleic acid, and protein. How far does the autonomy of this complex extend These glimpses have encouraged us to present every potentially fruitful lead that came to our notice. 

We are indebted to Drs. R. Bray, D. Shemin, B. E. Wright, and F. Korte for their generosity in allowing us to consult their manuscripts before publication, and to Dr. Use Schwinck for help with the literature of Drosophila genetics. 

Barchielli, R., Boretti, G., Julita, P., Migliacci, A., and Minghetti, A. 1657. Biochim. et Biophys. Acta 86, 452. 

The high thermal conductivity of SiC may turn out to facilitate new process designs for highly exothermic or endothermic reactions in which heat transfer must be carefully controlled. Furthermore, because the SiC can be formed from carbon in any shape or porosity due to the shape memory effect , a catalyst with good activity and selectivity in a particular reaction can be formed closer to a commercially acceptable form without an extensive development project. For all these reasons it is expected that research will accelerate rapidly in order to understand, improve and develop this novel material. 

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