The 12th JerusaLem'Symposium was devoted to the exciting sub- ject of CataLysis in Chemistry and Biochemistry. As usuaL in these Sym- posia Theory and Experiment have been considered simuLtaneousLy in dis- cussions> invoLving renowned experts from many countries. We wish to thank aLL those who made this meeting possibLe and contributed to its success: the Baron de RothschiLd whose continuous generosity is at the source of these gatherings, the IsraeL Academy of Sciences and Humanities which offers us the cordiaL hospitaLity of its impressive and beautifuL buiLding and gardens and the Hebrew University of JerusaLem, faithfuL cosponsor of the Symposia. THE MACROMOLECULAR ELECTROSTATIC EFFECT IN BIOCHEMICAL EACTIVITY OF THE NUCLEIC ACIDS. BERNARD PULUIAN Institut de BioLogie Physico-Chimique, Laboratoire de Biochimie Theorique, aSSOCle au C. N. R. S., 13, rue P. et M. Curie, Paris 75005, France. 1. INTRODUCTION The roLe of the macromoLecuLe and of its overaLL structure upon the reactivity of its reaction site(s) represents one of the fundamentaL probLems in the theory of cataLysis. The most impressive and most fre- quentLy considered exampLes occur in the fieLd of proteins where the probLem generaLLy consists of accounting for the enhancement of the reaction rate at the active site or at the coenzyme with respect to modeL systems, devoid of the macromoLecuLar superstructure. Different effects have been considered as possibLy responsibLe for the infLuence of the macromoLecuLe on such LocaLized-site reactions. I do not have the time to summarize or discuss them here.