INTRODUCTORY REMARKS

Joseph Harris

Barrow Neurological Institute St. Joseph’s Hospital

Phoenix. A riz.

Classically, the basic nature underlying chemical reactivity has been the domain of physical and inorganic chemistry. Coordination phenomena, initially the con- cern of the latter realm, have grown into individual disciplines of its own and have progressed t o include organic and biochemistry. The valuable constructs of ligand field or molecular orbital theory have not made much impact in biochemistry. Consequently, relatively very little of the bulk of knowledge at hand on chemical reactivity has been applied to understanding the mechanism of interaction between constituents in biological systems and especially the exact role of transition ele- ments in biocatalysis. Coordination between two molecular species through pi- complexation has been implicated as intermediate in many reactions and, more recently, has been shown to be involved in a number of important biological pro- cesses. As experimental techniques become more definitive and sophisticated, some investigators have recognized that the physical, organic, inorganic and biological chemists are concerned with the same underlying coordination phenomena. Fur- ther, the feeling persisted that information already available in coordination phenomena was not well distributed or understood by investigators in widely diver- gent disciplines of biology. Or, viewed from the other side of the same coin, those familiar with coordination developments were not acquainted with the mutual problems confronting the biological scientists.

The above considerations spurred the conference cochairmen t o organize a con- ference in which current research on pi-complexes would be reviewed to motivate interest and t o demonstrate that pi-interaction may well be the rule, and not the exception, in biological systems.

Accordingly, such a conference was held on March 28, 1967, bringing together investigators with wide interests. A multidisciplinary approach was emphasized to reduce inculcating the traditional pattern of a superspecialized meeting of experts in narrow fields of interests-a pattern which has dominated the scientific scene for so long. The present monograph constitutes the formal presentations made during the two-day sessions.

The opening sessions were devoted to a review of basic principles of pi- interactions especially of organic-organic pi-complexes. Current theories of pi- bonding in complexes of transition metals and organic compounds were covered. Examples of pi-interactions in biological systems were taken from diverse areas. Included among them are the interaction of nucleic acids and carcinogenic agents, the association of purine and pyrimidine nucleosides in solution, the stacking energies for base pairs in DNA, the interactions of proteins with well-defined

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metal pi-complexes, the nature of the carbon-cobalt bond in cobalamins, the action of antibiotics on oxidative phosphorylation, etc.

Informal discussion followed each paper and an entire afternoon, originally intended to discuss possible experimental approaches, was devoted to open, friend- ly informal commentary. These discussions have not been included in this volume in order to adhere to the principle of unbridled exchange of ideas and thoughts, without concern for retribution which could result from publication of such spontaneous remarks.

A number of important points were raised in the course of the discussions; among them was the existence of a language barrier, particularly with respect to the precise definition of commonly used terminology. A basic question existed, and seemingly remains, concerning the exact meaning of pi-interactions. Are the interactions involved in the initiation of a reaction, with the formation of transient intermediates, or restricted to stable intermediates, e.g. donor-acceptor states?

On behalf of the conference cochairmen, I should like to express appreciation to the conference councils of The New York Academy of Sciences for their far- sighted policies, coupled with the support which made this conference possible. We are indebted to Mrs. Eunice Thomas Miner for her confidence, and to Admiral E. S. Schanze and staff for their invaluable assistance in the preparation and man- agement of the conference details.

The term “prospectives” was not chosen arbitrarily, but was significantly related to the sesquicentennial celebration of The New York Academy of Sciences. At a time when there is a clear and, to our way of thinking, dangerous trend to- ward excessive specialization in science, meetings with the format and approach of the Pi-Conference should serve a very useful prototype. Indeed, the success of this conference will be assessed after a second meeting has been held, and a shared vocabulary developed to bring forth a dialogue.