This volume collects a number of the invited lectures and a few selected contrib utions presented at the International Symposium on Structure and Dynamics of Nucleic Acids, Proteins and Membranes held August 31st through September 5th, 1986, in Riva del Garda, Italy. The title of the conference as well as a number of the topics covered represent a continuation of two previous conferences, the first held in 1982 at the University of California in San Diego, and the second in 1984 in Rome at the Accademia dei Lincei. These two earlier conferences have been documented in Structure and Dynamics: Nucleic Acids and Proteins, edited by E. Clementi and R. H. Sarma, Adenine Press, New York, 1983, and Structure and Motion: Membranes, Nucleic Acids and Proteins, edited by E. Clementi, G. Corongiu, M. H. Sarma and R. H. Sarma, Adenine Press, New York, 1985. At this conference in Riva del Garda we were very hesitant to keep the name of the conference the same as the two previous ones. Indeed, a number of topics discussed in this conference were not included in the previous ones and even the emphasis of this gathering is only partly reflected in the conference title. An alternative title would have been Structure and Dynamics of Nucleic Acids, Proteins, and Higher Functions, or, possibly, "higher components" rather than "higher functions."

In a way the MOTECC-89 project started in the early sixties at the IBM Research Laboratory in San Jose, California. The six years of post-doctoral research, first with Giulio Natta on conductive polymers, with Michael Kasha on spin-orbit effects, with Kenneth S. Pitzer on high temperature molecules and thermo dynamics and with R. S. Mulliken in the quantum chemistry of small molecules had demonstrated pragmatically the importance of a broad-based research and also let me taste some of the excitement to be derived from interdisciplinarity. Thus when I started to gather a department in the newly opened IBM Research Laboratory in San Jose, California, I purposely named it "Large Scale Scientific Computation Department," avoiding reference to chemistry, physics, statistical mechanics or fluid dynamics, which were our main tasks. In the sixties interdisciplinarity was more and more recognized as a most important if not nec essary avenue to cope with the technical needs of our society. However, at that time interdisciplinarity was synonymous with "team work," and true interdisciplinarity was a formidably difficult objective. Although I headed an excellent group of scientists with different backgrounds and there was much progress and creativity, still each one of us was more or less conducting his own research in his own field with occasional cross-field partnerships and with some of the computational techniques as our common base. Later, in 1974, I made a second attempt, this time starting a new department at the Donegani Institute, Montedison, in Novara, Italy."

Any study on the historical evolution of nations and countries points out the decisive importance of productivity trends. We are all very familiar with the main evolution which started with a hunting society at the dawn of civilization, then moved to an agricultural society, and quickly to craftsmanship and com merce. The beginning of the industrial society dates back to the end of the eighteenth century in England, with the introduction of the assembly line in the textile and smelting industries. However, in the last few decades, we are becoming more and more acutely aware of the paramount importance of the production of "information." Indeed, according to a few economists today, we should be classified as living in an information society which has superseded the industrial society. At this point it simply becomes necessary to talk about the computer informa tion industry, which is more and more pervading our lives, from the personal computer, to the workstation, to information networks and electronic mail, to the blueprint executed by robots, to the supercomputer necessary in any major scientific and engineering task. The computer has already brought about a momentous change in the production line - less and less man-size, more and more robot-size. But this rush to tech nical innovation has not stopped at this point. Artificial intelligence and expert systems are becoming a more and more important factor for production by many enterprises and activities."

Any study on the historical evolution of nations and countries points out the decisive importance of productivity trends. We are all very familiar with the main evolution which started with a hunting society at the dawn of civilization, then moved to an agricultural society, and quickly to craftsmanship and com merce. The beginning of the industrial society dates back to the end of the eighteenth century in England, with the introduction of the assembly line in the textile and smelting industries. However, in the last few decades, we are becoming more and more acutely aware of the paramount importance of the production of "information". Indeed, according to a few economists today, we should be classified as living in an information society which has superseded the industrial society. At this point it simply becomes necessary to talk about the computer informa tion industry, which is more and more pervading our lives, from the personal computer, to the workstation, to information networks and electronic mail, to the blueprint executed by robots, to the supercomputer necessary in any major scientific and engineering task. The computer has already brought about a momentous change in the production line - less and less man-size, more and more robot-size. But this rush to tech nical innovation has not stopped at this point. Artificial intelligence and expert systems are becoming a more and more important factor for production by many enterprises and activities.

1. 1 STATEMENT OF THE PROBLEM Quantum chemistry judged not from the ever present possibility of unex pected developments but on the basis of the achievements in the last fifty years, is predominantly limited to attempts to solve for the energy and expectation values of wave functions representing, in the limit, an exact solution to the Schroedinger equation. Because of well-known dif ficulties in system with more than about 50 electrons, the adopted ap proximations are generally rather crude. As examples of quantum chemical approximations we mention the total or partial neglects of electron correlation, the neglect of relativistic effects, the use of subminimal basis sets, the still present neglect of inner-core electrons in semi-empirical methods, the acceptance of the Born-Oppenheimer approximations, and so on. In general, the larger the system, in terms of the number of electrons, the cruder the approxima tion. In a way, the present status of quantum chemistry might appear as nearly paradoxical. Indeed, for small systems, where very accurate ex periments are often available, and therefore, there is not a great need to obtain (from quantum chemistry) predictions of new data but rather, a theoretical interpretation of the existing data, we find increasi gly powerful and reliable quantum chemical methods and techniques."

One should distinguish between coordination numbers and hydration numbers. Following Bockris