More than 160 scientists who work with supramolecules will meet in Tucson March 11-13 for the 14th Biennial Carl Marvel Symposium. It will be held at the Henry Koffler Building (formerly called the Chemistry/Biological Sciences Building) on the University of Arizona campus and at the Doubletree Hotel, 445 S. Alvernon Way.

They will discuss the latest developments in supramolecular science, which has potential far-reaching applications in biology, environmental technology, engineering, materials sciences and pharmaceutical industry. The symposium theme is "Supramolecular Materials: Design and Discovery."

Detailed information on the conference is available at the conference website.

Scientists involved in supramolecular science design and study new chemical systems that are bound together reversibly by intermolecular forces rather than by conventional covalent bonds (shared electrons).

The field exploded in 1987, when three chemists shared the Nobel Prize for synthesizing molecules and compounds with cavities and cages within which metal ions and other molecules could be bound.

"The original thrust was to design exotic architectures of the supramolecules, but the field is now driven by scientists studying the potential of supramolecules in advanced materials," said Zhiping Zheng, UA assistant professor of chemistry and symposium co-chair. "It has become one of the intellectually most stimulating and technologically most important research frontiers."

Supramolecular phenomena are readily found in nature, Zheng said. "Many of the most spectacular biological functions are achieved by appropriate exploitation of the ubiquitous non-covalent interactions, for example, a substrate binding to an enzyme active site and the pairing up of bases in nucleic acid replication."

Scientists have analyzed natural systems and extracted two major principles involved in supramolecular chemistry -- molecular recognition and self-assembly.

In molecular recognition, a molecule "host" will combine with a molecule "guest." In self-assembly, molecular structures of a defined geometry add complementary molecular components, becoming ever larger arrays, Zheng said. "There is, not surprisingly, a degree of overlap between these two areas."

Chemists, biologists, engineers, physicists, optical scientists and materials scientists are effectively "architects" who apply the fundamental principles involved in biological processes to design and fabricate artificial supramolecular systems. Because of this approach, supramolecular chemistry will have a major impact on materials science in the next century,

Zheng said. "The ultimate goal is to generate molecule-based architectures with tailor-made structural and functional properties. Many exciting applications of supramolecules have been realized, and an even wider range of applications is envisioned."

For example, heavy metal ions that may be hazardous to human health are the "guest" molecules that can be removed by "host" molecules of EDTA (ethylenediaminetetraacetate).

EDTA serves as a chelating agent (from the Greek word for claw) that scavenges toxic metals from the body as a treatment for poisoning. EDTA is also used by toxicologists and physicians as an antidote known as Kelocyanor for acute cyanide poisoning and is a common ingredient in cosmetic products such as shampoo and moisturizing lotion and in metal-canned food.

Other applications use the principle of molecular recognition to remove radioactive pollutants from wastes generated by nuclear reactions, Zheng said. In addition, some host-guest complexes have been developed as contrast agents for magnetic resonance imaging (MRI) and are in current clinical use.

By the principle of self-assembly, researchers have been assembling "an astounding variety of highly sophisticated and programmed supramolecular arrays, ranging from the construction of molecular switches, wires and logic gates," Zheng said. "In this sense, researchers are drafting the blueprints for devices on the molecular scale and laying the groundwork for future nanotechnology."

Chemists and industrial scientists recently demonstrated the feasibility of using certain defect-tolerant supramolecular architectures to build fast, foolproof computers. Such defect-tolerant architectures could bridge the gap between the current generation of microchips and the next generation of molecular-scale computers, Zheng said.

The Southern Arizona Section of the American Chemical Society instituted the biennial symposium in 1975 to honor Carl Shipp "Speed" Marvel, whose work in the 1930s laid the groundwork for much of today's polymer plastics technology. The UA chemistry department now co-sponsors the symposium.

Marvel joined the UA chemistry faculty in 1961. He worked daily at his UA lab until a few months before he died, Jan. 4, 1988, at age 93. The UA named the Carl S. Marvel Laboratories of Chemistry in his honor in 1984. In 1986, President Reagan awarded him the National Medal of Science, the country's highest prize to a scientist.

[Contact: Dominic McGrath, Zhiping Zheng ]

06-Mar-2001