FROM FOOD TO FLESH: A NEW NOBEL FIELD

Author: By Dianne Dumanoski, Globe Staff

Date: Thursday, October 15, 1987
Page: 22
Section: NATIONAL/FOREIGN

Living things -- whether they are plants or animals, a single cell or an elephant -- depend on myriad subtle biochemical processes to maintain themselves.

These processes, which are governed by large molecules or collections of atoms, have long fascinated scientists, said Julius Rebek, an organic chemist
from the University of Pittsburgh. But, he said, it has been "hard to figure out how they operate because they are so complex."

The three who were named recipients of the 1987 Nobel Prize for chemistry yesterday opened the door to understanding these processes, Rebek said, by creating much simpler artificial molecules in the laboratory that simulate or mimic reactions that take place in living systems.

Rebek works in a closely related area of the field, which is called supramolecular chemistry.

This field came into existence more than two decades ago, Rebek said, when one of yesterday's prize winners, Charles J. Pedersen, then a research chemist at Du Pont Co. in Wilmington, Del., created a new class of molecules with unique properties.

The other two winners -- Donald J. Cram of the University of California at Los Angeles and Jean-Marie Lehn of the Universite Louis Pasteur in Strasbourg, France -- were able to build on his work to construct a molecule that simulates the action of the digestive enzyme, chymotrypsin, Rebek said.

In the body, this enzyme will seize a protein molecule, say from a tuna sandwich, at a certain part in its structure. Then it will break the chemical bonds of that protein molecule, converting the fish protein into simpler building blocks that the body then turns into human tissue such as muscle.

"This is the first chemical step toward understanding an area called molecular recognition," said George Whitesides, a professor of chemistry at Harvard, who noted that many fundamental biological processes depend on one molecule's recognizing another specific molecule.

To carry out its work, for example, chymotrypsin must recognize protein molecules that end up in the stomach.

Pedersen's original molecule was called a crown ether because of its shape -- a large ring or bracelet -- and its chemical composition.

Recognizing that this molecule should have unusual properties, Pederson found that it could take from the environment lithium and sodium ions, or atoms with electrons missing, in much the way that enzymes bind ions in nature.

Rebek described Pedersen's crown ether as a kind of "lasso" that could round up ions, until then a difficult feat to achieve in the laboratory.

Cram built on this work, Rebek said, by constructing more selective molecules that would seize a lithium ion but leave a potassium ion alone.

Subsequently, Cram and Lehn went beyond ion reactions and constructed molecules that could imitate natural functions such as the breakdown of protein in digestion.

Compared with the real thing, Rebek said, these new molecules have the simplicity of a model airplane, but they have given scientists much greater understanding of basic processes -- transport, recognition, regulation and catalysis -- and have shown that these processes can be imitated with much smaller and more understandable molecules than had been thought possible.

DUMANO;10/14 LDRISC;10/15,15:17 CHEM15