FAYETTEVILLE, Ark. - When John Pople and Walter Kohn received the 1998 Nobel Prize in Chemistry this fall, they cited the work of a scientist who has been quietly working at the University of Arkansas for almost two decades: Peter Pulay.

Thirty years ago Pulay figured out an efficient method to determine a molecule's shape, thus paving the way for Nobel winners Pople's and Kohn's work.

Kohn and Pople developed theoretical ways to study molecules and their interactions using computers. Pulay provided essential groundwork for their advances.

To do so, Pulay looked at the relationship between a molecule's shape and its energy state. Molecules tend to act like lazy people - they like to be at the lowest energy state. The energy state determines the arrangement of atoms in a molecule. Therefore the distances between atoms within the molecule - and the molecule's shape - can be determined by calculating the lowest energy state for a given molecule.

Pulay realized that since atomic forces can be directly calculated, the energy minimums, and therefore the shapes, could be determined. He created computer programs and software that made this easier to do.

"Originally the response wasn't overwhelming," Pulay said.

However, his methods made it easier to determine large molecular structures containing hundreds of atoms. Pretty soon theoretical work went from a stepchild of chemistry to an essential function that is applied hand in hand with experimentation.

Structure determines function in most molecules. You can't drive a truck if the wheels are perched on the hood, and the same philosophy applies to atom placement. Change a molecule's shape, and you get different properties and different reactions.

"All properties of molecules depend on molecular geometry," Pulay said.

Pulay's computational development enabled the Nobel Prize winner Pople to give extremely accurate descriptions of how chemicals react.

Today Pulay's work attracts professors and students from all over the world to Northwest Arkansas, where he has been since 1982 after leaving Communist Hungary for the United States in 1980. He has won most of the major awards given to chemists in his profession, including the Alexander Von Humboldt Senior Scientist Award and membership in the International Academy of Quantum Molecular Studies, an elite group of 32 experts in the field.

The soft-spoken professor takes this in stride, although his peers are more willing to brag about his accomplishments.

"Once a director at the National Science Foundation called, wanting to know why Pulay had not submitted a proposal before the deadline," said Collis Geren, a chemistry colleague and dean of the Graduate School. "They wanted a proposal from him and were willing to wait for it. Their reviewers would often say of his proposals, 'an ordinary person couldn't do this, but if Pulay says he can, then fund him.'"

The researchers in Pulay's lab work with increasingly faster computers to generate various molecular models and shapes.

Among other things, Pulay's computer contains the molecular structures of cocaine, capsaicin - the "heat" in hot peppers - and taxol, a cancer fighting drug.

They also manipulate molecular shapes on screen to see if they can determine how the chemical properties might change.

Take phosgene for example - a toxic gas which Pulay cheerfully states would kill everyone in a lab if it were to escape from its container.

"Obviously this is not desirable," he said.

However, phosgene is a very useful reagent, despite its deadly side effects. So Pulay and graduate student Matt Shirel have designed a new molecule on the computer which probably acts like phosgene but is a solid and thus less dangerous. They click on the computer screen to generate a rough drawing of the molecule, then refine this by extensive calculations. At this point, questions can be asked - to find, say, the stability of the new molecule, or its spectrum, which helps identification.

Of course, to be useful the new molecules must still be prepared in the laboratory.

Scientists can now predict whether a given molecule will be stable or not - as they did with the 60 and 70 carbon-based, soccer ball-shaped molecules known as buckyballs before their actual discovery in 1985.

As computers become more powerful, more complicated chemical calculations can be performed, which has profound implications for the future of chemical research.

"I think computational theory will change the way chemistry is done," Pulay said.

Pulay predicts that 30-40 years from now scientists will be able to create new materials based on the infinite possibilities of joining atoms. The applications include designer drugs targeted to specific cells and scanning unknown materials to determine molecular makeup.

Determining chemical structures and interactions leads to a basic understanding of the world, he said. "Everything is either a chemical or a mixture of chemicals."

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