DISCOVERING NEW CHEMISTRY IN CYBERSPACE
Finding an affordable way to turn carbon dioxide into fuel or deciphering the subtle processes that lead to heart disease or ageing are among the extraordinary possibilities now opening up thanks to advances in the field of computational quantum chemistry.
"Computational quantum chemistry is revolutionizing the practice of chemistry," says Professor Leo Radom of the University of Sydney, Australia's foremost exponent of the art of doing chemistry in cyberspace, without ever handling a chemical or a test-tube.
Using the NCI's supercomputer, Vayu, Professor Radom and his team can rapidly perform tens of millions of calculations that would otherwise occupy thousands of lifetimes; these in turn enable them to carry out thousands of virtual chemical "experiments", with huge savings in laboratory time and cost. By simulating the innumerable reactions that can occur between molecules, they can search for those offering the most promising solutions to pressing problems like tackling heart disease or climate change.
"This approach does not replace traditional chemistry – rather it complements it," Professor Radom explains. "By modelling all the possible chemical reactions for a particular substance, we can zero in on the few that offer the best prospects of success for a particular application – and then hand those to the experimental chemists to see if the molecules do what we have calculated they will do."
Generations of chemists spend years, even whole careers, in experiments that end in a sort of failure: finding out what doesn't work. Professor Radom's team cuts to the chase – and searches instead through their vast chemical models for the reactions most likely to deliver success.
In their research on Vayu, the team uses high-end computer calculations based on the laws of quantum mechanics to investigate an enormous array of different chemical structures, stabilities and reactions. They tackle problems that are both of a fundamental nature and of central relevance to biomedicine and industrial chemistry.
One goal of the work is to develop novel catalysts to assist the process of hydrogenation – the addition of hydrogen atoms to a substance – with the least possible expense of energy. A successful outcome could transform how we view the challenge of climate change and ways to overcome it – by converting problem CO2 into a usable liquid fuel, methanol. Such chemistry may, at one and the same time, help solve the twin problems of disposing of 'waste' CO2, and where Australia is to obtain sustainable energy in future.
"We use the NCI supercomputer to design and explore the properties of various possible forms of zeolites, clay-based minerals used as catalysts in many industrial processes. Our aim is to identify forms that offer a way to combine CO2 and hydrogen gases into the liquid fuel methanol (CH3OH) as cheaply and efficiently as possible," Professor Radom explains. The vast computational power of Vayu is used to test the performance of numerous specially-designed zeolites, so as to pinpoint the best prospect for doing the job. "We then hand the formula to the experimental chemists to see if they can produce the substance we have defined and make it work as predicted in the real world."
Already they have identified a number of promising leads that may one day result in the ability to recycle carbon: "The potential prize is very large," he observes.
In a second project Professor Radom's team are exploring the behaviour of free radicals – reactive atoms and molecules with unpaired electrons that mount a constant assault on the proteins and DNA in our bodies, causing them to break down in ways that can lead to heart disease, cancer and the ageing process. "A better understanding of what happens to these proteins when free radicals attack could lead, for example, to the design of improved antioxidants that prevent this sort of damage, or to therapies to repair it."
In a related project they are investigating B12, a vitamin used by every cell in our body but of especial significance to brain and nervous system function and to blood production. Resolving the many possible reactions such a complex molecule can undergo within our bodies poses an "enthralling puzzle," Professor Radom says – as well as offering fresh insights into the conditions caused by its deficiency, such as anaemia and various mental or nerve disorders, and how to treat them.
Carrying out computational quantum chemistry may not require a chemistry lab – but it does demand phenomenal calculating power and speed. "The NCI National Facility has been, and will continue to be, essential to this work. Our research is entirely computational in nature and the National Facility is overwhelmingly the main source of computing power for us," he says.
