Princeton Materials Institute (PMI) Related Activities Princeton Environmental Institute (PEI) Related Activities

Biophysical Studies of Enzyme Structure and Mechanisms
We employ magnetic resonance and diffraction methods to examine the structures and mechanisms of action of several metallo-enzymes, particularly metal clusters. Among them include enzymes required for light energy utilization by photosynthetic organisms (PSII reaction center), anti-oxidant enzymes (manganese catalases), hydrolysis of amino acids (arginase) and RNA, and oxidases/dehydrogenases (nicotinic acid hydroxylase and formate dehydrogenase). (funding: NIH, NSF, NATO, CRDF, CEBIC)

Photosynthetic Water Splitting Enzyme: The photosynthetic process of water oxidation which produces all of the dioxygen in our atmosphere is being investigated at the atomic level using biochemical, molecular biological and spectroscopic methods. Electron spin resonance and electron-nuclear double resonance spectroscopies are used to identify the paramagnetic intermediates produced during the photochemical charge separation events. "Inorganic mutants" of the enzymes are prepared to test for metal ion function.

Co-Evolution of Water Splitting and Nitrogen Fixation: A marine photosynthetic organism that is responsible for fixing the largest amount of atmospheric nitrogen in the oceans on a global scale is being studied as a model for understanding the co-evolution with water oxidation, since the two reactions are generally incompatible in the same organism. (Falkowski)

Manganese Catalases: Nature has provided us with different classes of enzymes which protect us against the destructive effects of reactive oxygen species. One of these, hydrogen peroxide, forms during normal cellular biochemistry and is destroyed by a metalloenzyme calledscatalase. In collaboration with Dr. V. V. Barynin, we study the rare catalase produced by a thermophillic bacterium using magnetic resonance methods and inorganic biochemistry. Our research is aimed at developing a fundamental understanding of catalysis so that the factors which distinguish catalases from peroxidases, oxygenases and hydrolases can be defined and, ideally, reproduced in completely synthetic molecules for practical applications in catalysis.

Paleobiochemistry
We are attempting to identify how evolution created the first photosynthetic organism that was capable of using water as a reductant circa 2.7-3.5 billion years ago and thus lead to the oxygenation of earth's atmosphere. The role which chemical speciation of the elements played in driving the chemical evolution of the early earth is under investigation. The creation and evolution of stable biogeochemical cycles is being studied as a model for understanding the creation of self-replicating chemical systems and the creation of the first biological life-forms as primitive organisms. (Falkowski, NASA Astrobiology Institute)

Inorganic Chemistry
The synthesis and characterization of novel inorganic materials incorporated into devices (fuel cells) and heterogeneous supports for applications in practical catalytic processes is under investigation in collaboration with colleagues in the PMI.

Water Oxidation Catalysts
We seek to use the photosynthetic water oxidizing enzyme as a "blueprint" for designing catalysts for generation of oxygen from water needed for replacing air by O2 for environmentally clean fuel combustion processes, and for selective oxidation reactions. Recently we have achieved a breakthrough, by synthesis of the closest structural model of the enzyme's active core and the first known cubical manganese-oxo core, [Mn4O4]6+. This highly reactive core was trapped within a coordination sphere of facially bridging chelates (L6Mn4O4). The chelates enable oxygen transfer reactions to various substrates that can be selected by choice of the chelate. Release of one chelate destabilizes the cubane core resulting in O2 release. We are investigating the mechanism of O2 formation and its relationship to photosynthesis.
Manganese Cubane Page