Many metalloproteins achieve exquisite control over cofactor coordination, which can be precisely known by employing X-ray crystallography and site-directed mutation. Justine combined this knowledge of coordinative environment, along with Marcus Theory, kinetic isotope effects, and other tools and concepts, to draw precise conclusions about reaction energetics and pathways, and to predict reaction rates. Through our extensive discussions and collaborations, I discovered that Justine's approaches and insight were also applicable to reactions of low molecular weight biochemical exudates employed by soil organisms for nutrient acquisition, signal exchange, receipt of environmental cues, and allelopathy. Within soil microenvironments, there is little control over the identities and concentrations of solutes encountered. Mineral surfaces sometimes serve as reactants or catalysts, or as adsorptive sinks. To explain the efficacy of exuded biochemicals, Justine helped me address several chemical questions. What are their design criteria? What approaches are available for discerning their speciation in heterogeneous media? Once speciation is known, how well can pathways and rates of reactions be predicted? Answers to these questions are relevant to our understanding of global cycles of carbon, nitrogen, phosphorus, and other important elements, appraisals of soil health, and our ability to predict consequences of human activity.

Reactivity in situations where life's control over coordination is weak or non-existent

254th National Meeting (2017)

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