My research lies at the interface between molecular biology and evolutionary biology, and focuses on the evolutionary design of biological "capacities" through natural selection. Examples of biological capacities include the Vmax of an enzyme or transporter, the number of ion permeation channels, the mass of a tissue, and the strength of a bone. Most current biological research is concerned with the proximate mechanisms responsible for setting capacities, such as rates of protein synthesis and degradation. However, there is also a little-explored problem of ultimate causation: what are the selective factors that result in capacities being expressed at their actual levels, rather than at some higher or lower levels? Observed biological safety factors (ratios of capacities to maximum natural loads) fall mostly in the range 1.2 - 5; why not higher? Large safety factors obviously increase performance but also incur costs: at the molecular level, are excess capacities limited by biosynthetic energy, occupied space, or other costs?
To study these problems, my lab uses nutrient transporters and hydrolases. We push animals to ceilings of metabolic rate, compare their transporter and enzyme capacities with dietary substrate loads, calculate safety factors, and compare safety factors of reaction steps arranged in series. We thereby seek to understand the observed natural variation in biological safety factors, and to identify limiting factors for biological performance.
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