= D. S. Bredt
{c}
<D. S. Bredt> is a <neuroscience> researcher who, with <S. H. Snyder>, investigated production of <nitric oxide>. Their 1990 paper isolated <nitric oxide synthase> and established its requirement for <calmodulin>.<Isolation of nitric oxide synthetase, a calmodulin-requiring enzyme by D. S. Bredt and S. H. Snyder>[Byline, affiliation and Abstract]{ref}
The researchers followed conversion of <arginine> into <citrulline>, associated with formation of <nitric oxide>. Using <affinity chromatography>, they purified the activity approximately 6000-fold from rat <cerebellum>. This tied a chemical transformation to an isolated <protein>.<Isolation of nitric oxide synthetase, a calmodulin-requiring enzyme by D. S. Bredt and S. H. Snyder>[Abstract: reaction, affinity column and purification factor]{ref}
The example illustrates activity-guided separation: measuring a reaction product lets one track a catalyst through successive fractions. Testing the isolated activity with different added components then investigates regulation. A purification factor describes enrichment of activity relative to total <protein>; it is not a 6000-fold increase in every biological response.
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