= Ronald R. Breaker
{c}
\b[Ronald R. Breaker] is a <biochemist> at Yale University whose research investigates catalytic and regulatory functions of <nucleic acids>. His university biography connects his laboratory's work on <deoxyribozymes> with its investigations of <riboswitches>, in which <RNA> recognizes a molecular signal and affects <gene expression>.<Ronald Breaker profile at Yale School of Medicine>[Biography: catalytic DNA and metabolite-binding messenger RNA]{ref}
In the 1994 primary paper with <Gerald F. Joyce>, Breaker reported a <DNA> catalyst that cleaves an <RNA> linkage. The experiment used <in vitro selection>: molecules with useful activity were enriched through successive selection and amplification rounds. The selected chemistry depended on lead ions, so the result established catalytic capacity under the tested conditions, not the existence of a natural cellular DNA enzyme.<A DNA enzyme that cleaves RNA by Ronald R. Breaker and Gerald F. Joyce>[Abstract, Background, Results and Conclusions]{ref}
The paper's intermolecular catalyst had a reported <turnover number> of about $1\,\mathrm{min^{-1}}$. An original counting example explains the term: if $2\,\mathrm{nmol}$ of active catalyst each process one substrate per minute under sustained substrate-saturating conditions, the initial production rate is approximately $2\,\mathrm{nmol/min}$. The catalyst can process more than its own molecular count over successive cycles. This differs from a reagent consumed once per cleavage. Binding, chemical reaction and product release can impose different kinetic limits.
Breaker later coauthored with <Yingfu Li> the primary study of chemically driven <RNA degradation>. That work supplies a baseline for interpreting <catalysis>: an apparent rate enhancement must compare a catalyzed reaction with the appropriate uncatalyzed reaction under specified conditions.<Kinetics of RNA Degradation by Specific Base Catalysis of Transesterification Involving the 2′-Hydroxyl Group by Yingfu Li and Ronald R. Breaker>[Abstract: background cleavage rates and interpretation of catalytic enhancement]{ref}
\Image[https://mbb.yale.edu/sites/default/files/ron_breaker_-_resized.jpg]
{title=Ronald R. Breaker in the Yale department's captioned profile photograph}
{description=Portrait identified as Ron Breaker by Yale Molecular Biophysics and Biochemistry; linked to the external provider.}
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