Yingfu Li

Yingfu Li is a biochemist at McMaster University who studies functional nucleic acids, including catalytic DNA and RNA and their use in molecular sensing. His institutional profile and laboratory biography verify the identity and research connection with Ronald R. Breaker.^[ref]

Li is first author, with Ronald R. Breaker, of the 1999 primary study measuring chemically driven cleavage of RNA phosphodiester bonds. Defined chimeric DNA/RNA substrates allowed the investigators to examine hydroxide-dependent transesterification involving the adjacent $2^{\prime }$-hydroxyl group. This addresses a necessary reference question for studying ribozymes and deoxyribozymes: how rapidly does the corresponding linkage break without the proposed catalyst?^[ref]

An original kinetic example illustrates the comparison. Suppose an uncatalyzed linkage has observed rate constant $k_0=10^{-5}\mathrm{mi}{\mathrm{n}}^{-1}$ and a tested catalytic condition gives $k_{\mathrm{obs}}=0.10\mathrm{mi}{\mathrm{n}}^{-1}$. The rate ratio is $k_{\mathrm{obs}}/k_0=10^4$. For a simple first-order reaction, the corresponding half-lives are $\ln 2/k_0$ and $\ln 2/k_{\mathrm{obs}}$, approximately 69,315 minutes and 6.93 minutes. These are constructed values, not the study's measured constants. Changing pH, temperature or substrate structure between the two measurements can change the baseline and therefore the meaning of that ratio.

The connection to molecular sensing is that molecular recognition and reaction are distinct functions. A useful signal can depend on binding a target, changing a catalyst's activity and detecting the resulting product. Quantifying each contribution is more informative than observing an output change without identifying its origin.