Reactivity-Dependent PCR: Direct, Solution-Phase In Vitro Selection for Bond Formation

(Figure Presented) In vitro selection is a key component of efforts to discover functional nucleic acids and small molecules from libraries of DNA, RNA, and DNA-encoded small molecules. Such selections have been widely used to evolve RNA and DNA catalysts and, more recently, to discover new reactions from DNA-encoded libraries of potential substrates. While effective, current strategies for selections of bond-forming and bond-cleaving reactivity are generally indirect, require the synthesis of biotin-linked substrates, and involve multiple solution-phase and solid-phase manipulations. In this work we report the successful development and validation of reactivity-dependent PCR (RDPCR), a new method that more directly links bond formation or bond cleavage with the amplification of desired sequences and that obviates the need for solid-phase capture, washing, and elution steps. We show that RDPCR can be used to select for bond formation in the context of reaction discovery and for bond cleavage in the context of protease activity profiling

A biomolecule-compatible visible-light-induced azide reduction from a DNA-encoded reaction-discovery system

Using a system that accelerates the serendipitous discovery of new reactions by evaluating hundreds of DNA-encoded substrate combinations in a single experiment, we explored a broad range of reaction conditions for new bond-forming reactions. We discovered reactivity that led to a biomolecule-compatible, Ru(II)-catalysed azide-reduction reaction induced by visible light. In contrast to current azide-reduction methods, this reaction is highly chemoselective and is compatible with alcohols, phenols, acids, alkenes, alkynes, aldehydes, alkyl halides, alkyl mesylates and disulfides. The remarkable functional group compatibility and mild conditions of the reaction enabled the azide reduction of nucleic acid and oligosaccharide substrates, with no detectable occurrence of side reactions. The reaction was also performed in the presence of a protein enzyme without the loss of enzymatic activity, in contrast to two commonly used azide-reduction methods. The visible-light dependence of this reaction provides a means of photouncaging functional groups, such as amines and carboxylates, on biological macromolecules without using ultraviolet irradiation.Chemistry and Chemical Biolog

Reactivity-Dependent PCR: Direct, Solution-Phase <i>in Vitro</i> Selection for Bond Formation

Reactivity-Dependent PCR: Direct, Solution-Phase <i>in Vitro</i> Selection for Bond Formatio

Development of a Chiral DMAP Catalyst for the Dynamic Kinetic Resolution of Azole Hemiaminals

A new catalyst for the dynamic kinetic resolution of azole hemiaminals has been developed using late-stage structural modifications of the <i>tert</i>-leucinol-derived chiral subunit of DMAP species

Development of a Chiral DMAP Catalyst for the Dynamic Kinetic Resolution of Azole Hemiaminals

A new catalyst for the dynamic kinetic resolution of azole hemiaminals has been developed using late-stage structural modifications of the <i>tert</i>-leucinol-derived chiral subunit of DMAP species

Distribution and pharmacokinetic profile of [¹⁸F]paroxetine ([¹⁸F]-1) from MR-PET imaging in non-human primates.

<p>(A) Summed images from 5–50 min of the dynamic PET collected following injection of <b>[¹⁸F]-1</b>. The images are fused with a structural (T1 weighted) MR image. Although <b>[¹⁸F]-1</b> is a potent and selective ligand for the serotonin transporter (SERT), the observed binding does not match the distribution of SERT. This is indicative of high non-specific binding. The images highlight the overall high blood-brain-barrier penetration of <b>[¹⁸F]-1</b> and heterogeneity of binding observed. (B) Whole-brain average time-activity curves from <b>[¹⁸F]-1</b> from baseline and pretreatment (citalopram) studies.</p

Palladium-mediated synthesis of [¹⁸F]-1 and [¹⁸F]-2 using [¹⁸F]-7 derived from [¹⁸F]fluoride.

<p>(A) Synthesis of the electrophilic fluorination reagent <b>[¹⁸F]-7</b> for reaction with palladium aryl complexes. (B) Synthesis of SSRI <b>[¹⁸F]-1</b> on a scale suitable for NHP PET imaging. (C) Synthesis of 5-HT_2C agonist <b>[¹⁸F]-2</b> on a scale suitable for NHP PET imaging.</p

Preliminary [¹⁸F]-2 MR-PET imaging in non-human primates.

<p>(A) Summed images from 5-50 min of the dynamic PET collected following two studies (baseline and ritanserin pretreated) with <b>[¹⁸F]-2</b>. The images highlight the overall high blood-brain-barrier penetration of <b>[¹⁸F]-2</b> and heterogeneity of binding observed. The highest concentrations were noted in the thalamus, cerebellum, and occipital cortex. (B) Time-activity curves from region-of-interest (ROI) analysis from the dynamic data represented in A. As seen in the kinetic profiles, ritanserin did not fully block the uptake of <b>[¹⁸F]-2</b>; however it did reduce binding and alter the pharmacokinetic profile in the thalamus and cortex but not the cerebellum. The extent to which this represents 5HT_2c binding will require validation by additional imaging experiments.</p

Two small molecule aryl fluorides chosen for radiofluorination and non-human primate PET imaging presented here.

<p>Two small molecule aryl fluorides chosen for radiofluorination and non-human primate PET imaging presented here.</p

Synthesis of palladium(II) aryl substrate 20.

<p>Synthesis of palladium(II) aryl substrate 20.</p