Broadly speaking, our group focuses on physical organic and supramolecular chemistry. Using mechanistic insights and knowledge of photophysics, we devise sensing systems for real-life applications. In particular, we create rapid screening assays for enantiomeric excess, diastereomeric excess, and reaction yield, as a means of facilitating reaction discovery in catalytic asymmetric induction. In addition, our analytical efforts involve the area of differential sensing, where an array of cross-reactive sensors are used to create patterns that are diagnostic of individual analytes or the consistency of complex mixtures. The current focus is on the classification of kinase activity in cells, and the potential to rapidly screen kinase inhibitors in a parallel fashion. Very recently, our group has delved into the area of reversible covalent bonding, creating a suite of reactions that can all occur simultaneously in the same solution with no crossover between them. We are exploiting these reactions for material applications, polymer synthesis, complex assembly formation, and self-replicating oligomers. Finally, we have active collaborations with the Ellington and Marcotte groups for generating sequence defined polymers and single molecule peptide sequencing routines.
Sequence-defined polymers, such as DNA, have gained attention for their potential in biomimetics, catalysis, and information storage. Our group has developed the solid phase synthesis of sequence-defined oligourethanes (sd-OU) using commercially available amino alcohols. We have shown that sd-OU self-sequence in a controlled manner through 5-exo-trig cyclization of the urethane backbone, which can be monitored with LC-MS. We then applied this self-sequencing ability to information storage. As a proof of concept, a passage from Jane Austen’s Mansfield Park was encoded into hexadecimal through the sequence of –R functional groups in sd-OUs and then decoded by a third party with full accuracy. To further expand upon this work in information storage, we are synthesizing longer sequence-defined polyurethanes, thereby increasing the storage capacity of each molecule, as well as investigating techniques to increase the speed of information retrieval. To demonstrate the versatility of sd-OU for information storage in languages other than English, we are encoding information in pictographic languages, such as Mandarin. Lastly, we are using sd-OU to study enzymatic degradation of polyurethane plastics.
ACS Cent. Sci. 2022, 8, 8, 1125-1133.
High-throughput experimentation (HTE) is a major focus of our group. HTE technologies in chemistry settings are often used for asymmetric reaction discovery and optimization in parallel. Although the methods for conducting reactions on such a scale is mature, the analysis of yield and enantiomeric excess (ee) is usually determined by chiral high-performance liquid chromatography (HPLC) with which reactions are analyzed sequentially. Our group and others have addressed this analysis bottleneck by developing chiroptical methods for the ee determination. These chiroptical assays can be conducted in 96-well plates and are conducive to high-throughput experimentation.
One of our multicomponent assays involves an circular dichroism (CD) active octahedral iron complex which incorporates a chiral amine to produce CD out of the absorbance region of common chiral interference compounds. When coupled with a fluorescent indicator displacement assay, both reaction yield and ee can be determined optically and thus in parallel.
Along with developing chiroptical assays for various functional groups, we’ve parameterized and computationally modeled multicomponent assemblies to understand the physicochemical parameters which govern the CD signal. A predictive model for the CD signal at 100% ee allows operators to circumvent the calibration experiments which relate CD signal to ee further increasing the speed benefits of chiroptical methods over HPLC.
Tetrahedron 2021, 94, 132315.
Proteins are biomacromolecules constructed from one or multiple polypeptide chains, which play essential roles in metabolism. The abnormal expression of specific proteins could be taken as one of the symptoms for diseases. However, proteins often exist in very complex environment and a human cell typically contains >10,000 unique proteins which make it extremely challenging to identify and quantify a single molecule in biological samples. Recently, our group, teamed with the Marcotte lab developed a single molecule fluorosequencing technology which offers the capability to identify and quantify every single peptide and protein molecule with low detection limits. The development of new chemical approaches for specific labeling of amino acids and differentiating end groups of peptides are crucial for the application of fluorosequencing technology. To this end, a part of the research in our lab focuses on the following areas: (i) Screening several orthogonal conjugation methods for the efficient labeling of fluorophores; (ii) Developing new chemical methods for the reversible/irreversible capture of N- and C-terminal of peptides; (iii) Exploring mild conditions for Edman degradation, particularly suitable for the fluorosequencing technology; (iv) Discovering chemical approaches to specifically label certain amino acids and peptide sequences. We believe that these chemical tools will not only benefit our fluorosequencing technology but also broadly applicable to other protein and peptide related researches.
Nat. Biotechnol. 2018, 36, 1076–1082.