Systematic Assessment of the Catalytic Reactivity of Frustrated Lewis Pairs in C-H Bond Activation.

Unreactive C-H bond activation is a new horizon for frustrated Lewis pair (FLP) chemistry. This study provides a systematic assessment of the catalytic reactivity of recently reported intra-molecular FLPs on the activation of typical inert C-H bonds, including 1-methylpyrrole, methane, benzyl, propylene, and benzene, in terms of density functional theory (DFT) calculations. The reactivity of FLPs is evaluated according to the calculated reaction thermodynamic and energy barriers of C-H bond activation processes in the framework of concerted C-H activation mechanisms. As for 1-methylpyrrole, 14 types of N-B-based and 15 types of P-B-based FLPs are proposed to be active. Although none of the evaluated FLPs are able to catalyze the C-H activation of methane, benzyl, or propylene, four types of N-B-based FLPs are suggested to be capable of catalyzing the activation of benzene. Moreover, the influence of the strength of Lewis acid (LA) and Lewis base (LB), and the differences between the influences of LA and LB on the catalytic reactivity of FLPs, are also discussed briefly. This systematic assessment of the catalytic activity of FLPs should provide valuable guidelines to aid the development of efficient FLP-based metal-free catalysts for C-H bond activation.

A New HEK293 Cell with CR2 Region of E1A Gene Deletion Prevents the Emergence of Replication-Competent Adenovirus.

PURPOSE: To eliminate the contaminants of Replication-Competent Adenovirus (RCA) during high titer recombinant oncolytic adenovirus production. METHODS: At first, we detected E1A copy numbers of different sources of 293 cells using Q-PCR, and we screened a subclone JH293-C21 of the JH293 cell line (purchased from ATCC) with lower early region 1A (E1A) copy numbers and higher adenovirus production ability. Then, we deleted the conserved region (CR)2 of the E1A gene in this subclone using the CRISPR-Cas9 system and obtained a stable cell clone JH293-C21-C14 with lower E1A expression, but the RCA formation had no significant reduction. Then, we further deleted the CR2 of JH293-C21-C14 cells with the CRISPR-Cas9 system and obtained a strain of cells named JH293-C21-C14-C28. Finally, we detected the capacity for cell proliferation, adenovirus production, and RCA formation in the production of recombinant adenovirus. RESULTS: The JH293-C21-C14-C28 cells had a similar cell proliferation ability and human adenovirus production as JH293-C21 cells. Most importantly, RCA production in JH293-C21-C14-C28 cells was lower than in JH293-C21 cells. CONCLUSION: Human adenovirus producer cell clone JH293-C21-C14-C28 with CR2 deletion can effectively prevent the RCA production of replication-competent oncolytic adenovirus; this will provide significant advantages in utility and safety in gene therapy.