3-Substituted indolin-2-ones have been designed and synthesized as a novel class of tyrosine kinase inhibitors which exhibit selectivity toward different receptor tyrosine kinases (RTKs). These compounds have been evaluated for their relative inhibitory properties against a panel of RTKs in intact cells. By modifying the 3-substituted indolin-2-ones, we have identified compounds which showed selective inhibition of the ligand-dependent autophosphorylation of various RTKs at submicromolar levels in cells. Structure-activity analysis for these compounds and their relative potency and selectivity to inhibit particular RTKs has determined that (1) 3-[(five-membered heteroaryl ring)methylidenyl]indolin-2-ones are highly specific against the VEGF (Flk-1) RTK activity, (2) 3-(substituted benzylidenyl)indolin-2-ones containing bulky group(s) in the phenyl ring at the C-3 position of indolin-2-ones showed high selectivity toward the EGF and Her-2 RTKs, and (3) the compound containing an extended side chain at the C-3 position of the indolin-2-one (16) exhibited high potency and selectivity when tested against the PDGF and VEGF (Flk-1) RTKs. Recent published crystallographic data for two of these 3-substituted indolin-2-ones provides a rationale to suggest that these compounds may bind in the ATP binding pocket of RTKs. The structure-activity analysis supports the use of subsets of these compounds as specific chemical leads for the development of RTK-specific drugs with broad application for the treatment of human diseases.

Receptor tyrosine kinases (RTKs) have been implicated as therapeutic targets for the treatment of human diseases including cancers, inflammatory diseases, cardiovascular diseases including arterial restenosis, and fibrotic diseases of the lung, liver, and kidney. Three classes of 3-substituted indolin-2-ones containing propionic acid functionality attached to the pyrrole ring at the C-3 position of the core have been identified as catalytic inhibitors of the vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) RTKs. Some of the compounds were found to inhibit the tyrosine kinase activity associated with isolated vascular endothelial growth factor receptor 2 (VEGF-R2) [fetal liver tyrosine kinase 1 (Flk-1)/kinase insert domain-containing receptor (KDR)], fibroblast growth factor receptor (FGF-R), and platelet-derived growth factor receptor (PDGF-R) tyrosine kinase with IC(50) values at nanomolar level. Thus, compound 1 showed inhibition against VEGF-R2 (Flk-1/KDR) and FGF-R1 tyrosine kinase activity with IC(50) values of 20 and 30 nM, respectively, while compound 16f inhibited the PDGF-R tyrosine kinase activity with IC(50) value of 10 nM. Structural models and structure-activity relationship analysis of these compounds for the target receptors are discussed. The cellular activities of these compounds were profiled using cellular proliferation assays as measured by bromodeoxyuridine (BrdU) incorporation. Specific and potent inhibition of cell growth was observed for some of these compounds. These data provide evidence that these compounds can be used to inhibit the function of these target receptors.

Earth-abundant, nonprecious, and efficient electrocatalysts for effective hydrogen evolution reaction (HER) are crucial for future large-scale green energy production. Low-cost two-dimensional MXenes have been widely studied in energy-storage devices owing to their unique chemical and physical properties and have recently attracted scientists in the electrocatalysis field. Nevertheless, their electrocatalytic activity still remains unsatisfactory. Herein, we present a facile and general strategy using ammonia heat treatment to enhance the hydrogen evolution catalysis of Ti 3 C 2 T x MXenes by modification with a nitrogen heteroatom. Importantly, our approach is focused on revealing: (1) the contribution of all possible incorporated N species including Ti−N, N−H, and N in O−Ti−N, rather than considering only that of Ti−N x motifs as previously reported for N-doped MXene electrocatalysts, and their role in inducing a change in the electronic configuration of the as-prepared catalysts, which then leads to increased electrical conductivity and improved intrinsic catalytic reactivity; and (2) the importance of controlling the proper amount of N obtained at a suitable calcined temperature to assist the shift of the Gibbs free energy for hydrogen adsorption (ΔH ad *) approaching 0 eV (ideal value), as proved by the density functional theory. Moreover, experimental findings indicate that nitrogen-doped Ti 3 C 2 T x annealed at 600 °C shows superior improved HER electrocatalytic performance compared to pristine Ti 3 C 2 T x , with an onset potential of −30 mV and an overpotential as low as 198 at 10 mA cm −2 , as well as a much smaller Tafel slope of 92 mV dec −1 .

Interactions between gene 4 helicase and gene 5 DNA polymerase (gp5) are crucial for leading-strand DNA synthesis mediated by the replisome of bacteriophage T7. Interactions between the two proteins that assure high processivity are known but the interactions essential to initiate the leading-strand DNA synthesis remain unidentified. Replacement of solution-exposed basic residues (K587, K589, R590, and R591) located on the front surface of gp5 with neutral asparagines abolishes the ability of gp5 and the helicase to mediate strand-displacement synthesis. This front basic patch in gp5 contributes to physical interactions with the acidic C-terminal tail of the helicase. Nonetheless, the altered polymerase is able to replace gp5 and continue ongoing strand-displacement synthesis. The results suggest that the interaction between the C-terminal tail of the helicase and the basic patch of gp5 is critical for initiation of strand-displacement synthesis. Multiple interactions of T7 DNA polymerase and helicase coordinate replisome movement.DNA polymerase-helicase interaction | strand-displacement DNA synthesis | T7 bacteriophage | T7 replisome B acteriophage T7 has a simple and efficient DNA replication system whose basic reactions mimic those of more complex replication systems (1). The T7 replisome consists of gene 5 DNA polymerase (gp5), the processivity factor, Escherichia coli thioredoxin (trx), gene 4 helicase-primase (gp4), and gene 2.5 ssDNA binding protein (gp2.5) (Fig. 1A). Gp5 forms a high-affinity complex with trx (gp5/trx) to increase the processivity of nucleotide polymerization (2). The C-terminal helicase domain of gp4 assembles as a hexamer and unwinds dsDNA to produce two ssDNA templates for leading-and lagging-strand gp5/trx. The N-terminal primase domain of gp4 catalyzes the synthesis of tetraribonucleotides that are used as primers for the lagging-strand gp5/trx. This gp5/trx also binds to helicase to form a replication loop containing the nascent Okazaki fragment. Gp2.5 coats the ssDNA to remove secondary structures and it also physically interacts with gp4 and gp5/trx, interactions essential for coordination of leading and lagging-strand synthesis (3).Other DNA replication systems are generally more complicated than the T7 system. In E. coli, at least 13 proteins are required for a functional replisome and eight proteins are required in bacteriophage T4 infected cells (1, 4, 5). The two essential helicase and primase are separate proteins although they must physically interact to properly function (5). The additional proteins include processivity clamps and loading proteins. The existing T7 gp4 has usurped helicase and primase functions. The proofreading exonuclease activity resides within the N-terminal portion of gp5, whereas in the E. coli system it resides within ϵ subunit of the polymerase holoenzyme (5). Trx not only binds to gp5 to increase processivity but it also configures the trx-binding loop in gp5 for the binding of gp2.5 and gp4 (6). An interaction of the C-terminal tail of gp2.5 with...