Jinzhi Tan

pH-dependent Conformational Flexibility of the SARS-CoV Main Proteinase (M pro ) Dimer: Molecular Dynamics Simulations and Multiple X-ray Structure Analyses

n n The SARS coronavirus main proteinase (Mpro) is a key enzyme in the processing of the viral polyproteins and thus an attractive target for the discovery of drugs directed against SARS. The enzyme has been shown by X-ray crystallography to undergo significant pH-dependent conformational changes. Here, we assess the conformational flexibility of the Mpro by analysis of multiple crystal structures (including two new crystal forms) and by molecular dynamics (MD) calculations. The MD simulations take into account the different protonation states of two histidine residues in the substrate-binding site and explain the pH-activity profile of the enzyme. The low enzymatic activity of the Mpro monomer and the need for dimerization are also discussed.n n

Design, synthesis and antitumor evaluation of a new series of N-substituted-thiourea derivatives

AbstractAim:To design and synthesize a novel class of protein tyrosine kinase inhibitors, featuring the N-(2-oxo-1,2-dihydroquinolin-3-yl-methyl)-thiourea framework.Methods:First, compounds 1 and 2 were identified using the virtual screening approach in conjunction with binding assay based on surface plasmon resonance. Subsequently, 3 regions of compounds 1 and 2 were selected for chemical modification. All compounds were characterized potent inhibitory activities toward the human lung adenocarcinoma cell line SPAC1.Results:Forty new compounds (1–2, 3a–g, 4a–w, and 5a–l) were designed, synthesized and bioassayed. Six compounds (1, 3e, 4l, 4w, 5a, and 5b) were found to show promising inhibitory activity against the SPAC1 tumor cell line. The inhibitory activity of compound 5a increases approximately 10 times more than that of the original compound 1.Conclusion:This study provides a promising new template with potential antitumor activity.

In vitro pharmacological characterization of TKI-28, a broad-spectrum tyrosine kinase inhibitor with anti-tumor and anti-angiogenic effects

Tyrosine kinases are used as important biomarkers in many tumor types. Preclinical and clinical anti-tumor studies have shown that broadly acting tyrosine kinase inhibitors may be more useful than specific inhibitors, since the former might overcome redundancies and crosstalk in tumor cell growth signaling pathways. Here, we aim to identify a novel potent tyrosine kinase inhibitor. Computer modeling of the pyrido-pyrimidine class compound, TKI-28 (6-(2,6-dichlorophenyl)-8-methyl-2-phenylamino-8H-pyrido[2,3-d]pyrimidine-7-one), predicted that the compound would dock well in the ATP pocket of the ErbB-2 tyrosine kinase, yielding a high binding affinity for ErbB receptors. Biochemical studies revealed that TKI-28 potently inhibited the activities of tyrosine kinases such as ErbB-2, EGFR, KDR, PDGFR_, c-kit and c-Src, but had little effect on Flt-1 in cell-free system. TKI-28 also efficiently blocked autophosphorylation of the listed receptor tyrosine kinases, and subsequently downregulated phosphorylation of many downstream signaling proteins at the cellular level. TKI-28 exhibited a more potent anti-proliferative activity against EGF- and neuregulin-stimulated SK-OV-3 cells versus serum-stimulated cells, accompanied by apparent induction of apoptosis. Finally, TKI-28 was found to possess anti-angiogenic effects, characterized by inhibition of cell proliferation driven by EGF, VEGF and PDGF, as well as decreased cell migration and tube formation in HMECs. These results collectively highlight the pharmacological characteristics of TKI-28 as a broad-spectrum tyrosine kinase inhibitor, suggesting that it has great potential as an anti-cancer and anti-angiogenesis agent.