Caixia Yuan

Synthesis, characterization, and protein tyrosine phosphatases inhibition activities of oxovanadium(IV) complexes with Schiff base and polypyridyl derivatives

Seven new mixed-ligand vanadyl complexes, [V(IV)O(5-Br-SAA)(NN)] and [V(IV)O(2-OH-NAA)(NN)] (1-7) (5-Br-SAA for 5-bromosalicylidene anthranilic acid, 2-OH-NAA for 2-hydroxy-1-naphthaldehyde anthranilic acid and NN for N,N-donor heterocyclic base, namely, 2,2-bipyridine (bpy, 1 and 5), 1,10-phenanthroline (phen, 2 and 6), dipyrido[3,2-d:2,3-f]quinoxaline (dpq, 3 and 7), dipyrido[3,2-a:2,3-c]phenazine (dppz, 4)), were synthesized and characterized. X-ray crystal structure of [V(IV)O(5-Br-SAA)(phen)] revealed a distorted octahedral geometry with the Schiff base ligand coordinated in a tridentate ONO-fashion and the phenanthroline ligand in a bidentate fashion. Density-functional theory (DFT) calculations suggest a similar structure and the same coordination mode for all the other oxovanadium complexes synthesized. Biochemical assays demonstrate that the mixed-ligand oxovanadium(IV) complexes are potent inhibitors of protein tyrosine phosphatase 1B (PTP1B), with IC(50) values approximately 41-75 nM. Kinetics assays suggest that the complexes inhibit PTP1B in a competitive manner. Notably, they had moderate selectivity of PTP1B over T-cell protein tyrosine phosphatase (TCPTP) (about 2-fold) and good selectivity over Src homology phosphatase 1 (SHP-1) (about 4 approximately 7-fold). Thus, these mixed-ligand complexes represent a promising class of PTP1B inhibitors for future development as anti-diabetic agents.

Exploration of α-aminophosphonate N-derivatives as novel, potent and selective inhibitors of protein tyrosine phosphatases.

Seventeen α-aminophosphonates are synthesized. Their compositions and structures are established by EA, UV, FT-IR, (1)H NMR, (13)C NMR, (31)P NMR and ESI-MS. Compounds 1-4 are confirmed by X-ray crystallography. PTP inhibition shows compounds 1-5, 12, 15 are moderate competitive inhibitors with some selectivity. The most potent inhibitor is compound 5 with the lowest IC(50) value about 6.64 μM against PTP1B, about 2-fold and 25-fold stronger than against TCPTP and PTP-MEG2 while it doesnt inhibit SHP-1 and SHP-2. The binding constant of 5 to PTP1B is 2.23 × 10(5) M(-1) and binding ratio approximates 1:1. Cell viability and apoptosis assays indicate 5 is cell permeable with lower cytotoxicity. The results indicate α-aminophosphonates are possibly developed to effective and selective inhibitors of PTPs.

Ternary oxovanadium(IV) complexes with amino acid-Schiff base and polypyridyl derivatives: Synthesis, characterization, and protein tyrosine phosphatase 1B inhibition

To investigate the structure-activity relationship of vanadium complexes in inhibiting protein tyrosine phosphatase1B (PTP1B), eight mixed-ligand oxovanadium(IV) complexes, [V(IV)O(SalAla)(NN)] (H(2)SalAla for salicylidene alanine, NN for N,N-donor heterocyclic base, namely, 2,2-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), dipyrido[3,2-d:2,3-f]quinoxaline (dpq, 3), dipyrido[3,2-a:2,3-c]phenazine (dppz, 4)), [V(IV)O(SalLys)(dpq)] (5), [V(IV)O(SalLys)(dppz)] (6), [V(IV)O(SalAsp)(dppz)], (7) and [V(IV)O(SalTrp)(dppz)] (8)), of which 3-8 are new, have been prepared and characterized by elemental analysis, infrared, UV-visible, electrospray ionization mass spectrometry and conductivity. The molar conductance data confirmed the non-electrolytic nature of the complexes in DMSO solution. The coordination in [V(IV)O (SalAla)(phen)] (2) was confirmed by X-ray crystal structure analysis. The oxidation state of V(IV) with d(1) configuration in 2 was confirmed by EPR. The speciation of VO-SalAla-phen in aqueous solution was investigated by potentiometric pH titrations. The results indicate that the main species are two ternary complexes at the pH range 7.0-7.4. Biochemical assays demonstrate that the mixed-ligand oxovanadium(IV) complexes are potent inhibitors of PTP1B with IC(50) values in the range of 62-597nM, approximately 3-10 fold weaker in potency than those of similar mixed-ligand oxovanadium(IV) complexes of salicylidene anthranilic acid (SAA) derivative with polypyridyl ligands, except complex 8, which exhibits comparable or better inhibition activity than those of the mixed-ligand oxovanadium(IV) complexes of SAA derivative with polypyridyl ligands. The results demonstrate that the structures of vanadium complexes influence the PTP1B inhibition activity. Kinetics assays reveal that complex 2 inhibits PTP1B in a competitive manner.

Potent inhibition of protein tyrosine phosphatases by copper complexes with multi-benzimidazole derivatives

A series of copper complexes with multi-benzimidazole derivatives, including mono- and di-nuclear, were synthesized and characterized by Fourier transform IR spectroscopy, UV–Vis spectroscopy, elemental analysis, electrospray ionization mass spectrometry. The speciation of Cu/NTB in aqueous solution was investigated by potentiometric pH titrations. Their inhibitory effects against human protein tyrosine phosphatase 1B (PTP1B), T-cell protein tyrosine phosphatase (TCPTP), megakaryocyte protein tyrosine phosphatase 2 (PTP-MEG2), srchomology phosphatase 1 (SHP-1) and srchomology phosphatase 2 (SHP-2) were evaluated in vitro. The five copper complexes exhibit potent inhibition against PTP1B, TCPTP and PTP-MEG2 with almost same inhibitory effects with IC50 at submicro molar level and about tenfold weaker inhibition versus SHP-1, but almost no inhibition against SHP-2. Kinetic analysis indicates that they are reversible competitive inhibitors of PTP1B. Fluorescence study on the interaction between PTP1B and complex 2 or 4 suggests that the complexes bind to PTP1B with the formation of a 1:1 complex. The binding constant are about 1.14xa0×xa0106 and 1.87xa0×xa0106 M−1 at 310xa0K for 2 and 4, respectively.

Potent and selective inhibition of T-cell protein tyrosine phosphatase (TCPTP) by a dinuclear copper(II) complex

A dinuclear Cu(II) complex, [Cu(2)(μ-IDA)(phen)(3)(NO(3))]NO(3)·4H(2)O (phen = 1,10-phenanthroline, H(2)IDA = iminodiacetic acid), was found to potently and selectively inhibit T-cell protein tyrosine phosphatase, and lead to the anti-proliferation and apoptosis of C6 glioma cells.

Dinuclear copper complexes of organic claw: Potent inhibition of protein tyrosine phosphatases

Three dinuclear copper complexes of organic claw ligands (2,2,2″,2-(5-R-2-hydroxy-1,3-phenylene)bis(methylene)bis(azanetriyl)tetraacetic acid, R=methyl (H(5)L1), chloro (H(5)L2) and bromo (H(5)L3)): [Cu(2)NaL1(H(2)O)(2)] (1), [Cu(2)HL2(H(2)O)(2)] (2), [Cu(2)NaL3(H(2)O)(2)] (3), have been synthesized and characterized by elemental analyses, infrared spectra, thermo-gravimetric analyses, X-ray diffraction analysis, electrospray ionization mass spectra, pH-potentiometric titration, molar conductivity. Their inhibitory effects against human protein tyrosine phosphatase 1B (PTP1B), T cell protein tyrosine phosphatase (TCPTP), Megakaryocyte protein tyrosinephosphatase 2 (PTP-MEG2), srchomology phosphatase 1 (SHP-1) and srchomology phosphatase 2 (SHP-2) are evaluated in vitro. The three copper complexes exhibit potent and almost same inhibition against PTP1B and SHP-1 with IC(50) values ranging from 0.15 to 0.31μM, about 2-fold stronger inhibition than against PTP-MEG2, 10-fold stronger inhibition than against TCPTP, but almost no inhibition against SHP-2. Kinetic analysis indicates that they are reversible competitive inhibitors of PTP1B. Molecular docking analyses confirm the inhibition model. Fluorescence titration studies suggest that the complexes bond to PTP1B with the formation of a 1:1 complex. The results demonstrate that copper complexes that are potent PTPs inhibitors but have different inhibitory effects over different PTPs, may be explored as new practical inhibitors towards individual PTP with some specificity.

A dioxidovanadium (V) complex of NNO-donor Schiff base as a selective inhibitor of protein tyrosine phosphatase 1B: Synthesis, characterization, and biological activities

A new dioxidovanadium (V) complex, VO2(HPPCH) (1) (H2PPCHxa0= N-picolinoylpyridin-1-ium-2-carbohydrazonate) has been synthesized and characterized by elemental analysis, IR, X-ray diffraction analysis and electrospray ionization mass spectra. Complex 1 crystallized in the monoclinic system with space group P21/c. It potently inhibited PTP1B with IC50 of 0.13xa0μM, about 7, 15 and 125-fold stronger against PTP1B than over TCPTP, SHP-1 and SHP-2, displaying obvious selectivity against PTP1B. Western blotting analysis indicated that complex 1 effectively increased the phosphorylation of PTP1B substrates, especially the phosphorylation of IR/IGF 1R and IRS-1. It exhibited lower cytotoxicity than positive control VOSO4. These results make complex 1 a promising candidate for novel anti-diabetic drug development.

Linear, planar, and tubular molecular structures constructed by double planar tetracoordinate carbon D2h C2(BeH)4 species via hydrogen‐bridged BeH2Be bonds

This computational study identifies the rhombic D2h C2(BeH)4 (2a) to be a species featuring double planar tetracoordinate carbons (ptCs). Aromaticity and the peripheral BeBeBeBe bonding around CC core contribute to the stabilization of the ptC structure. Although the ptC structure is not a global minimum, its high kinetic stability and its distinct feature of having a bonded C2 core from having two separated carbon atoms in the global minimum and other low‐lying minima could make the ptC structure to be preferred if the carbon source is dominated by C2 species. The electron deficiency of the BeH group allows the ptC species to serve as building blocks to construct large/nanostructures, such as linear chains, planar sheets, and tubes, via intermolecular hydrogen‐bridged bonds (HBBs). Formation of one HBB bond releases more than 30.0 kcal/mol of energy, implying the highly exothermic formation processes and the possibility to synthesize these nano‐size structures.

Ultrashort Beryllium−Beryllium Distances Rivalling Those of Metal−Metal Quintuple Bonds Between Transition Metals

Chemical bonding is at the heart of chemistry. Recent work on high bond orders between homonuclear transition metal atoms has led to ultrashort metal-metal (TM-TM) distances defined as dM-M <1.900u2005Å. The present work is a computational design and characterization of novel main group species containing ultrashort metal-metal distances (1.728-1.866u2005Å) between two beryllium atoms in different molecular environments, including a rhombic Be2 X2 (X=C, N) core, a vertical Be-Be axis in a 3D molecular star, and a horizontal Be-Be axis supported by N-heterocyclic carbene (NHC) ligands. The ultrashort Be-Be distances are achieved by affixing bridging atoms to attract the beryllium atoms electrostatically or covalently. Among these species are five global minima and one chemically viable diberyllium complex, which provide potential targets for experimental realization.

Zigzag double-chain C–Be nanoribbon featuring planar pentacoordinate carbons and ribbon aromaticity

Low-dimensional materials (LDMs) involving planar hypercoordinate carbon bonding were predicted to have applications in electronic devices, energy materials, and optical materials, etc. The majority of carbon atoms in such LDMs adopt a tetracoordinate structure, while examples with a higher coordination number are extremely rare and the bonding geometries of those carbons are not perfectly planar. In this work, we designed ribbon-like clusters CnBe3n+2H2n+22+ with planar pentacoordinate carbons (ppCs) and extended the corresponding structural model under 1D periodic boundary conditions (PBCs), leading to a zigzag double-chain C–Be nanoribbon. The beryllium atoms in such a nanoribbon arrange in a cosine shape around the perfect ppCs, which are unprecedented in LDMs. Detailed analyses revealed that the perfect ppC structure in the nanoribbon was geometrically achieved by opening a Be–Be edge of small Be5 rings, thereby making the intra-ring space adjustable to fit the size of the carbons. Electronically, the structure is stabilized by a favourable sandwich type charge distribution and satisfaction of the octet rule for ppCs. Note that all the valence electrons in the nanoribbon are locally delocalized within each ppC moiety, representing a new type of ribbon aromaticity, which should be useful in nanoelectronics. The nanoribbon and its cluster precursor C2Be8H62+ are thermodynamically stable, and are promising targets for experimental realization. The nanoribbon was predicted to be an indirect band gap semiconductor; thus it has potential applications in designing light-weight electronic devices.