NMR Studies of a New Binding Mode of the Amino Acid Esters by Porphyrinatozinc(Ⅱ)

The binding mode of the amino acid ethyl esters(guest) by 5 (2 carboxylphenyl) 10,15,20 triphenylporphyrinatozinc(Ⅱ)(host 1) was studied by means of 1H NMR spectra. The binding mode is the hydrogen bonding between the amino group of the guest and the carboxyl group of host 1 plus the coordination between the zinc atom of porphyrinatozinc(Ⅱ) and the carbonyl group of the guest. This is a novel binding mode of the metalloporphyrin to amino acid derivatives.

STUDY ON BINDING MODE OF CISPLATIN TO F-ACTIN ON THE BASIS OF LIGAND-METAL CHARGE TRANSFER SPECTRA

The binding mode and configuration of cisplatin with F-actin were studied on the basis of charge transfer bands of cisplatin-F-actin complex The binding mode was discussed on the basis of the results of LMCT.Raman and fluorescence spectra.

Insight understanding into influence of binding mode of carboxylate with metal ion on ligand-centered luminescence properties in Pb-based coordination polymers

In the crystal engineering area,it is important to clearly demonstrating the relationship of structure and certain functionality.Herein,we present the study of the relationship of structure with phosphorescent nature for two new room temperature phosphorescence(RTP) coordination polymers(CPs).[Pb(FDA)(H_(2)O)](1) and [NH_(3)(CH_(3))NH_(2)(CH_(3))_(2)][Pb_(4)(FDA)_(5)](2),where H_(2) FDA is 2,5-furandicarboxylic acid,have been synthesized by solvothermal method using different solvents and Pb^(2+) sources and characterized by microanalysis,powderX-ray diffraction(PXRD),thermogravimetric(TG),IR and UV-vis spectra.The Pb^(2+)ions adopt bicapped triangle prism coordination sphere in 1 and 2,which are connected together via FDA^(2-) ligands into bilayer structure in 1 while pillared-layer framework in 2.The FDA^(2-) ligands show different bridging modes in 1 and 2,leading to distinct coordination interactions between Pb^(2+) ion and FDA^(2-) ligand in both CPs.Both 1 and 2 emit ligand-centered RTP due to the heavy atom of Pb^(2+) ion,with a lifetime and quantum yield of 0.62 ms and 14.9% in 1 versus 1.69 ms and 15.7% in 2.The emission peak shows significant redshift(79 nm) in 2 regarding 1,which arises from their distinction of coordination interactions between Pb^(2+) ion and FDA^(2-) ligand in both CPs.

Study of the Binding Mode of Quaternary Ammonium Cationic Surfactant to Firefly Luciferase and the Prediction of Binary Mixture Toxicity

The wide use of quaternary ammonium cationic surfactants(QACs)results in their release into the environment.Most surfactants have significant biotoxicity.However,existing toxicity data on QACs are still lacking,especially regarding the joint toxic effects of their mixtures.In computer simulation technology,molecular docking technology is commonly used for studying the mode of action of receptors docking with ligands.The research of QACs mixture interaction is relatively rare,and the binding mode of QACs is unknown.In this study,molecular docking technology was applied to explore the QAC binding mode,and the concentration addition(CA)and independent action(IA)models were applied for predicting the mixture toxicity.Firefly luciferase(FLuc)was used as a macromolecular receptor,and five typical QACs:benzalkonium bromide(BLB),tetraethylammonium bromide(TLB),N,N,N-trimethyl-1-tetradecyl ammonium bromide(CTE),tetrabutylammonium chloride(TAC),and dodecyltrimethylammonium chloride(DTC)were used as small molecule ligands.Molecular docking technology was used to investigate the binding mode of macromolecules and small molecules.The luminescence inhibitory effects of individual compounds and binary mixture on FLuc were determined by microplate toxicity assay of luciferase.The prediction of mixture toxicity was performed by CA and IA.The results showed that the relative toxicity follows:TLB<TAC<DTC<BLB<CTE.TLB and TAC showed the BS-Ⅱbinding mode,and BLB,CTE and DTC showed the BS-Ⅲbinding mode.The toxicity of compounds with binding mode BS-Ⅱwas less than that of those with BS-Ⅲbinding mode.Not all mixtures with the same binding mode could be predicted by CA model,and the IA model did not effectively predict the toxicity of mixtures with compound with different binding modes.The mixture toxicities of QACs with the same binding mode mostly presented additive and synergistic effects,while the mixture toxic effects of QACs with different binding modes presented additive or antagonistic effects.

Studies on the Binding Mode of Pinacyanol Chloride to Nucleic Acids

The interaction of pinacyanol chloride (PC) with nucleic acids has been investigated by a series of experiments. Extensive hypochromism, appreciable peak shifts, isosbestic points and new peaks of the product of binding to nucleic acids in the spectra were observed. They showed that the interaction between PC and nucleic acids occurred. The results from absorption spectra of DNA, DNA melting, electrophoresis and fluorescence polarization studies have indicated that PC binds to DNA in nonintercalative way. Consistent with the nonintercalation, the studies of fluorescence titration and absorption titration specified that the binding of PC to nucleic acids occurred by an outside stacking binding, in which nucleic acids served for acting templates. The fact that the new absorption peaks of bound PC at ca. 485 nm are just close to the absorption bands of H aggregate of PC at high concentrations without DNA further supports the outside stacking binding mode. In addition, other evidence indicated that the interaction between PC and nucleic acids is not purely electrostatic.

Studies on the Binding of Tris(1,10-phenanthroline) Nickel(Ⅱ) to Calf Thymus DNA

Absorbance and fluorescence methods were used to study the interaction of - and A-tris (phenanthroline) nickel ( Ⅱ) complex with calf thymus DNA. It was con- cluded that -Ni(phen). preferentially bound to DNA. Especially the fluorescence Scatchard plots were discussed for the binding of EthBr to calf thymus DNA in the presence of varying concentrations of the metal complex. Theses studies indicated that both the isomers bound to DNA by two acting types , namely , intercalative and electrostatic bound modes.

Studies on the Interaction of Cobalt Mixed-Ligand Coordination Compound Containing Tetrapyrido [3,2-a:2′,3′-c:3″, 2″-h:2■,3■-j] phenazine with DNA

A new monometallic complex [Co(phen)_2tpphz]^(3+) (where tpphz is tetrapyrido [3,2-a:2′,3′-c:3″,2″-h:2′″,3′″-j] phenazine) was synthesized by the reaction of 5, 6-diamino-1,10-phenanthroline with [Co(phen)_2(phendione)]^(3+). It was characterized by elemental analysis, molar conductivity, IR, ~1H NMR, ultraviolet and fluorescence spectroscopy. The interaction of the complex with DNA was also investigated. The complex shows the absorption hypochromicity, fluorescence enhancement, the specific viscosity increased when bound to calf thymus DNA. The cyclic voltammetry (CV) measurement showed a change in peak current with the addition of DNA. All the results provide the support for the intercalative binding mode of the mononuclear complex.

Binding studies of DNA with Co(Ⅲ) coordination compound

The binding of Co(bpy)2dppz3+ to calf thymus DNA was investigated by using absorption and emission spectroscopy,DNA melting techniques,cyclic voltammetry,viscosity and electro-phoresis measurements,where bpy is 2,2'-bipyridyl,dppz is dipyrido[3,2-o:2',3'-c] phenazine.The binding compound shows absorption hypochromicity,fluorescence enhancement,and increasing of DNA melting temperature and the specific viscosity.CV measurement shows the shifts in oxidation-reduction potential and change in peak current with addition of DNA.The compound is also shown to be more efficient photosensitisers for strand breaks in plasmid DNA.

Computational Characterization of Binding of Small Molecule Inhibitors to HIV-1 gp41

Developing orally available small molecule inhibitors of HIV-1 fusion has attracted significant interest over many years. Frey had recently reported several synthetic compounds which are experimentally shown to inhibit cell-cell fusion in the low micromolar range. We carried out computational study to help identify possible binding modes by docking these compounds onto the hydrophobic pocket on gp41 and to characterize structures of binding complexes. The detailed gp41-molecule binding interactions and free energies of binding are obtained through mo- lecular dynamics simulation and MM-PBSA calculation. Specific molecular interactions in the gp41-inhibitor com- plexes are identified. The present computational study complements the corresponding experimental investigation and helps establish a good starting point for further refinement of small molecular gp41 inhibitors.

A Novel Cobalt(III) Mixed-polypyridyl Complex: Synthesis, Characterization and DNA Binding

A novel complex [Co(phen)2HPlP]Cl3[phen= phenanethroline, HPIP=2-(2-hydroxyphenyl) imidazo [4,5-f][l,10]phenanethroline] has been synthesized and structurally characterized by elemental analysis, UV, IR and 1H NMR spectroscopies. The interaction of the complex with calf thymus DNA (CT DNA) has been studied using absorption and emission spectroscopy, DNA melting techniques and cyclic voltammetry. The compound shows absorption hypochromicity, fluorescence enhancement and DNA melting temperature increment when binding to CT DNA. CV measurement shows a shift in reduction potential and a change in peak current with addition of DNA. These results prove mat the compound inserts into DNA base pairs. The shift of peak potential indicates the ion interaction mode between the complex and DNA. The binding constant of the compound to DNA is 4.37 × 104. The complex also seems to be an efficient photocleavage reagent.

Bufotenine and its derivatives:synthesis,analgesic effects identification and computational target prediction

Natural product bufotenine(5)which could be isolated from Venenum Bufonis,has been widely used as a tool in central nervous system(CNS)studies.We present here its quaternary ammonium salt(6)which was synthesized with high yields using 5-benzyloxyindole as raw materials,and we firstly discover its analgesic effects in vivo.The analgesic evaluation showed that compounds 5 and 6 had stronger effects on the behavior of formalin induced pain in mice.Moreover,the combination of compound 6 and morphine has a synergistic effect.We intended to explain the molecular mechanism of this effect.Therefore,36 analgesic-related targets(including 15 G protein-coupled receptors,6 enzymes,13 ion channels,and 2 others)were systemically evaluated using reverse docking.The results indicate that bufotenine and its derivatives are closely related to acetyl cholinesterase(AChE)orα_(4)β_(2) nicotinic acetylcholine receptor(nAChR).This study provides practitioners a new insight of analgesic effects.

Molecular Recognition of Bridged Bis(β-cyclodextrin)s Linked by Phenylenediseleno Tether on the Primary or Secondary Side with Fluorescent Dyes

A Novel β-cyclodextrin dimer,2,2′-o-phenylenediseleno-bridgedbis（β-cyclodextrin）（2）,has been synthesized by reaction ofmono-[2-O-（p-tolylsulfonyl）]-β-cyclodextrin and poly（o-phenylenediselenide）.The complexation stability constants（Ks）and Gibbs free energy changes（-ΔG°）of dimer 2 with fourfluorescence dyes,that is,ammonium 8-anilino-1-naphthalene-sulfonate（ANS）,sodium 6-（p-toluidino）-2-naphthalenesul-fonate（TNS）,Acridine Red（AR）and Rhodamine B（RhB）have been determined in aqueous phosphate buffer solution(pH=7.2,0.1 mol·L-1at 25℃ by means of fluorescence spec-

Fluorescent Properties of the Amidinophenylporphyrins Interacting with DNA

5,10,15,20-Tetrakis（4-amidinolphenyl）porphyrin, its Zn complex and amidinolphenyl bispophyrin interacting with calf thymus DNA were investigated by fluorescence emission spectra and fluorescence life time measurements were also shown. The binding modes of these compounds were recorded and lifetimes of luminescence were meas- ured as a function of the nature to understand the interaction with DNA. The results suggest those amidinopor-phyrins are promising new photodynamic therapeutic agents.

Crystal structures, absolute configurations and molecular docking studies of naftopidil enantiomers as α1D-adrenoceptor antagonists

Chiral drug naftopidil(NAF), a specific α1D-adrenoceptor(AR) antagonist for the treatment of benign prostatic hyperplasia, was used in racemic form for several decades. Our recent work declared that NAF enantiomers showed the same antagonistic effects on the α1D-AR, but the binding mechanism of these two stereochemical NAF isomers to the α1D receptor remained unclear. Herein, we reported the crystallographic structures of optically pure NAF stereoisomers for the first time and unambiguously determined their absolute configurations. The crystal data of R and S enantiomers matched satisfactorily the pharmacophore model for α1D-selective antagonists. Based on the constructed α1D homology model,molecular docking studies shed light on the molecular mechanism of NAF enantiomers binding to α1D-AR. The results indicated that NAF enantiomers exhibited the very similar binding poses and occupied the same binding pocket.

A Novel Sarsolenane Diterpene as a PTPIB Inhibitor from Hainan Soft Coral Sarcophyton trocheliophorum Marenzeller

A novel sarsolenane diterpene, named secodihydrosarsolenone （1）, as a minor component was obtained from the South China Sea soft coral Sarcophyton trocheliophorum Marenzeller. Its structure was elucidated by detailed spectroscopic analysis. Compound 1 exhibited moderate inhibitory activity （IC50= 13.7 μmol·L^-1） against protein tyrosine phosphatase 1B （PTP1B）, a key target for the treatment of type 2 diabetes, representing the first report of PTP1B inhibitory activity for sarsolenane diterpenes. This discovery promotes computational prediction of binding mode between the enzyme and the metabolite, suggesting a crucial role of the residues Tyr46, Ser216 and Arg221 in the binding action.

Recent Developments of Dinitrogen Activation on Metal Complexes and Clusters

Dinitrogen(N_(2)) is the major component of the atmosphere and many factors bring about dinitrogen inertness with low reactivity. Dinitrogen activation on metal complexes and clusters under ambient condition is the long-standing goal in the modern chemistry. In this review,an attempt has been made to survey the mechanistic aspects of dinitrogen activation and functionalization based on different coordination binding modes of dinitrogen. Our goal is to provide a comprehensive survey of dinitrogen activation in order to guide the relevant research in the future.