Determination of Seven Major Ginsenosides in Different Parts of Panax quinquefolius L.（American Ginseng） with Different Ages

Ginsenosides Rgl, Re, Rb1, Rc, Rb2, Rb3, and Rd in different parts of the American ginseng plant were investigated. The extraction process was a pressurized microwave-assisted extraction（PMAE）. The seven ginsenosides were separated and determined by high-performance liquid chromatography（HPLC） with a ultraviolet（UV） detector, at 203 nm. The experiment results showed significant variations in the individual ginsenoside contents of the American ginseng in different parts and ages of the plant. The results demonstrated that the leaves, root hairs, and rhizomes of Panax quinquefolius L. contained higher ginsenoside contents, followed by the main roots and stems. The leaves contained dramatically higher levels of ginsenoside Rg1 Rb3, and Rd than the other four parts. Higher contents of Rb1 and Re were present in the main roots, root hairs, and rhizomes. The amount of ginsenoside content in the stems was the lowest. The total content of the seven ginsenosides in main roots, root hairs and rhizomes increased with the age of the plant. In contrast, the ginsenoside contents in the leaves and stems decreased with a year of growth.     

Molecular Dynamics Simulation of the Binding Interaction between Hormone Glucagon Protein and Self-Assembled Monolayer Molecules

Restrained molecular dynamics simulations were performed to study the binding affinity of the peptide with alkanethiols of different tail-groups, S（CH2）7CH3, S（CH2）7OH and S（CH2）7COOH, which self-assembled on Au（111） surface in the presence of water molecules. The curves of binding affinity were calculated by fixing the center of mass of the peptide at various distances from the assembling surface. Simulation results show that the binding affin- ity is in the order as COOH-SAMs〉OH-SAMs〉CH3-SAMs, while 100% COOH-SAMs〉5% COOH-SAMS in concentration. The effects on binding affinity by different tail-groups were also studied. Results show that the binding affinity between COOH-SAMs and the peptide is bigger than those of the others and increasing the acidity of COOH-SAMs will result in stronger attractive power.     

DNA Binding Properties and Cytotoxic Activities of Two Trinuclear Ruthenium（Ⅱ） Polypyridyl Complexes

The interactions between two trinuclear Ru（II） complexes and calf thymus DNA（CT DNA） were studied via absorption spectroscopy, reverse salt titrations, binding stoichiometry, DNA melting experiments, as well as viscosity measurement. The results indicate that complexes 1 and 2 bind to DNA via the interaction of the planar π-delocalized system of the complexes with intrinsic binding constants of 4.18 × 10^5 and 3.85 × 10^6 L/tool, respectively, and non-electrostatic binding free energy makes a predominant contribution to the binding free energy. The in vitro cytotoxic activity of complexes 1 and 2 was evaluated by the MTT[3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyl- 2H-tetrazolium bromide] method. Complex I shows higher anticancer potency than complex 2 against four tumor cell lines. Further mechanism study indicates that complexes 1 and 2 can cause cell cycle arrest in the G2/M phase.     

Spectral Studies on the Interaction between Mercuric Ion and ApoCopC

The interaction between mercuric ion and apoCopC in the absence or presence of cupric ion was investigated through difference UV spectra in Hepes buffer （10 mmol·L^-1） at pH 7.4. The results suggest that mercuric ion can bind to C- and N-terminal binding sites of apoCopC, and the conditional binding constants were calculated to be kN=（6.79± 1.12）× 10^6 mol^-1·L and kc=（3.06±0.05）× 10^5 mol^-1·L. Using urea as a chemical agent, the conformational stabilities of apoCopC and HgN^2＋ -CopC-Hgc^2＋ were monitored by fluorescence spectrum in Hepes buffer （50 mmol·L^-1） at pH 7.4. The free energy of stabilization is （14.69±0.85） and （16.66±0.55） kJ.mol^-1, respectively. HgN^2＋ -CopC-Hgc^2＋ is more stable than apoCopC.     

STRUCTURE AND CATALYTIC ACTIVITY OF RHODIUM COMPLEX COORDINATED ON 2-VINYLPYRIDINE-METHYL ACRYLATE COPOLYMER FOR THE CARBONYLATION OF METHANOL

A series of rhodium complexes coordinated on the hybrid ligand. 2-vinylpyridine-methyl acrylate copolymers, as catalyst for the carbonylation of methanol were synthesized by the reaction of the copolymers with tetracarbonyldichlorodirhodium. These complexes were in general very reactive in carbonylation of methanol to form acetic acid and methyl acetate without other by-product. The XPS studies of the complexes showed that the binding energies of Nls(399.1-399.4 eV) and that of Ols(532.5-532.9 eV) were higher than that of the copolymer ligand (Nls 398.1-398.3 eV and Ols 532.2-532.3 eV), indicating the fromation of N→Rh and O→Rh coordination bonds. The IR spectra of complexes showed that the appearance of two absorption peaks of terminal carbonyl at 1990-2100 cm~(-1), characteristic of the cis-dicarbonyl rhodium moiety. These XPS and IR studies confirm the formation of cis-dicarbonylrhodium complex with the active centers(A) and (B) as shown in the text. The increase of activity of the complex in the c     

甾体磷酰胺类缀合物在电喷雾质谱中的裂解特征

Novel steroidal phosphoramidate conjugates of 3'-azido-2',3'-dideoxythymidine(AZT)and amino acid esterswere synthesized and determined by positive and negative ion electrospray ionization mass spectrometry.The MSfragmentation behaviors of the steroidal phosphoramidate conjugates have been investigated in conjunction withtandem mass spectrometry of ESI-MS/MS.There were three characteristic fragment ions in the positive ion ESImass spectra,which were the Na adduct ions with loss of steroidal moiety,amino acid ester moiety from pseudomolecular ion(M Na)~ ,and the phosphoamino acid methyl ester Na adduct ion by α-cleavage of the phosphora-midate respectively.The main fragment ions in negative ion ESI mass spectra were the ion(M-HN_3)~-,the ion(M-AZT-H)~-,and the ion(M-steroidal moiety-H)~- besides the pseudo molecular ion(M-H)~-.Thefragmentation patterns did not depend on the attached amino acid ester moiety.     

Interaction of Ethylene-N,N＇-dianthranilate to Ni（Ⅱ）： Binding Properties and Coordination Mode Studies

The binding properties of ethylene-N,N＇-dianthranilate （EDA） and Ni（II） were studied by difference UV-Vis in 0.05 M Tris-HCl buffer （pH 7.4）. The stoichiometric ratio of EDA to nickel （1：1） was confirmed and the conditional binding constant （IogKNi-EDA = 12.33 ± 0.06） was obtained. In addition, an interesting tetranuclear complex [Nin（EDA）4]·2CH3CH2OH-9H2O was obtained unexpectedly in alcohol-water solution and characterized by X-ray crystallography and electrospray ionization mass spectra （ESI-MS）. It is found that EDA acts as a pentadentate ligand and performs a chelating-bridging coordination mode.     

Theoretical Studies on Complexes of Calcium Ion with Amino Acids

The complexes formed by calcium ion and 12 common amino acids were investigated systematically in the gas phase at the level of MP2/6-311＋＋G（d,p）//MP2/6-3 1G（d,p）.The results show that the salt-bridge structure is the most preferred motif for Ca2＋ binding aliphatic amino acids without heteroatom in the side chain,while charge-solvated（CS） structure is the most preferred motif for Ca2＋ binding other amino acids except for glutamine and lysine.IR spectra of Gln-Ca2＋ and Asn-Ca2＋ complexes were calculated and compared well with the available experiments.From the study in aqueous solution,the bidentate salt-bridge structure was determined to be the most favorable for all the twenty kinds of amino acids to chelate Ca2＋ to both the oxygen atoms of the negatively carboxylate group in the backbone.     

Chuan-Cai Fan;Li-Jin Xu;Han-Yuan Gong;%T Neutral C–H bond vs. electron pair of N（sp~2）： A binding site effect study of macrocycle anion receptor

To evaluate the effect of neutral C–H bond or electron pair of nitrogen atom with sp2hybridization（N（sp2）） involving into the same chemical environment for anion binding, two analogous tetracationic imidazolium macrocycles, namely cyclo[2]（2,6-bis-（1H-imidazol-1-yl）pyridine） [2]（1,3-dimethylenebenzene）（14＋）, and cyclo[2]（2,6-bis-（1H-imidazol-1-yl）pyridine）[2]（2,6-di methylenepyridine）（24＋）were studied in detail as small inorganic anion receptors. The guest anions with different shapes are Cl,N3, NO3, and H2PO4. The host–guest interactions were characterized via1 H NMR spectroscopy,electrospray ionization mass spectrometry（ESI-MS） and single crystal X-ray crystallography. The results implied that macrocyclic hosts with similar backbone but two distinct binding sites（14＋with neutral C–H vs. 24＋with N（sp2）） vary markedly in their response to anions, including the binding modes and association constants. The finding will serve to the construction of new anion receptors, even improve insights into the anion binding process in biology.     

Optical evodiamine derivatives:Asymmetric synthesis and antitumor activity

Evodiamine and its derivatives have an asymmetric center at the C13 b position.Herein,isomers of evodiamine derivatives 2 and 3 were obtained by straightforward asymmetric total synthesis.Their inhibitory activities toward topoisomerases I and II and their cytotoxicities in cancer cell lines were evaluated.All the four isomers exhibited good to excellent antitumor potency and the(S)-isomers were generally more active than the(R)-isomers.The binding modes of(S)-2 with topoisomerases I and II were also clarified by molecular docking.     

Optical 2-benzyl-5-hydroxy-4-oxopentanoic acids against carboxypeptidase A: synthesis, kinetic evaluation and X-ray crystallographic study

<正>2-Benzyl-5-hydroxy-4-oxopentanoic acid 1 and its enantiomers were designed,synthesized and assayed for inhibitory activity against carboxypeptidase A(CPA,EC 3.4.17.1).To verify the role of the terminal hydroxyl group in 1 binding to CPA,2-benzyl-5- benzyloxy-4-oxopentanoic acid 2 was also synthesized and evaluated.The inhibition constants show that both L-1 and D-1 were shown to have strong binding affinity with L-1 being more potent than its enantiomer by 165-fold.On the other hand,the inhibition constant of 2 increases 4-fold comparing with that of 1.In order to explore the exact binding mode of the hydroxyacteyl group of 1 to the active site zinc ion of CPA,we have solved the crystal structure of CPA complexed with L-1 up to 1.85(?) resolution.In CPA·L-1 complex,the phenyl ring is fitted in the substrate recognition pocket at the S′_1 subsite,and the carboxylate forms bifurcated hydrogen bonds with the guanidinium moiety of Arg-145 and Arg-127 and a hydrogen bond with the phenolic hydroxyl of the down-positioned Tyr-248.The carbonyl oxygen of L-1 does coordinate to the active site zinc ion of CPA as expectedly.Unexpectedly,the terminal hydroxyl group of L-1 is engaged in hydrogen bonding with carbonyl oxygen of Ser-197 instead of coordinating to the active site zinc ion.     

CARBONACEOUS PRODUCTS OF POLYMER-PALLADIUM COMPLEXES AS CATALYSTS FOR THE HYDROGENATION OF METHYL ACRYLATE

Many catalysts were pcrpared by carbonization of ion exchange resin-PdCl_2 complexes at high temperature in nitrogen, hydrogen atmosphere. The rates for the hydrogenation of methyl acrylate and the amounts of Pd elution of the carbonaceous products were measured and compared with those of commercial Pd/C catalyst. It indicates that the carbonaceous products are less active than Pd/C. However, the leaching of Pd from carbonaceous products is very small and much less than that from Pd/C.     

Synthesis,characterization, and catalytic ethylene oligomerization of pyridine-imine palladium complexes

Two neutral five-membered pyridine-imine palladium complexes with the bulky dibenzhydryl (CH(Ph)2) substituted aniline were synthesized and fully characterized by nuclear magnetic resonance (NMR) and X-ray crystal diffraction.Well-defined cationic palladium complexes were further obtained by treatment of chloromethylpalladium complexes with sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate (NaBArF) in CH3CN.Cationic palladium complexes were capable of catalyzing ethylene oligomerization without any cocatalysts.The influences of catalyst structure,reaction temperature,and ethylene pressure on ethylene oligomerization were studied in detail.The introduction of bulky benzhydryl (CH(Ph)2) on the ortho position of the aniline moiety enhanced catalytic activity,thermal stability of the catalyst,and molecular weight of the obtained products.Highly branched oligomers with molecular weights of 600-800 g/mol and narrow polydispersities (1.03-1.12) were produced.     

Electrospray ionization tandem mass spectrometric studies to probe the interaction of Cu(II) with amoxicillin简

This study describes the application of electrospray ionization mass spectrometry(ESI-MS) to investigate copper ion interaction with amoxicillin. ESI mass spectra of Cu–amoxicillin complexes show complex ions at m/z 828, 792, 753, 731, 428, 388 and 366 corresponding to [63Cu+(2A-H)+2H2 O]+, [63Cu+(2A-H)]+, [2A+Na]+, [2A+H]+, [63Cu+(A-H)]+, [A+Na]+and [A+H]+(where A = amoxicillin). Based on the observed m/z values of Cu–amoxicillin complex ions, it is found that the Cu–amoxicillin ratios are 1:1 and 1:2, and the copper ions exhibited three feasible coordination numbers(2, 4 and 6) with amoxicillin complexes. The structures and coordination numbers of copper–amoxicillin complex ions were probed from their collisionally activated dissociation(CAD) spectra. Based on these results, it is confirmed that the copper ions could form stable tetrahedral and octahedral complexes with amoxicillin. This study validates the applicability of ESI-MS for probing copper–amoxicillin complex ions.     

STUDIES ON THE MECHANISM OF INDIRUBIN ACTION IN THE TREATMENT OF CHRONIC GRANULOCYTIC LEUKEMIA——V.BINDING BETWEEN INDIRUBIN AND DNA AND IDENTIFICATION OF THE TYPE OF BINDING

The binding between indirubin and calf thymus DNA in vitro has been verified by meansof the isotope labelling method, spectrophotometric method and thermal denaturation meas-urements. The λ_max 207 nm of indirubin shifted toward longer wave length with decrease ofabsorbance after the incubation of indirubin with DNA. The escalation of Tm value of DNAinduced by indirubin was about 2.4°C and it was reproducible. The binding force between themwas rather weak, as indirubin molecules were easily released during the precipitation withalcohol or the gel filtration. The binding was not affected by sodium chloride even at high con-centration but greatly decreased (to 20-30% of the control) in the presence of 8 M urea.These results showed that the binding between indirubin and DNA might be of hydrogen bondrather than ionic. The amount of bound ~3H-indirubin was directly proportional to the con-centration of indirubin. However, it increased abruptly when the concentration of indirubinreached 1.5×10~(-4) M. This     

Analysis of the linkage positions and isomers of monosaccharide units in oligosaccharides by negative secondary ion mass spectrometry in combination with the stereoselective reaction with substituted boronic acid

The negative secondary ion mass spectrometry,in combination with the stereoselectivederivatizations with substituted boronic acid RB(OH)_2,was used in the analysis of fourteen oligosac-charides.The mass spectra of the derivatives provide information on their linkage Positions and iso-merism of the individual monoscaccharide units.The results indicated that among the derivativesof the oligosaccharides analyzed,those with 1—4 and 1—6 linkages all presented the ion peaks at m/z287,sometimes one more peak at m/z 449.Furthermore,a relationship was found between the linkagepositions and the intensity orders of the derivative ions.Finally,the derivatives of the disaccharideswith a galactose presented an intense ion peak at m/z 347,and those of oligosaccharides with 1—6linkage to a galactose at terminal presented the ion at m/z 317.In the case of oligosaccharides witha fructose residue,characteristic ion of m/z 155 was produced.The conditions of stereoselectivederivatizations and mass spectrometry were studied,in order to obtain a better reproducibility of themass spectra.     

Conventional and microwave irradiated synthesis,biological activity evaluation and molecular docking studies of highly substituted piperazine-azole hybrids

Azole derivatives(3,6) obtained starting from 1-(2-methoxyphenyl) piperazine were converted to the corresponding Mannich bases containing β-lactame or flouroquinolone core via a one pot three component reaction.The synthesis of conazole analogues was carried out starting from triazoles by three steps.Reactions were carried out under conventional and microwave mediated conditions.All the newly synthesized compounds were screened for their antimicrobial,enzyme inhibition and antioxidant activity,and most of them displayed good-moderate activity.Binding affinities and non-covalent interactions between enzyme-ligand complexes were predicted with molecular docking method at molecular level.Docking results complemented well the experimental results on α-glucosidase and urease inhibitory effects of the compounds.Higher binding affinities and much more interaction networks were observed for active compounds in contrary to inactive ones.It was predicted with the docking studies that triazole and anisole moieties in the structure of the synthesized compounds contributed to the stabilization of corresponding enzymes through noncovalent interactions.     

表面等离子体共振生物传感器研究人参皂甙与血清白蛋白的相互作用

To use a newly developed wavelength modulation surface plasmon resonance （SPR） biosensor, an experimental protocol was developed to investigate the interaction of ginsenosides with serum albumin. With a known concentration of the ginsenosides, bound percentages of the ginsenosides with human serum albumin （HSA） or bovine serum albumin （BSA） were obtained. SPR technique could require no labeling and this method provided the detailed information on association and disassociation of molecules in real time. The results indicate that the sensitivity of wavelength modulation SPR biosensor is sufficient for detection and characterization of binding events involving low-molecular weight compounds and their immobilized protein targets.     

Crystal Structures of Urokinase-type Plasminogen Activator in Complex with 4-（Aminomethyl） Benzoic Acid and 4-（Aminomethyl-phenyl）-methanol

Urokinase-type plasminogen activator （uPA） is a trypsin-like serine protease and plays a key role in several biological processes, including tissue remodeling, cell migration, and matrix degradation. The inhibitors of uPA have been shown to prevent the spread of metastasis and tumor growth, and accordingly uPA is widely recognized as a target for the treatment of cancer. In this work, we report the crystal structures of the complexes of uPA with its inhibitors： 4- （aminomethyl）-benzoic acid （AMBA） and 4-（aminomethyl-phenyl）-methanol （AMPM）, both at a resolution of 2.35 А. The inhibitory constants of these two inhibitors were measured by a chromogenic competitive assay, and it was found that AMBA is a better inhibitor for uPA （Ki = 2.68 mM） than AMPM （Ki = 13.99 mM）. The structural study shows that the binding mode of inhibitor AMBA on uPA is similar to that of AMPM on uPA, both docked into the active site S1 pocket of uPA. Structural details of these complexes are provided to explain the difference of inhibitory constants.     

Study on EPR Spectra of Three Gadolinium Complexes With Noncyclic Polyether Schiff Bases

The EPR spectra of three new gadolinium complexes with noncyclic polyether Schiff bases in powder and those of these complexes in organic solvents were investigated at different temperatures. It was observed that EPR spectra of nine and four peaks of Gd(Ⅲ) complexes in polycrystalline powder and freezing samples appeared at low temperature respectively for the first time. The interpretations of these results obtained on the basis of spin Hamiltonian of s = 7/2 system are satisfactory. The correlations of EPR feature between crystal-field strength in complexes and local symmetry around Gd3+ ions were revealed. The crystal-field parameters b20 and the asymmetry parameters λ' of complexes were estimated. A series of interesting regularity and new results were obtained.