REFINED CRYSTAL STRUCTURE OF INSULIN AT 1.8A RESOLUTION——HYDROGEN BONDS AND BOUND WATER

The hydrogen bonds in insulin fall into three cases: the helical hydrogen bonds in α- or 3_(10)helices, the non-helical one formed by polar groups of insulin itself, and the hydrogen bondsformed between insulin and water. By using the information obtained, the results of a seriesof biochemical investigations on insulin analogs related to B-chain C-terminal peptide can beinterpreted and it can also be inferred that the complex behaviours of the aggregation ofinsulin may play a protective role for the unique conformation of the molecule. Water structure also appears in the refined model. About one third of the water in anasymmetric unit is hydrogen-bonded to insulin molecules or each other, which are referred toas bound water. The polar and charged groups of insulin all show the tendencies to bind towater molecules as many as possible, which is a significant factor for the stabilization of theunique conformation of the molecule. The binding way of water molecules to insulin mole-cules is also analysed.     

THE POSSIBLE MECHANISM OF BINDING INTERACTION OF INSULIN MOLECULE WITH ITS RECEPTOR

Detailed structural comparisons and investigation of DPI, 2Zn insulin and some other derivatives of insulin were performed by the least-squares superimposition technique and the graphics technique. It is pointed out in this paper that the binding interaction with the receptor molecule should take place mainly on an amphipathic surface of the insulin molecule. In the middle, there is a hydrophobic surface with an area of about 150 consisting of many hydrophobic residues; while the polar or charged groups distributing around the hydro. phobic surface construct a hydrophilic zone. The hydrophobic surface is usually covered by the extended B-chain C-terminal peptides with great mobility and protected from the solvent molecules. The angle between the amphipathic surface and the surface of dimerization is about 20 degrees. The results from the detailed structural comparison between A1-(L-Trp) insulin and A1-(D-Trp) insulin have provided a very good explanation to their great difference in biological activity,     

GROUP TRANSFER POLYMERIZATION OF ETHYL ACRYLATE WITH LEWIS ACID CATALYST

This paper reports the kinetics of group transfer polymerization (GTP)of ethyl acrylate (EA)with zinc iodide catalyst in 1,2-dichloroethane using dimethyl ketene methyl trimethylsilyl acetal (MTS) as initiator at 0℃and above 0℃. The amount of catalyst used was studied. When zinc iodide catalyst used is more than 10mol% relative to monomer, the rate of polymerization is proportional to the concentration of monomer, whereas zinc iodide catalyst used is less than 10 mol% of the monomer, the rate of polymerization is independent of the monomer concentration.In the GTP of EA an induction period was observed when the zinc iodide contents are less than l0mol%. If the reaction temperature is over 0℃, living species become unstable and diminish, leading to incomplete monomer conversion. The reaction curves equations are obtained. The polymers have narrow molecular weight distributions which are not changed as decreasing zinc iodide contents. The polydispersity is about 1.2.     

Changes of conformation and aggregation state induced by binding of lanthanide ions to insulin

To clarify the mechanism of lanthanide ions (Ln3+) on the across-membrane transport of insulin and subsequent reducing blood glucose, the interactions of Ln3+with Zn-insulin and Zn-free insulin are investigated by spectroscopic methods. The results reveal that the binding of Ln3+ to insulin can induce its structure changes from secondary to quaternary structure, depending on the Ln3+ concentration. In the lower concentration, it triggers the conformational changes of insulin monomer in the binding region with insulin receptor (B(24-30)). It would affect insulin-insulin receptor interaction. Moreover, Ln3+ binding promotes the assembly of insulin monomer from dimer to polymer. The potency of Ln3+ in inducing insulin's aggregation is stronger than that of Zn2+. Furthermore, the aggregation can be reversed partly by EDTA-treatment, indicating that it is not due to denaturation. Similar to Zn2+ effect, Ln3+ can stabilize insulin hexamer in a certain range of concentration, but is stronger than the former.     

Synthesis of a New Chiral Ligand Containing 1,5—Diazacyclooctane and the Application in Diethyl Zinc Addition to Benzaldehyde

A new chiral tetradentate ligand (S,S)-1,5-bis (4-benzyloxazolin-2-yl-methyl)-1,5-diazacyclo-octane I has been synthesized and the application of 1 as catalyst in the enantioselective addition of diethyl zinc to benzaldehyde is also described.     

Synthesis and Structural Characterization of Mono-and Di-nuclear Zinc（ Ⅱ ） Coordination Compounds of Triphenylphosphoniopropionate

IntroductionThe coordination chemistry of zinc(Ⅱ)has beensubjected to extensive study in the past decades owingto its importance in life science[1].It has been foundthat zinc(Ⅱ)ions are crucially involved in the activesites of over300metalloenzymes and their role is notonly confined to catalysis and gene expression.Further-more,the presence of zinc(Ⅱ)helps to stabilize thetertiary and quaternary structures of proteins and nucle-ic acids[2—4].Like cadmium(Ⅱ),zinc(Ⅱ)is clearly amongthose m…     

Synthesis,Crystal Structure and Luminescent Properties of a Novel Zinc(II) Complex of N-Acetyl-L-glutamic Acid and Imidazole Ligands

1 INTRODUCTION As is well known, some transition metal ions play an important role in controlling the behavior of many biological macromolecules and produce pro- found effects on their biological actions, medicine and people’s health[1～3]. Zinc is an essential com- ponent of many proteins. In the active sites of zinc enzymes, zinc is bound to the nitrogen of imidazole groups and oxygen of carboxylate groups of amino acids[4～6]. Additional interest in these proteins lies in the fact th…     

Theoretical Investigation on the Second-order Nonlinear Optical Properties of Chiral Amino Acid Zinc（Ⅱ） Porphyrins

Static second-order nonlinear optical effects of amino acid zinc(Ⅱ) porphyrins 1, 2,3 and 4 were calculated by the TDHF/PM3 method based on the molecular structures optim.zed at the semiempirical PM3 quantum chemistry level, showing due to the cancellation of symmetric center, these amino acid zinc(H) porphyrins exhibit second order nonlinear optical response. The analysis of β components indicated that these amino acid zinc(Ⅱ) porphyrins are of multipolarizabilities, and they may be ascribed as the “mixture” of octupolar and dipoar molecules with ||βJ=3||/||βJ=1||≈5. It is found that there are no significant differences between the static β values of non-chiral and chiral amino acid zinc(Ⅱ) porphyrins. However, the βxyz component, which is quite important to quadratic macroscopic X^(2) susceptibility of chiral material, is increased significantly with the increase of side chain group of amino acids.     

REFINED CRYSTAL STRUCTURE OF INSULIN AT 1.8A RESOLUTION——CRYST

The structure of insulin has been refined by difference Fourier method at 1.8A resolu-tion. A set of computer programs calculating the mF_o-nF_c Fourier synthesis and the cor-rections of parameters automatically has been set up. With the programs to refine theinsulin model obtained from MIR map at 1.8A resolution for 11 cycles, the R index(R=∑|KF_o- F_c|/∑KF_o) is reduced to 0.210 from the initial value of 0.388. Duringthe refinement the stereochemistry of the insulin molecules is constantly detected andadjusted to fit the reasonable geometry. The refinement has greatly improved the structuremodel of insulin and provided more detailed structure information. On the basis of this thesystems of hydrogen bond in an insulin dimer are determined and the interaction betweenwater and insulin molecules in the crystal is investigated.     

纳米碳酸锌的制备和热分解动力学参数的测定

Nanosized zinc carbonate was prepared in the droplet of nano-reactor based on microemusion. The influences of the concentration of the surfactant and reactant on the diameter of nanoparticles were studied and the kinetic pa-rameters of thermal decomposition reaction were determined. It can be shown from experimental results， the di-ameter of the droplet in the microemulsion which have dissolved reactant zinc nitrate and sal volatile is between 4.9nm and 7.7nm， 6.2nm and 12.4nm， respectively. Nanosized zinc carbonate prepared by the method of mi-croemusion has shown good dispersion， narrow distribution and light agglomeration. The particle size of nanosized zinc carbonate is between 5nm and 40nm， and its kinetic parameters of thermal decomposition reaction-activation energy E and reaction order n are 110kJ·mol^-1 and 0.9， respectively.     

Photoinduced intramolecular electron transfer and charge separation in zinc phthalocyanine-viologen linked system

Photoinduced electron transfer and charge separation processes in zinc phthalocya-nine-viologen linked system have been studied and the distance effect of donor/acceptor on electron transfer reaction is discussed. It is indicated that the fluorescence from the zinc phthalocyanine moiety is appreciably quenched and the life-time of singlet excited state is reduced by the pendant viologen. Time-resolved transient absorption spectra measurements show that intramolecular quenching of the triplet state of zinc phthalocyanine by the attached viologen results in charge separation giving reduced viologen radical alive for a rather long period with hundred microsecond duration. The effect of the carbon chain length on the electron transfer rate constant and charge separation efficiency suggests that upon excitation, the zinc phthalocyanine and viologen groups tend to take closer conformation with the increase of the carbon chain examined. The rate constant for the intramolecular electron transfer ket with n = 3     

X-RAY STUDIES ON THE STRUCTURE OF DES-PENTAPEPTIDE INSULIN AT 2.4 RESOLUTION——THE DPI MOLECULE AND ITS STRUCTURAL RELATIONSHIP WITH INSULIN

The structure of the monomeric insulin analogue des(B26—B30) insulin is presented.; A detailed comparison with the 2Zn insulin structures shows that while there are some large changes in the structure, the basic secondary structural units maintain their integrity. The DPI structure is broadly similar to molecule Ⅰ in the 2Zn structure, and in this respect is like other crystal forms of insulin. In addition to changes on the surface of the structure there are some subtle but extensive changes in the heart of the molecule. The molecules are closely packed in the crystal with many and varied contacts, including a complex network of protein-cadmium interactions and a considerable number of water mediated contacts. The molecular surface has an unusually large number of hydrophobic groups which tend to cluster in a thick band running around the protein. The crystal structure is well ordered, indeed the clarity of some side chains and the definition of the water molecules is superior to that found in the mor     

新颖的双胰岛素取代钴(III)卟啉的制备和表征

A novel insulin-disubstituted Co(Ⅲ)protoporphyrin IX,CoPI,where I is insulin and CoP is Co(Ⅲ)protopor-phyrin IX,was prepared by covalently coupling the propionate groups on the porphyrin ring to the ε-amino groupsof B29-Lys on insulin via amide linkages.The FTIR spectra in the amide I region(1600—1700 cm~(-1))and circulardichroism study show that CoPI has a conformation similar to the insulin at pH 6.9,whereas it exhibits significantconformational changes in structure as compared with the insulin self at pH 8.2.The pH absorption titration indi-cates that the alkaline conditions(pH≥8.0)are required for the formation of complexes between the free CoP andthe insulin.The thermodynamic and kinetic data reveal that free CoP is bound to either the zinc-insulin or free insu-lin with a dissociation constant of(2.0±0.3)×10~(-5)or(2.2±0.3)×10~(-5)mol/L.     

Spectrophotometric Simultaneous Determination of Zinc(II), Manganese(II) and Iron(II) in Pharmaceutical Preparations Using OSC-PLS

The purpose of this paper is to develop a fast and sensitive spectrophotometric method for the simultaneous determination of zinc(II), manganese(II) and iron(II) in pharmaceutical preparations. The method presented in this work is based on the well-known reaction of these ions with 4-(pyridylazo)resorcinol (PAR)1. The application of quantitative chemometric methods, particularly PLS to multivariate chemical data is becoming more widespread owing to the availability of digitized spectroscop…     

Studies on the Renaturation with Simultaneous Purification of Recombinant Human Proinsulin with Unit of Simultaneous Renaturation and Purification of Protein in Semi－preparative Scale

The recombinant human proinsulin (rh-proinsulin) is the precursor of insulin, which is connected with C- peptide between the carboxyl-terminal of chain A and NH2-terminal of chain B of insulin. In the presences of trypsin and carboxypeptides B (CPB), the C-peptide can be cleaved from the special two peptides of rh-proinsulin and the recombinant human insulin (rh-insulin) can be, thus, obtained1,2. The rh-proinsulin expressed in E. coli exists as inclusion body, hardly dissolves in water,…     

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.     

Properties of lysine-containing zinc amino acid mixed complexes and evaluation of their zinc supplying ability

Zinc deficiency is one of the serious problems of trace element nutrition in the world, which causes a series of pathologic effects. Based on the principles of bioinorganic chemistry, the ternary complexes of Zn-lysiue-histidine were studied as a substitution of zinc sulfate for zinc supplementation. It has also been proved by animal trail.     

Investigation of the Crystallization Kinetics of Zn(Met)(AcO)_2·H_2O in Mixed Solution of Water and Acetone by Microcalorimetry

Introduction The complexes of zinc salts with -amino acid as additive have a wide application in medicine, foodstuff and cosmetics.1-3 The synthesis methods of the com-plexes of zinc salts with -amino acid have been re-viewed.4 The solubility of Zn(AcO)2-Met-H2O system at 298.15 K has ever been investigated by the semi-micro-phase equilibrium method.5 The phase diagram is a simple one, in which the solid complex of Zn(AcO)2 and Met can not be obtained at 298.15 K. Zn(Met)2+ in solution w…     

STUDIES ON THE CRYSTAL STRUCTURE OF Al-(L-TRYPTOPHAN) INSULIN AT 2.1RESOLUTION

In order to study the biological effect of alterations to the N-terminus of the insulin A-chain, we have determined the crystal structure of Al-(L-Trp) insulin and discovered that it belongs to the trigohal system with space group R3. The parameters oof the unit cell are a=b=80.3A, c=37.5A. The model was adjusted and refined by using a stereochemically-restrained least squares program, assisted by manual revision of the model based on the difference Fourier map, to a final R-factor of 0.195. The main and side chains of both Al-(L-Trp) residues in the asymmetric unit are well ordered. It was found that the Al-Trp residue of molecule I occupied two distinct positions. We have proposed from the results of the three-dimensional structure that the 4-zinc insulin hexameric form is a stored state of insulin molecules in a conformation of low activity. The structural details of the insulin molecule and its structure and function relationship have also been discussed.     

Effect of a Hybrid Zinc Stearate-Silver System on the Properties of Polylactide and Its Abiotic and the Biotic Degradation and Antimicrobial Activity Thereof

This work investigates the degradation and properties of a thermoplastically prepared composite comprising a polylactide/hybrid zinc stearate-silver system.The influence of the zinc stearate-silver system on the properties of the composite is investigated by electron microscopy,differential scanning calorimetry and tensile tests.Furthermore,the antimicrobial activities of the systems are examined.The degradation behaviour of the composites is studied in both abiotic and biotic(composting) environments at an elevated temperature of 58 °C.The results reveal good dispersion of the additive in the PLA matrix,a stabilizing effect exerted by the same on the polylactide matrix during processing,and slight reduction in glass transition temperature.The zinc stearate-silver component also reduces brittleness and extends elongation of the composite.Abiotic hydrolysis is not significantly affected,which is in contrast with pure PLA,although mineralization during the early stage of biodegradation increases noticeably.The composite exhibits antimicrobial activity,even at the lowest dosage of the zinc stearate/silver component(1 wt%).Moreover,Ag and Zn contents were found to be present in the composite during abiotic hydrolysis,which was demonstrated by minimal diffusion of Ag ions from the matrix and very extensive washing of compounds that contained Zn.