Metal Ions Zn Research Articles

Natural Minerals Coated by Biopolymer Chitosan: Synthesis, Physicochemical, and Adsorption Properties.

Natural minerals are widely used in treatment technologies as mineral fertilizer, food additive in animal husbandry, and cosmetics because they combine valuable ion-exchanging and adsorption properties together with unique physicochemical and medical properties. Saponite (saponite clay) of the Ukrainian Podillya refers to the class of bentonites, a subclass of layered magnesium silicate montmorillonite. Clinoptilolits are aluminosilicates with carcase structure. In our work, we have coated biopolymer chitosan on the surfaces of natural minerals of Ukrainian origin — Podilsky saponite and Sokyrnitsky clinoptilolite. Chitosan mineral composites have been obtained by crosslinking of adsorbed biopolymer on saponite and clinoptilolite surface with glutaraldehyde. The obtained composites have been characterized by the physicochemical methods such as thermogravimetric/differential thermal analyses (DTA, DTG, TG), differential scanning calorimetry, mass analysis, nitrogen adsorption/desorption isotherms, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy to determine possible interactions between the silica and chitosan molecule. The adsorption of microquantities of cations Cu(II), Zn(II), Fe(III), Cd(II), and Pb(II) by the obtained composites and the initial natural minerals has been studied from aqueous solutions. The sorption capacities and kinetic adsorption characteristics of the adsorbents were estimated. It was found that the obtained results have shown that the ability of chitosan to coordinate heavy metal ions Zn(II), Cu(II), Cd(II), and Fe(III) is less or equal to the ability to retain ions of these metals in the pores of minerals without forming chemical bonds.

Light-Stimulated Generation of Free Radicals by Quinones-Chelators

Abstract The role of metal ions in the mechanism of light-stimulated redox activity of potential anticancer agent 2-phenyl-4-(butylamino)naphtha[2,3-h]quinoline-7,12-dione (Qc) has been studied by CIDNP (chemically induced dynamic nuclear polarization) and EPR methods. The photo-induced oxidation of NADH and its synthetic analog – substituted dihydropyridine (DHP) – by quinone Qc was used as a model. The Qc capability of producing chelating complexes with divalent metal ions of Fe, Zn and Ca was studied quantitatively by optical absorption spectroscopy. A significant decrease of electrochemical reduction potential of Qc (ΔE=0.4−0.6 eV for ACN and ACN/PBS solutions) in chelating complexes and in protonated form of Qc was observed. A pronounced increase in efficiency of DHP oxidation in chelating complexes with Zn2+ and Ca2+ ions compared with free Qc was demonstrated. The yields of free radicals, including reactive oxygen species (ROS) and reaction products, were a few times higher than those in the absence of metal ions. Application of such chelating compounds to enhance ROS generation looks very promising for anti-cancer therapy, including the photodynamic therapy.

The Remarkable Character of Porphobilinogen Synthase.

Porphobilinogen synthase (PBGS), also known as 5-aminolevulinate dehydratase, is an essential enzyme in the biosynthesis of all tetrapyrroles, which function in respiration, photosynthesis, and methanogenesis. Throughout evolution, PBGS adapted to a diversity of cellular niches and evolved to use an unusual variety of metal ions both for catalytic function and to control protein multimerization. With regard to the active site, some PBGSs require Zn2+; a subset of those, including human PBGS, contain a constellation of cysteine residues that acts as a sink for the environmental toxin Pb2+. PBGSs that do not require the soft metal ion Zn2+ at the active site instead are suspected of using the hard metal Mg2+. The most unexpected property of the PBGS family of enzymes is a dissociative allosteric mechanism that utilizes an equilibrium of architecturally and functionally distinct protein assemblies. The high-activity assembly is an octamer in which intersubunit interactions modulate active-site lid motion. This octamer can dissociate to dimer, the dimer can undergo a hinge twist, and the twisted dimer can assemble to a low-activity hexamer. The hexamer does not have the intersubunit interactions required to stabilize a closed conformation of the active site lid. PBGS active site chemistry benefits from a closed lid because porphobilinogen biosynthesis includes Schiff base formation, which requires deprotonated lysine amino groups. N-terminal and C-terminal sequence extensions dictate whether a specific species of PBGS can sample the hexameric assembly. The bulk of species (nearly all except animals and yeasts) use Mg2+ as an allosteric activator. Mg2+ functions allosterically by binding to an intersubunit interface that is present in the octamer but absent in the hexamer. This conformational selection allosteric mechanism is purported to be essential to avoid the untimely accumulation of phototoxic chlorophyll precursors in plants. For those PBGSs that do not use the allosteric Mg2+, there is a spatially equivalent arginine-derived guanidium group. Deprotonation of this residue promotes formation of the hexamer and accounts for the basic arm of the bell-shaped pH vs activity profile of human PBGS. A human inborn error of metabolism known as ALAD porphyria is attributed to PBGS variants that favor the hexameric assembly. The existence of one such variant, F12L, which dramatically stabilizes the human PBGS hexamer, allowed crystal structure determination for the hexamer. Without this crystal structure and octameric PBGS structures containing the allosteric Mg2+, it would have been difficult to decipher the structural basis for PBGS allostery. The requirement for multimer dissociation as an intermediate step in PBGS allostery was established by monitoring subunit disproportionation during the turnover-dependent transition of heteromeric PBGS (comprised of human wild type and F12L) from hexamer to octamer. One outcome of these studies was the definition of the dissociative morpheein model of protein allostery. The phylogenetically variable time scales for PBGS multimer interconversion result in atypical kinetic and biophysical behaviors. These behaviors can serve to identify other proteins that use the morpheein model of protein allostery.

Support effect of zinc tin oxide on gold catalyst for CO oxidation reaction

Nanostructured gold catalyst supported on metal oxide is highly active for the CO oxidation reaction. In this work, a new type of oxide support, zinc tin oxide, has been used to deposit 0.7 wt% Au via a deposition-precipitation method. The textural properties of Zn2SnO4 support have been tuned by varying the molar ratio between base (N2H4·H2O) and metal ion (Zn2+) to be 4/1, 8/1 and 16/1. The catalytic tests for CO oxidation reaction revealed that the reactivity on Au-Zn2SnO4 with N2H4·H2O/Zn2+ = 8/1 was the highest, while the reactivity on Au-Zn2SnO4 with N2H4·H2O/Zn2+ = 16/1 was almost identical to that of the pure support. Both fresh and used catalysts have been characterized by multiple techniques including nitrogen adsorption-desorption, X-ray diffraction, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray adsorption fine structure, and temperature-programmed reduction by hydrogen. These demonstrated that the textural properties, especially pore volume and pore size distribution, of Zn2SnO4 play crucial roles in the averaged size of gold nanoparticles, and thus determine the catalytic activity of Au-Zn2SnO4 for CO oxidation.

Novel Bioactive Co(II), Cu(II), Ni(II) and Zn(II) Complexes with Schiff Base Ligand Derived from Histidine and 1,3-Indandione: Synthesis, Structural Elucidation, Biological Investigation and Docking Analysis.

Novel bioactive complexes of Co(II), Cu(II), Ni(II) and Zn(II) metal ions with Schiff base ligand derived from histidine and 1,3-indandione were synthesized and thoroughly characterized by various analytical and spectral techniques. The biological investigations were carried out to examine the efficiency of the binding interaction of all the complexes with calf thymus DNA (CT-DNA). The binding properties were studied and evaluated quantitatively by Kb and Ksq values using UV-visible, fluorescence spectroscopy and voltammetric techniques. The experimental results revealed that the mode of binding of all the complexes with CT-DNA is via intercalation. It is further verified by viscosity measurements and thermal denaturation experiments. From the results of the cleavage study with pUC19 DNA it is inferred that all the complexes possess excellent cleaving ability. The present investigation proved that the binding interaction of all the complexes are significantly strong and the order of binding strength of the complexes is [Ni(L)2] (Kb=3.11×106M-1)>[Co(L)2] (Kb=2.89×106M-1)>[Cu(L)2] (Kb=2.64×106M-1)>[Zn(L)2] (Kb=2.41×105M-1). The complexes were also screened for antibacterial and anticandidal activity. The in vitro cytotoxicity of the ligand and complexes on the NIH/3T3 mouse fibroblast cell lines were examined using CellTiter-Blue® (CTB) Cell viability assay, which unveiled that all the complexes exhibit more potent activities against NIH/3T3 cells. Among all the complexes [Zn(L)2] complex showed the maximum efficiency.

New designed naphthalimide-phthalocyanine pentads: Synthesis, photophysical and photochemical properties in DMSO and room temperature ionic liquids

Abstract The synthesis and photoproperties of two novel multichromophoric compounds were unveiled. Their molecular design consisted of a phthalocyanine core bearing either Zn(II) or Ga(III) metal ions in the cavity and four naphthalimide chromophores in the periphery. Ground state absorption, fluorescence emission, fluorescence lifetime, fluorescence quantum yield and singlet oxygen generation properties of Zn(II) ( 1 ) and Ga(III) ( 2 ) pentads were investigated in DMSO and room temperature ionic liquids (RTILs) as well. 1 was aggregated in RTILs, however 2 exhibited monomeric and photostable behavior in 1-ethyl-3-methylimidazolium hexafluorophosphate. The singlet oxygen quantum yields were determined as 0.75 for 1 and 0.72 for 2 in DMSO, which were remarkably high compared to unsubstituted Zn(II) and Ga(III) phthalocyanines (0.67 and 0.41 in DMSO, respectively). In addition, their photostability were excellent; even they were more photostable than reference molecules. The observed attractive photophysical and photochemical properties of these novel pentads qualify them as promising photosensitizers for photodynamic therapy.

RETENTION OF ZN, PB, CU AND CD METAL IONS ONTO SEWAGE IRRIGATED SOIL

The sorption isotherm and kinetic of Cu2+, Pb2+, Zn2+ , and Cd2+ ions onto sewage irrigated soil (El-Gebal El Aasfar-Qalubia) was examined as a function of the retention time and initial ion concentration using batch equilibrium sorption experiments. Results show that the Cu, Pb, Zn and Cd metal ions onto the soil is relatively rapid and sorption reaches equilibrium at about 240 minutes. Kinetics of the sorption process on the soil is well characterized by the pseudo-second order reaction rate. Langmuir, Freundlich and D–R isotherm models are fitted for the sorption of Cu2+, Pb2, Zn2+, and Cd2+ ions onto the soil. The constants of all models were calculated for each metal ion and compared. It indicated clear differences between the sorption characteristics of Cu2+, Pb2+, Zn2+, and Cd2+ ions on the sewage irrigated soil.

Comparison of sorption and desorption studies of heavy metal ions from biochar and commercial active carbon

In the first stage on the effectiveness of various operating factors such as: adsorbent dose, contact time, solution pH, initial concentration and temperature on the sorption of heavy metal ions of Cu(II), Zn(II), Cd(II), Co(II) and Pb(II) were carried out using the commercial active carbon Purolite AC 20 and biochar. It was found that the sorption capacity increases with the increasing phase contact time and concentration of the initial solution. It was found that biochar removes more efficiently heavy metal ions from aqueous solutions than the activated carbon. Sorption kinetic data provide a complex mechanism of sorption and better fit of the pseudo second order model than the pseudo first order and the intraparticle diffusion ones. In the second stage the desorption of the above mentioned heavy metal ions from the biochar and commercial activated carbon was conducted. It was proved that biochar has excellent properties and can be used as a sorbent of multi-use 0.1M HNO3 was the best eluent for desorption of heavy metal ions in the sorption/desorption studies in the third stage. In order to characterize the mechanism of sorption/desorption for both biochar and activated carbon, the Brunauer Emmett Teller surface area was determined and point of zero charge was measured. Moreover, the elemental analysis and the Fourier transform infrared spectroscopy were applied. The thermogravimetric and derivative thermogravimetric analyses were conducted.

A Biphenol-Based Chemosensor for Zn(II) and Cd(II) Metal Ions: Synthesis, Potentiometric Studies, and Crystal Structures.

We synthesized and characterized the ligand N,N'-bis[(2,2'-dihydroxybiphen-3-yl)methyl]-N,N'-dimethylethylenediamine (L), which contains two biphenol moieties linked as side arms to an N,N'-dimethylethylenediamine scaffold. The ligand is highly soluble in a 50/50 (v/v) water/ethanol mixture and, in its deprotonated form H-2L(2-), is able to coordinate transition-metal ions such as Ni(II), Zn(II), Cu(II), Cd(II), and Pd(II). The crystal structures of [Ni(H-2L)·2n-BuOH], [Ni(H-2L)·2MeOH], [Cd(H-2L)·2DMF], [Cu(H-2L)(DMF)], and [Pd(H-2L)(DMF)] were also determined and described. Potentiometric titrations were carried out in a mixed solvent with Zn(II), Cu(II), and Ni(II) metal ions to determine the acid-base and stability constants. L was highly fluorescent in the visible range (400 nm). Moreover, its emission intensity increased upon the addition of Zn(II) or Cd(II) ions in an ethanol/water solution and behaved as a chemosensor for the presence of these ions in the solution.

Synthesis and characterization Studies of Metal Complexes with Schiff base derived from 4-[5-(2-hydoxy-phenyl)-[1,3,4-oxadiazol-2-ylimino methyl]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one

New metal complexes of the ligand 4-[5-(2-hydoxy-phenyl)-[1,3,4- oxadiazol -2-ylimino methyl]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (L) with the metal ions Co(II), Ni(II), Cu(II) and Zn(II) were prepared in alcoholic medium. The Schiff base was synthesized through condensate of [4-antipyrincarboxaldehyde] with[2-amino-5-(2-hydroxy-phenyl-1,3,4- oxadiazol] in alcoholic medium . Two tetradentate Schiff base ligand were used for complexation upon two metal ions of Co2+, Ni2+, Cu2+ and Zn2+ as dineucler formula M2L2.4H2O. The metal complexes were characterized by FTIR Spectroscopy, electronic Spectroscopy, elemental analysis, magnetic susceptidbility measurements, and also the ligand was characterized by 1H-NMR spectra, and mass spectra. The Structures of complexes were proposed from the measurements.

Fe(2+) binding on amyloid β-peptide promotes aggregation.

The metal ions Zn(2+) , Cu(2+) , and Fe(2+) play a significant role in the aggregation mechanism of Aβ peptides. However, the nature of binding between metal and peptide has remained elusive; the detailed information on this from the experimental study is very difficult. Density functional theory (dft) (M06-2X/6-311++G (2df,2pd) +LANL2DZ) has employed to determine the force field resulting due to metal and histidine interaction. We performed 200 ns molecular dynamics (MD) simulation on Aβ1-42 -Zn(2+) , Aβ1-42 -Cu(2+) , and Aβ1-42 -Fe(2+) systems in explicit water with different combination of coordinating residues including the three Histidine residues in the N-terminal. The present investigation, the Aβ1-42 -Zn(2+) system possess three turn conformations separated by coil structure. Zn(2+) binding caused the loss of the helical structure of N-terminal residues which transformed into the S-shaped conformation. Zn(2+) has reduced the coil and increases the turn content of the peptide compared with experimental study. On the other hand, the Cu(2+) binds with peptide, β sheet formation is observed at the N-terminal residues of the peptide. Fe(2+) binding is to promote the formation of Glu22-Lys28 salt-bridge which stabilized the turn conformation in the Phe19-Gly25 residues, subsequently β sheets were observed at His13-Lys18 and Gly29-Gly37 residues. The turn conformation facilitates the β sheets are arranged in parallel by enhancing the hydrophobic contact between Gly25 and Met35, Lys16 and Met35, Leu17 and Leu34, Val18 and Leu34 residues. The Fe(2+) binding reduced the helix structure and increases the β sheet content in the peptide, which suggested, Fe(2+) promotes the oligomerization by enhancing the peptide-peptide interaction. Proteins 2016; 84:1257-1274. © 2016 Wiley Periodicals, Inc.

Cloning, Expression and 3D Structure Prediction of Chitinase from Chitinolyticbacter meiyuanensis SYBC-H1

Two CHI genes from Chitinolyticbacter meiyuanensis SYBC-H1 encoding chitinases were identified and their protein 3D structures were predicted. According to the amino acid sequence alignment, CHI1 gene encoding 166 aa had a structural domain similar to the GH18 type II chitinase, and CHI2 gene encoding 383 aa had the same catalytic domain as the glycoside hydrolase family 19 chitinase. In this study, CHI2 chitinase were expressed in Escherichia coli BL21 cells, and this protein was purified by ammonium sulfate precipitation, DEAE-cellulose, and Sephadex G-100 chromatography. Optimal activity of CHI2 chitinase occurred at a temperature of 40 °C and a pH of 6.5. The presence of metal ions Fe3+, Fe2+, and Zn2+ inhibited CHI2 chitinase activity, while Na+ and K+ promoted its activity. Furthermore, the presence of EGTA, EDTA, and β-mercaptoethanol significantly increased the stability of CHI2 chitinase. The CHI2 chitinase was active with p-NP-GlcNAc, with the Km and Vm values of 23.0 µmol/L and 9.1 mM/min at a temperature of 37 °C, respectively. Additionally, the CHI2 chitinase was characterized as an N-acetyl glucosaminidase based on the hydrolysate from chitin. Overall, our results demonstrated CHI2 chitinase with remarkable biochemical properties is suitable for bioconversion of chitin waste.

Interactions of Divalent and Trivalent Metal Counterions with Anionic Sulfonate Gemini Surfactant and Induced Aggregate Transitions in Aqueous Solution.

Interactions of multivalent metal counterions with anionic sulfonate gemini surfactant 1,3-bis(N-dodecyl-N-propanesulfonate sodium)-propane (C12C3C12(SO3)2) and the induced aggregate transitions in aqueous solution have been studied. Divalent metal ions Ca(2+), Mg(2+), Cu(2+), Zn(2+), Mn(2+), Co(2+), and Ni(2+) and trivalent metal ions Al(3+), Fe(3+), and Cr(3+) were chosen. The results indicate that the critical micelle concentration (CMC) of C12C3C12(SO3)2 is greatly reduced by the ions, and the aggregate morphologies of C12C3C12(SO3)2 are adjusted by changing the nature and molar ratio of the metal ions. These metal ions can be classified into four groups because the ions in each group have very similar interaction mechanisms with C12C3C12(SO3)2: (I) Cu(2+) and Zn(2+); (II) Ca(2+), Mn(2+) and Mg(2+); (III) Ni(2+) and Co(2+); and (IV) Cr(3+), Al(3+) and Fe(3+). Cu(2+), Mg(2+), Ni(2+), and Al(3+) then were selected as representatives for each group to further study their interaction with C12C3C12(SO3)2. C12C3C12(SO3)2 interacts with the multivalent metal ions by electrostatic interaction and coordination interaction. C12C3C12(SO3)2 forms prolate micelles and plate-like micelles with Cu(2+), vesicles and wormlike micelles with Al(3+) or Ni(2+), and viscous three-dimensional network structure with Mg(2+). Moreover, precipitation does not take place in aqueous solution even at a high ion/surfactant ratio. The related mechanisms have been discussed. The present work provides guidance on how to apply the anionic surfactant into the solutions containing the multivalent metal ions, and those aggregates may have potential usage in separating heavy metal ions from aqueous solutions.

Quantum chemical insights into Alzheimer's disease: Curcumin's chelation with Cu(II), Zn(II), and Pd(II) as a mechanism for its prevention

We provide quantum chemical insights into curcumin's prevention of Alzheimer' disease through curcumin's scavenging of neurotoxic Cu(II), Zn(II), and Pd(II) transition metal ions that catalyze polymerization of amyloid-β and promote misfolding of amyloid into neurotoxic conformations. We have employed high level quantum chemical computations to study the chelate complexes of curcumin with Cu(II), Zn(II), and Pd(II). Quantum chemically derived structures, IR spectra, and UV-visible spectra of these complexes corroborate with the observed spectra, confirming that the primary site of chelation is the β-diketone bridge through the loss of an enolic proton of curcumin. We have also obtained the various structural parameters such as the Mulliken charges on various centers, highest occupied, lowest unoccupied molecular orbitals—all of which confirm that curcumin forms chelate complexes and thus acts as a scavenger of these neurotoxic metal ions preventing Alzheimer's disease. We find that the open-d-shell Cu(II) and Pd(II) form nearly square planar complexes while the closed-d-shell Zn(II) forms a tetrahedral complex with curcumin. © 2016 Wiley Periodicals, Inc.

The influence of ph and waterborne metals on egg fertilization of the blue mussel (Mytilus edulis), the oyster (Crassostrea gigas) and the sea urchin (Paracentrotus lividus).

This study evaluated the combined effect of pH and metals on the egg fertilization process of two estuarine species, the blue mussel (Mytilus edulis), the oyster (Crassostrea gigas) and a marine species, the sea urchin (Paracentrotus lividus). The success of egg fertilization was examined after exposure of gametes to sediment extracts of various degrees of contamination at pH 6.0, 6.5, 7.0, 7.5 and 8.0. At the pH levels from 6.5 to 8.0, the egg fertilization of the different species demonstrated different sensitivity to metal and/or acidic exposure. In all species, the results revealed that egg fertilization was almost completely inhibited at pH 6.0. The egg fertilization of the blue mussel M. edulis was the least sensitive to the exposure while that of the sea urchin P. lividus demonstrated a concentration-dependent response to the pH levels from 6.5 to 8.0. The results of this study revealed that acidity increased the concentration of several metal ions (Cr, Ni, Cu, Zn, Cd, and Pb) but reduced its availability to the organisms, probably related to the reactivity of the ions with most non-metals or to the competition among metals and other waterborne constituents.

Investigation of Zn2+ and Cd2+ Adsorption Performance by Different Weathering Basalts

Geological barriers play an important role in preventing pollution of groundwater. Basalts are common geological media; however, there have not been any studies that report the effect of basalt type on the metal ion adsorption performance. In this study, we explored the metal ion (Zn2+ and Cd2+) adsorption ability of two kinds of weathering basalts, the origin weathering basalt (WB) and the eluvial deposit (ED), both of which were derived from same basaltic formation. Characteristics of the sediments were examined by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Barrett-Joyner-Halenda (BJH) measurement, and the rapid potentiometric titration (RPT) method. Batch experiments were performed to evaluate the Zn2+ and Cd2+ adsorption performance of WB and ED and how adsorption was affected by contact time, initial metal ion concentration, pH, and ionic strength. Despite WB and ED having similar chemical compositions, WB exhibited better adsorption than ED likely due to the fact that WB was rougher and had more small-sized spherical structures and stronger electrostatic forces. The adsorption process fits the Freundlich isotherm model well. The adsorption efficiency decreased with a decrease of pH (from 4 to 2) and with increasing ionic strength. These results suggest that a geological barrier composed of WB media might be able to effectively sequester metallic contaminants to prevent them from reaching groundwater.

Investigations of the divalent metal ions Zn2+, Co2+, Ni2+ doped ultra-wide temperature stable BBNN system

Multi-component BaTiO3–Bi0.5Na0.5TiO3–Nb2O5 (BBNN) system doped with divalent metal ions (Zn2+, Co2+, Ni2+) was prepared by the conventional solid–state method.The X-ray diffraction patterns revealed all samples exhibited perovskite (P4mm) single phase. The dielectric properties and micro-mechanisms were discussed and validated. Novel theories, based on the characteristics of the different kinds of dielectric polarization, are proposed to explain the dielectric anomalies in the dielectric system. The relationships between microstructure and the dielectric properties were investigated systematically for the first time. The samples doped with 15mol% Zn2+/Co2+presented good dielectric properties of an ultra-broad temperature stable range (from −50 and >300), high dielectric constant (ε~1925 for Zn2+/ ε~1341 for Co2+) and low dielectric loss (tanδ<0.02) were obtained. These features made the ceramics system have high practical values for miniaturization and harsh environments applications.

Crystallization of Enantiomerically Pure Proteins from Quasi-Racemic Mixtures: Structure Determination by X-Ray Diffraction of Isotope-Labeled Ester Insulin and Human Insulin.

As a part of a program aimed towards the study of the dynamics of human insulin-protein dimer formation using two-dimensional infrared spectroscopy, we used total chemical synthesis to prepare stable isotope labeled [(1-(13) C=(18) O)Phe(B24) )] human insulin, via [(1-(13) C=(18) O)Phe(B24) )] ester insulin as a key intermediate product that facilitates folding of the synthetic protein molecule (see preceding article). Here, we describe the crystal structure of the synthetic isotope-labeled ester insulin intermediate and the product synthetic human insulin. Additionally, we present our observations on hexamer formation with these two proteins in the absence of phenol derivatives and/or Zn metal ions. We also describe and discuss the fractional crystallization of quasi-racemic protein mixtures containing each of these two synthetic proteins.

Synthesis and characterization of terepthalaldehyde–thiocarbohydrazide polymer doped with Cu(II) and Zn(II) Metal ions for solar cell applications

A convenient synthesis method and the properties of a polynuclear Cu(II) and Zn(II) terapthaldehyde-thiocarbohydrazide polymeric metal complexes has been discussed in this work. A product of terepthalaldehyde–thiocarbohydrazide as condensed polymer (TThP) was synthesized by polycondensation reaction of terepthalaldehyde with thiocarbohydrazide. Two polymeric metal complexes of the condensed product [(C15H12N4S)2CuCl2]n (TThP–CuCl2) and [(C15H12N4S)2ZnCl2]n (TThP–ZnCl2) were prepared with CuCl2 and ZnCl2 metal salts separately and compared for property evaluation. Structural analysis was carried out by elemental analysis, SEM and FTIR, thermal analysis with the help of TGA and optical properties was carried with UV–visible and fluorescence techniques. TThP shows fluorescence at 424nm at an excitation wavelength of 435nm and its polymer complexes TThP–CuCl2 and TThP–ZnCl2 show fluorescence at the same wavelength with higher intensity. The band gap of the synthesized polymer metal complexes decrease from 3.3 to 2.6eV as metals varied from M=Cu(II)–Zn(II). This confirms the successful inclusion of metals in polymer back bone.

Effects of dopamine-containing curing agents on the water resistance of epoxy adhesives

Epoxy adhesive as an engineering material has more and more applications in industry. But to date, water resistance of the adhesive is still a very difficult problem to be solved. By mimicking mussel adhesive proteins, dopamine (DA) was applied as one of the two curing agents of epoxy adhesive to improve the water resistance of the adhesive, and the other was phenethylamine (PEA). The effects of the contents of DA on both adhesion property and water absorption of epoxy/PEA/DA adhesives were investigated in detail. The results of lap shear test (LST) showed that the adhesion strength of the epoxy adhesives after the introduction of proper amount of DA was still up to 7 MPa even after the sample was immersed in water for over 230 days. And then the effects of metal ions Zn(II) and Fe(III) on the adhesion properties of the epoxy adhesives were also further studied. It was found that the adhesion strength of the adhesives, when the content of DA was no more than 5 wt%, can be further increased through the complexation of a small quantity of ferric ions with DA. The coordination mechanism of catechol with Fe(III) ions in the system has been investigated by both UV/Vis spectra and XRD curves. The results testified that more bis-catecholate complexes form at high DA: Fe ratios and thus the adhesives have higher cohesion strength for having more regular structures after curing. In a word, the introductions of proper amount of DA and metal ion endow the epoxy adhesive better water resistance and excellent adhesion properties.