HIV-1 reverse transcriptase (RT) RNase H (HIV-RH) is a key target of anti-AIDS drugs. Metal-chelating compounds are an important class of chemicals in pharmacological drug discovery, especially in relation to HIV-RT and the highly-related HIV-integrase. The correlation between the metal-chelating properties and enzyme activities of the metal chelators is always of high scientific interest, as an understanding of this may accelerate the rational optimization of this class of inhibitors. Our NMR data show that Mg 2+ and Ca 2+ bind specifically to the active site of the RNase H domain and two Mg 2+ ions sequentially bind one molecule of RNase H. We also demonstrate here, using saturated and unsaturated tricyclic N-hydroxypyridones designed to block the active site, that the primary binding sites and affinities of divalent metal ions are correlated with the structures of the chelating motifs. Chemical shift perturbation studies of protein/metal-ion/compound ternary complexes also indicate that divalent metal ions play important roles for the specific interaction of the compounds with the RNase H active site.
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This article presents the method of extraction-preconcentration of Lead, Cadmium, and Nickel ions from food samples using the Ghezeljeh montmorillonite nanoclay (Geleh-Sar-Shoor) as a new native adsorbent in batch single component systems. The extraction- preconcentration of heavy metals were carried out by applying the solid phase extraction (SPE) method followed by atomic absorption spectroscopy (AAS), and inductively coupled with plasma atomic emission spectroscopy (ICP-AES). The Ghezeljeh nanoclay was characterized by using Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy-energy dispersive spectrometer operating (SEM-EDS), X-ray diffractometry (XRD), X-ray fluorescence (XRF), Cation Exchange Capacity (CEC) measurements, BET specific surface area and Zeta potential. According to BET theory, the specific surface areas of the Ghezeljeh nanoclay was calculated to be 19.8 m 2 g -1 whereas the cation exchange capacity was measured to be 150 meq/100 g. The results of XRD, XRF, FT-IR, Zeta potential and BET surface area of the nanoclay confirmed that montmorillonite was the dominant mineral phase. Based on SEM images of this clay, it can be seen that the distance between the plates is nm level. For all three ions, the detection and quantification limits, dynamic linear range, preconcentration factor, and adsorption capacity were obtained. The effect of various interfering ions was studied. The experimental method was successfully applied for the extraction of heavy metals in different tea and rice samples.
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The current investigation deals with utilizing Treated Goat Hoof (TGH), a no cost material derived from butcher shop for the removal of Pb(II) and Cd(II) ions from aqueous media. FTIR / SEM analyses are carried out for the functional groups identification and describe the surface morphology of the chosen material respectively. Batch studies are experimented under varied operating factors viz., particle size, dosage, initial concentration, contact time and pH of the medium to assess the sorptive nature of the chosen material. Verification of the experimental data reveal the optimized conditions for the uptake of Pb(II) and Cd(II) by TGH. Langmuir model registered the best linearity amongst the isothermal plots derived for Langmuir, Freundlich and Tempkin models. Experimental results of both the systems: Pb(II) – TGH and Cd(II)- TGH are subjected to Statistical tool analyses using SPSS 20 software for significance and correlation assessment.
Chandigarh. Electronic Spectra (in DMSO) were recorded on a Hitachi 330 spectrophotometer (850 -200 mm) at room temperature. The EI mass spectra (at room temperature) were recorded on TOF ME ES + mass spectrometer. The metal content in the complexes was determined by literature methods . Molar conductivities were measured on a digital conductivity meter (HPG system, G-3001). Melting points were determined using capillaries in an electrical melting point apparatus.
Single crystals of potassium acid phthalate (KAP), Nickel Doped KAP (NiKAP) and Cobalt doped KAP(Co KAP) have been grown from aqueous solutions by solvent evaporation method. The effect of these metal irons on surface morphology, structure, optical and mechanical properties have been studied. Single crystal XRD studies of these crystals confirm that both the added impurities have modified the structure of the KAP crystals in a similar manner. The presence of dopants in the crystal lattice have been further confirmed by FTIR analysis. The stoichiometric composition of both the doped crystals have been studied using EDAX analysis. Optical absorbance was carried out for all the crystals. The absorbance in the visible region observed in both the doped crystals was assigned to their d-d transitions. Micro hardness of the pure and doped crystals were found using Vickers’s Hardness Technique.
Water pollution due to noxious heavy metals such as Hg(II), Cr(VI), Cd(II) and Pb(II) ions etc., has been tremendously focused gaining attention towards social benefit. Increasing concentrations of these metals into the ecosystem constitute a severe health hazard due to their toxicity, accumulation and bio-magnification throughout the food chain. Lead contamination of drinking water is a great threat through varied sources viz., lead pipes, plating units etc. Pistachio vera shell (PVS) is a hard layer that surrounds the delicious kernel of the nut. The current work evaluates the feasibility of powdered Pistachio vera shell (PVSP) - a biowaste for sequestering Pb (II) ions is treated with 0.1N HCl and 0.1N NaOH to enhance its sorption efficacy (TPVSP). SEM, FTIR and microscopic analyses are recorded for characterising the chosen sorbent. Batch experimental studies are performed to assess the equilibration between the sorbate and the sorbent. The competence of the sorbent material is experimentally verified through various operating factors viz., particle size and dosage of TPVSP, agitation time interval between TPVSP and Pb(II) ions, initial concentrations of Pb(II) ions, pH of the adsorption medium, effects of cations, anions, co-ions and influence of temperatures on Pb(II) – TPVSP system. The residual concentrations of Pb (II) ions from aqueous solutions are analysed using Atomic Absorption Spectrophotometer (Shimadzu-AA-6200). Langmuir and Freundlich models are applied to describe the adsorption capacity. Column studies are conducted to ensure the quantitative estimation of TPVSP in trapping 99% of sorbate species at a dose of 40 mg the flow rate being, 100 ml/10 min. assuring the bulkiness of the material.
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In the present work we have synthesized new ligand of Schiff base and its complexes, characterized by different analytical techniques and found that the complexes are inconsistence with our expected structures and revealed square planar geometry around metal ion, where the ligand act as tetradentate chelate with N 2 O 2
Our results showing that the metal ion inhibition is competitive with aeetyl-CoA (Pig* 6) seem to rule out the possibility that the metal ions bind to the enzyme and thus cause the inhibition* A fuller answer to this question might be obtained by investigating whether a complex forms between the metal ions and the enzyme using a variety of available techniques. Some of these techniques are: ultra violet spectroscopy, optical rotatory dispersion spectros copy, ultracentrifugation (47) > nuclear magnetic resonance spectroscopy (42), electron spin resonance spectroscopy (57), equilibrium dialysis (58,110) and atomic absorption. Kine tic studies cannot give us a full picture of enzyme mechani sms. In order to complement these, it would be necessary to study the binding of the metal ions with the enzyme as well as with the substrates and the binding between the
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Quinoid entities, in which quinone and hydroquinone groups equilibrate via a semiquinone radical interme- diate, are a common structural feature in humic materials. The electron paramagnetic resonance (EPR) sig- nals of these radicals are significantly enhanced in the presence of diamagnetic divalent metal ions such as Mg 2+ , while monovalent ions do not show the effect. The addition of trivalent ions leads to rapid precipita- tion, leaving little room for observation. It was noted that the metal ions producing EPR signal enhancement were also underwent effective bridging interactions with humic subunits, forming pseudomicellar structures. Particle growth determined through dynamic light scattering measurements coincided with the onset of EPR signal enhancement, and surface tension measurements further corroborated the coincidence of aggregation. The addition of a chaotrope (urea), which broke up the humic structures, eliminated the EPR signal increases. These observations strongly suggested that bridging interactions by divalent metal ions, and the intramo- lecular aggregation that accompanied it, led to significant stabilization of semiquinone radicals within the humic structure.
instrumentation.Regulation and control are correcttools so that decision making may be rationalised.Applications of metal and metalloid speciesdeterminations are numerous and speciation analysesshould soon be substituted for current total metaldeterminations.Many areas, however, cannot waitfor the implementationof regulations. The food, pharmaceutical,biomedical and chemical industries willrapidlyrequire high-quality information obtained by metalspecies determination to improve and consolidatetheir developments. Many organic compounds (natural and synthetic) possess electron rich centres due to the presence of N,O and S are capable of forming metal complexes. Metal complexes have spectacular colors. These colors arise from the absorption of lightwhich excites electrons within the metal's orbitals or, in the case of charge-transfer, excites electrons from metal-based orbitals to ligand-based orbitals (or the reverse). The interaction of metal ions with electron rich species leading to the formation of metal complexes is exploited to develop analytical procedures for the estimation of metal ions in soil, sea, sewage and natural waters. This aspect of study is being helpful in monitoring the pollution level. Instrumental analysis is opened many doors to scientific progress in support of both traditional core areas of chemistry, and new ones like biotechnology, material chemistry, environmental chemistry, chemical toxicology and small domain chemistry. UV-visible spectrophotometric methods continue to be popular for carrying out single component assays on a variety of metal ions via complex formation with suitable ligands. Represantative examples of UV-visible spectrophotometric methods of metal analysis [117-137] that have been published are given in Table 2.
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The interaction between Ni(II), Cu(II) and Zn(II) metal ions and substituted imidazolinone have been studied at 0.1 M Ionic Strength in 70 % DMF-water mixture by Bjerrum method as adopted by Calvin and Wilson. It is observed that Ni(II), Cu(II) and Zn(II) metal ions form 1:1 and 1:2 complexes with ligands (L1& L2). The data obtained were used to estimate and compare the values of proton-ligand stability constant (pK) and metal-ligand stability constants (logk). From estimated data (pK and log k), the effects of substituents were studied. Ligand used for present work were (L1) 1-[2-hydroxy-5-(phenyl azo) benzylidene amino]-2-phenyl-4-benzylidene-5-oxoimidazoline (L2)1-[2-hydroxy-5-(4-methoxy phenyl azo) benzylidene amino]-2-phenyl-4-benzylidene- 5-oxoimidazoline
The first point to note about these complexes is that despite the increase in ionic radii of the metals across Table 3.1, the geometry of the pyrazolylborate at the boron atom does not alter significantly - the N(1)-B-N(1b) bond angle remaining approximately tetrahedral. This rather rigid geometry is probably enforced to some degree by the 5-Me substituents in Tp *^®2 por example, a comparison of the two unsubstituted fr/s-(pyrazolyl)borate com plexes TpaFe^®® and Tp 2 Ca^®^ (for which the ionic radii of the metals differ by 0.45 A ) / 5 reveals that the average N -B -N angle (107.6(5) and 110.3(4)% respectively) does alter significantly upon increasing the size of the metal. Table 3.1 shows that there is a good correlation between the observed M - N(2) bond lengths in the [(Tp'^^^j^M] compounds and literature values of the ionic radii for the (six coordinate) ions. The increasing size of the metal as one moves across the table is accommodated by the [(Tp"^® 2 )g|\/|] system in two ways. Firstly, by a slippage of the pair of pyrazolylborate ligands back along the Sg axis (revealed by an increase in the M - B separation), and secondly, by subtle changes in the geometry of the Tp '^®2 jjgand itself. These are fairly insignificant in themselves (a slight lengthening of the B-N(1) bonds and a steady increase in the N(2)-N (1)-B angles), but taken together they amount to a definite opening up of the pyrazolylborate ‘bite’ angle (shown by an increase in N(2) • N(2b) distance). The overall effect of this is that, in general, the smaller the size of the metal ion, the further into the pocket of the TpMe 2 ligand it moves. This is seen clearly as a steady decrease in N (2 )-M - N(2b) bond angles with increasing ionic radius.
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migration in the cathode material during charge-discharge an electrochemically controlled process. Therefore, different methods have been employed to overcome this problem, including carbon coating [6-9], metal phosphide coating  and cation doping . It should be pointed out that the carbon coating will reduce the tap density of the material, thereby reducing the volume energy density of the battery, while the metal phosphide coating will increase the resistance of the material in the process of lithium intercalation/deintercalation. Furthermore, carbon or phosphide coating can only impact the surface of the particles and cannot improve the intrinsic electron (ion) conductivity of the material.
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sintering technique in air has been characterized to be polycrystalline single phase cubic spinel belonging to the space group F d-3m. The final sintering temperature, as determined by trial and error method, is found to be 1300 ˚C in air. The neutron diffraction measurements have given a clear picture of the distribution of cations for each member of the series having three different types of cations of which some of them are very close in atomic number. The occupation numbers of different cations over the A and B sites have been determined precisely since this technique is capable of differentiating them due to the large variation of the scattering length of these atoms for neutron. For all the compositions, Fe ions are distributed over both A and B sites. Ni ions invariably occupy the octahedral (16d) site only for x ≤ 0.6, while Co ions are distributed in both A and B sites for this compositional range. For x ≥ 0.8, some Ni ions enter into the tetrahedral (A) site, while all the Co ions enter into the octahedral (B) site. The knowledge of the cation distribution will be helpful in determining the magnetic and other properties of the system. The deduced sublattice and net moments reveal the system exhibited ferrimag- netic ordering at room temperature for the whole range of composition studied. In order to know the detailed magnetic behavior of the system, temperature dependent neutron diffraction studies will be performed and re- ported later on.
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Page | 258 on N(4)substituted thiosemicarbazones have concluded that the presence of bulky groups at the N(4) position of the thiosemicarbazone moiety greatly enhances biological activity [10-12]. On the other hand, the biological properties of metal thiosemicarbazones often differ from those of either ligands or the metal ions which are considered to be related to metal ion coordination [13-15]. In some cases, the highest biological activity is associated with a metal complex rather than the parent ligand and some side effects may decrease upon complexation.[16-18]. Thiosemicarbazones are compounds that have been studied for a considerable period of time for their biological properties. Traces of interest date back to the beginning of the 20th century but the first reports on their medical applications began to appear in the Fifties as drugs against tuberculosis and leprosy [19- 22].
better activity compared to the ligands alone (Patel et al., 2007). Keeping this view in mind it was planned to synthesize such a novel polymer, which beers combined properties of all of its monomers. The newly synthesized polymer was characterized by elemental analysis, UV-Visible, FT-IR, 1 H NMR spectral, SEM and number average molecular weight determination studies. One of the important applications of chelating and functional copolymers is their capability to remove/recover metal ions from waste solutions. Hence, the chelating ion-exchange properties of the 2-HAAT polymer resin have also been studied for specific metal ions along with its biological/antimicrobial properties for certain common microbes.
study both in its pure and in its substituted form. They are found to be used in certain applications like magnetic components, microwave devices such as isolators, circulators, gyrators and phase shifters, memory core, power transformers in electronics, antennae, etc.[1-6]. There are various factors which play the role in tailoring the properties of basic ferrite material. Substitution type and amount, processing methods, finishing etc are few which can be mentioned. As far as substitution is concern the metal ions can be distributed over the tetrahedral A and octahedral B sites. Consequently there arise changes in ionic radii of metal ions, the electronicconfiguration, theelectrostaticenergyofthespinel structures etc. and hence the properties of the
Acid plays a vital role in energy production and is a ma- jor excitatory neurotransmitter. It is involved in building DNA (genetic structures in cells), in carbohydrate me- tabolism & protein metabolism. It helps detoxify ammo- nia in the body, helps reduce fatigue and depression, and it also supports liver protection. Mineral Chelates (for example AbSolu) are chelates of L-Aspartic Acid and one of the minerals such as calcium, magnesium and zinc. They are chemically synthesized by proprietary technology developed by Elixir Industry . New products are anhydrous chelates of two L-Aspartic Acid molecules and a single metal ion. The technology of achieving this structure is patented and was jointly de- veloped by Elixir Industry and the Chinese National Institute of Pharmaceutical Industry. Mineral Chelates to be completely soluble over a wide range of pH val- ues.The chelated minerals are soluble in the small intes- tine for absorption and subsequent bio-utilization. These products are compatible with most nutritional additives commonly used in formulations and tableting applica- tions.
The present study aims to prepare and characterize the geometrical structures two mixed ligand chelates of Co(II) and Ni(II) ions with a Schiff base formed by the condensation of 2-methoxybenzaldehyde and L-valine amino acid as main ligand and anthranilic acid as secondary ligand.
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The Mycobacterium tuberculosis (Mtb) pathogen encodes a GlcNAc-6-phosphate deacetylase enzyme, NagA (Rv3332), that belongs to the amidohydrolase superfamily. NagA enzymes cat- alyze the deacetylation of GlcNAc-6-phosphate (GlcNAc6P) to glucosamine-6-phosphate (GlcN6P). NagA is a potential antitu- bercular drug target because it represents the key enzymatic step in the generation of essential amino-sugar precursors required for Mtb cell wall biosynthesis and also influences recy- cling of cell wall peptidoglycan fragments. Here, we report the structural and functional characterization of NagA from Myco- bacterium smegmatis (MSNagA) and Mycobacterium marinum (MMNagA), close relatives of Mtb. Using a combination of X-ray crystallography, site-directed mutagenesis, and biochemical and biophysical assays, we show that these mycobacterial NagA enzymes are selective for GlcNAc6P. Site-directed mutagenesis studies revealed crucial roles of conserved residues in the active site that underpin stereoselective recognition, binding, and catalysis of substrates. Moreover, we report the crystal structure of MSNagA in both ligand-free form and in complex with the GlcNAc6P substrate at 2.6 and 2.0 Å resolutions, respectively. The GlcNAc6P complex structure disclosed the precise mode of GlcNAc6P binding and the structural framework of the active site, including two divalent metals located in the ␣ / ␤ binuclear site. Furthermore, we observed a cysteine residue located on a flexible loop region that occludes the active site. This cysteine is unique to mycobacteria and may represent a unique subsite for targeting mycobacterial NagA enzymes. Our results provide critical insights into the structural and mechanistic properties
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