Glycine Ligands Research Articles

Synthesis and Crystal Structure of [Pb(gly)2]n; New lead(II) Coordination Polymer with Glycine Ligand

[Pb(gly)2]n (1) (gly is the abbreviation of Glycine) have been synthesized and characterized by elemental analyses, IR, 1H NMR and 13C NMR spectroscopy. The single crystal structure of 1 show the complex is 2D coordination polymer with octahedral environment that is formed into 3D supramolecule through hydrogen bond. Structural determination of compound 1 reveals the Pb(II) ion is four coordinated, bonded to a nitrogen, oxygen and two carbon atoms from the Glycine ligand.The crystal structure of compound 1 consists of a 3D supramolecular compound and shows the coordination number in the Pb(II) ions is six. PbO nanoparticles were synthesized by calcination of compound 1 at 500, 550 and 600 °C under air atmosphere. Calcination of the compound 1 at these temperatures yields mixture of orthorhombic and tetragonal PbO nanoparticles and nanorods. The PbO nanostructure was characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The thermal stability of compound 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA).

Photocoloration in Hybrid Amino Acid Polyoxometalates

The study of four different salts of a hybrid glycine–polyoxotungstate has revealed photocoloration that is dependent on the intramolecular hydrogen bonding between glycine ligand ammonium groups and the polyoxotungstate. Four compounds comprised of the hybrid polyoxometalate [As4{W3Y}W44Y4O159(Gly)8(H2O)12]9– (Gly = glycine) with glycinium, benzylammonium, 4‐methylbenzylammonium, or benzyltriethylammonium countercations have been synthesized and structurally characterized. In the solid state, two of the compounds exhibit coloration associated with photoreduction, cycling from white to blue under UV irradiation, and bleaching back to white following reoxidation in air. The ability of the hybrid POM to undergo photoreduction correlates with the orientation of the zwitterionic ammonium groups of the glycine ligands and the intramolecular hydrogen bonding to POM oxo ligands. The kinetics of coloration of these POMs follows a pseudo‐second‐order rate law.

Early life esophageal acid exposure reduces expression of NMDAR1 in the adult rat dorsal hippocampus and medial prefrontal cortex: Potential relationship with hyperlocomotion.

Early life esophageal acid exposure causes long-term molecular alterations in the rostral cingulate cortex; however, whether it induces behavioral changes remains unverified. Little is known about the molecular changes resulting from this event in the developing hippocampus and medial prefrontal cortex (mPFC). This study aimed to investigate the influence of early life esophageal acid exposure on spontaneous locomotor behavior and N-methyl-D-aspartate receptor (NMDAR), expression in these brain regions of adult rats. Male Sprague-Dawley rats were administered with an esophageal acid or saline infusion once per day (postnatal days 7-14). Some of these rats were given acute esophageal acid rechallenge in adulthood (postnatal day 60). The spontaneous locomotor behavior and expressions of esophageal epithelial caludin-1 and NMDAR subunits in the dorsal hippocampus (DH), ventral hippocampus (VH) and mPFC of the adult rats were recorded. Neonatal esophageal acid stimulation caused long-term impairment of the tight junctions in the adult esophagus. Simultaneously, hyperlocomotion and reduced expression of NMDAR1 subunits in both the DH and mPFC were observed, but not in the VH regions. Adult acute acid rechallenge reversed the decreased NMDAR1 expression in the DH and mPFC. The glycine ligand to NMDAR1 subunits was also changed. Peripheral visceral stimulation such as esophageal acid exposure during cerebral development induces increased locomotor activity, which may be related to the alteration of central sensitivity via NMDAR1 subunit reduction in the DH and mPFC. The impairment of tight junctions in the esophageal epithelium may contribute to the formation of central neuroplasticity.

Synthesis, Characterization and Bioactivities of Some Novel Oxovanadium(IV) Glycinato Complexes

The novel oxovanadium(IV) complexes, [VIVO(GlyH)(Gly)]+ClO4 - .H2O (1), [VIVO(GlyH)(Gly)]+NO3 - .H2O (2), [VIVO(GlyH)(Gly)]+CH3COO- .H2O (3) were synthesized and characterized by FT-IR, UV-Vis and 1H NMR spectroscopic measurements. The cumulative spectroscopic assessment envisaged that, the complexes adopt a square pyramidal structure, in which the two glycine ligands coordinate to vanadium(IV) center in bidentate fashions conforming a homoleptic structure. The amino nitrogen and a carboxylato oxygen atom coordinate the vanadium(IV) center from both sides making a five members chelate by each side. All the complexes are stable in amorphous state and in aerobic and anaerobic solution. Significantly, all the complexes have the antifungal activities against Aspergillus niger and Penicillium notatum but ineffective against Candida tropicalis. No antibacterial activity was observed for the complexes against tested bacteria and unfortunately, they were found cytotoxic against brine shrimp bioassay.

Molecular Modeling Study toward Development of H2S-Free Removal of Iron Sulfide Scale from Oil and Gas Wells.

A common problem that faces the oil and gas industry is the formation of iron sulfide scale in various stages of production. Recently an effective chemical formulation was proposed to remove all types of iron sulfide scales (including pyrite), consisting of a chelating agent diethylenetriaminepentaacetic acid (DTPA) at high pH using potassium carbonate (K2CO3). The aim of this molecular modeling study is to develop insight into the thermodynamics and kinetics of the chemical reactions during scale removal. A cluster approach was chosen to mimic the overall system. Standard density functional theory (B3LYP/6-31G*) was used for all calculations. Low spin K4Fe(II)4(S2H)12 and K3Fe(II)(S2H)5 clusters were derived from the crystal structure of pyrite and used as mimics for surface scale FeS2. In addition, K5DTPA was used as a starting material too. High spin K3Fe(II)DTPA, and K2S2 were considered as products. A series of KmFe(II)(S2H)n complexes (m = n–2, n = 5–0) with various carboxylate and glycinate ligands was used to establish the most plausible reaction pathway. Some ligand exchange reactions were investigated on even simpler Fe(II) complexes in various spin states. It was found that the dissolution of iron sulfide scale with DTPA under basic conditions is thermodynamically favored and not limited by ligand exchange kinetics as the activation barriers for these reactions are very low. Singlet–quintet spin crossover and aqueous solvation of the products almost equally contribute to the overall reaction energy. Furthermore, seven-coordination to Fe(II) was observed in both high spin K3Fe(II)DTPA and K2Fe(II)(EDTA)(H2O) albeit in a slightly different manner.

Tetrameric copper(II) metallocyclic complex bearing an amino acid derived Schiff base ligand: Structure, catalytic and antioxidant activities

The synthesis, characterization of a new anhydro copper(II) complex derived from N-(2′-hydroxy acetophenone)glycinate ligand (LGly) is reported. The structure of the copper(II) complex was determined by single crystal X-ray diffraction (SCXRD), showing a tetranuclear metallocycle. The structure and spectroscopic characterization, as well as catalytic and antioxidant applications, are reported.

Structures, Magnetic and Thermodynamic Properties of a 3d–4f Mixed Metal Cluster [ErZn6(μ3-O)3(μ3-C2H4NO2)6(H2O)9]6+

A heterometallic 3d–4f complex with hepta-nuclear hexagonal cluster, [ErZn6(μ3-O)3(μ3-C2H4NO2)6(H2O)9]6+ (C2H4NO2 = glycine) was synthesized and characterized. The cluster belongs to hexagonal crystal system. It crystallizes in the P-6 space group. In each cluster, Er3+ ion is in the center of a prism, which is composed of six zinc atoms. Er3+ ion coordinates to nine oxygen atoms. Each glycine ligand chelates to two Zn2+ and one Er3+ ions using a μ3-coordination mode. Fluorescent, thermodynamic and magnetic studies of the cluster were performed. The complex does not show single molecule magnet behavior.

Thermodynamic studies on metal ions – Ninhydrin – Glycine interactions in aqueous solutions

The experimental protonation and complex formation equilibrium constants of ligands (ninhydrin (NHN) and glycine (Gly)) with trivalent (iron(III), aluminium(III), and chromium (III)), divalent (copper(II), cobalt(II), nickel(II), strontium(II), manganese(II), and mercury(II)) and monovalent silver(I) metal ions have been investigated at 310.15 K in water solutions at ionic strength of 13.60 g·dm−3 NaNO3 using pH-potentiometric, UV–visible spectrophotometric, and cyclic voltammetry techniques, and by means of Hyperquad 2008 estimation model program. Also, the dissociation constants of NHN and the equilibrium constants of its binary complexes and ternary complexes with the studied metal ions in 13.60 g·dm−3 NaNO3 water solutions were observed at different temperatures such as (298.15, 310.15, 318.15 and 328.15) K. The theoretical calculations of overall protonation and stability constants of the metal ion-ninhydrin complex species in aqueous solutions were predicted as the free energy change associated with the ninhydrin protonation, and metal ion – ninhydrin – glycine complex formation equilibria using ab initio and density function theory calculations by applying Gaussian 09 software molecular modelling. The convention of the experimental Potentiometry/Spectrophotometry techniques and theoretical calculations provide a complete picture of the microscopic equilibria of the studied metal ions – ninhydrin – glycine systems. Precisely, this theoretical predication could be useful to control the most real protonation constants of ninhydrin and glycine ligands in which the binding sites change due to the ligand protonation/deprotonation equilibria. Also, the complexing capacities of different metal ions towards ninhydrin and glycine in solutions were evaluated and discussed. From the determined experimental stability constants of different metal complex species, the concentration distribution diagrams of the various metal ions – ninhydrin – glycine complex species in solutions were estimated using HySS 2009 software.

Alkane oxidation reactivity of homogeneous and heterogeneous metal complex catalysts with mesoporous silica-immobilized (2-pyridylmethyl)amine type ligands

Attachment of N,N-bis(2-pyridylmethyl)amine (L1) and N-(2-pyridylmethyl)glycine (L2) ligands on the azide-functionalized SBA-15 type mesoporous silica support and subsequent insertion of metal salts into the ligand-immobilized supports yielded heterogeneous metal complex catalysts, M(A)/SBA*-Ln-x, where M, A, *, n, and x indicate the metal ion (MnII, FeII, CoII, NiII, CuII), counter anion (Cl, OAc, OTf), trimethylsilyl end-capped silica, the numbering of the ligands, and the initial content of the azide tether group (tether/Si mol%) respectively. The cyclohexane oxidation activity of these immobilized catalysts and corresponding homogeneous complexes have been evaluated with the use of m-chloroperbenzoic acid as an oxidant. The activity of the immobilized catalysts is influenced by the ligand density on the support. Both the site-isolated immobilized catalysts and the related homogeneous catalysts of ligand L1 show similar trends of their final TONs on the type of metal ions (Co≈Ni>Fe>Mn>Cu). These results suggest that all of the metal complex sites are successfully immobilized without structural changes under the site-isolated condition. The reactivity trends of the complexes with the L2 ligand and their dependence on the ligand density were complicated. The observed results may be explained by the formation of cluster complexes via bridging carboxylate moieties of the ligand.

U(IV) Aqueous Speciation from the Monomer to UO2 Nanoparticles: Two Levels of Control from Zwitterionic Glycine Ligands.

The fate of U(IV)O2 in the environment in a colloidal form and its dissolution and growth in controlled environments is influenced by organic ligation and redox processes, where both affect solubility, speciation, and transport. Here we investigate U(IV) aqueous speciation from pH 0 to 3 with the glycine (Gly) ligand, the smallest amino acid. We document evolution of the monomeric to the hexameric form from pH 0 to 3 via UV-vis spectroscopy and small-angle X-ray scattering (SAXS). Crystals of the hexamer [U6O4(OH)4(H2O)6(HGly)12]·12Cl-·12(H2O) (U6) were isolated at pH 2.15. The structure of U6 is a hexanuclear oxo/hydroxo cluster U6O4(OH)4 decorated by 12 glycine ligands and 6 water molecules. The effect of pH and temperature on U6 conversion to UO2 nanoparticles, or simply reversible aggregation, is detailed by transmission electron microscopy imaging, in addition to SAXS and UV-spectroscopy. Because of the zwitterion behavior of glycine, pH and temperature control over U(IV) speciation is complex. Unexpectedly, stability of the polynuclear cluster actually increases with increased pH. Speciation is sensitive to not only metal-oxo hydrolysis but also ligand lability and hydrophobic ligand-ligand interactions.

Ligand-Mediated Folding of the OmpA Periplasmic Domain from Acinetobacter baumannii

The periplasmic domain of OmpA from Acinetobacter baumannii (AbOmpA-PD) binds to diaminopimelate and anchors the outer membrane to the peptidoglycan layer in the cell wall. Although the crystal structure of AbOmpA-PD with its ligands has been reported, the mechanism of ligand-mediated folding of AbOmpA remains elusive. Here, we report that in vitro refolded apo-AbOmpA-PD in the absence of ligand exists as a mixture of two partially folded forms in solution: mostly unfolded (apo-state I) and hololike (apo-state II) states. Binding of the diaminopimelate or glycine ligand induced complete folding of AbOmpA-PD. The apo-state I was highly flexible and contained some secondary structural elements, whereas the apo-state II closely resembled the holo-state in terms of both structure and backbone dynamics, except for the ligand-binding region. 15N-relaxation-dispersion analyses for apo-state II revealed substantial motion on a millisecond timescale of residues in the H3 helix near the ligand-binding site, with this motion disappearing upon ligand binding. These results provide an insight into the ligand-mediated folding mechanism of AbOmpA-PD in solution.

Single-Molecule Patch-Clamp FRET Anisotropy Microscopy Studies of NMDA Receptor Ion Channel Activation and Deactivation under Agonist Ligand Binding in Living Cells.

N-methyl-d-aspartate (NMDA) receptor ion channel is activated by the binding of two pairs of glycine and glutamate along with the application of action potential. Binding and unbinding of ligands changes its conformation that plays a critical role in the open-close activities of NMDA receptor. Conformation states and their dynamics due to ligand binding are extremely difficult to characterize either by conventional ensemble experiments or single-channel electrophysiology method. Here we report the development of a new correlated technical approach, single-molecule patch-clamp FRET anisotropy imaging and demonstrate by probing the dynamics of NMDA receptor ion channel and kinetics of glycine binding with its ligand binding domain. Experimentally determined kinetics of ligand binding with receptor is further verified by computational modeling. Single-channel patch-clamp and four-channel fluorescence measurement are recorded simultaneously to get correlation among electrical on and off states, optically determined conformational open and closed states by FRET, and binding-unbinding states of the glycine ligand by anisotropy measurement at the ligand binding domain of GluN1 subunit. This method has the ability to detect the intermediate states in addition to electrical on and off states. Based on our experimental results, we have proposed that NMDA receptor gating goes through at least one electrically intermediate off state, a desensitized state, when ligands remain bound at the ligand binding domain with the conformation similar to the fully open state.

Ternary Complexes Formed Among Pd(II) Ions, Nucleobases, Nucleosides, Nucleotides and Some Biologically Important Compounds

Potentiometric measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol·L−1 KNO3 for the interaction of guanine, thymine, uracil, aminouracil, guanosine, inosine, cytidine, guanosine 5′-monophosphate, adenosine 5′-diphosphate, adenosine 5′-triphosphate and palladium Pd(II) with the biologically important secondary ligands glycine, leucine, N,N-bis(2-hydroxyethyl) glycine, N-[tris(hydroxymethyl)methyl] glycine, d-2-t-butylglycine and Boc-N-methyl-l-leucine. The formation of various 1:1:1 ternary complexes and 1:1:2 quaternary complex species as well as the polynuclear species was inferred from the potentiometric pH-titration curves. The experimental conditions were selected such that self-association of the nucleobases, nucleosides or nucleotides and their complexes due to stacking interaction is negligibly small; that is, the normal monomeric protonated ternary complexes were studied. Formation of the ternary complexes of some systems was confirmed using cyclic voltammetry, differential pulse voltammetry and conductance measurements in solution.

Crystal Structure of the Dietary Supplement Ferrous Glycine Sulfate

AbstractThe crystal structure of ferrous glycine sulfate (a ferroglycine sulfate complex with chemical formula FeSO4(C2H5NO2), a compound extensively used as an iron dietary supplement, was refined from synchrotron X‐ray powder diffraction data. The crystal structure of an (so‐far unreported) isostructural manganese analogue was also structurally detailed by a Rietveld refinement against the corresponding X‐ray powder diffraction pattern. All studied compounds crystallize in the monoclinic P21 space group, building layers of metal cations coordinated by the oxygen atoms of sulfate groups and glycine ligands. Neighboring layers are parallel packed, bonded by hydrogen bonds. The coordination polyhedra around the cations can be regarded as distorted and elongated octahedral, presumably due to severe strains present in the crystal structure of the layers.

A Translational Biomedical Approach to Structural Arrangement of Amino Acids Complexes: A Combined Theoretical and Computational Study

In this short communication, respectively bonding among Boron (B3+), Aluminum (Al3+), Gallium (Ga3+), Indium (In3+) and Thallium (Tl3+) cations and Alanine, Arginine, Asparagine, Aspartic Acid, Cysteine, Glutamic Acid, Glutamine, Glycine, Proline, Selenocysteine, Serine, Tyrosine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan and Valine ligands and also structural arrangement of the present compounds were studied, theoretically and computationally

Crystal structure of bis-[N,N-bis-(2-hydroxy-eth-yl)glycinato-κ(3) O (1),N,O (2)]cobalt(II) monohydrate.

The title compound, [Co(C6H12O4)2]·H2O, was prepared by mild heating of an aqueous solution. The CoII ion has a slightly distorted octahedral coordination environment which is defined by two N atoms occupying the apical position, while the equatorial plane is furnished by two hy­droxy O atoms and two carboxyl­ate O atoms. The four hy­droxy O atoms from two distinct N,N-bis­(2-hy­droxy­eth­yl)glycine (bicH2 −) ligands act as hydrogen-bond donors with two carboxyl­ate O atoms as acceptors to form O—H⋯O hydrogen-bonded layers extending parallel to (100). In addition, the guest water mol­ecule acts as both a hydrogen-bond donor and acceptor, so that each Co(bicH2)2 mol­ecule is connected simultaneously to six neighbouring Co(bicH2)2 and two guest water mol­ecules by hydrogen bonding.

Crystal structure of catena-poly[[[tri-aqua-strontium]-di-μ2-glycinato] dibromide

In the title coordination polymer, {[Sr(C2H5NO2)2(H2O)3]Br2} n , the Sr(2+) ion and one of the water mol-ecules are located on twofold rotation axes. The alkaline earth ion is nine-coordinated by three water O atoms and six O atoms of the carboxyl-ate groups of four glycine ligands, two in a chelating mode and two in a monodentate mode. The glycine mol-ecule exists in a zwitterionic form and bridges the cations into chains parallel to [001]. The Br(-) counter-anions are located between the chains. Inter-molecular hydrogen bonds are formed between the amino and carboxyl-ate groups of neighbouring glycine ligands, generating a head-to-tail sequence. Adjacent head-to-tail sequences are further inter-connected by inter-molecular N-H⋯Br hydrogen-bonding inter-actions into sheets parallel to (100). O-H⋯Br and O-H⋯O hydrogen bonds involving the coordinating water mol-ecules are also present, consolidating the three-dimensional hydrogen-bonding network.

ChemInform Abstract: A Simple and Efficient Palladium Catalyst of Nitrogen‐Based Ligand for Cu(I)‐ and Amine‐Free Sonogashira Reaction.

AbstractA green approach for Sonogashira coupling of aryl halides and terminal alkynes is developed using copper‐, amine‐, and phosphine—free catalytic system based on palladium glycine ligand complex.

Site-Directed Spin Labeling Evidence of the Leader-Linker Interaction in the Glycine Riboswitch using Electron Paramagnetic Resonance Spectroscopy

Riboswitches are mRNA transcripts that function to modulate genetic expression through selective recognition and binding of cognate ligands which, subsequently, induces RNA conformational changes. Continuous wave electron paramagnetic resonance (CW EPR) spectroscopy, when employed with site-directed spin labeling (SDSL), is a useful technique for investigating changes in site-specific dynamics within biological systems. In this work, SDSL CW EPR was used to study the leader-linker interaction in the Vibrio cholerae glycine riboswitch. The glycine riboswitch binds two molecules of glycine to regulate the expression of genes associated with glycine metabolism. The recently described leader-linker interaction in the glycine riboswitch has been investigated using biochemical methods and was shown to play a functional role in the ligand binding process. To probe local RNA backbone dynamics of select sites within the leader-linker interaction SDSL, using the R5 spin label, was employed. Incorporation of spin labels was achieved through the use of optimized ligation methodologies that allow small, synthetically modified RNA to be joined to the larger riboswitch RNA sequence. Empirical analysis of X-band EPR line shapes was used to characterize dynamics of the interaction at varying temperatures for differing folded states of the riboswitch in the absence or presence of salts and glycine ligand. Spectral variation at the labeled sites is in agreement with postulated secondary structural elements and has provided spectroscopic evidence in support of the leader-linker interaction.

Structural features and cytotoxic activities of [Ru(AA-H)(dppb)(bipy)]PF6 complexes

Amino acid/diphosphine ruthenium complexes, of general formula [Ru(AA-H)(dppb)(bipy)]PF6 [AA=amino acid: glycine (gly), l-alanine (ala), l-tyrosine (tyr), l-methionine (met), l-leucine (leu), l-valine (val), l-serine (ser), l-tryptophan (trp), and l-lysine(lys); dppb=1,4-bis(diphenylphosphino)butane; bipy=2,2′-bipyridine], were synthesized and characterized. The X-ray structures of the glycine and leucine complexes showed that the amino acids are coordinated to the metal center through the carboxylate and amine groups. The complexes, except for the glycine ligand, form two different conformational isomers, as suggested by X-ray structure determination of the complex with leucine, and shown by 31P{1H} NMR analysis. The cyclic and differential pulse voltammograms of the complexes exhibited an oxidation potential (RuII/RuIII) close to 1.0V, against Ag/AgCl. Toxicity tests against the MDA-MB-231 and DU 145 human tumor cell lines and the Ehrlich mouse cell line indicated a high degree of cytotoxicity for the amino acid complexes. The intrinsic binding constants (Kb) for the amino acid complexes were determined and found to be in the range of 1.40×104–1.80×104M−1, suggesting weak interactions of the complexes with DNA.