L-Leucinamide hydrogensquarate: spectroscopic and structural elucidation

The hydrogensquarate [LeuNH(2)] (HSq) of L-leucinamide has been synthesized and its structure has been determined by single crystal X-ray diffraction. A three dimensional network is formed by hydrogen bonds with participation of the O=C-NH(2) function, the hydrogensquarate ion and the N(+)H(3) group [NH(2)...O=C((Sq)) (2.840 and 2.749 A), ((Sq))OH...O=C(NH(2)) (2.618 A), NH(3) (+)...O=C((Sq)) (3.246, 2.804 and 2.823 A)], respectively. A theoretical approximation of the electronic structure was carried out by means of ab initio UMP2 and MP2 level of theory at the 6-311++G** basis set. The IR-spectroscopic assignment in the solid-phase was obtained by linear-polarized IR-spectroscopy of oriented samples as colloid suspensions in a nematic host and application of the reducing-difference procedure for the interpretation of polarized IR-spectra.     

Synthesis,spectroscopic and structural elucidation of sympathomimetic amine,tyraminium dihydrogenphosphate

The synthesis, isolation, spectroscopic and structural elucidation of sympathomimetic amine, tyramine dihydrogenphosphate are of interest due to its biological activity and the establishing correlation between spectroscopic properties and structure. The complex approach for investigation included single crystal X-ray diffraction, new technique in linear-polarized IR-spectroscopy in solid state and quantum chemical calculations with a view to predict the electronic structure and vibrational data of interacting species in entitled compound, the correlation structure–spectroscopic properties as well as the influence of intermolecular interaction on IR-characteristic bands are carried out.     

Structural and spectroscopic elucidation of tetrapetide glycyl-(L)-prolyl-glycyl-glycine and its hydrogensquarate

The IR-spectroscopic and structural elucidation of tetrapeptide glycyl-(L)-prolyl-glycyl-glycine and its hydrogensquarate was performed by employing linear-polarized IR-spectroscopy of oriented colloid suspensions in nematic host as well as mass spectrometry. Quantum-chemical ab initio calculations were carried out in order to evaluate both the electronic structure and optical properties of the compound studied.     

Linear-polarized IR-spectroscopic and structural elucidation of glycyl-L-phenylalanyl-glycine hydrochloride monohydrate

As a part of our spectroscopic and structural elucidation of small peptides, their salts and metal complexes, the polarized IR-spectroscopic and structural elucidation of the protonated form of glycyl-(L)-phenylalanyl-glycine as hydrochloride monohydrate (H-Gly-Phe-Gly-OHxHClxH(2)O) is reported. The obtained structure of the protonated tripeptide is supported by quantum chemical ab initio calculations at UHF level of theory and 6-31++G, showing only one stable conformer with two intermolecular NH(3)(+)OH(2) and (C=O)OHOH(2) hydrogen bonds. The N(terminus) amide O=C-N-H amide fragment is flat trans-configured with a dihedral angle value of 179.0(7)degrees, while the corresponding group at C(terminus) is with transoide-configurated and value of the dihedral angle of 151.1(3)degrees, respectively. In addition data of (1)H- and (13)C magnetic resonance spectroscopy (NMR), thermogravimetry (TGA), differential scanning calorimetry (DSC) and high performed liquid chromatography (HPLC) with tandem mass spectrometry (HPLC-MS/MS) as presented.     

Mononuclear Au(III)-complexes with tryptophan-containing dipeptides: Synthesis, spectroscopic and structural elucidation

The coordination ability of dipeptides l-tryptophyl-l-phenylalanine (H-Trp-Phe-OH) and l-tyrosyl-l-tryptophan (H-Tyr-Trp-OH) with Au(III) have been elucidated both in solid state and in solution by means of series of methods as UV, ¹H and ¹³C NMR, conventional and linear-polarized IR-spectroscopic tool in solid-state, based on orientation technique as suspension in nematic liquid crystal, FAB-MS, TGV, DSC methods and elemental analysis. The structures of the Au(III)-complexes have been predicted theoretically by DFT calculations at B3LYP level of theory and Lanl2DZ (Au)/6-31+G(3df) (Cl, C, H) basis set. The last data are compared with IR-LD spectroscopic ones giving the experimental evidence of the structures of the complexes studied. The dipeptides interact as tridentate ligands in obtained mononuclear complexes via their -NH₂, deprotonated N⁻-amide and -groups at molar ratio metal to ligand 1:1. One Cl⁻ ion is joined to the Au(III) as terminal ligand, forming [Au^III(LH₋₁)Cl] species. A near to square-planar flat geometry of the chromophores AuN₂OCl is yielded with maximal deviation of total planarity less than 0.9°.     

Tyrammonium 4-nitrophthalate dihydrate: structural and spectroscopic elucidation

Tyrammonium 4-nitrophthalate has been synthesized and its structural and spectroscopic properties elucidated by single-crystal X-ray diffraction, solid-state polarized IR-spectroscopy of oriented colloids in a nematic host, HPLC with tandem mass spectrometry (HPLC ESI-MSMS), and TGV and DSC methods. The compound crystallizes in the monoclinic P2₁/c space group and its structure consists of a 3D network of molecules joined by intermolecular interactions with the participation of cations, anions and two solvent molecules. The tyrammonium cation adopts a T trans configuration with corresponding angles of ϕ ₁ = 76.0(4)°, ϕ ₂ = 54.8(1)° and ϕ ₃ = 63.4(1)°, respectively. In the 4-nitrophthalate anion, the COO⁻ and COOH groups are turned off the plane of the benzene ring at angles of τ ₁ = 88.1(5)° and τ ₂= 22.1(7)°, respectively.     

Synthesis and structural elucidation of novel camphor-derived thioureas

Nine novel (+)-camphor-derived thioureas have been prepared. 3-((Dimethylamino)methylene)camphor (2) served as the common precursor for the preparation of both, 2-thiourea 15-20 and 3-thiourea functionalized camphor derivatives 6, 7/7', respectively. Starting from 2, the latter were prepared in two or three steps whereas the former in five steps, respectively. Configuration of all novel compounds has been meticulously determined using NMR techniques and/or single crystal X-ray crystallography.     

Synthesis, spectroscopic, structural and electrochemical studies of carboxyl substituted 1,4-naphthoquinones

Two carboxyl substituted quinones and their ethyl esters were prepared by alkylation of 2-methyl-1,4-naphthoquinone (MNQ), also known as menadione or vitamin K₃. All products were characterized by spectroscopic (¹H NMR, ¹³C NMR, IR) and electrochemical (cyclic voltammetry) methods, and the crystal structure of the two carboxylic derivatives was also determined. Both carboxyl substituted quinones crystallize in the system as hydrogen bonded dimers. In MeCN, the cyclic voltammograms of the ester derivatives present two reversible one-electron redox waves very similar to those of the parent quinone, MNQ. However, in the same solvent, the corresponding carboxyl substituted quinones show one cathodic and one anodic additional irreversible waves at more positive potentials and a decrease in current intensity of the two quinone reduction waves accompanied by loss of the quasi-reversible character of the second wave. These results show that the presence of the carboxylic substituent does not greatly modify the redox behaviour of the quinone, except for a small anodic shift of the potentials, but the associated presence of H⁺ ions in solution causes an important perturbation to the system, stabilizing the electrogenerated semiquinones by intermolecular self-protonation and/or hydrogen bonding.     

Synthesis, structural elucidation, DNA-PK inhibition, homology modelling and anti-platelet activity of morpholino-substituted-1,3-naphth-oxazines

A number of new angular 2-morpholino-(substituted)-naphth-1,3-oxazines (compound 10b), linear 2-morpholino-(substituted)-naphth-1,3-oxazines (compounds 13b-c), linear 6, 7 and 9-O-substituted-2-morpholino-(substituted)-naphth-1,3-oxazines (compounds 17-22, 24, and 25) and angular compounds 14-16 and 23 were synthesised. The O-substituent was pyridin-2yl-methyl (15, 18, and 21) pyridin-3yl-methyl (16, 19, and 22) and 4-methylpipreazin-1-yl-ethoxy (23-25). Twelve compounds were tested for their inhibitory effect on collagen induced platelet aggregation and it was found that the most active compounds were compounds 19 and 22 with IC(50)=55±4 and 85±4 μM, respectively. Furthermore, the compounds were also assayed for their ability to inhibit DNA-dependent protein kinase (DNA-PK) activity. The most active compounds were 18 IC(50)=0.091 μM, 24 IC(50)=0.191 μM, and 22 IC(50)=0.331 μM. Homology modelling was used to build a 3D model of DNA-PK based on the X-ray structure of phosphatidylinositol 3-kinases (PI3Ks). Docking of synthesised compounds within the binding pocket and structure-activity relationships (SAR) analyses of the poses were performed and results agreed well with observed activity.     

Synthesis, spectroscopic, structural and complexation studies of a new tetra-naphthylmethylene pendant-armed macrocyclic ligand

A novel emissive tetra-naphthylmethylene pendant-armed macrocyclic ligand and a series of complexes with monovalent and divalent metal ions have been synthesized. Solid compounds have been isolated as mononuclear (Co(II), Cu(II) and Zn(II)) or dinuclear (Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Ag(I)), complexes, depending on the counterions used. The chemical and photophysical properties of the free ligand, the protonation behavior and its metal complexes have been investigated in solution. UV-Vis spectroscopy has revealed a 1:1 binding stoichiometry for Cu(II), Zn(II), Cd(II), Ni(II) and Co(II), and 2:1 molar ratio for Ag(I). In chloroform, the free ligand presents two emission bands related to the monomer naphthalene emission and a red-shifted band attibutable to an exciplex due to a charge transfer from the nitrogen lone electron pair to the excited chromophore. Upon protonation of the free amines or due to metal complexation, the exciplex band disappears. The crystal structure of [Ag₂L(NO₃)₂] is also reported. The structure reveals that both metal ions are into the macrocyclic cavity in a distorted square plane {AgN₃O} environment. Each Ag(I) atom interacts with two neighbouring amine nitrogen atoms, one pyridine nitrogen and one oxygen atom from a monodentate nitrate ion.     

Magnesium-sugar interaction. Synthesis, spectroscopic and structural characterization of Mg-sugar complexes containing beta-D-fructose

The interaction between beta-D-fructose and hydrated magnesium salts has been studied and complexes of the type Mg(beta-D-fructose)Cl2.4H2O and Mg(beta-D-fructose)Br2.4H2O have been isolated and characterized. On the basis of comparisons of the spectroscopic and other chemical properties of several structurally known calcium-fructose compounds with those of the corresponding magnesium complexes, it is concluded that Mg2+ binds to two sugar moieties via O(2), O(3) of the first and O(4), O(5) of the second and to two water molecules, resulting in a six-coordinate geometry around the Mg2+. The strong sugar hydrogen-bonding network is rearranged upon sugar metallation and the sugar moiety shows the beta-anomer conformation in these magnesium-sugar complexes.     

Structural and vibrational spectroscopic elucidation of sulpiride in solid state

The study on the conformational and vibrational behaviors of sulpiride molecule which is known as a neuroleptic or antipsychotic drug that is widely used clinically in the treatment of schizophrenic or depressive disorders is an important scientific and practical task. In here, a careful enough study of monomer and dimeric forms of sulpiridine {5-(aminosulfonyl)-N-[(1-ethyl-2-pyrrolidinyl) ethyl]-2-methoxy-benzamide (C₁₅H₂₃N₃O₄S)} is undertaken by density functional theory (DFTB3LYP) method with the B3LYP/6-31G(d,p) basis set. The conformations of free molecule were searched by means of torsion potential energy surfaces scan studies through dihedral angles D₁ (8?N, 18C, 20C, 23?N), D₂ (18C, 20C, 23?N, 25C) and D₃ (28C, 30C, 41S, 44?N) in electronically ground state, employing 6-31G basic set. The final geometrical parameters for the obtained stable conformers were determined by means of geometry optimization, carried out at DFT/B3LYP/6-31G(d,p) theory level. Afterwards, the possible dimer forms of the molecule were formed and their energetically preferred conformations were investigated. Moreover, the effect of basis set superposition error on the structure and energy of the three energetically favourable sulpiride dimers has been determined. The optimized structural parameters of the most stable monomer and three low energy dimer forms were used in the vibrational wavenumber calculations. Raman and IR (4000–400?cm^?1) spectra of sulpiride have been recorded in the solid state. The assignment of the bands was performed based on the potential energy distribution data. The natural bond orbital analysis has been performed on both monomer and dimer geometries in order to elucidate delocalization of electron density within the molecule. The predicted frontier molecular orbital energies at DFT/B3LYP/6-31G(d,p) theory level show that charge transfer occurs within the molecule. The first-order hyperpolarizability (β₀) and related properties (μ and α) of the title molecule were also calculated.     

Synthesis of 2-deoxy-beta-D-ribose 1-phosphate, NMR comparison and its enzymatic activity for structural elucidation of synthetic alpha-isomer

2-Deoxy-beta-D-ribose 1-phosphate (1) was synthesized in a stereoselective manner and isolated with no detectable contamination by its alpha-isomer (4). Explicit configuration of 4 was first determined by NMR comparison with 1 judging from NOE results and their coupling constants. Natural purine nucleoside phosphorylase (PNPase) did not recognize 1 and gave no products such as alpha- or beta-deoxynucleosides.     

Pollen sporopollenin: degradation and structural elucidation

We report the isolation of purified sporopollenin from pollen grains of different species and its complete solubilization. Exine from Pinus pinaster, Betula alba, Ambrosia elatior and Capsicum annuum was extracted by treatment with hydrogen fluoride in pyridine. These exines were purified from their aromatic moieties and from fatty acids linked by ester bonds using acidolysis and saponification treatments. The biopolymer obtained retains almost completely the shape of the original pollen grain. Fourier-transform infrared spectroscopy analysis of the isolated sporopollenin showed the absence of polysaccharide and phenolic material and the presence of carboxylic acid groups joined to unsaturations and ether linkages. Sporopollenin samples were successfully degraded by exhaustive 24-h ozonolysis at room temperature. Gentle ozonolysis (3 h at 0°C) did not completely degrade the biopolymer. The compounds obtained after exhaustive ozonolysis were analysed by gas chromatography-mass spectrometry. Dicarboxylic acids with a low number of carbon atoms were identified as major components of sporopollenin from P. pinaster, A. elatior and C. annuum, representing 28.8%, 63.2% and 88.5%, respectively, of the total compounds obtained. Fatty acids and n-alkanes also were identified in P. pinaster, A. elatior and B. alba sporopollenin. From the data obtained, an hypothesis about the chemical nature and structural arrangement of the sporopollenin is proposed. Received: 8 November 1998 / Revision accepted: 14 April 1999     

Isolation, structural elucidation, and neuroprotective effects of iridoids from Valeriana jatamansi

Two new iridoids, jatadoids A (1) and B (2), and two known compounds (3 and 4) were isolated from Valeriana jatamansi. Their structures were elucidated on the basis of extensive spectroscopic analyses (IR, ESI-MS, HR-ESI-MS, 1D and 2D NMR). Compound 1 possessed an isovaleroxy group at the C-3 position that has previously been unreported in the class of iridoids. Four compounds were evaluated and compounds 1 and 3 showed moderate neuroprotective effects against MPP⁺-induced neuronal cell death in human dopaminergic neuroblastoma SH-SY5Y cells.     

Structural and spectroscopic characterization of aqua-diargininate-copper(II)-carbonate monohydrate

The molecular structure of the title complex, [Cu(C6H14N4O2)2(H2O)]CO3.H(2)O, was determined by single crystal X-ray diffractometry. It crystallizes in the monoclinic space group P2(1), with Z = 2. The Cu(II) ion is in a square pyramidal environment, trans coordinated at the basis by two argininate groups acting as bidentate ligands through their amino nitrogen and carboxylate oxygen atoms. The coordination around copper is completed by a water molecule at the pyramid apex. The infrared, Raman and electronic spectra are briefly discussed on the basis of the structural peculiarities of the complex.     

普鲁兰酶的异源表达、结构解析及分子改造研究进展

淀粉是由葡萄糖单元通过α-1,4-葡萄糖苷键和α-1,6-葡萄糖苷键连接而成,不仅是食物的主要成分,也是淀粉深加工工业的基本原料来源。普鲁兰酶能够高效水解淀粉分子中的α-1,6-葡萄糖苷键,与其他的淀粉加工酶复合使用,能够有效提高淀粉的利用率,在淀粉深加工工业中具有“提质增效”的重要作用。本文综述了普鲁兰酶产酶菌株的筛选及编码基因的克隆表达,总结了表达元件及发酵条件优化对普鲁兰酶产酶水平的影响,探讨了普鲁兰酶结构解析及分子改造等方面的研究进展。同时分析了当前研究中存在的问题,并对未来的研究进行了展望,以期为普鲁兰酶的研究及应用提供参考和启示。     

Naturally occurring naphthalenes: chemistry,biosynthesis, structural elucidation,and biological activities

Phytochemistry Reviews - In the recent years, discovery, identification, and development of biologically active compounds have gained a lot of importance. Naphthalenes are a class of arenes,...     

Neurospora tyrosinase: structural,spectroscopic and catalytic properties

Summary Tyrosinase is a copper containing monooxygenase catalyzing the formation of melanin pigments and other polyphenolic compounds from various phenols. This review deals with the recent progress on the molecular structure of the enzyme from Neurospora crassa and the unique features of the binuclear active site copper complex involved in the activation of molecular oxygen and the binding of substrates. The results of the spectroscopic properties of Neurospora tyrosinase will also be discussed in the light of the structural similarity of the copper complex in the oxygen binding hemocyanins.     

Progress towards structural elucidation of Photosystem II

In recent years Photosystem II, and in particular the oxygen evolving component of the enzyme, have been the subject of intense biochemical and biophysical analysis. To date no high resolution structural model of the complex has been produced. As a consequence unambiguous interpretation of much experimental data has proven difficult, leading to a lack of consensus over many basic questions regarding the mechanisms involved, the oligomerization state of the enzyme in vivo and even the exact biochemical composition.This review is a summary of the progress towards the production of a structural model of PS II-derived from either X-ray crystallography or electron microscopy based techniques-and the current opinions, which have arisen from these structural analyses, on the structural topology and assemblage of the various subunits that constitute the complex.Abbreviations C₁₂-M dodecyl maltoside - CP chlorophyll protein - cyt b-559 cytochrome b-559 - DMPC dimyristoyl phosphatidyl choline - EC electron crystallography - EM electron microscopy - LHC II light harvesting complex II - OEC oxygen evolving complex - OG octyl--glucopyranoside - PS I Photosystem I - PS II Photosystem II - Tris N-tris (hydroxymethyl) amino ethane