共查询到20条相似文献,搜索用时 15 毫秒
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Carl Henrik Grbitz Kari Rissanen Arto Valkonen smund Husab 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(6):o267-o272
The amino acid l ‐phenylalanine has been cocrystallized with d ‐2‐aminobutyric acid, C9H11NO2·C4H9NO2, d ‐norvaline, C9H11NO2·C5H11NO2, and d ‐methionine, C9H11NO2·C5H11NO2S, with linear side chains, as well as with d ‐leucine, C9H11NO2·C6H13NO2, d ‐isoleucine, C9H11NO2·C6H13NO2, and d ‐allo‐isoleucine, C9H11NO2·C6H13NO2, with branched side chains. The structures of these 1:1 complexes fall into two classes based on the observed hydrogen‐bonding pattern. From a comparison with other l :d complexes involving hydrophobic amino acids and regular racemates, it is shown that the structure‐directing properties of phenylalanine closely parallel those of valine and isoleucine but not those of leucine, which shares side‐chain branching at Cγ with phenylalanine and is normally considered to be the most closely related non‐aromatic amino acid. 相似文献
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Joanna S. Stevens Alba C. de Luca Michalis Pelendritis Giorgio Terenghi Sandra Downes Sven L. M. Schroeder 《Surface and interface analysis : SIA》2013,45(8):1238-1246
The C 1 s, N 1 s, and O 1 s core level binding energies (BEs) of the functional groups in amino acids (glycine, aspartic acid, glutamic acid, arginine, and histidine) with varied side‐chains and cell‐binding RGD‐based peptides have been determined and characterized by X‐ray photoelectron spectroscopy with a monochromatic Al Kα source. The zwitterionic nature of the amino acids in the solid state is unequivocally evident from the N 1 s signals of the protonated amine groups and the C 1 s signature of carboxylate groups. Significant adventitious carbon contamination is evident for all samples but can be quantitatively accounted for. No intrinsic differences in the XP spectra are evident between two polymorphs (α and γ) of glycine, indicating that the crystallographic differences have a minor influence on the core level BEs for this system. The two nitrogen centers in the imidazole group of histidine exhibit an N 1 s BE shift that is in line with previously reported data for theophylline and aqueous imidazole solutions, while the nitrogen and carbon chemical shifts reflect the unusual guanidinium chemical environment in arginine. It is shown that the complex envelopes of C 1 s and O 1 s photoemission spectra for short‐chain peptides can be analyzed quantitatively by reference to the less complex XP spectra of the constituent amino acids, provided the peptides are of high enough purity. The distinctive N 1 s photoemission from the amide linkages provides an indicator of peptide formation even in the presence of common impurities, and variations in the relative intensities of N 1 s were found to be diagnostic for each of the three peptides investigated (RGD, RGDS, and RGDSC). Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Joshua Watts Elizabeth Howell John K. Merle 《International journal of quantum chemistry》2014,114(5):333-339
In this study, ab initio and density functional theory methods have been used to understand the structures and thermodynamic stabilities of complexes formed between l ‐cysteine and mercury (II) ions in neutral aqueous solution. To better understand the interaction between sulfur and mercury (II) ion, the MP2, B3LYP, M06‐2X, and TPSS methods have been used to optimize [HgSHx]2?x, x = 1–4, complexes and compared to benchmark QCISD(T) structures. Furthermore, energies from these same methods are compared to CCSD(T)/CBS(2,3) energies. From these benchmark calculations, the M06‐2X method was selected to optimize l ‐cysteinate‐Hg(II) complexes and the MP2 method for estimating complex energies. l ‐cysteinate‐mercury (II) ion complexes are formed primarily by forming a bond between cysteinate sulfur and the mercury ion. Stable complexes of l ‐cysteinate and mercury can be formed in 1:1, 2:1, 3:1, and 4:1 ratios. Each complex is stabilized further by interaction between carboxylate oxygen and mercury as well as hydrogen bonding among complex cysteinate ligands. The results indicate that at high cysteinate to Hg(II) ratios high‐coordinate complexes can be present but at lower ratios the 2:1 complex should be dominant. © 2013 Wiley Periodicals, Inc. 相似文献
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Mathieu Guerain Patrick Derollez Luisa Roca-Paixo Catherine Dejoie Natlia T. Correia Frdric Affouard 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(3):225-230
The crystal structure of a new cocrystal of carbamazepine (systematic name: 5H‐dibenzo[b,f]azepine‐5‐carboxamide, C15H12N2O) and dl ‐tartaric acid (C4H6O6), obtained by liquid‐assisted grinding, was solved by powder X‐ray diffraction (PXRD). The high‐resolution PXRD pattern of this new phase was recorded at room temperature thanks to synchrotron experiments at the European Synchrotron Radiation Facility (Grenoble, France). The starting structural model was generated by a Monte‐Carlo simulated annealing method. The final structure was obtained through Rietveld refinement and an energy minimization simulation was used to estimate the H‐atom positions. The stability of the proposed structure as a function of temperature was also assessed from molecular dynamics simulations. The symmetry is monoclinic (space group P21/c) and contains eight molecules per unit cell, namely, four dl ‐tartaric acid and four carbamazepine molecules. 相似文献
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Summary The formation and stability of the mixed-ligand complexes of copper(II) with diethylenetriamine (dien) and amino acids or peptides have been investigated by potentiometric and conductometric techniques. The results indicate that the apical coordination of the ionized amide group of the peptide and the ionized alcoholatogroup of the amino acid is not possible. 相似文献
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《Surface and interface analysis : SIA》2004,36(12):1550-1563
Photoelectron spectra of a number of chromium oxides and other compounds were studied under high spectral resolution conditions chosen to reduce the possibility of differential charging. Some of the suite of Cr(III) compounds chosen for study produced Cr 2p spectra containing fine structure that could be identified with multiplet splitting. The splitting patterns produced were similar for all trivalent binary and ternary oxides and sulphides whose patterns closely reproduced the splitting predicted for the Cr(III) free ion by Gupta and Sen. The fine structure observed for compounds such as chromium (III) chloride had a distinctly different pattern. A number of other chromium (III) compounds were studied that did not exhibit the fine structure described above; nonetheless, well‐defined line shapes and reproducible peak centroids were obtained by fitting protocols. The use of such information to determine surface chemistry on chromated steels is described, based on the spectral knowledge of chromium (III) oxides and hydroxides and the chromium (VI) oxide systems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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Binary and ternary complex formation equilibria of copper(II) with glycyl-dl-leucine and amino acids or their esters were investigated potentiometrically at 25°C and a constant ionic strength. The kinetics of base hydrolysis of amino acid esters in their ternary complexes were monitored using the pH-stat method. The ester groups, with the exception of the histidine methyl ester, undergo rapid promoted hydrolysis. The rate and catalysis constants were evaluated from the experimental data. 相似文献
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Changes in the lamellar and crystalline structures were followed as a function of applied stress to understand the influence of the interactions between the crystalline and amorphous domains on the fiber properties. We observed a reversible transformation from a structure giving a four‐point small‐angle pattern to a structure giving a two‐point pattern; these structures corresponded to the lamellae with oblique and normal lamellar surfaces, respectively. The characteristics of these two structures such as the stack diameter, stack height, and tilt angle were different and were determined by the processing conditions and did not change when the fiber was elastically deformed. The structure giving a two‐point pattern was probably the load‐carrying lamellar entity in these fibers. The diameter of the lamellar stacks, tilt angle of the lamellae, and the strain in the lamellar spacing appeared to have the most influence on properties such as tenacity and dimensional stability. The long‐spacing strain, which is about the same as the fiber strain, determined the modulus at low elongation as well as ultimate elongation. These indicate that the lamellar stacks have at least as much influence as the interfibrillar chains on fiber properties. Structural features that determine the performance in semicrystalline polymers were investigated by analyzing four generations of polyethylene terephthalate fibers. Some of the fiber properties correlate with changes in the crystalline domains such as the crystalline orientation, size, and unit cell dimensions. Fibers in which the crystalline strain was large because of their strong linkages to the amorphous chains, and better load transfer, had the highest modulus and lowest ultimate elongation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1538–1553, 2003 相似文献
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Edgar Gonzlez‐Jurez Armando Ortega‐Guevara Irma Linzaga‐Elizalde Jaime Escalante 《Heteroatom Chemistry》2006,17(2):81-87
We report the preparation of four diastereoisomeric pairs of ethyl {[(3‐hydroxypropyl)‐ amino](aryl)methyl}phenylphosphinates. In two cases, the phosphinates were transformed to 1,4,2‐oxazaphosphepane heterocycles through one‐pot intramolecular esterification. The analogous reaction with formaldehyde gave the six‐membered ethyl (1,3‐oxazinan‐3‐ylmethyl)phenylphosphinate, which could be transformed in a posterior reaction to the corresponding aminomethanephosphinic acid. The new compounds were characterized by IR, 1H, 13C, and 31P NMR. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:81–87, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20179 相似文献
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Mohsen Rostamizadeh Malek Taher Maghsoodlou Sayyed Mostafa Habibi‐Khorassani Nourallah Hazeri Faramarz Rostami Charati Mohammad Amin Kazemian Brian W. Skelton Mohamed Makha 《Heteroatom Chemistry》2011,22(6):715-722
The reaction between dialkyl acetylenedicarboxylates and NH heterocyclic compounds in the presence of triethyl phosphite leads to stable phosphorus ylide derivatives in good yields. The X‐ray crystallographic data and theoretical study show that there is a resonance between two bonds of C19P1 and C191O191 in phosphorus ylide 4d . This compound crystallizes in the orthorhombic system, space group (Pca21), with unit cell parameters a = 17.3699(3) Å, b = 13.5500(2) Å, c = 18.4627(3) Å, α = 90°, β = 90°, γ = 90°, Z = 8, and V = 4345.4(12) Å3. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:715–722, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20739 相似文献
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The complexing properties of nitrilo-tris(methylphosphonic acid) (NTP) with cadmium(II) were investigated pH-metrically at 25 degrees C and at ionic strength of 0.1 mol dm(-3) (NaNO3). Stoichiometry and stability constants for the complexes formed are reported. Cadmium (II) forms Cd(NTP)(4-) and the corresponding hydroxy complexes. The ternary complexes are formed in a stepwise mechanism whereby NTP binds to cadmium(II), followed by coordination of amino acids, peptides or DNA. The concentration distribution of the various complex species has been evaluated. 相似文献
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Jarmo Ropponen Tero Tuuttila Manu Lahtinen Sami Nummelin Kari Rissanen 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5574-5586
The syntheses and thermal and X‐ray powder diffraction analyses of three sets of aliphatic polyester dendrimers based on 2,2‐bis(hydroxymethyl)propionic acid as a repeating unit and 2,2‐dimethyl‐1,3‐propanediol, 1,5‐pentanediol, and 1,1,1‐tris(hydroxymethyl)ethane as core molecules are reported. These dendritic polyesters were prepared in high yields with the divergent method. The thermal properties of these biodendrimers were evaluated with thermogravimetric analysis and differential scanning calorimetry. The thermal decomposition of the compounds occurred around 250 °C for the hydroxyl‐ended dendrimers and around 150 °C for the acetonide‐protected dendrimers. In addition, the crystallinity of the lower generation dendrimers was evaluated with X‐ray powder diffraction. The highest crystallinity and the highest melting points were observed for the first‐generation dendritic compounds. The higher generation dendrimers showed weaker melting transitions during the first heating scan. Only the glass‐transition temperatures were observed in subsequent heating scans. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5574–5586, 2004 相似文献
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Shoukry Mohamed M. Khairy Ezzat M. El-Sherif Ahmed A. 《Transition Metal Chemistry》2002,27(6):656-664
Binary and ternary complexes of copper(II) involving picolylamine (Pic) and amino acids, peptides (HL) or DNA constituents have been investigated. Ternary complexes of amino acids or peptides are formed by simultaneous reactions. Amino acids form the Cu(Pic)L complex, whereas peptides form Cu(Pic)L and Cu(Pic)(LH–1). The ternary complexes of copper(II) with picolylamine and DNA are formed in a stepwise process, whereby binding of copper(II) to picolylamine is followed by ligation of the DNA components. The stability of the ternary complexes is compared with the stabilities of the corresponding binary complexes. The hydrolysis of glycine methyl ester (MeGly) is catalysed by the Cu(pic)2+ complex. The kinetic data is fitted assuming that the hydrolysis proceeds in two steps. The first step, involving coordination of the amino acid ester by the amino and carbonyl groups, is followed by rate-determining attack by the OH– ion. The second step involves equilibrium formation of the hydroxo-complex, Cu(pic)(MeGly)(OH), followed by intramolecular attack. 相似文献
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Yasemin Yahsi 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(7):585-592
The coordination chemistry of multinuclear metal compounds is important because of their relevance to the multi‐metal active sites of various metalloproteins and metalloenzymes. Multinuclear CuII and MnIII compounds are of interest due to their various properties in the fields of coordination chemistry, inorganic biochemistry, catalysis, and optical and magnetic materials. Oxygen‐bridged binuclear MnIII complexes generally exhibit antiferromagnetic interactions and a few examples of ferromagnetic interactions have also been reported. Binuclear CuII complexes are important due to the fact that they provide examples of the simplest case of magnetic interaction involving only two unpaired electrons. Two novel dioxygen‐bridged copper(II) and manganese(III) Schiff base complexes, namely bis(μ‐4‐bromo‐2‐{[(3‐oxidopropyl)imino]methyl}phenolato)dicopper(II), [Cu2(C10H10BrNO2)2], (1), and bis(diaqua{4,4′‐dichloro‐2,2′‐[(1,1‐dimethylethane‐1,2‐diyl)bis(nitrilomethanylylidene)]diphenolato}manganese(III)) bis{μ‐4,4′‐dichloro‐2,2′‐[(1,1‐dimethylethane‐1,2‐diyl)bis(nitrilomethanylylidene)]diphenolato}bis[aquamanganese(III)] tetrakis(perchlorate) ethanol disolvate, [Mn(C18H16Cl2N2O2)(H2O)2]2[Mn2(C18H16Cl2N2O2)2(H2O)2](ClO4)4·2C2H5OH, (2), have been synthesized and single‐crystal X‐ray diffraction has been used to analyze their crystal structures. The structure analyses of (1) and (2) show that each CuII atom is four‐coordinated, with long weak Cu…O interactions of 2.8631 (13) Å linking the dinuclear halves of the centrosymmetric tetranucelar molecules, while each MnIII atom is six‐coordinated. The shortest intra‐ and intermolecular nonbonding Mn…Mn separations are 3.3277 (16) and 5.1763 (19) Å for (2), while the Cu…Cu separations are 3.0237 (3) and 3.4846 (3) Å for (1). The magnetic susceptibilities of (1) and (2) in the solid state were measured in the temperature range 2–300 K and reveal the presence of antiferromagnetic spin‐exchange interactions between the transition metal ions. 相似文献
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Seyyed Javad Sabounchei Parisa Shahriary Zabiholla Bolboli Nojini Hamid Reza Khavasi Cengiz Arici Hakan Dal 《Heteroatom Chemistry》2010,21(7):475-485
Stable phosphoranes, Ar3P = CHCOR (R = C6H5, C6H4NO2, C6H4OCH3, CH3, OCH2C6H5; Ar = p‐tolyl or phenyl), have been C‐acylated by acetic anhydride to obtain new types of phosphorus ylides. Synthesis and characterization of six phosphorus ylides of the type Ar3PC(COCH3)(COR) are reported. The reaction of {(p‐tolyl)3PCHCOC6H5} ( I ), {(p‐ tolyl)3PCHCOC6H4NO2} ( II ), {Ph3PCHCOC6H4NO2} ( III ), {Ph3PCHCOC6H4OCH3} ( IV ), {(p‐tolyl)3PCHCOCH3} ( V ), and {Ph3PCHCOOCH2C6H5} ( VI ) with acetic anhydride in dry chloroform as solvent gives (p‐tolyl)3PC(COMe)(COC6H5), α‐acetyl‐α‐benzoylmethy‐lenetriphenylphosphorane ( 1 ), {(p‐tolyl)3PC(COMe) (COC6H4NO2)} ( 2 ), {Ph3PC(COMe)(COC6H4NO2)} ( 3 ), {Ph3PC(COMe)(COC6H4OCH3)} ( 4 ), {(p‐tolyl)3 PC(COCH3)2} ( 5 ), and {Ph3PC(COMe)(COOCH2 C6H5)} ( 6 ). Single crystal X‐ray analyses for ylides 2 , 5 , and 6 reveal the monoclinic ( 2, 5 ) and triclinic ( 6 ) crystal systems. Characterization of the obtained compounds was also performed by elemental analysis, IR, 1H, 31P, and 13C NMR. The geometries of these compounds have been investigated using density functional theory (DFT). In addition, electronic parameters of these compounds such as HOMO and LUMO energy, Mulliken partial charge, and dipole moment were obtained. In this paper, the reactivity of these ylides is discussed in regard to the aforementioned data. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:475–485, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20633 相似文献
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Huey‐San Melanie Siah Carl Henrik Görbitz Lise‐Lotte Gundersen 《Journal of heterocyclic chemistry》2011,48(6):1375-1378
8‐Bromoadenine was benzylated in the presence of base to give a mixture of two regioisomers. One was easily recognized as 9‐benzyl‐8‐bromoadenine, but the other structure could not be determined with absolute certainty by NMR. Therefore, X‐ray crystallography was used to prove that the benzyl group was attached to N‐3. Furthermore, it is shown that the 3‐benzyl adenine derivative exists as the amine tautomer both in the crystalline state as well as in solution (DMSO‐d6), with restricted rotation around the N6? C6 bond. J. Heterocyclic Chem., (2011). 相似文献
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The acid-base equilibria of tetracycline and its copper(II) complex formation equilibria are investigated in dioxane-water mixtures. The ternary complexes of copper(II) with tetracycline as primary ligand and amino acid or DNA constituent as secondary ligand are studied in 50% dioxane-water solution. The formation constants of the ternary and binary complexes with amino acids or DNA constituents are determined. The concentration distribution of the various complex species are evaluated. Probable mode of chelation with tetracycline and DNA constituents is discussed. 相似文献
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Carbon-13 magnetic resonance studies of amino acids and peptides 总被引:3,自引:0,他引:3