Search results for "X-ray diffraction"
showing 10 items of 280 documents
Glucagon fibril polymorphism reflects differences in protofilament backbone structure
2010
Amyloid fibrils formed by the 29-residue peptide hormone glucagon at different concentrations have strikingly different morphologies when observed by transmission electron microscopy. Fibrils formed at low concentration (0.25 mg/mL) consist of two or more protofilaments with a regular twist, while fibrils at high concentration (8 mg/mL) consist of two straight protofilaments. Here, we explore the structural differences underlying glucagon polymorphism using proteolytic degradation, linear and circular dichroism, Fourier transform infrared spectroscopy (FTIR), and X-ray fiber diffraction. Morphological differences are perpetuated at all structural levels, indicating that the two fibril class…
Confinement effects on the interactions of native DNA with Cu(II)-5-triethyl ammonium methyl salicylidene orto-phenylendiiminate in C12E4 liquid crys…
2008
Confinement effects of native calf thymus DNA interacting with the complex Cu(ii)-5-(triethylammoniummethyl)salicylidene ortho-phenylendiiminate (CuL(2+)) perchlorate in tetraethylene glycol monododecyl ether (C(12)E(4)) liquid crystals have been investigated by UV absorption spectrophotometry, circular dichroism (CD) and small angle X-ray scattering (SAXS). The results indicate the occurrence of dramatic structural changes of both the DNA and the CuL(2+)-DNA system, when going from aqueous solution to C(12)E(4) liquid crystals, due to confinement constrains imposed by the closed structure of C(12)E(4) reverse micelles. Further marked departures from the behaviour observed in aqueous soluti…
Cytotoxic hydrophilic iminophosphorane coordination compounds of d8 metals. Studies of their interactions with DNA and HSA
2012
The synthesis and characterization of a new water-soluble N,N-chelating iminophosphorane ligand TPAN-C(O)-2-NC(5)H(4) (N,N-IM) (1) and its d(8) (Au(III), Pd(II) and Pt(II)) coordination complexes are reported. The structures of cationic [AuCl(2)(N,N-IM)]ClO(4) (2) and neutral [MCl(2)(N,N-IM)] M=Pd (3), Pt(4) complexes were determined by X-ray diffraction studies or by means of density-functional calculations. While the Pd and Pt compounds are stable in mixtures of DMSO/H(2)O over 4 days, the gold derivative (2) decomposes quickly to TPAO and previously reported neutral gold(III) compound [AuCl(2)(N,N-H)] 5 (containing the chelating N,N-fragment HN-C(O)-2-NC(5)H(4)). The cytotoxicities of co…
Formation of a novel ferromagnetic end-to-end cyanate bridged homochiral helical copper(ii) Schiff base complex via spontaneous symmetry breaking
2014
A homochiral helical coordination polymer of copper(II) has been synthesized using achiral precursors via spontaneous symmetry breaking and has been confirmed by single crystal X-ray diffraction and solid-state CD spectroscopy. The variable temperature magnetic measurements indicate the presence of weak ferromagnetic exchange interactions mediated by end-to-end cyanate bridges (J = +0.12 cm(-1)).
Enantiomerically pure trinuclear helicates via diastereoselective self-assembly and characterization of their redox chemistry.
2014
A tris(bipyridine) ligand 1 with two BINOL (BINOL = 2, 2′-dihydroxy-1, 1′-binaphthyl) groups has been prepared in two enantiomerically pure forms. This ligand undergoes completely diastereoselective self-assembly into D2-symmeteric double-stranded trinuclear helicates upon coordination to copper(I) and silver(I) ions and to D3-symmetric triple-stranded trinuclear helicates upon coordination to copper(II), zinc(II), and iron(II) ions as demonstrated by mass spectrometry, NMR and CD spectroscopy in combination with quantum chemical calculations and X-ray diffraction analysis. According to the calculations, the single diastereomers that are formed during the self-assembly process are strongly …
Corrosion of Heritage Objects: Collagen‐Like Triple Helix Found in the Calcium Acetate Hemihydrate Crystal Structure
2020
Abstract Helical motifs are common in nature, for example, the DNA double or the collagen triple helix. In the latter proteins, the helical motif originates from glycine, the smallest amino acid, whose molecular confirmation is closely related to acetic acid. The combination of acetic acid with calcium and water, which are also omnipresent in nature, materializing as calcium acetate hemihydrate, was now revealed to exhibit a collagen‐like triple helix structure. This calcium salt is observed as efflorescence phase on calcareous heritage objects, like historic Mollusca shells, pottery or marble reliefs. In a model experiment pure calcium acetate hemihydrate was crystallized on the surface of…
The Synthesis and Structure of Palladium 2,4-dimethyl-8-hydroselenoquinolinate
2014
The internal complex palladium 2,4-dimethyl-8- hydroselenoquinolinate Pd[C9H4(CH3)2NSe]2 (I) has been synthesized in the course of study of the complexing activity of 8- hydroselenoquinoline and investigation of the nature of chemical bond metal-selenium in the five-membered metal-containing ring. X-ray diffraction data for I: Monoclinic, space group P21/n, a = 9.0092(4), b = 16.3290(7), c = 14.1073(6) A, = 106.710(2)o, V = 1987.7(2) A3, Z = 4, R1=0.0477, wR2=0.1182 for 4499 reflections (diffractometer Bruker-Nonius KappaCCD, MoK). The crystal structure of the complex I is formed by neutral asymmetric molecules Pd[C9H4(CH3)2NSe]2 in which the central atom palladium is connected bidentic…
Preparation and structural studies on diorganotin(IV) complexes of N-nitroso-N-phenylhydroxylaminates
2007
Abstract Diorganotin(IV)-complexes of the N -nitroso- N -phenylhydroxylaminates (hereinafter cupf), Et 2 Sn(cupf) 2 ( 1 ), Bu 2 Sn(cupf) 2 ( 2 ), {[Bu 2 Sn(cupf)] 2 O} 2 ( 3 ), t -Bu 2 Sn(cupf) 2 ( 4 ) and Oc 2 Sn(cupf) 2 ( 5 , 6 ) were prepared and characterised by FT-IR and Mossbauer spectroscopic measurements. The binding modes of the ligand were identified by FT-IR spectroscopy, and it was found that the ligand is coordinated in chelating or bridging mode to the organotin(IV) center. The 119 Sn Mossbauer and FT-IR studies support the formation of trans -O h ( 1 – 6 ) structures. The X-ray diffraction analysis of 4 revealed that the tin centre is in a skew-trapezoidal geometry defined by…
Fabrication of quercetin and curcumin bionanovesicles for the prevention and rapid regeneration of full-thickness skin defects on mice
2013
In the present work biocompatible quercetin and curcumin nanovesicles were developed as a novel approach to prevent and restore skin tissue defects on chronic cutaneous pathologies. Stable and suitable quercetin- and curcumin-loaded phospholipid vesicles, namely liposomes and penetration enhancer-containing vesicles (PEVs), were prepared. Vesicles were made from a highly biocompatible mixture of phospholipids and alternatively a natural polyphenol, quercetin or curcumin. Liposomes were obtained by adding water, while PEVs by adding polyethylene glycol 400 and Oramix®CG110 to the water phase. Transmission electron microscopy, cryogenic-transmission electron microscopy and small- and wide-ang…
Synthesis, spectroscopic, cyclic voltammetry properties and molecular structure of the thiocyanato-N meso-tetratolylporphyrinato zinc(II) ion complex
2017
International audience; This paper describes the synthesis of the (thiocyanato-N)(meso-tetratolylporphyrinato)zinc(II) chlorobenzene monosolvate complex with the formula [K(2,2,2-crypt)][Zn(TTP)(NCS)]·C6H5Cl (I) using the cryptand-222 to solubilize potassium thiocyanate in chlorobenzene solvent. Complex (I) has been characterized by elementary analysis, IR, UV–vis, 1H NMR and MS, and the structure of this new zinc(II) metalloporphyrin been examined crystallographically. A cyclic voltammetry investigation was also carried out on this species. The title compound crystallizes in the triclinic, space group P-1, with a = 11.5151(7) Å, b = 15.212(10) Å, c = 20.1093(12) Å, α = 80.428(4)°, β = 74.9…