Search results for "Crystallization"
showing 10 items of 774 documents
NMR Solution Conformation of the Proposed Recombin Like Structure D(CCGCGG)2
1997
Long repeated stretches of d(CCG) trinucleotide are the crucial mutation of gen that causes hereditary form of mental retardation (fragile X-syndrome). Moreover, the alternating (CG) dinucleotide is one of the candidates for Z-DNA conformation. Both sequences are part of the hexanucleotide d(CCGCGG)2- d(CCGCGG)2 forms different crystals depending on the crystallisation conditions. In one of these forms, the central alternating tetramer has a Z-DNA conformation, while the initial cytosine swings out and forms a Watson-Crick base-pair with the terminal guanine of a symmetry-related molecule. In this communication a detailed comparison between solid and solution spatial conformation by NMR of …
The influence of Fe3+ doping on thermally induced crystallization and phase evolution of amorphous calcium phosphate
2021
The present study investigates thermally induced crystallization and phase evolution of amorphous calcium phosphate (ACP) partially substituted with Fe3+ ions (M/P = 1.5 : 1). It was demonstrated that the presence of Fe3+ ions radically changes the crystallization behavior of ACP and completely prevents the formation of α-tricalcium phosphate (α-TCP, Ca3(PO4)2), which is the first crystalline phase obtained from non-substituted ACP upon thermal treatment. Surprisingly, calcium deficient hydroxyapatite (CDHA) was obtained instead of α-TCP. Such unusual crystallization behavior was observed with a doping level as low as 0.1 mol% with respect to Ca ions. Moreover, it was shown that the presenc…
Solubility-Driven Isolation of a Metastable Nonagold Cluster with Body-Centered Cubic Structure.
2020
The conventional synthetic methodology of atomically precise gold nanoclusters using reduction in solutions offers only thermodynamically most stable nanoclusters. We report herein a solubility‐driven isolation strategy to access the synthesis of a metastable gold cluster. The cluster, with the composition of [Au 9 (PPh 3 ) 8 ] + ( 1 ), displays an unusual, nearly perfect body‐centered‐cubic (bcc) structure. As revealed by ESI‐MS and UV/Vis measurement, the cluster is metastable in solution and converts to the well‐known [Au 11 (PPh 3 ) 8 Cl 2 ] + ( 2 ) within just 90 min. DFT calculations revealed that while both 1 and 2 are eight‐electron superatoms, there is a driving force to convert 1 …
Alkylsilyl compounds as enablers of atomic layer deposition: analysis of (Et3Si)3As through the GaAs process
2016
A new chemistry has been developed to deposit GaAs, the quintessential compound semiconductor. The ALD process is based on a dechlorosilylation reaction between GaCl3 and (Et3Si)3As. Characteristic ALD growth was demonstrated, indicating good applicability of the alkylsilyl arsenide precursor. ALD of GaAs produced uniform, amorphous and stoichiometric films with low impurity content. This was done with saturating growth rates and an easily controlled film thickness. Crystallization was achieved by annealing. Even though the growth rate strongly decreased with increasing deposition temperature, good quality film growth was demonstrated at 175 to 200 °C, indicating the presence of an ALD wind…
Density functional/molecular dynamics simulations of phase-change materials
2013
The room temperature crystal structure of a bacterial phytochrome determined by serial femtosecond crystallography
2016
Scientific reports 6, 35279 (2016). doi:10.1038/srep35279
A Simple Complex on the Verge of Breakdown: Isolation of the Elusive Cyanoformate Ion
2014
Cyanide Hitches a Ride Cyanide is a by-product of the biosynthesis of ethylene in plants and it has been somewhat puzzling how the ion is safely removed before it can shut down enzymatic pathways by coordination to catalytic iron centers. A proposed mechanism has implicated the cyanoformate ion—essentially, a weak adduct of cyanide and carbon dioxide—as the initial product, although its lifetime was uncertain. Murphy et al. (p. 75 ; see the Perspective by Alabugin and Mohamed ) crystallized this previously elusive adduct and found that its solution-phase stability varies inversely with the dielectric properties of the medium. The results bolster a picture in which the adduct shuttles the cy…
Geometrical and conformational preferences of the 9‐fluorenylmethoxycarbonyl‐amino moiety
2004
Structural parameters, originating from x-ray crystallographic data, have been compiled for 13 derivatives of amino acids, peptides and related compounds, which contain a total of 14 Fmoc-NH- moieties. For these moieties, molecular geometries and conformations--described by the omegao, theta1, theta2 and theta3' torsion angles--were analysed and compared with the corresponding parameters for the Z-NH- and Boc-NH-moieties (290 and 553, respectively). To gain a deeper insight into the conformational features of the Fmoc-NH- moiety, ab initio free molecule calculations were performed for fully relaxed minima. Also the potential energy surface as a function of the torsion angles (theta3', theta…
Crystal structure of [tris(4,4-bipyridine)]diium bis(1,1,3,3-tetracyano-2-ethoxypropenide) trihydrate
2016
In the title hydrated salt, which was obtained from the hydrothermal reaction between between potassium 1,1,3,3-tetracyano-2-ethoxypropenide and 4,4′-bipyridine in the presence of iron(II) sulfate heptahydrate, the ionic components are linked into a three-dimensional network by C—H⋯N hydrogen bonds.
Crystal structure of 2-methyl-1H-imidazol-3-ium hydrogen oxalate dihydrate
2016
In the title molecular salt 2-methyl-1H-imidazol-3-ium hydrogen oxalate dihydrate, N—H⋯(O,O) and O—H⋯O hydrogen bonds link the components into a bilayer-like assembly.