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The structures and solid-state dynamics of the supramolecular salts of the general formula [(12-crown-4)2 ⋅ DABCOH2](X)2 (where DABCO=1,4-diazabicyclo[2.2.2]octane, X=BF4, ClO4) have been investigated as a function of temperature (from 100 to 360 K) and pressure (up to 3.4 GPa), through the combination of variable-temperature and variable-pressure XRD techniques and variable-temperature solid-state NMR spectroscopy. The two salts are isomorphous and crystallize in the enantiomeric space groups P3221 and P3121. All building blocks composing the supramolecular complex display dynamic processes at ambient temperature and pressure. It has been demonstrated that the motion of the crown ethers is maintained on lowering the temperature (down to 100 K) or on increasing the pressure (up to 1.5 GPa) thanks to the correlation between neighboring molecules, which mesh and rotate in a concerted manner similar to spiral gears. Above 1.55 GPa, a collapse-type transition to a lower-symmetry ordered structure, not attainable at a temperature of 100 K, takes place, proving, thus, that the pressure acts as the means to couple and decouple the gears. The relationship between temperature and pressure effects on molecular motion in the solid state has also been discussed.  相似文献   
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The reuse of waste as well as the production of biodegradable compounds has for years been the object of studies and of global interest as a way to reduce the environmental impact generated by unsustainable exploratory processes. The conversion of linear processes into cyclical processes has environmental and economic advantages, reducing waste deposition and reducing costs. The objective of this work was to use biopolymer extraction waste in the cultivation of Spirulina sp. LEB 18, for the cyclic process of polyhydroxybutyrate (PHB) synthesis. Concentrations of 10, 15, 20, 25, and 30% (v/v) of biopolymer extraction waste were tested. For comparison, two assays were used without addition of waste, Zarrouk (SZ) and modified Zarrouk (ZM), with reduction of nitrogen. The assays were carried out in triplicate and evaluated for the production of microalgal biomass and PHB. The tests with addition of waste presented a biomass production statistically equal to ZM (0.79 g L?1) (p?<?0.1). The production of PHB in the assay containing 25% of waste was higher when compared to the other cultivations, obtaining 10.6% (w/w) of biopolymer. From the results obtained, it is affirmed that the use of PHB extraction waste in the microalgal cultivation, aiming at the synthesis of biopolymers, can occur in a cyclic process, reducing process costs and the deposition of waste, thus favoring the preservation of the environment.  相似文献   
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A simple and fast chromatographic method using ultraviolet diode-array detector (UV-DAD) was developed for the high performance liquid chromatography determination of the content of 1-deoxynojirimycin (DNJ) in a new dietary supplement in the form of granules for oral solution preparation. The derivatization reaction was carried out at room temperature for 15 min at pH 7. The reaction reached completeness at a reagent to analyte molar ratio of about 60. The chromatographic separations were performed on a C18 Phenomenex Synergi Fusion stainless steel column (250 mm?×?4.6 mm; 4 µm) with detection at λ?=?254 nm. The mobile phase consisted of triethylammonium (TEA) phosphate buffer (0.05 M; pH 3) and acetonitrile under gradient conditions at a flow-rate ramping from 1 to 1.2 mL/min. The validation parameters (linearity, sensitivity, accuracy, precision, specificity and stability) were satisfactory. Intra-day precision (relative standard deviation, RSD) was ≤?2.23% for peak area and retention time without significant differences between intra- and inter-day data. Recovery studies gave good results (93.59%; n?=?15) with a RSD of 2.64%. The developed method is suitable for the quality control of DNJ in raw material and industrial products. The method can be applied in any analytical laboratory and does not require sophisticated instrumentation.  相似文献   
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Background

Stilbene cleaving oxygenases (SCOs), also known as lignostilbene-α,β-dioxygenases (LSDs) mediate the oxidative cleavage of the olefinic double bonds of lignin-derived intermediate phenolic stilbenes, yielding small modified benzaldehyde compounds. SCOs represent one branch of the larger carotenoid cleavage oxygenases family. Here, we describe the structural and functional characterization of an SCO-like enzyme from the soil-born, bio-control agent Pseudomonas brassicacearum.

Methods

In vitro and in vivo assays relying on visual inspection, spectrophotometric quantification, as well as liquid-chormatographic and mass spectrometric characterization were applied for functional evaluation of the enzyme. X-ray crystallographic analyses and in silico modeling were applied for structural investigations.

Results

In vitro assays demonstrated preferential cleavage of resveratrol, while in vivo analyses detected putative cleavage of the straight chain carotenoid, lycopene. A high-resolution structure containing the seven-bladed β-propeller fold and conserved 4-His-Fe unit at the catalytic site, was obtained. Comparative structural alignments, as well as in silico modelling and docking, highlight potential molecular factors contributing to both the primary in vitro activity against resveratrol, as well as the putative subsidiary activities against carotenoids in vivo, for future validation.

Conclusions

The findings reported here provide validation of the SCO structure, and highlight enigmatic points with respect to the potential effect of the enzyme’s molecular environment on substrate specificities for future investigation.
  相似文献   
269.
In this paper we study some basic properties of multiresolution analysis of multiplicityd in several variables and discuss some examples related to the spaces of cardinal splines with respect to the unidiagonal or the crisscross partition of the plane. Furthermore, in analogy with [8], we show that if the scaling functions are compactly supported, then it is possible to find compactly supported mother wavelets l ,l=1,...,2 n dd, in such a way that the family {2 jn/2 l (2 j xv)} is a semiorthogonal basis ofL 2 ( n ).  相似文献   
270.
Let Hg be a genus g handlebody and MCG2n(Tg) be the group of the isotopy classes of orientation preserving homeomorphisms of Tg=∂Hg, fixing a given set of 2n points. In this paper we find a finite set of generators for , the subgroup of MCG2n(Tg) consisting of the isotopy classes of homeomorphisms of Tg admitting an extension to the handlebody and keeping fixed the union of n disjoint properly embedded trivial arcs. This result generalizes a previous one obtained by the authors for n=1. The subgroup turns out to be important for the study of knots and links in closed 3-manifolds via (g,n)-decompositions. In fact, the links represented by the isotopy classes belonging to the same left cosets of in MCG2n(Tg) are equivalent.  相似文献   
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