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121.
Ricerche di Matematica - We study the Dirichlet problem for a second order linear elliptic partial differential equation with discontinuous coefficients in unbounded domains. We establish an... 相似文献
122.
Giangiacomo Beretta Fabrizio Gelmini Fabrizio Fontana Roberta Manuela Moretti Marina Montagnani Marelli Patrizia Limonta 《Natural product research》2018,32(10):1130-1135
In this work, we report a rapid and convenient HPLC-UV-DAD method for the isolation of δ-T3 on semi-preparative scale from two different vitamin E rich processed, commercially available products obtained from the fruits of Elaeis guineensis Jacq. (oil palm) and from the seeds of Bixa orellana L. (achiote tree). Chromatography was run using reverse phase (RP) C-18 columns and HPLC-grade acetonitrile as mobile phase. The purity of the isolated δ-T3, assessed by GC–MS and 1H NMR was above 98%. The δ-T3 cytotoxic activity found in vitro against the proliferation of human A375 melanoma cells compared to that of the other δ-T3 free tocols mixture suggest its primary role in the experimental anticancer activity observed for palm oil derived products. Taken altogether, the results of this study highlight the importance of the application of suitable purification systems for the preparations of tocotrienols prior to their experimental or clinical testing. 相似文献
123.
Giulia Marsico Barbara A. Pignataro Marco Masi Antonio Evidente Francesca Casella Maria Chiara Zonno Jun-Hyung Tak Jeffrey R. Bloomquist Stefano Superchi Patrizia Scafato 《Tetrahedron》2018,74(28):3912-3923
The first asymmetric total synthesis of both enantiomers of the natural products colletorin A and colletochlorin A is presented. The proposed methodology is based on the coupling reaction between highly substituted aromatic Gilman cuprates and optically active allyl bromides, in turn obtained by Sharpless asymmetric dihydroxylation. The latter ensured a high degree of regio- and stereocontrol in the enantioselective step of the synthesis. The same synthetic strategy has been also applied for the preparation of differently halogenated synthetic analogues of colletochlorin A in high enantiomeric purity. The enantioselective synthesis of colletorin A and colletochlorin A allows to reliably assign their absolute configuration. Preliminary assessment of their herbicidal and insecticidal properties evidence the possibility to modulate the bioactivity of these compounds, highlighting its dependence on both the absolute stereochemistry and the halogen nature. 相似文献
124.
Let M be a differentiable manifold and [0, )×MM be a C1 map satisfying the condition (0, p)=p for all pM. Among other results, we prove that when the degree (also called Hopf index or Euler characteristic) of the tangent vector field wMTM, given by w(p)=(/)(0, p), is well defined and nonzero, then the set (of nontrivial pairs) admits a connected subset whose closure is not compact and meets the slice {0}×M of [0, )×M. This extends known results regarding the existence of harmonic solutions of periodic ordinary differential equations on manifolds. 相似文献
125.
Comandini P Blanda G Cardinali A Cerretani L Bendini A Caboni MF 《Journal of separation science》2008,31(18):3257-3264
Anthocyanins, the major colourants of strawberries, are polar pigments that are positively charged at low pH. Herein, we have assessed a new analytical method for the separation of anthocyanins using CZE. Acidic buffer solutions (pH <2) were employed in order to maintain pigments in the cation flavylium form and achieve high molar absorptivity at 510 nm. These spectral properties enabled us to identify strawberry anthocyanins in a preliminary stage by detection in the visible range, although the method was optimised at 280 nm to obtain the best S/N. The effects of buffer composition highlighted the necessity of adding an organic modifier to the running buffer to obtain a suitable separation. The electrophoretic method permitted the separation of the three main anthocyanins of strawberry extracts, namely pelargonidin 3-glucoside (Pg-glu), pelargonidin 3-rutinoside and cyanidin 3-glucoside. The electrophoretic results, expressed as retention time and separation efficiency of the major anthocyanin (Pg-glu), were compared to those achieved in HPLC, the analytical technique traditionally used for the investigation of anthocyanins in vegetable matrix. The content of Pg-glu in strawberries (cv. Camarosa), calculated with HPCE and HPLC methods, resulted respectively in 11.41 mg/L and 11.37 mg/L. 相似文献
126.
Bizzarri M Cavaliere C Foglia P Guarino C Samperi R Laganà A 《Analytical and bioanalytical chemistry》2008,391(5):1969-1976
A label-free absolute quantitation method based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
(MALDI-TOF MS) has been developed. This methodology was applied to mouse heart in order to quantify cardiac troponin T (cTnT),
which is considered to be a sensitive marker of heart damage. The cTnT was extracted, isolated by reversed-phase high-performance
liquid chromatography, digested, and analyzed by MALDI-TOF MS. The MS-based quantitation was performed using matrix-matched
calibration curves (due to a matrix effect) of two synthetic peptides, one cTnT-specific peptide and one internal standard
peptide, respectively. Recoveries at three spiking levels ranged from 87–96%, with relative standard deviations of below 10%.
The method detection limit and the method quantitation limit, expressed as the amount of cTnT for the amount of total sarcomeric
protein extract, were 0.03 mg g−1 and 0.15 mg g−1, respectively. This method appears to be accurate and generally suitable for improving absolute protein quantitation. 相似文献
127.
Bacteria communicate among themselves using certain chemical signaling molecules. These signaling molecules generally are
N-acyl homoserine lactones (AHLs) in Gram-negative bacteria and oligopeptides in Gram-positive bacteria. In addition, both
Gram-positive and Gram-negative bacteria produce a family of signaling molecules known as autoinducer-2 that they employ for
their communications. Bacteria coordinate their behavior by releasing and responding to the chemical signaling molecules present
in proportion to their population density. This phenomenon is known as quorum sensing. The role of bacteria in the pathogenesis
of several diseases, including gastrointestinal (GI) disorders, is well established. Moreover, rather recently bacterial quorum
sensing has been implicated in the onset of bacterial pathogenicity. Thus, we hypothesized that the signaling molecules involved
in bacterial communication may serve as potential biomarkers for the diagnosis and management of several bacteria-related
diseases. For that, we previously developed a method based on genetically engineered whole-cell sensing systems for the rapid,
sensitive, cost-effective and quantitative detection of AHLs in biological samples, such as saliva and stool, from both healthy
and diseased individuals with GI disorders. Although various analytical methods, based on physical-chemical techniques and
bacterial whole-cell biosensors, have been developed for the detection of AHLs in the supernatants of bacterial cultures,
only a few of them have been applied to AHL monitoring in real samples. In this paper, we report work performed in our laboratory
and review that from others that describes the detection of AHLs in biological, clinical samples, and report some of our recent
experimental results. 相似文献
128.
Mária Szűcs Patrizia Vaghi Giuseppina Sandri M. Cristina Bonferoni Carla M. Caramella Piroska Szabó-Révész I. Erős 《Journal of Thermal Analysis and Calorimetry》2008,94(1):271-274
Polymeric emulsifiers provide exceptional stability to oil-in-water, water-in-oil or multiple emulsions by their steric stabilization.
Pemulens as polymeric emulsifiers are able to stabilize o/w type emulsions because their short lipophilic part integrates into the oil droplets while their long hydrophilic part forms
a micro gel around the droplet. In our present study the microstructure and integration of the polymeric emulsifier at the
water-oil interface was investigated with thermogravimetric and microscopical methods. It was established that depending on
the amount of both of the polymeric emulsifier and added coemulsifier the microstructure of the system changes. 相似文献
129.
Micellar solutions made of a fully fluorinated surfactant, LiPFN, form water-soluble complexes with lysozyme in a wide concentration range. Such complexes are stabilized by electrostatic and, very presumably, double-layer interactions. The mixtures were investigated by combining electrophoretic mobility, DLS, and dielectric relaxation methods. The former gives information on the surface charge density of protein-micelle complexes and indicates that the resulting adducts retain a negative charge (i.e., charge neutralization is incomplete). The double-layer thickness of proteins, micelles, and protein-micelle complexes is also connected to the dielectric relaxation frequency. Changes in particle size (inferred by DLS), charge density, and double-layer thickness are closely interrelated to each other. A model was developed to quantify such properties. 相似文献
130.
Several 17α-monoesters of cortexolone and its Δ9-derivative are endowed with antiandrogenic activity. Their synthesis can be accomplished by means of a lipase-catalyzed chemoselective alcoholysis of the corresponding 17α,21-diesters. 相似文献