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311.
Maria Letizia Ciavatta M. Pilar Lopez-Gresa Rosario Nicoletti Ernesto Mollo Guido Cimino 《Tetrahedron》2008,64(22):5365-5369
Chemical investigation of the culture broth of the fungus Eutypella scoparia ICB-OBX, isolated from the marine pulmonate mollusc Onchidium sp., led to the finding of novel compounds 1 and 2, structurally related to angiotensin II binding inhibitors cytosporins, along with unrelated known nitrogen metabolites (compounds 3-5). The structure and the relative stereochemistry of the novel metabolites were assigned mainly by a detailed analysis of two-dimensional NMR techniques whereas the absolute stereochemistry was proposed by modified Mosher's method. Compound 2 contains an unusual cyclic carbonate functionality that is rare among natural products. 相似文献
312.
Binolfi A Lamberto GR Duran R Quintanar L Bertoncini CW Souza JM Cerveñansky C Zweckstetter M Griesinger C Fernández CO 《Journal of the American Chemical Society》2008,130(35):11801-11812
The aggregation of alpha-synuclein (AS) is a critical step in the etiology of Parkinson's disease (PD) and other neurodegenerative synucleinopathies. Protein-metal interactions play a critical role in AS aggregation and might represent the link between the pathological processes of protein aggregation and oxidative damage. Our previous studies established a hierarchy in AS-metal ion interactions, where Cu(II) binds specifically to the protein and triggers its aggregation under conditions that might be relevant for the development of PD. In this work, we have addressed unresolved structural details related to the binding specificity of Cu(II) through the design of site-directed and domain-truncated mutants of AS and by the characterization of the metal-binding features of its natural homologue beta-synuclein (BS). The structural properties of the Cu(II) complexes were determined by the combined application of nuclear magnetic resonance, electron paramagnetic resonance, UV-vis, circular dichroism spectroscopy, and matrix-assisted laser desorption ionization mass spectrometry (MALDI MS). Two independent, noninteracting copper-binding sites with significantly different affinities for the metal ion were detected in the N-terminal regions of AS and BS. MALDI MS provided unique evidence for the direct involvement of Met1 as the primary anchoring residue for Cu(II) in both proteins. Comparative spectroscopic analysis of the two proteins allowed us to deconvolute the Cu(II) binding modes and unequivocally assign the higher-affinity site to the N-terminal amino group of Met1 and the lower-affinity site to the imidazol ring of the sole His residue. Through the use of competitive chelators, the affinity of the first equivalent of bound Cu(II) was accurately determined to be in the submicromolar range for both AS and BS. Our results prove that Cu(II) binding in the C-terminal region of synucleins represents a nonspecific, very low affinity process. These new insights into the bioinorganic chemistry of PD are central to an understanding of the role of Cu(II) in the fibrillization process of AS and have implications for the molecular mechanism by which BS might inhibit AS amyloid assembly. 相似文献
313.
Implications of interfacial characteristics of food foaming agents in foam formulations 总被引:2,自引:0,他引:2
Rodríguez Patino JM Carrera Sánchez C Rodríguez Niño MR 《Advances in colloid and interface science》2008,140(2):95-113
The manufacture of food dispersions (emulsions and foams) with specific quality attributes depends on the selection of the most appropriate raw materials and processing conditions. These dispersions being thermodynamically unstable require the use of emulsifiers (proteins, lipids, phospholipids, surfactants etc.). Emulsifiers typically coexist in the interfacial layer with specific functions in the processing and properties of the final product. The optimum use of emulsifiers depends on our knowledge of their interfacial physico-chemical characteristics - such as surface activity, amount adsorbed, structure, thickness, topography, ability to desorb (stability), lateral mobility, interactions between adsorbed molecules, ability to change conformation, interfacial rheological properties, etc. -, the kinetics of film formation and other associated physico-chemical properties at fluid interfaces. These monolayers constitute well defined systems for the analysis of food colloids at the micro- and nano-scale level, with several advantages for fundamental studies. In the present review we are concerned with the analysis of physico-chemical properties of emulsifier films at fluid interfaces in relation to foaming. Information about the above properties would be very helpful in the prediction of optimised formulations for food foams. We concluded that at surface pressures lower than that of monolayer saturation the foaming capacity is low, or even zero. A close relationship was observed between foaming capacity and the rate of diffusion of the foaming agent to the air-water interface. However, the foam stability correlates with the properties of the film at long-term adsorption. 相似文献
314.
Csok Z Vechorkin O Harkins SB Scopelliti R Hu X 《Journal of the American Chemical Society》2008,130(26):8156-8157
A new pincer-type bis(amino)amine (NN2) ligand and its lithium and nickel complexes, including Ni(II) methyl, ethyl, and phenyl complexes, were synthesized. The Ni(II) alkyl complexes react cleanly with alkyl halides including chlorides to form C-C coupled products and Ni(II) halides. More interestingly, the Ni(II) alkyls undergo unprecedented reactions with CH2Cl2 and CHCl3 to cleave all the C-Cl bonds and replace them with C-C bonds. The reactions are highly selective and lead to the first efficient catalytic coupling of CH2Cl2 with alkyl Grignards. A conversion of 82% and a turnover number of 47 are achieved within minutes. Coupling of CD2Cl2 and 1,1-dichloro-3,3-dimethylbutane with nBuMgCl is also realized. Preliminary mechanistic study suggests a radical initiated process for these reactions. 相似文献
315.
Daniela Aiello Luca Malfatti Tongjit Kidchob Rosario Aiello Flaviano Testa Iolinda Aiello Mauro Ghedini Massimo La Deda Tonino Martino Maria Casula Plinio Innocenzi 《Journal of Sol-Gel Science and Technology》2008,47(3):283-289
Highly fluorescent materials have been prepared by incorporation of a zinc complex in mesoporous silica thin films with ordered
pore structure. The zinc complex has been introduced into the mesoporous materials via impregnation in an ethanol solution.
The incorporation into the films has been monitored by UV–Vis, Fourier transform infrared spectroscopy and spectroscopic ellipsometry.
After 18 h of immersion in the doping solution the films showed strong blue emission, increase in the refractive index. Leaching
experiments performed by immersing the samples in ethanol or tetrahydrofuran have shown that the chromophore is retained in
the porous matrix.
相似文献
Plinio InnocenziEmail: |
316.
Pedro Rosario José Luis Martínez José Miguel Silván 《Accreditation and quality assurance》2008,13(9):493-499
In analytical chemistry, proficiency testing usually consists in tests that laboratories conduct under routine conditions
and report the result to the PT provider who then converts the result to a score which helps the participant to assess the
accuracy of the result. The aim of this work is to show PT providers, accreditations bodies, and participating laboratories
that different scoring results can be achieved depending on the evaluation system selected. The influence of different evaluation
techniques on the results of an interlaboratory comparison for determination of gold in precious metals alloys was investigated.
Results from 19 participating laboratories were evaluated by means of the three procedures: (1) classical statistical approach—outliers
detection; (2) robust methods—(2A) robust procedure and (2B) ISO 13528; and (3) fitness for purpose. Evaluation of the same
PT data revealed very interesting issues depending on the different scoring systems that were used and the robustness of the
statistical methods used for detecting outliers. As a general rule, laboratories with scoring Z > 2 offered clearly poorer performance in robust approaches than classical ones. In order to support this first evidence,
we evaluated a second data set with results from 24 laboratories (mercury from soil samples) by means of the four mentioned
approaches. Selection and comparison of different scoring systems must be done very carefully, because sometimes they are
not the best approach for studying the data population or the more appropriate one for evaluating the distribution of the
data. Finally it should be taken into account that sometimes the robust scoring systems are not always suitable for evaluating
the results of some PT schemes. 相似文献
317.
Adrian B. Chaplin Zoltán Béni Christian G. Hartinger Hisham Ben Hamidane Andrew D. Phillips Rosario Scopelliti Paul J. Dyson 《Journal of Cluster Science》2008,19(1):295-309
The new mixed-metal complex {anti-[(p-cymene)RuCl]-μ-[κ
2-P,P′;κ
1-P′′-(PPh2CH2)3CMe]-[AuCl]}PF6 and its cluster derivative {anti-[(p-cymene)RuCl]-μ-[κ
2-P,P′;κ
1-P′′-(PPh2CH2)3CMe]-[AuPt3(CO)3(PCy3)3]}(PF6)2 have been prepared and characterized. Notably, NMR spectroscopy and high resolution FT-ICR mass spectrometry, including a
tandem mass spectrometric analysis, demonstrated the formation of these compounds that was also confirmed by single crystal
X-ray diffraction analysis. 相似文献
318.
Sanz-Medel A Montes-Bayón M del Rosario Fernández de la Campa M Encinar JR Bettmer J 《Analytical and bioanalytical chemistry》2008,390(1):3-16
In the last decade mass-spectrometry-based proteomics has become an indispensable analytical tool for molecular biology, cellular
biology and, lately, for the emerging systems biology. This review summarises the evolution and great potential of analytical
methods based on elemental mass-spectrometric detection for quantitative proteomic analysis. 相似文献
319.
Concellón JM Rodríguez-Solla H Méjica C Blanco EG García-Granda S Díaz MR 《Organic letters》2008,10(2):349-352
A novel chromium-promoted alkyl- and silyl cyclopropanation of (E)- or (Z)-alpha,beta-unsaturated amides in which the C-C double bond is di-, or trisubstituted is described. This process takes place with total stereospecificity, and the new stereogenic center is generated with high or total stereoselectivity. A mechanism is proposed to explain the cyclopropanation reaction. 相似文献
320.
Delgado JL Cardinali F Espíldora E Torres MR Langa F Martín N 《Organic letters》2008,10(17):3705-3708
A new building block for fullerene chemistry, endowed with a formyl group on C-3 of the 2-pyrazoline ring, has been prepared in a simple two-step synthesis by oxidation of readily available 3-alkyl-substituted 2-pyrazolino[60]fullerenes; the new building block paves the way for the preparation of new light-harvesting fullerenes. 相似文献