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排序方式: 共有163条查询结果,搜索用时 31 毫秒
81.
The atomic force microscope (AFM) is a powerful instrument for microbiological investigation. It has evolved from an imaging tool used to investigate microbial surfaces at high resolution in their physiological environment into a lab-on-a-tip device, which allows more quantitative analysis of biological samples (from molecules to cells) in aqueous liquids. Atomic force microscopy provides information about the nanoscale architecture of microbes and about the localization and interactions of their individual constituents. Microbial interactions play essential roles in biology, medicine, ecology, biotechnology, food science and contribute to phenomena as varied as bacterial infections, biofilm formation, and bacterial adhesion to surfaces. In this review, we focus on recent developments offered by the rapid advances in AFM imaging and force spectroscopy with emphasizes on microbial research. 相似文献
82.
Tan JC Civalleri B Lin CC Valenzano L Galvelis R Chen PF Bennett TD Mellot-Draznieks C Zicovich-Wilson CM Cheetham AK 《Physical review letters》2012,108(9):095502
Using Brillouin scattering, we measured the single-crystal elastic constants (C(ij)'s) of a prototypical metal-organic framework (MOF): zeolitic imidazolate framework (ZIF)-8 [Zn(2-methylimidazolate)(2)], which adopts a zeolitic sodalite topology and exhibits large porosity. Its C(ij)'s under ambient conditions are (in GPa) C(11)=9.522(7), C(12)=6.865(14), and C(44)=0.967(4). Tensorial analysis of the C(ij)'s reveals the complete picture of the anisotropic elasticity in cubic ZIF-8. We show that ZIF-8 has a remarkably low shear modulus G(min) < or approximately 1 GPa, which is the lowest yet reported for a single-crystalline extended solid. Using ab initio calculations, we demonstrate that ZIF-8's C(ij)'s can be reliably predicted, and its elastic deformation mechanism is linked to the pliant ZnN(4) tetrahedra. Our results shed new light on the role of elastic constants in establishing the structural stability of MOF materials and thus their suitability for practical applications. 相似文献
83.
Donato Monti Dr. Massimo De Rossi Dr. Alessandro Sorrenti Dr. Giuseppe Laguzzi Dr. Emanuela Gatto Dr. Manuela Stefanelli Dr. Mariano Venanzi Prof. Loredana Luvidi Dr. Giovanna Mancini Dr. Roberto Paolesse Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(3):860-870
The solvent‐promoted aggregation behavior of some amphiphilic porphyrin derivatives bearing chiral functionality in the form of a charged L ‐proline group has been investigated by UV/Vis, resonance light scattering, fluorescence and circular dichroism spectroscopy. The investigated macrocycles give rise to aggregates featuring supramolecular chirality with high ellipticity. Kinetic studies reveal peculiar differences in the fashion of aggregation, depending on the intimate nature of the chiral functionality, namely, cationic (nitrogen‐quaternized L ‐proline, 3H2 ) or anionic (carboxylate residue, 6H2 ) group. Formation of anionic 6H2 aggregates shows a diffusion‐limited kinetic behavior. AFM topography studies show formation of tighter globular structures. On the other hand, the corresponding 3H2 aggregates are formed by a cooperative, fractal‐type decay, and appear as long‐fibrous, looser structures. In the templated aggregation of 3H2 over preformed 6H2 aggregates, AFM images show formation of globular structures with reduced sizes, as a likely consequence of shorter interchromophore distances, due to favorable Coulombic interactions. The results obtained show an interesting parallelism between the solution behavior and the solid‐state aggregate structures, corroborating the sergeant–soldier effect observed in the templated aggregation. The results presented give important insights for understanding the complex mechanisms involved in these issues, which are of key importance for the development of chiral supramolecular materials and stereoselective sensors and devices. 相似文献
84.
Jaime Ortega Jorge San Martín Loredana Smaranda 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,188(4):969-993
In this paper, we use the Bloch wave method to study the asymptotic behavior of the solution of the Laplace equation in a
periodically perforated domain, under a non-homogeneous Neumann condition on the boundary of the holes, as the size of the
holes goes to zero more rapidly than the domain period. This method allows to prove that, when the hole size exceeds a given
threshold, the non-homogeneous boundary condition generates an additional term in the homogenized problem, commonly referred
to as “the strange term” in the literature. 相似文献
85.
Fabio Mazzotti Leonardo Di Donna Barbara Macchione Loredana Maiuolo Enzo Perri Giovanni Sindona 《Rapid communications in mass spectrometry : RCM》2009,23(10):1515-1518
Crop control is an important issue in both developed and developing countries. An environmentally friendly approach is represented by the so‐called Integrated Pest Management (IPM), whereby synthetic pesticides are only applied as a last resort, under the strict control of suitable experts. European and US regulatory authorities, such as the US EPA, are constantly assessing the risks of exposure to the organophosphate (OP) class of pesticides and, among these, specifically dimethoate. The use of dimethoate is still allowed in many crops, including olives, which once was based in the Mediterranean area but now is expanding rapidly throughout the world. An important aspect of IPM protocols is represented by the availability of reliable and sensitive methods to detect pesticides residues. This paper describes an isotope dilution dimethoate assay based on the application of electrospray ionization tandem mass spectrometry (ESI‐MS/MS) by means of a deuterium‐labeled internal standard. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
86.
Marta L. Borges Loredana Latterini Fausto Elisei Palmira F. Silva Rui Borges Ralph S. Becker António L. Maçanita 《Photochemistry and photobiology》1998,67(2):184-191
The larger photobiological activity of visnagin (VI) versus khellin (KH) toward several living organisms, including fungi, viruses, yeasts and bacteria, induced a detailed investigation of the photophysical properties of these naturally occurring furanochromones, using laser-flash-photolysis, photoacoustic calorimetry and fluorescence (steady-state and time-resolved) techniques in solvents with different polarity and content of water, including micelles and vesicles. The results have shown that the magnitude of all the three rate constants out of S1 (radiative, kf; internal conversion, kic and intersystem crossing, kisc) for VI and KH strongly depend on the solvent, namely on its hydrogen bonding ability and polarity. The changes of kf and kisc are due to the solvent-assisted mixing and/or inversion of the two first singlet excited states (1n,π* and 1π,π*), while kic increases with a decrease of the So–S1 energy gap. As a consequence, the quantum yield of triplet formation (φT) strongly decreases from values of ?0.8 in dioxane to < 0.05 in water for both compounds. The magnitude of solvent polarity/hydrogen bonding ability required, at which the state order is inverted and φT starts to decrease, is greater for VI than for KH and consequently φT (VI) > φT (KH) over a broad range of water content including that appropriate to the environment of the compounds in a living system. These facts account for the larger photobiological activity of VI with respect to KH, regarding both the fungus Fusarium culmorum L. and the wild strain of Escherichia coli, studied by us. 相似文献
87.
Renato DalpozzoAntonio De Nino Loredana MaiuoloAntonio Procopio Monica NardiGiuseppe Bartoli Roberto Romeo 《Tetrahedron letters》2003,44(30):5621-5624
Cerium(III) triflate is a powerful catalyst for the acetylation of alcohols. The reaction works well for a large variety of simple and functionalized alcohols, without isomerisation of chiral centres. Changes of hydroxyl protective groups are possible in a one-pot procedure. The catalyst can be easily recycled. 相似文献
88.
Tanţa Spătaru Maria Marcu Loredana Preda Petre Osiceanu Jose Maria Calderon Moreno Nicolae Spătaru 《Journal of Solid State Electrochemistry》2011,15(6):1149-1157
Polytyramine (PTy) is shown to be a possible alternative to other conducting polymers as a support material for fuel cell
electrocatalysts such as platinum. In this work, a Pt–PTy composite was prepared via potentiodynamic deposition of polytyramine
on graphite substrate, followed by the electrochemical deposition of Pt nanoparticles. The material obtained by this straightforward
method exhibited, for platinum loadings as low as ca. 0.12 mg cm−2, a specific electrochemically active surface area of the electrocatalyst of ca. 54 m2 g−1, together with a good electrocatalytic activity for methanol oxidation in acidic media, thus ensuring better efficiency of
Pt utilization. The system Pt–PTy appears to be worthy of development for methanol fuel cell applications also because the
results suggested that, when deposited as small particles in a PTy matrix, platinum is less sensitive to fouling during CH3OH oxidation. 相似文献
89.
Adinolfi M Capasso D Di Gaetano S Iadonisi A Leone L Pastore A 《Organic & biomolecular chemistry》2011,9(18):6278-6283
Symmetrical glycosyl disulfides can be prepared within a few hours from per-O-acetylated precursors via a sequential approach entailing short reactions and no purification of any intermediate. The final thiolate-to-disulfide oxidation step is noticeably accelerated by low amounts of phenyl diselenide under air. Applicability of the strategy to non-saccharidic symmetrical alkyl disulfides has also been examined. A preliminary assay of the cytotoxic activity of symmetrical 1,1'- disulfides was performed on two human tumor cell lines, and a noteworthy activity was recorded for a range of these synthetic compounds. 相似文献
90.
Raffaella Polito Mattia Musto Maria Eleonora Temperini Laura Ballerini Michele Ortolani Leonetta Baldassarre Loredana Casalis Valeria Giliberti 《Molecules (Basel, Switzerland)》2021,26(4)
Extracellular vesicles are membrane-delimited structures, involved in several inter-cellular communication processes, both physiological and pathological, since they deliver complex biological cargo. Extracellular vesicles have been identified as possible biomarkers of several pathological diseases; thus, their characterization is fundamental in order to gain a deep understanding of their function and of the related processes. Traditional approaches for the characterization of the molecular content of the vesicles require a large quantity of sample, thereby providing an average molecular profile, while their heterogeneity is typically probed by non-optical microscopies that, however, lack the chemical sensitivity to provide information of the molecular cargo. Here, we perform a study of individual microvesicles, a subclass of extracellular vesicles generated by the outward budding of the plasma membrane, released by two cultures of glial cells under different stimuli, by applying a state-of-the-art infrared nanospectroscopy technique based on the coupling of an atomic force microscope and a pulsed laser, which combines the label-free chemical sensitivity of infrared spectroscopy with the nanometric resolution of atomic force microscopy. By correlating topographic, mechanical and spectroscopic information of individual microvesicles, we identified two main populations in both families of vesicles released by the two cell cultures. Subtle differences in terms of nucleic acid content among the two families of vesicles have been found by performing a fitting procedure of the main nucleic acid vibrational peaks in the 1000–1250 cm−1 frequency range. 相似文献