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排序方式: 共有402条查询结果,搜索用时 15 毫秒
91.
92.
Sciacca B Pace S Rivolo P Geobaldo F 《Physical chemistry chemical physics : PCCP》2012,14(15):5251-5254
A nanostructured porous silicon chip functionalized with dichlorofluorescein is employed as a nanoreactor to respond to Reactive Oxygen Species (ROS) and to real-time studying redox reactions. 相似文献
93.
Nature performs a vital but uniquely energetic reaction within Photosystem II (PS II), resulting in the oxidation of two water molecules to yield O(2) and bio-energetic electrons, as reducing equivalents. Almost all life on earth ultimately depends on this chemistry, which occurs with remarkable efficiency within a tetramanganese and calcium cluster in the photosystem. The thermodynamic constraints for the operation of this water oxidising Mn(4)/Ca cluster within PS II are discussed. These are then examined in the light of the known redox chemistry of hydrated Mn-oxo systems and relevant model compounds. It is shown that the latest high resolution crystal structure of cyanobacterial PS II suggests an organization of the tetra-nuclear Mn cluster that naturally accommodates the stringent requirements for successive redox potential constancy with increasing total oxidation state, which the enzyme function imposes. This involves one region of the Mn(4)/Ca cluster being dominantly involved with substrate water binding, while a separate, single Mn is principally responsible for the redox accumulation function. Recent high level computational chemical investigations by the authors strongly support this, with a computed pattern of Mn oxidation states throughout the catalytic cycle being completely consistent with this interpretation. Strategies to design synthetic, bio-mimetic constructs utilising this approach for efficient electrolytic generation of hydrogen fuel within Artificial Photosynthesis are briefly discussed. 相似文献
94.
Deep-ultraviolet resonance Raman (DUVRR) spectra is sensitive to secondary structural motifs but, similar to circular dichroism (CD) and infrared spectroscopy, requires the application of multivariate and advanced statistical analysis methods to resolve the pure secondary structure Raman spectra (PSSRS) for determination of secondary structure composition. Secondary structure motifs are selectively enhanced by different excitation wavelengths, a characteristic that inspired the first methods for quantifying secondary structures by DUVRR. This review traces the evolution of multivariate methods and their application to secondary structure composition analyses of proteins by DUVRR spectroscopy from the first experiments using two-wavelengths, and culminating with recent studies utilizing time-resolved DUVRR measurements. 相似文献
95.
Pace S Seantier B Belamie E Lautrédou N Sailor MJ Milhiet PE Cunin F 《Langmuir : the ACS journal of surfaces and colloids》2012,28(17):6960-6969
Classical methods for characterizing supported artificial phospholipid bilayers include imaging techniques such as atomic force microscopy and fluorescence microscopy. The use in the past decade of surface-sensitive methods such as surface plasmon resonance and ellipsometry, and acoustic sensors such as the quartz crystal microbalance, coupled to the imaging methods, have expanded our understanding of the formation mechanisms of phospholipid bilayers. In the present work, reflective interferometric Fourier transform spectrocopy (RIFTS) is employed to monitor the formation of a planar phospholipid bilayer on an oxidized mesoporous Si (pSiO(2)) thin film. The pSiO(2) substrates are prepared as thin films (3 μm thick) with pore dimensions of a few nanometers in diameter by the electrochemical etching of crystalline silicon, and they are passivated with a thin thermal oxide layer. A thin film of mica is used as a control. Interferometric optical measurements are used to quantify the behavior of the phospholipids at the internal (pores) and external surfaces of the substrates. The optical measurements indicate that vesicles initially adsorb to the pSiO(2) surface as a monolayer, followed by vesicle fusion and conversion to a surface-adsorbed lipid bilayer. The timescale of the process is consistent with prior measurements of vesicle fusion onto mica surfaces. Reflectance spectra calculated using a simple double-layer Fabry-Perot interference model verify the experimental results. The method provides a simple, real-time, nondestructive approach to characterizing the growth and evolution of lipid vesicle layers on the surface of an optical thin film. 相似文献
96.
97.
M. D. Pace 《Applied magnetic resonance》1996,11(2):253-261
Thermal and photochemical free radical reaction products of C60 with polymethyl methacrylate (PMMA) and polystyrene (PS) in orthodichlorobenzene solution were detected by EPR (electron paramagnetic resonance). Thermal radicals (<100°C) of C60/PMMA and C60/PS samples gave single line first-derivative EPR spectra withg=2.0029. Ultraviolet photolysis of a C60/PMMA solid phase sample gave two radical species; whereas, photolysis of a C60/PS solid phase sample gave only one free radical. EPR signals were also recorded for UV and thermal C60 reaction with free radical initiator, azobis(isobutyronitrile). 相似文献
98.
Multi-nucleon transfer reactions in 40Ca + 208Pb have been studied at several bombarding energies close to the Coulomb barrier. Light reaction products have been identified in mass and charge with a time-of-flight spectrometer. The energy spectra of the inclusive two-neutron pick-up channel show a population in a narrow region of excitation energies which corresponds to the predicted energy of pairing-vibration states in 42Ca.Received: 30 September 2003, Revised: 9 December 2003, Published online: 13 July 2004PACS:
25.70.Hi Transfer reactions - 24.10.-i Nuclear reaction models and methods - 21.60.Cs Shell model - 21.10.Pc Single-particle levels and strength functionsA.M. Vinodkumar: Present address: Tokyo Institute of Technology, Japan. 相似文献
99.
100.
Phenanthroline complexes bearing fused dipyrrolylquinoxaline anion recognition sites: efficient fluoride anion receptors 总被引:2,自引:0,他引:2
Novel anion recognition host molecules, tris-1,10-phenanthroline cobalt(III) and bis-2,2'-bipyridine mono-1,10-phenanthroline ruthenium(II) complexes bearing fused dipyrrolylquinoxaline moieties have been synthesized. As determined by UV-vis spectroscopic and electrochemical studies, these metal complexes bind fluoride with high affinity in polar media both in absolute terms and relative to the metal-free phenanthroline dipyrrolylquinozaline precursor from which they are derived (fluoride is bound to the tris-1,10-phenanthroline cobalt(III) dipyrrolylquinoxaline system with a 1:1 binding constant of 54 000 M-1 in DMSO). The large observed binding constants are ascribed to two factors, (i) the presence of a phenanthroline-coordinated cationic charge that decreases the electron density on the pyrrole NH protons and (ii) pure electrostatic effects. 相似文献