Structure and dynamics of photosystem II light-harvesting complex revealed by high-resolution FTICR mass spectrometric proteome analysis

Structure and dynamics of membrane-bound light-harvesting pigment-protein complexes (LHCs), which collect and transmit light energy for photosynthesis and thereby play an essential role in the regulation of photosynthesis and photoprotection, were identified and characterized using high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LHCs from photosystem II (LHCII) were isolated from the thylakoid membrane of Arabidopsis thaliana leaves after light stress treatment using sucrose density gradient centrifugation, and separated by gel-filtration into LHCII subcomplexes. Using reversed-phase high-performance liquid chromatography and two-dimensional (2D) gel electrophoresis, the LHCII proteins, Lhcb1-6 and fibrillins, were efficiently separated and identified by FTICR-MS. Some of the LHCII subcomplexes were shown to migrate from photosystem II to photosystem I as a result of short-term adaptation to changes in light intensity. In the mobile LHCII subcomplexes, decreased levels of fibrillins and a modified composition of LHCII protein isoforms were identified compared to the tightly bound LHCII subcomplexes. In addition, FTICR-MS analysis revealed several oxidative modifications of LHCII proteins. A number of protein spots in 2D gels were found to contain a mixture of proteins, illustrating the feasibility of high-resolution mass spectrometry to identify proteins that remain unseparated in 2D gels even upon extended pH gradients.     

Construction of a porous homochiral coordination polymer with two types of Cu(n)I(n) alternating units linked by quinine: a solvothermal and a mechanochemical approach

The polymer network: The reaction of quinine (QN) with CuI under solvothermal, as well as liquid-assisted grinding, conditions afforded a unique 1D homochiral coordination polymer {[Cu(4)(μ(3)-I)(4)(QN)(2)][Cu(3)(μ(3)-I)(2)(μ(2)-I)(QN)(2)](2)}(n), containing both triangular Cu(3)I(3) and cubane Cu(4)I(4) clusters as connecting nodes (see scheme). Van der Waals interactions between the adjacent 1D polymer chains lead to an extended quasi-honeycomb homochiral pillared 3D network with solvent-free 1D channels.     

Voltammetry as a Reference Method in the Preparation Process of Plant Control Material Containing As,Pt and Tl

Voltammetric methods are very suitable and versatile techniques for the simultaneous metal determination in complex matrices after thorough mineralization. In the presented work, voltammetric methods were used as reference methods in the preparation process of control plant material. Determination of As, Pt, Tl and other elements (Cd, Cu, Pb, Zn) in plant material prepared in our laboratory is described. For quantitative determination of the elements two independent analytical methods were applied. To obtain plant material containing As, Pt and Tl white mustard (Sinapis alba L.) was hydroponically cultivated under controlled conditions in a nutrient solution with addition of As, Pt and Tl salts.     

Artificial light-harvesting arrays: electronic energy migration and trapping on a sphere and between spheres

A sophisticated model of the natural light-harvesting antenna has been devised by decorating a C(60) hexa-adduct with ten yellow and two blue boron dipyrromethene (Bodipy) dyes in such a way that the dyes retain their individuality and assist solubility of the fullerene. Unusually, the fullerene core is a poor electron acceptor and does not enter into light-induced electron-transfer reactions with the appended dyes, but ineffective electronic energy transfer from the excited-state dye to the C(60) residue competes with fluorescence from the yellow dye. Intraparticle electronic energy transfer from yellow to blue dyes can be followed by steady-state and time-resolved fluorescence spectroscopy and by excitation spectra for isolated C(60) nanoparticles dissolved in dioxane at 293 K and at 77 K. The decorated particles can be loaded into polymer films by spin coating from solution. In the dried film, efficient energy transfer occurs such that photons absorbed by the yellow dye are emitted by the blue dye. Films can also be prepared to contain C(60) nanoparticles loaded with the yellow Bodipy dye but lacking the blue dye and, under these circumstances, electronic energy migration occurs between yellow dyes appended to the same nanoparticle and, at higher loading, to dye molecules on nearby particles. Doping these latter polymer films with the mixed-dye nanoparticle coalesces these multifarious processes in a single system. Thus, long-range energy migration occurs among yellow dyes attached to different particles before trapping at a blue dye. In this respect, the film resembles the natural photosynthetic light-harvesting complexes, albeit at much reduced efficacy. The decorated nanoparticles sensitize amorphous silicon photocells.     

Magnetic resonance study of carbon encapsulated Ni nanoparticles

Magnetic resonance study of six samples consisting of carbon encapsulated nickel nanoparticles or carbon nanotubes ended with such nickel nanoparticles was carried out at room temperature. Samples of Ni/C were prepared by carburization of nanocrystalline nickel by ethylene (C₂H₄) and methane (CH₄). Hydrocarbons decomposition on nickel nanoparticles was done at temperatures 500, 600 and 700°C. Magnetic resonance spectra of samples designated as CH₄/500, CH₄/600, CH₄/700, C₂H₄/500, C₂H₄/600 and C₂H₄/700 were obtained by Bruker E 500 spectrometer. The integrated intensities of the resonance spectra were correlated with the carburization conditions (temperature, type of hydrocarbon) during samples preparation. A core-shell model of the investigated samples allowed rough estimation of appropriate shell sizes.      

Ion-selective electrode for measuring low Ca2+ concentrations in the presence of high K+, Na+ and Mg2+ background

In this work, ion-selective electrodes for calcium ion were investigated. Two ionophores were used in the membranes: ETH 1001 and ETH 129. An internal filling solution buffered for primary ion was used that allowed the lower detection limit to be decreased down to 10^−8.8 M. Theoretical and experimental electrode characteristics pertaining to both primary and interfering ions are discussed. Better behavior was obtained with the electrode prepared with ETH 129 in the membrane. This electrode would be the most likely candidate for obtaining a low Ca²⁺ detection limit in measurements performed with high K⁺, Na⁺, Mg²⁺ background, which is found inside the cells of living organisms, for example. The potentiometric response of the electrode in solutions containing main and interfering ions is in good agreement with simulated curves obtained using the Nernst–Planck–Poisson (NPP) model.     

Fullerene Derivatives Functionalized with Diethylamino‐Substituted Conjugated Oligomers: Synthesis and Photoinduced Electron Transfer

Diethylamino‐substituted oligophenylenevinylene (OPV) building blocks have been prepared and used for the synthesis of two [60]fullerene–OPV dyads, F‐D1 and F‐D2 , which exhibit different conjugation length of the OPV fragments. The electrochemical properties of these acceptor–donor dyads have been studied by cyclic voltammetry. The first reduction is always assigned to the fullerene moiety and the first oxidation centered on the diethylaniline groups of the OPV rods, thus making these systems suitable candidates for photoinduced electron transfer. Both the OPV and the fullerene‐centered fluorescence bands are quenched in toluene and benzonitrile, which suggests the occurrence of photoinduced electron transfer from the amino‐substituted OPVs to the carbon sphere in the dyads in both solvents. By means of bimolecular quenching experiments, transient absorption spectral fingerprints of the radical cationic species are detected in the visible (670 nm) and near‐IR (1300–1500 nm) regions, along with the much weaker fullerene anion band at λ_max=1030 nm. Definitive evidence for photoinduced electron transfer in F‐D1 and F‐D2 comes from transient absorption measurements. A charge‐separated state is formed within 100 ps and decays in less than 5 ns.     

Weak convergence of products of sums of independent and non-identically distributed random variables

We study limit properties in the sense of weak convergence in the space D[0,1] of certain processes based on products of sums of independent and non-identically distributed random variables. The obtained results extend and generalize results known in the i.i.d. case.     

1,3‐Alternate calix[4]arene‐bonded silica stationary phases. Effect of calixarene skeleton substituents on the retention mechanism and column selectivity

Four novel 1,3‐alternate calix[4]arene‐bonded silica gel stationary phases possessing different aromatic and aliphatic substituents at the upper rim (CalixNph, CalixBph, CalixHex, and CalixDdc) were prepared and structurally characterized. The comparison and selectivity of these phases were done by using alkylbenzenes, fatty acid p‐bromophenacyl esters, aromatic positional isomers, and polynuclear aromatic hydrocarbons as analytes. Quantum chemistry calculations have also been performed (using an ab initio method) to support the experimental findings. The effect of the type and content of organic modifier on the retention and selectivity of the alkylbenzenes was studied. The retention mechanism is also discussed. The results indicate that the stationary phases behave like RP packings. However, inclusion complex formation and hydrophobic and π–π interactions seem to be involved in the separation process.