An improved pixel-based approach for analyzing images in two-dimensional gel electrophoresis

An improved pixel-based approach for analyzing 2-DE images is presented. The key feature of the method is to create a mask based on all gels in the experiment using image morphology, followed by multivariate analysis on the pixel level. The method reduces the impact of noise and background by identifying regions in the image where protein spots are present, but make no assumption on individual spot boundaries for isolated spots. This makes it possible to detect significant changes in complex regions, and visualize these changes over multiple gels in an easy way. False missing values and spot volumes caused by imposing erroneous spot boundaries are thus circumvented. The approach presented gives improved pixel-based information from the gels, and is also an alternative to existing methods for data-reduction, significance testing and visualization of 2-DE data. Results are compared with software using a common spot boundary approach on an experiment consisting of 35 full size gel images. Gel alignment is required before analysis.     

One-step controllable synthesis for high-quality ultrafine metal oxide semiconductor nanocrystals via a separated two-phase hydrolysis reaction

A one-step synthesis method is described to prepare high-quality ultrafine inorganic semiconductor nanocrystals via a two-phase interface hydrolysis reaction under hydrothermal conditions. With the synthesis of ZrO2 quantum dots as an example, we show that the prepared nanocrystals have good monodispersity and high crystallinity, as well as other related superior properties, e.g., strong photoluminescence and excellent photocatalytic activities. Also the crystal size can be conveniently adjusted in the range below 10 nm through controlling the reaction temperature. Besides that, this method also shows other distinct advantages compared with other methods reported previously. First, the preparation process is simple and cheap and does not contain any complicated posttreatment procedure. Second, products (without coating) can be collected from the organic phase which effectively avoids grain aggregation induced by the capillary concentration in the water environment. Third, the production yield is very high (almost 100%) and the organic and water phases after reaction can be easily recycled for next reaction. Therefore, it provides a promising strategy for the large-scale industrial production of different kinds of high-quality inorganic nanocrystals.     

Immobilization of light-harvesting chlorophyll a/b complex (LHCIIb) studied by surface plasmon field-enhanced fluorescence spectroscopy

The major light-harvesting chlorophyll a/ b complex (LHCIIb) of the photosynthetic apparatus in green plants can be viewed as a protein scaffold binding and positioning a large number of pigment molecules that engage in rapid excitation energy transfer. This property makes LHCIIb potentially interesting as a light harvester (or a model thereof) in photoelectronic applications. Such applications would require the immobilization of LHCIIb (or similar dye-protein complexes) on a solid surface. In this work, the immobilization of recombinant LHCIIb is tested and optimized on functionalized gold surfaces via a histidine 6 tag (His tag) in the protein moiety. Immobilization efficiency and kinetics are analyzed by using surface plasmon resonance (SPR) and surface plasmon field-enhanced fluorescence spectroscopy (SPFS). The latter was also used to assess the integrity of immobilized LHCIIb by recording Chl b-sensitized Chl a emission spectra. Since His tags have been included in a substantial number of recombinant proteins, the immobilization technique developed here for LHCIIb presumably can be extended to a large range of other membrane and water-soluble proteins.     

Doubly pH-responsive pickering emulsion

A pH-responsive Pickering emulsion has been designed on the basis of commercially available alumina-coated silica nanoparticles (Ludox CL silica particles) and potassium hydrogen phthalate (KHP). KHP was found to bind to cationic particle surfaces at pH values between 3.5 and 5.5, enabling the resulting surface-active particles to stabilize emulsions of xylenes in water. Above and below this pH range, the system demulsifies, resulting in a reversible Pickering emulsifier having two pH-controlled, reversible transitions.     

Iron chelates of 2,2'-bidipyrrin: stable analogues of the labile iron bilins

A unique series of halogenidoiron(III) complexes of the open-chain tetrapyrrolic ligand 2,2'-bidipyrrin (bpd) ([FeX(bdp)] X=F, Cl, Br, I) was prepared from simple pyrrolic and bipyrrolic precursors and iron chloride by a one-pot condensation/metalation strategy, followed by salt metathesis with CsF, LiBr, or NaI. Crystallographic analysis revealed that in all cases the 2,2'-bidipyrrin ligand is forced to reside in a helical conformation when bound to the iron atom. Whereas the extremely sensitive fluorido derivative was isolated as a CsF adduct and forms 1D polymeric chains in the solid state, the more stable chlorido, bromido, and iodido derivatives crystallize as discrete monomeric molecules with a distorted pentacoordinate iron(III) ion in an intermediate spin ground state. Magnetic susceptibility measurements and M?ssbauer data of the compounds are in agreement with this interpretation. In solution, however, all the compounds are pentacoordinate with the iron atom in the high-spin (S=5/2) state and dynamic with respect to helix inversion. In the presence of air, the iron chelates react stepwise with the nucleophiles methanol and imidazolate at the tetrapyrrole terminal alpha,omega-positions, presumably through the hexacoordinate species [Fe(bdp)(MeOH)2]+ and [Fe(im)2-(bdp)](-), respectively. The successive increase of strain at these positions results in increasingly labile intermediates that spontaneously release the iron ion from the mono- or disubstituted tetrapyrrole ligands.     

A microwave and quantum chemical study of cyclopropaneselenol

The microwave spectrum of cyclopropaneselenol, C 3H 5SeH, has been investigated in the 21.9-80 GHz frequency range. The microwave spectra of the ground vibrational state of five isotopologues of cyclopropaneselenol (C 3H 5 (82)SeH, C 3H 5 (80)SeH, C 3H 5 (78)SeH, C 3H 5 (77)SeH, and C 3H 5 (76)SeH) of one conformer, as well as the spectra of two vibrationally excited states of each of the C 3H 5 (80)SeH and C 3H 5 (78)SeH isotopologues of this rotamer, have been assigned. The H-C-Se-H chain of atoms is synclinal in this conformer, and there is no indication of further rotameric forms in the microwave spectrum. The b-type transitions of the ground vibrational state of the more abundant species C 3H 5 (80)SeH and C 3H 5 (78)SeH were split into two components, which is assumed to arise from tunneling of the proton of the selenol group between two equivalent synclinal potential wells. The tunneling frequencies were 0.693(55) MHz for C 3H 5 (80)SeH and 0.608(71) MHz for C 3H 5 (78)SeH. The microwave study has been augmented by high-level density functional and ab initio quantum chemical calculations, which indicate that the H-C-Se-H dihedral angle is approximately 75 degrees from synperiplanar (0 degrees).     

A microwave and quantum chemical study of cyclopropanethiol

The microwave spectra of cyclopropanethiol, C(3)H(5)SH, and one deuterated species C(3)H(5)SD, have been investigated in the 20 - 80 GHz frequency range. The spectra of the ground vibrational state and of three vibrationally excited states of the parent species of a conformer which has a synclinal ("gauche") arrangement for the H-C-S-H chain of atoms, was assigned. The H-C-S-H dihedral angle is 76(5)° from synperiplanar (0°). The b-type transitions of the ground and of the vibrationally excited states of the parent species were split into two components, which is assumed to arise from tunneling of the proton of the thiol group between two equivalent synclinal potential wells. No splitting was resolved in the spectrum of C(3)H(5)SD. The tunneling frequency of the ground vibrational state of C(3)H(5)SH is 1.664(22) MHz. The tunneling frequency of the first excited-state of the C-S torsion is 52.330(44) MHz, whereas this frequency is 26.43(13) and 3.286(61) MHz, respectively, for the first excited states of the two lowest bending vibrations. The dipole moment of the ground vibrational state of the parent species is μ(a) = 4.09(5), μ(b) = 2.83(11), μ(c) = 0.89(32), and μ(tot) = 5.06(16) × 10(-30) C m. The microwave study has been augmented by high-level density functional and ab initio quantum chemical calculations.     

An IEF-PCM study of solvent effects on the Faraday {\mathcal{B}} term of MCD

We present the first theoretical investigation of solvent effects on the Faraday ${\mathcal{B}}$ term of magnetic circular dichroism (MCD) at the density–functional level of theory. In our model, the solvent is described by the polarizable continuum model in its integral-equation formulation. We present the extensions required for including electron correlation effects using density–functional theory (DFT) as well as the necessary extensions for including the effects of a dielectric continuum. The new code is applied to the study of the Faraday ${\mathcal{B}}$ term of MCD in a series of benzoquinones. It is demonstrated that electron correlation effects, as described by DFT, are essential in order to recover the experimentally observed signs of the ${\mathcal{B}}$ term. Dielectric continuum effects increase, in general, the magnitude of the ${\mathcal{B}}$ term, leading to an overestimation of the experimental observations in most cases.