Synthesis and x-ray crystal structure of the TiMgCl5(OOCCH2Cl) · (ClCH2COOC2H5)3 Adduct

The synthesis of the TiMgCl₅(OOCCH₂Cl) · (ClCH₂COOC₂H₅)₃ adduct, obtained by reacting TiCl₄ with a solution of MgCl₂ in dry ClCH₂COOC₂H₅, is reported together with its molecular and crystal structure as determined by x-ray diffraction. The structure was solved by direct and Fourier methods and refined by least-squares techniques to R = 0.057 for 1318 independent observed reflections. Crystals are monoclinic, space-group P2₁/c, with 4 formula units in a unit-cell of dimensions a = 10.480(4), b = 19.641(9), c = 16.597(6) Å, β = 120.21(5)°. The titanium(IV) atom is octahedrally coordinated by five chlorine atoms and an oxygen atom of a OOCCH₂Cl residue. The magnesium atom is similarly coordinated by two chlorine atoms, the carbonyl oxygen atoms of three ClCH₂COOC₂H₅ molecules and an oxygen atom of the OOCCH₂Cl residue. The two octahedra share an edge by a double chlorine bridge between the magnesium and the titanium atoms and are also connected by the COO group of the OOCCH₂Cl residue. Changes in the configurations and dimensions with respect to the free acceptor and donor molecules are discussed.     

What is syncrystallization? States of the pH indicator methyl red in crystals of phthalic acid

The concept of syncrystallization was reinvestigated by focusing on phthalic acid (PA) grown with methyl red (MR). Crystals are alternately red and yellow in adjacent growth sectors. X-ray structures of MR and its cocrystals, revealing MR in the neutral, zwitterionic, and protonated states, as well as measurements of linear birefringence and linear dichroism of mixed crystals, were used to investigate mechanisms of PA coloring. These experiments were complemented by force field calculations of the lowest energy stable surfaces of expressed facets and energies of MR on and in crystals, as well as molecular orbital calculations of MR. Two MR species were detected in PA having distinct energies, polarizations, and face selectivities. Assignments of structures to these MRs, previously thought to be neutral and protonated, required a nuanced analysis of hydrogen bonds. The essential difference between yellow and red species is whether the MR carboxylic acid proton is inter- or intramolecularly hydrogen bound. Inferences about mixed crystal structure drawn from an examination of cocrystals of PA and MR are inconsistent with polarization spectroscopy signaling caution when using stoichiometric compounds as models of dilute solid solutions. Upon heating mixed crystals, linear dichroism diminishes and oriented, elongated pools of MR separate and pass through the bulk in directions perpendicular to the direction of elongation. These batonnets subsequently crystallize leaving macroscopic oriented crystals of a MR-rich phase within PA. No evidence was found for the simultaneous crystallization of MR and PA; however, the MR reorientation on heating as well as the separation and recrystallization of a MR-rich phase are distinct processes that could be embraced by the literal meaning of syncrystallization.     

Controlling the supramolecular assembly of redox-active dendrimers at molecular printboards by scanning electrochemical microscopy

Redox-active ferrocenyl (Fc)-functionalized poly(propylenimine) (PPI) dendrimers solubilized in aqueous media by complexation of the Fc end groups with beta-cyclodextrin (betaCD) were immobilized at monolayers of betaCD on glass ("molecular printboards") via multiple host-guest interactions. The directed immobilization of the third-generation dendrimer-betaCD assembly G3-PPI-(Fc)16-(betaCD)16 at the printboard was achieved by supramolecular microcontact printing. The redox activity of the patterned dendrimers was mapped by scanning electrochemical microscopy (SECM) in the positive feedback mode using [IrCl(6)](3-) as a mediator. Local oxidation of the Fc-dendrimers by the microelectrode-generated [IrCl(6)](2-) resulted in an effective removal of the Fc-dendrimers from the host surface since the oxidation of Fc to the oxidized form (Fc+) leads to a concomitant loss of affinity for betaCD. Thus, SECM provided a way not only to image the surface, but also to control the binding of the Fc-terminated dendrimers at the molecular printboard. Additionally, the electrochemical desorption process could be monitored in time as the dendrimer patterns were gradually erased upon multiple scans.     

Proteomics in cancer research: methods and application of array-based protein profiling technologies

With the human genome sequence now determined, the field of molecular medicine is moving beyond genomics to proteomics, the large-scale analysis of proteins.It is now possible to examine the expression of more than 1000 proteins using mass spectrometry technology coupled with various separation methods.Microarray technology is a new and efficient approach, for extracting relevant biomedical data and has a wide range of applications. It provides a versatile tool to study protein-protein, protein-nucleic acid, protein-lipid, enzyme-substrate and protein-drug interactions.This review paper will explore the key themes in proteomics and their application in clinical cancer research.     

Annual variation in photo acclimation and photoprotection of the photobiont in the foliose lichen Xanthoria parietina

Seasonal variation in maximal photochemical quantum yield (F(V)/F(M)) of photosystem II (PS II), light adapted quantum yield (Phi(II)) of PS II, non-photochemical quenching (NPQ), contents of chlorophylls, and xanthophyll cycle pigments (VAZ) was studied in Xanthoria parietina repeatedly sampled in one location in S Norway during one year. The seasonal course in the susceptibility to photoinhibition was evaluated as high light-induced changes (1,800 micromol photons m(-2) s(-1) for 24h) in F(V)/F(M), Phi(II), and NPQ, measured as the ability to recover after 2 and 20 h at low light in control thalli with a natural cortical parietin screen, and in thalli from which parietin had been removed prior to high light exposures. F(V)/F(M), Phi(II), chlorophyll content, and the conversion state of VAZ (DEPS) reached minimum in spring. At the same time, yearly maxima of VAZ content and NPQ were recorded. Thereafter, F(V)/F(M), Phi(II), and chlorophyll content increased gradually, reaching maximum values in late autumn. DEPS peaked already in summer. Similarly, VAZ and NPQ decreased from early summer until winter. All data show that the X. parietina photobiont acclimates to seasonal changes in solar radiation, consistent with the lichen's preference for well-lit habitats. However, a comparison with a study of seasonal acclimation in the X. parietina mycobiont shows that in order to understand the seasonal photobiont acclimation, one has to consider the seasonal variation in internal screening caused by the fungal regulation of the PAR-absorbing parietin. A joint effort of both bionts seems to be required to avoid serious photoinhibition.     

Potential‐induced optimization of ultra‐thin rear surface passivated CIGS solar cells

Ultra‐thin Cu(In,Ga)Se₂ (CIGS) solar cells with an Al₂O₃ rear surface passivation layer between the rear contact and absorber layer frequently show a “roll‐over” effect in the J–V curve, lowering the open circuit voltage (V_OC), short circuit current (J_SC) and fill factor (FF), similar to what is observed for Na‐deficient devices. Since Al₂O₃ is a well‐known barrier for Na, this behaviour can indeed be interpreted as due to lack of Na in the CIGS absorber layer. In this work, applying an electric field between the backside of the soda lime glass (SLG) substrate and the SLG/rear‐contact interface is investi‐gated as potential treatment for such Na‐deficient rear surface passivated CIGS solar cells. First, an electrical field of +50 V is applied at 85 °C, which increases the Na concentration in the CIGS absorber layer and the CdS buffer layer as measured by glow discharge optical emission spectroscopy (GDOES). Subsequently, the field polarity is reversed and part of the previously added Na is removed. This way, the J –V curve roll‐over related to Na deficiency disappears and the V_OC (+25 mV), J_SC(+2.3 mA/cm²) and FF (+13.5% absolute) of the rear surface passivated CIGS solar cells are optimized. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Rapid preparation of multifunctional surfaces for orthogonal ligation by microcontact chemistry

Microcontact chemistry has been applied to patterned glass and silicon substrates by successive reaction of unprotected and monoprotected heterobifunctional linkers with alkene-terminated self-assembled monolayers (SAMs) to produce bi-, tri-, and tetrafunctional surfaces. Photochemical microcontact printing of an azide thiol linker followed by immobilization of an acid thiol linker on an undecenyl-terminated SAM results in a well-defined, micropatterned surface with terminal azide, acid, and alkene groups. Biologically relevant molecules (biotin, carbohydrates) have been selectively attached to the surface by means of orthogonal ligation chemistry, and the resulting microarrays display selective binding to fluorescently labeled proteins. An orthogonally addressable, tetrafunctional surface (azide, acid, alkene, and amine) can be prepared by an additional printing step of a tert-butyloxycarbonyl (Boc)-protected alkyne amine linker on the azide structures by using the copper(I)-catalyzed azide-alkyne Huisgen cycloaddition and subsequent removal of the protective group.     

Mapping of surface-enhanced fluorescence on metal nanoparticles using super-resolution photoactivation localization microscopy

Photoactivation localization microscopy (PALM) was applied to study surface-enhanced fluorescence (SEF) on metal nanostructures (SEF-PALM). The detection of fluorescence from individual single molecules can be used to image the point-spread-function and spatial distribution of the fluorescence emitted in the vicinity of a metal surface. Due to the strong scattering effect, the angular distribution of the fluorescence is altered by metals, resulting in a spatial shift of fluorescence spots with respect to the metal nanostructures, and has to be taken into account in the analysis. SEF-PALM can be used to discriminate effects of labelling density when estimating the enhancement factor in SEF. Furthermore, nanostructures with sizes below the diffraction limit can be resolved using this technique. SEF-PALM is established as a powerful tool to study plasmon-mediated phenomena on metal nanostructures.