Synthesis,structure and radiative and nonradiative properties of a new Dy3+ complex with sulfonylamidophosphate ligand

In recent years there has been growing interest in lanthanide-based multifunctional materials that exhibit interesting photophysical properties. This work presents spectroscopic and crystallographic characterization of a new dysprosium complex with sulfonylamidophosphate ligand. The crystal structure of [NaDy(SP)₄]₂·i-PrOH was determined and refined. It turns out that the Dy(III) complex is not isostructural with earlier reported compounds and crystallizes in the monoclinic system (space group P2₁). Two crystallographically independent dysprosium atoms are in eight-fold coordination, with a triangular dodecahedron geometry. Absorption, emission (77 and 300 K) and excitation spectra as well as fluorescence decay time measurements allowed optical characterization of obtained complex. Efficient energy transfer from SP^– ligand to Dy³⁺ ion has been demonstrated. The Judd-Ofelt theory was applied to predict fundamental fluorescence properties of Dy³⁺ ion in the title chelate. The Judd-Ofelt intensity parameters were used to determine the emission transition probabilities, fluorescence branching ratios and radiative lifetime of the emitting ⁴F_9/2 level. The obtained results indicate that the investigated chelate can be a potential candidate for OLEDs emitting yellow light.     

Linking ABCC6 Deficiency in Primary Human Dermal Fibroblasts of PXE Patients to p21-Mediated Premature Cellular Senescence and the Development of a Proinflammatory Secretory Phenotype

Pseudoxanthoma elasticum (PXE) is a rare autosomal-recessive disorder that is mainly caused by mutations in the ATP-binding cassette sub-family C member 6 (ABCC6) gene. Clinically PXE is characterized by a loss of skin elasticity, arteriosclerosis or visual impairments. It also shares some molecular characteristics with known premature aging syndromes like the Hutchinson–Gilford progeria syndrome (HGPS). However, little is known about accelerated aging processes, especially on a cellular level for PXE now. Therefore, this study was performed to reveal a potential connection between premature cellular aging and PXE pathogenesis by analyzing cellular senescence, a corresponding secretory phenotype and relevant factors of the cell cycle control in primary human dermal fibroblasts of PXE patients. Here, we could show an increased senescence-associated β-galactosidase (SA-β-Gal) activity as well as an increased expression of proinflammatory factors of a senescence-associated secretory phenotype (SASP) like interleukin 6 (IL6) and monocyte chemoattractant protein-1 (MCP1). We further observed an increased gene expression of the cyclin-dependent kinase inhibitor (CDKI) p21, but no simultaneous induction of p53 gene expression. These data indicate that PXE is associated with premature cellular senescence, which is possibly triggered by a p53-independent p21-mediated mechanism leading to a proinflammatory secretory phenotype.     

Comparison of Different Mechanical Methods for the Modification of the Egg White Protein Ovomucin,Part A: Physical Effects

Egg white (EW) is required to be reduced in viscosity and particle size prior to chromatographic fractionation of single EW proteins. This study reports on an assessment of various shear devices for this purpose. Evaluation criteria for the head-to-head comparison of high-pressure homogenization, colloid mill, and toothed disc dispersing machine treatment were the achieved viscosity reduction as well as the network diminution, determined by particle size measurements. It was shown that each of the devices was able to decrease the viscosity by a reduction of fibril size. However, only the high-pressure homogenizer fulfills the requirement to disintegrate the fibrils sufficiently, so that they can be filtered through membranes with a pore size of 0.45 μm, which is indispensable for chromatographic fractionations. Generally, the achieved viscosities decreased with increasing energy input, independently of the specific shear forces resulting from the applied device. Otherwise, there was no direct correlation between the energy density and the extent of fibril destruction, indicating that the kind of energy depending on the respective device with its specific destruction mechanism was not decisive. To sum up, this study provides profound knowledge concerning the effects on the EW structure that result from different mechanical forces.     

Separation of the oxidation products of fatty acids by means of gas-liquid partition chromatography

Conclusions The oxidation of oleic, and particularly of linoleic and linolenic acids, indicated the presence of a considerable number of unexpected products in addition to those foreseen from a simple severance of the double bonds. The chromatograms of the oxidized pure C₁₈ acids, of Neo-Fat No. 140, and of a mixture of fatty acids from hydrolyzed soybean oil showed a striking similarity in many respects. It was not possible to identify all the peaks, especially those of trace amounts, in the chromatograms and to obtain a quantitative estimate of the oxidation products. Further work on this is in progress. The results indicate that gas-liquid partition chromatography is a sensitive method for the study of the oxidation of vegetable oils. Presented at the fall meeting, American Oil Chemists' Society, Chicago, Ill., September 24–26, 1956. One of the divisions of the Agricultural Research Service, U. S. Department of Agriculture.     

Exploiting the substrate tolerance of farnesyltransferase for site-selective protein derivatization

The site-selective modification of proteins with a functional group is an important biochemical technique, but covalent attachment of a desired group to a chosen site is complicated by the reactivity of other amino acid side chains, often resulting in undesired side reactions. One potential solution to this problem involves exploiting the activity of protein-modifying enzymes that recognize a defined protein sequence. Protein farnesyltransferase (FTase) covalently attaches an isoprenoid moiety to a cysteine unit in the context of a short C-terminal sequence that can be easily grafted onto recombinant proteins. Here we describe the synthesis of four phosphoisoprenoids functionalized with biotin, azide, or diene groups. These phosphoisoprenoids bound to FTase with affinities comparable to that of the native substrate. With the exception of the biotin-functionalized analogue, all the phosphoisoprenoids generated could be transferred to peptide and protein substrates by FTase. Unlike proteins modified with farnesyl moieties, Ypt7 prenylated with (2E,6E)-8-(azidoacetamido)-3,7-dimethylocta-2,6-dienyl groups did not oligomerize and showed no detectable increase in hydrophobicity. To assess the suitability of the functionalized isoprenoids for protein modifications they were further derivatized, both by Diels-Alder cycloaddition with 6-maleimidohexanoic acid and by Staudinger ligation with a phosphine. We demonstrate that the Staudinger ligation proceeds more rapidly and is more efficient than the Diels-Alder cycloaddition. Our data validate the use of FTase as a protein-modification tool for biochemical and biotechnological applications.     

Solution-state (15)N NMR spectroscopic study of alpha-C-phycocyanin: implications for the structure of the chromophore-binding pocket of the cyanobacterial phytochrome Cph1

The detailed structure of the chromophore-binding pocket in phytochrome proteins and the structural changes associated with its photocycle are still matters of debate. Insight into the structure and dynamics of the binding pocket has been gained through the comparison of a (15)N NMR spectrum of alpha-C-phycocyanin, which is often used as a model system for the study of phytochromes, with the previously described (15)N NMR spectrum of the cyanobacterial phytochrome Cph1. The former spectrum supports the hypothesis that all four nitrogen atoms of the alpha-C-phycocyanin chromophore are protonated, in analogy with the proposed protonation state for the P(r) and P(fr) forms of Cph1. The spectra show that the chromophores in both proteins exhibit a distinct dynamic behavior, as also indicated by a NOESY spectrum of Cph1. Finally, stereochemical arguments and a Cph1 homology model support the hypothesis that the chromophore in Cph1 is most likely in the ZZZssa conformation in the P(r) form of the protein.     

Synthesis,properties, and application of new benzothiazole‐based sensitisers in polymer chemistry

New photoinitiating systems composed of benzothiazolestyrylium dyes as chromophores and n‐butyltriphenylborate anion as electron donor were prepared and characterised. Photoredox pairs consisting of hemicyanine dyes and organoborate salts may act as visible‐light photoinitiators for the radical polymerisation of multifunctional acrylates. The efficiences of these photoinitiator systems are based on the free energy changes of an electron transfer from borate salt to the dye. Experimental results show that the photoinitiating ability of the photoredox pair tested strongly depends upon the reduction potential of hemicyanine dye, the oxidation potential of borate salt, and the structure of the dicationic dye.     

Development of new heterobicationic monomethine dyes as effective photoinitiator of free radical polymerization in visible‐light region

The dye initiators consisting of N‐[3‐(p‐alkylpyridine)propyl]‐2‐[N‐(3‐bromopropyl)quinoline]‐2‐methylenebenzotiazolium diiodides as chromophores and n‐butyltriphenylborate anion as electron donor were prepared to achieve an efficient photoinitiator of free radical polymerization in a visible‐light region. The relative photoinitiating efficiencies of novel photoinitiators of vinyl monomers polymerization were evaluated. The results obtained clearly documented that the bicationic photoinitiators exhibit a marked increase in the photoinitiation ability compared to the initiators consisting of a single charged hemicyanine dye. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A reference string sampling method with dynamically changing parameters

Wittneben proposed a technique which determines the structural characteristics of a program's memory referencing behavior based only on a sampling of the complete reference string. This method controls the cost of the measurement by adjusting the sampling rate while simultaneously attempting to determine accurately the referencing behavior as reflected in its working set measurements. Wittneben's method is controlled by parameters with statically determined values. The aim of this paper is to present a modified sampling method in which sampling parameters are updated dynamically according to the actual program referencing behavior. The updating process is controlled by the phase-transition structure of a program. Furthermore, working set measurements of the program are based on modified principles which take into account the most probable sources of errors made during the sampling process. Experiments conducted with synthetic and real reference strings seem to demonstrate the superiority of the modified method in comparison with the technique originally formulated by Wittneben.     

Abnormal Phenomena of Multi-Way Sodium Storage in Selenide Electrode

Transition-metal chalcogenides have gained special attention as potential anodes for Na-ion batteries due to their high capacities to originate from complex charge storage mechanisms. Although the sodium storage process in chalcogenides is still unclear, it is common to assume that it can occur via one of the following routes: intercalation, conversion, or alloying. In this paper, an anomalous multi-way mechanism in MoSe₂ electrode, including all three of the above scenarios, is reported. The intercyclic product of the discharge/charge process is a mixture of Se, Mo, and 1T-structured Na_xMoSe₂. An unexpected phenomena of Se precipitation leads to the additional alloying reaction, which is exclusive among all chalcogenides, and runs together with conversion and intercalation reactions in the same cycle. This new concept of sodium storage process includes two models, previously seemed to be mutually exclusive. Despite of complex electrode mechanisms, MoSe₂ retains high capacity and coulombic efficiency even after 50 cycles.