Polyhydroxybutyrate/Chitosan 3D Scaffolds Promote In Vitro and In Vivo Chondrogenesis

Applied Biochemistry and Biotechnology - The articular cartilage is an avascular and aneural tissue and its injuries result mostly in osteoarthritic changes and formation of fibrous tissue. Efforts...     

Ascorbigen A—NMR identification

The connectivities of all atoms in ascorbigen A, an important metabolite, were determined unambiguously for the first time. The connectivity between carbon atoms was established by 2D INADEQUATE, and one-bond ¹³C–¹³C coupling constants were determined for all pairs of directly connected carbon atoms except for two strongly coupled carbon pairs. The ¹³C–¹³C coupling in one of the pairs was proved by a modification of standard INADEQUATE; however, the signals from the other pair were too weak to be observed. The connectivity within the two strongly coupled C–C pairs was confirmed by a combination of COSY and gHSQC; the latter experiment also identified all C–H bonds. The proton nuclear magnetic resonance (¹H NMR) spectra in dry dimethyl sulfoxide allowed identification and assignment of the signals due to NH and OH protons. The derived structure, 3-((1H-indol-3-yl)methyl)-3,3a,6-trihydroxytetrahydrofuro[3,2-b]furan-2(5H)-one, agrees with the structure suggested for ascorbigen A in 1966. The density functional theory (DFT) calculations showed that among 16 possible stereoisomers, only two complied with the almost zero value of the measured ³J(H6–H6a). Of the two stereoisomers, 3S,3aS,6S,6aR and 3R,3aR,6R,6aS, the latter was excluded on synthetic grounds. The nuclear Overhauser effect measurements unveiled close proximity between H2′ proton of the indole and the H6a proton of the tetrahydrofuro[3,2-b]furan part. Detailed structural interpretation of the measured NMR parameters by means of DFT NMR was hampered by rotational flexibility of the indole and tetrahydrofuro[3,2-b]furan parts and inadequacy of Polarizable Continuum Model (PCM) solvent model.     

Self‐Assembly of Spheroidal Structures: The Coordination Chemistry of Pentacyanocyclopentadienide

Modelling studies show that the anion pentacyanocyclopentadienide, 1 , can complex linearly coordinating cations such as silver(I) and copper(I) to form a spheroidal complex [M₃₀( 1 )₁₂]¹⁸⁺ with minimum distortion. The anion 1 complexes transition metal ions to give species which appear to be polymers in the solid state. The structure of Ag( 1 ) was determined by powder diffraction and shows a one‐dimensional polymeric structure with three coordinate Ag^I and two CN functions of the ligand 1 non‐coordinated. No evidence for the formation of the spheroidal complex was found.     

Dinuclear Fe(III) complexes with spin crossover

Abstract  A series of dinuclear Fe(III) complexes was synthesized in which the Schiff-base blocking ligand L⁵ coordinates each of the centers which are linked by a bidentate, bipyridine-type ligand. For these systems, [L⁵Fe^III{bridge}Fe^IIIL⁵](BPh₄)₂, thermally induced spin crossover is observed. The corollary of the systems is that the spin crossover interferes with the magnetic exchange interaction. The overlap of the energy bands of the LL and HH reference states (L, low-spin; H, high-spin) causes the exchange interaction to act against the spin crossover (leading to incompleteness or gradual behavior). Graphical abstract        

Effects of methanol on photosynthetic processes and growth of Lemna gibba

Effects of methanol on growth and photosynthetic activity of Lemna gibba exposed under continuous illumination were examined. As a higher plant, L. gibba appeared to be much more sensitive to methanol inhibitory effect compared with some algae (Theodoridou et al. [2002] Biochim. Biophys. Acta, 1573, 189-198). We found that stimulatory or inhibitory effects were strongly dependent on the methanol concentration and the time of exposure. When the exposure was up to 0.2% methanol, the growth rate of biomass was improved by 50%. However, stimulatory effect of methanol appeared to be smaller when plants were exposed for 48 h compared with 24 h. Increase in biomass induced by methanol was not based on the increase in primary photosynthetic process but rather on accommodation of energy dissipation during photosynthesis. Inhibitory effect on the growth of L. gibba already observed for 0.5% methanol was strongly associated with the increase in the nonphotochemical energy dissipation. The ratio between biomass and methanol concentration appeared to determine the stimulatory or the inhibitory effect. Suggested explanations for the stimulatory and the inhibitory effects are presented.     

Retro‐Brook Rearrangement of Ferrocene‐Derived Silyl Ethers

An intramolecular Li–Si exchange was observed on various lithiated ferrocenylbenzyl silyl ethers. The thermodynamically more stable C‐silylated isomers were isolated in good yields and fully characterized. The reaction mechanism of the [1,4] retro‐Brook rearrangement was investigated by DFT calculations. Two distinct reaction routes were proposed and a possible stabilization effect of the ferrocenyl fragment on the C‐silylated isomers was described. The diastereoselective rearrangement of the trimethylsilyl group to the ortho position of the ferrocenyl cyclopentadienyl ring was also accomplished and the absolute configuration of the product was determined.     

Evaluation of mass spectrometric data using principal component analysis for determination of the effects of organic lakes on protein binder identification

Matrix‐assisted laser desorption/ionisation–time of flight (MALDI‐TOF) mass spectrometry is commonly used for the identification of proteinaceous binders and their mixtures in artworks. The determination of protein binders is based on a comparison between the m/z values of tryptic peptides in the unknown sample and a reference one (egg, casein, animal glues etc.), but this method has greater potential to study changes due to ageing and the influence of organic/inorganic components on protein identification. However, it is necessary to then carry out statistical evaluation on the obtained data. Before now, it has been complicated to routinely convert the mass spectrometric data into a statistical programme, to extract and match the appropriate peaks. Only several ‘homemade’ computer programmes without user‐friendly interfaces are available for these purposes. In this paper, we would like to present our completely new, publically available, non‐commercial software, ms‐alone and multiMS‐toolbox, for principal component analyses of MALDI‐TOF MS data for R software, and their application to the study of the influence of heterogeneous matrices (organic lakes) for protein identification. Using this new software, we determined the main factors that influence the protein analyses of artificially aged model mixtures of organic lakes and fish glue, prepared according to historical recipes that were used for book illumination, using MALDI‐TOF peptide mass mapping. Copyright © 2015 John Wiley & Sons, Ltd.     

Magnetic properties of a manganese(II) trinuclear complex involving a tridentate Schiff-Base ligand

The Schiff condensation of 2-pyridinecarboxaldehyde N-oxide with 2-aminophenol gave a tridentate ligand, abbreviated as Hpoxap. This ligand bears the functionality of a terminating group in a trinuclear complex [Mn(poxap)Mn(ac)4Mn(poxap)], where ac- is the acetate bridge. The magnetic data were treated simultaneously during the fitting procedure with the spin Hamiltonian containing isotropic exchange, the zero-field splitting parameters, and the molecular-field correction and resulted in JMn-Mn/hc = -4.73 cm-1, gMn(t) = 1.96, DMn(t)/hc = -0.45 cm-1, and zj/hc = +0.45 cm-1 with ground state S = 5/2, where t = terminal atom. At low temperature, the features of a ferromagnetic correlation become evident.