A Hydrogel Platform that Incorporates Laminin Isoforms for Efficient Presentation of Growth Factors – Neural Growth and Osteogenesis

Laminins (LMs) are important structural proteins of the extracellular matrix (ECM). The abundance of every LM isoform is tissue-dependent, suggesting that LM has tissue-specific roles. LM binds growth factors (GFs), which are powerful cytokines widely used in tissue engineering due to their ability to control stem cell differentiation. Currently, the most commonly used ECM mimetic material in vitro is Matrigel, a matrix of undefined composition containing LM and various GFs, but subjected to batch variability and lacking control of physicochemical properties. Inspired by Matrigel, a new and completely defined hydrogel platform based on hybrid LM-poly(ethylene glycol) (PEG) hydrogels with controllable stiffness (1–25 kPa) and degradability is proposed. Different LM isoforms are used to bind and efficiently display GFs (here, bone morphogenetic protein (BMP-2) and beta-nerve growth factor (β-NGF)), enabling their solid-phase presentation at ultralow doses to specifically target a range of tissues. The potential of this platform to trigger stem cell differentiation toward osteogenic lineages and stimulate neural cells growth in 3D, is demonstrated. These hydrogels enable 3D, synthetic, defined composition, and reproducible cell culture microenvironments reflecting the complexity of the native ECM, where GFs in combination with LM isoforms yield the full diversity of cellular processes.     

A mass spectral study of 1-(aryldimethylsilyl)-2-propanones and their isomeric 2-(aryldimethylsiloxy)-1-propenes

The mass spectra of a series of β-ketosilanes, p-Y? C₆H₄Me₂SiCH₂C(O)Me and their isomeric silyl enol ethers, p-Y? C₆H₄Me₂SiOC(CH₃)?CH₂, where Y = H, Me, MeO, Cl, F and CF₃, have been recorded. The fragmentation patterns for the β-ketosilanes are very similar to those of their silyl enol ether counterparts. The seven major primary fragment ions are [M? Me·]⁺, [M? C₆H₄Y·]⁺, [M? Me₂SiO]⁺˙, [M? C₃H₄]⁺˙, [M? HC?CCF₃]⁺˙, [Me₂SiOH]⁺˙ and [C₃H₆O]⁺˙ Apparently, upon electron bombardment the β-ketosilanes must undergo rearrangement to an ion structure very similar to that of the ionized silyl enol ethers followed by unimolecular ion decompositions. Substitutions on the benzene ring show a significant effect on the formation of the ions [M? Me₂SiO]⁺˙ and [Me₂SiOH]⁺˙, electron donating groups favoring the former and electron withdrawing groups favoring the latter. The mass spectral fragmentation pathways were identified by observing metastable peaks, metastable ion mass spectra and ion kinetic energy spectra.     

Studies on the extraction of Copper(II) with 4-alkyldithiocarboxylate derivatives of 1-phenyl-3,5-dioxopyrazolidine

The extraction behaviour of copper(II) from acid solutions (pH 0-6) was studied with the new reagent 4-alkyldithiocarboxylate-3,5-dihydroxy-l-phenylpyrazol (HL; alkyl = n-butyl, n-dodecyl). The species extracted was found to be ML(2). The reagent was used to separate copper(II) from iron(III) in an acidic lixiviation solution of a mineral sample composed of enarguite (Cu(3)AsS(4)) and pyrite (FeS(2)). Additionally, the extraction efficiency of this new reagent was compared with the commercially available LIX 984 N extradant of copper (II).     

meso-Me2Si(1-indenyl)2ZrCl2/methylalumoxane catalyzed polymerization of the ethylene to ethyl-branched polyethylene

The meso ansa zirconocene with dimethylsilyl bridge, activated by methylalumoxane, catalyses the ethylene polymerization, producing ethyl-branched polyethylene. With respect to the polymers obtained with the previously investigated meso zirconocenes, we have found higher branching amount and lower molecular weight. The rapid β-H transfer from the growing chain to the coordinated monomer could account for both these features of the polymer. The investigation on the structural parameters of the complex, through X-ray diffraction analysis, and on the electrophilicity of the cationic center, through NMR experiments, suggests, as a possible rationalization of this behavior, the obstruction in the inward site.     

Molecular features of organic matter in diagnostic horizons from andosols as seen by analytical pyrolysis

Andosols are usually formed from volcanic substrates, with thick A horizons high in organic carbon mainly in the form of stabilized humic fractions. The peculiar properties of these soils are, to large extent, affected by poorly crystalline materials like allophanes, imogolite and other Fe and Al oxyhydroxides that induce intense organo-mineral interactions which are considered to play a relevant role in OM protection against biodegradation as regards other soils developed under similar climatic conditions. Little is known about the molecular composition of this stabilized OM in a soil scenario often considered as an efficient C-sink in terms of C sequestration processes.

Whole soil samples in addition to isolated humic and fulvic acids from organic A horizons of three soils with andic properties and one non-andic soil (Sodic Cambisol) from the island of Tenerife (Canary Islands, Spain) were analysed by double shot pyrolysis-gas chromatography–mass spectrometry (Py-GC/MS) in order to get some insight on the molecular composition of different structural domains of progressive structural stability.

Clear differences were found between soils, both in thermal desorption and pyrolysis behaviour of humic substances. In general the results suggest large yields of aliphatic (both alkyl and carbohydrate-derived pyrolysis compounds) pointing to high-performance processes of incorporation of aliphatic humic constituents in andosols probably favoured by interactions with amorphous minerals, whereas in non-andic soils the latter are comparatively less stabilized and are removed in early pyrolysis stages as if they occurred as loosely joined, thermoevaporation-released products.

In fact, compared to Cambisol, humic and fulvic acids from andic soils led to comparatively richer pyrograms and compound assemblages. The lack of similar amounts of these loosely joined, mainly aliphatic structures after thermal desorption of the whole andic soils indicate an origin for humic substances based on rapid sequestration of C-forms of recent (litter or microbial) origin.     

Effect of inhibitors released during steam-explosion pretreatment of barley straw on enzymatic hydrolysis

The influence of the liquid fraction (prehydrolysate) generated during steam-explosion pretreatment (210°C, 15 min) of barley straw on the enzymatic hydrolysis was determined. Prehydrolysate was analyzed for degradation compounds and sugars' content and used as a medium for enzymatic hydrolysis tests after pH adjusting to 4.8. Our results show that the presence of the compounds contained in the prehydrolysate strongly affects the hydrolysis step (a 25% decrease in cellulose conversion compared with control). Sugars are shown to be more potent inhibitors of enzymatic hydrolysis than degradation products.     

Thermodynamic statistical evaluation ofS andF from ESR experimental order parameters.

Summary A statistical analytical procedure for calculating entropy (S) and Helmholtz free energy (F) from the order parameters obtained from ESR spectra of spin-labelled membranes is described. The method is here applied to some literature data. A brief discussion on the results is also reported.

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Riassunto Si descrive un metodo statistico per calcolare l'entropia (S) e l'energia libera di Helmholtz (F) dai parametri d'ordine ottenuti da spettri ESR di membrane spin-marcate. Il metodo è applicato da alcuni dati di letteratura e sono brevemente discussi i risultati ottenuti.

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Резюме Описывается статистическая аналитическая процедура вычисления энтропии (S) и свободной энергии Гельмгольца (F) из параметров порядка , полученных из ESR спектров для мембран со спиновыми метками. Развитый мэтод применяется к некоторым данным, имеюшимися в литературе. Проводится обсуждение полученных результатов.

     

Percolative small-polarons conduction regime in Ce1−xGdxO2−x/2, probed by the EPR spectral intensity of Gd

EPR analysis is carried out with Ce_1−xGd_xO_(4−x)/2 (x=0.1; 0.2) nanopowders aiming at obtaining information about their oxidation and reduction properties. The EPR spectrum of these systems is composed of a single feature. The first derivative peak-to-peak spectral intensity decreases at higher temperatures, but this trend deviates from that of Curie's law with the x=0.1 sample, at difference with the x=0.2 sample. This unexpected result is related to oxygen deficiency, due to gas-solid equilibrium, present in the former sample only. As a consequence, some Ce³⁺ ions would form providing it with conduction electrons propagating as small polarons in a percolative way. This would result in a thinner skin depth at higher temperatures, able to explain the deviation of the spectral intensity from its expected value. Indeed, this deviation from Curie's law is reduced or disappears at all after thermal treatment of the x=0.1 sample with O₂.     

The Fluorenyl Cation

The fluorenyl cation is a textbook example for a 4π antiaromatic cation. However, contrasting results have been published on how the annelated benzene rings compensate the destabilizing effect of the 4π antiaromatic five‐membered ring in its core. Whereas previous attempts to synthesize this cation in superacidic media resulted in undefined polymeric material only, we herein report that it can be generated and isolated in amorphous water ice at temperatures below 30 K by photolysis of diazofluorene. Under these conditions, the fluorenylidene is protonated by water to give the fluorenyl cation, which could be characterized spectroscopically. Its absorption in the visible‐light range matches that previously obtained by ultrafast absorption spectroscopy, and furthermore, its IR spectrum could be recorded. The IR bands in amorphous ice very nicely match predictions from DFT and DFT/MM calculations, suggesting the absence of strong interactions between the cation and surrounding water molecules.