Diruthenium(III,III) ethynyl-phenyleneimine molecular wires: preparation via on-complex Schiff base condensation

The diruthenium compound trans-Ru(2)(DMBA)(4)(C≡C-C(6)H(4)-4-CHO)(2) (1; DMBA is N,N'-dimethylbenzamidinate) was prepared from the reaction between Ru(2)(DMBA)(4)(NO(3))(2) and HC≡C-C(6)H(4)-4-CHO under the weak base conditions. The aldehyde groups of 1 undergo a condensation reaction with NH(2)C(6)H(4)-4-Y (Y = H and NH(2)) to afford new compounds trans-Ru(2)(DMBA)(4)(C≡C-C(6)H(4)-4-CH═N-C(6)H(4)-4'-Y)(2) (Y = H (2) and NH(2) (3)). A related compound, Ru(2)(DMBA)(4)(C≡C-C(6)H(4)-4-N═C(Me)Fc)(2) (4), was also prepared from the reaction between Ru(2)(DMBA)(4)(NO(3))(2) and HC≡C-C(6)H(4)-N═C(Me)Fc. X-ray structural studies of compounds 1 and 2 revealed significant deviation from an idealized D(4h) geometry in the coordination sphere of the Ru(2) core. Voltammetric measurements revealed four one electron redox processes for compounds 1-3: the Ru(2) centered oxidation and reduction, and a pair of reductions of the imine or aldehyde groups. Compound 4 displays an additional oxidation attributed to the Fc groups. DFT calculations were performed on model compounds to gain a more thorough understanding of the interaction of the organic functional groups across the diruthenium bridge.     

Lithological and seasonal variations in radon concentrations in Cypriot groundwaters

The paper presents and discusses radon activity concentrations in Cypriot groundwater systems as a function of the background lithology and seasonal/meteorological conditions using an airborne radon monitoring system (ARM) after separation of radon by out-gassing. Radiometric analysis of groundwater samples obtained from non-contaminated systems showed that radon concentration in groundwaters varies strongly (0.1–10 Bq L⁻¹) depending mainly on the hosting geological matrix but also to lesser degree on atmospheric/meteorological conditions. The associated excess annual dose has been estimated to range between 10⁻⁶ and 10⁻⁴ mSv y⁻¹, which is an insignificant contribution to the radiation exposure of the Cypriot population caused by airborne radon (0.5 ± 0.4 mSv y⁻¹).     

Rapid and efficient purification of naphthodianthrones from St. John's wort extract by using liquid–liquid extraction and SEC

Hypericin and pseudohypericin, the main naphthodianthrones present in Hypericum species are among the most promising natural products, but the research concerning their biological activities is hindered by their low content in the plant. In this paper a method for the rapid isolation of hypericin and pseudohypericin from Hypericum perforatum hydro‐alcoholic dried extracts has been developed. Briefly, the method consists of a partition of the extract between organic and aqueous layers and further purification of the richest extract in naphthodianthrones with Sephadex LH‐20 column chromatography. A final separation of hypericin from pseudohypericin was achieved using Sephadex LH‐60 column chromatography. All partitions were carried out in triplicate and monitored by LC‐MS and NMR analyses. The best results were obtained by successive extraction with n‐hexane, Et₂O and EtOAc. A three‐step fractionation resulted in 98% content in total naphthodianthrones. To the best of our knowledge this is the first report on the separation of hypericin from pseudohypericin using size exclusion chromatography.     

Natural convection in porous annular domains: Mimetic scheme and family of steady states

Natural convection of the incompressible fluid in the porous media based on the Darcy hypothesis (Lapwood convection) gives an intriguing branching off of one-parameter family of steady patterns. This scenario may be suppressed in computations when governing equations are approximated by schemes which do not preserve the cosymmetry property. We consider the problem for the annular porous domain in polar coordinates and derive a mimetic finite-difference scheme. This scheme allows to compute the family of convective regimes accurately and to detect the instabilities on some parts of the family.     

Head-to-Tail Dimerization of N-Heterocyclic Diazoolefins

The head-to-tail dimerization of N-heterocyclic diazoolefins is described. The products of these formal (3+3) cycloaddition reactions are strongly reducing quinoidal tetrazines. Oxidation of the tetrazines occurs in a stepwise fashion, and we were able to isolate a stable radical cation and diamagnetic dications. The latter are also accessible by oxidative dimerization of diazoolefins.     

A Fixable Fluorescence-Quenched Substrate for Quantitation of Lysosomal Glucocerebrosidase Activity in Both Live and Fixed Cells

Fluorogenic substrates are emerging tools that enable studying enzymatic processes within their native cellular environments. However, fluorogenic substrates that function within live cells are generally incompatible with cellular fixation, preventing their tandem application with fundamental cell biology methods such as immunocytochemistry. Here we report a simple approach to enable the chemical fixation of a dark-to-light substrate, LysoFix-GBA, which enables quantification of glucocerebrosidase (GCase) activity in both live and fixed cells. LysoFix-GBA enables measuring responses to both chemical and genetic perturbations to lysosomal GCase activity. Further, LysoFix-GBA permits simple multiplexed co-localization studies of GCase activity with subcellular protein markers. This tool will aid studying the role of GCase activity in Parkinson's Disease, creating new therapeutic approaches targeting the GCase pathway. This approach also lays the foundation for an approach to create fixable substrates for other lysosomal enzymes.     

Photolithographically Patterned Cell-Repellent PEG-b-PTHPMA Diblock Copolymer for Guided Cell Adhesion and Growth

Surfaces for guided cell adhesion and growth are indispensable in several diagnostic and therapeutic applications. Towards this direction, four diblock copolymers comprising polyethylene glycol (PEG) and poly(2-tetrahydropyranyl methacrylate) (PTHPMA) are synthesized employing PEG macroinitiators of different chain lengths. The copolymer with a 5000 Da PEG block and a PEG-PTHPMA comonomers weight ratio of 43–57 provides a film with the highest stability in the culture medium and the strongest cell repellent properties. This copolymer is used to develop a positive photolithographic material and create stripe patterns onto silicon substrates. The highest selectivity regarding smooth muscle cell adhesion and growth and the highest fidelity of adhered cells for up to 3 days in culture is achieved for stripe patterns with widths between 25 and 27.5 µm. Smooth muscle cells cultured on such patterned substrates exhibit a decrease in their proliferation rate and nucleus area and an increase in their major axis length, compared to the cells cultured onto non-patterned substrates. These alterations are indicative of the adoption of a contractile rather than a synthetic phenotype of the smooth muscle cells grown onto the patterned substrates and demonstrate the potential of the novel photolithographic material and patterning method for guided cell adhesion and growth.