A multi-analytical study of a wall painting in the Satyr domus in Córdoba, Spain.

In this work, we conducted a careful study of the mortar and paint in the Roman wall painting housed by the triclinium of the so-called Domus in the Road Safety Education Park of Córdoba, Spain. A combination of X-ray diffraction, Raman and X-ray fluorescence spectroscopies allowed the different substances used to obtain the pigments present in the painting to be identified. The painting was found to contain five different colours (red, yellow, blue, green and white) in various hues. The red pigment was obtained from hematite and the yellow pigment from goethite. The blue pigment, which was the least abundant, was prepared from Egyptian blue, and the green pigment from green earths. Finally, the white pigment came from lime. The binders used were identified by infrared spectroscopy and gas chromatography with mass spectrometry detection. The painting fragments studied contained vestiges of bee wax or its decomposition products, which suggests that the paint was applied encaustically.

A Comparative Study of Particle Size Distribution of Graphene Nanosheets Synthesized by an Ultrasound-Assisted Method.

Graphene-based materials are highly interesting in virtue of their excellent chemical, physical and mechanical properties that make them extremely useful as privileged materials in different industrial applications. Sonochemical methods allow the production of low-defect graphene materials, which are preferred for certain uses. Graphene nanosheets (GNS) have been prepared by exfoliation of a commercial micrographite (MG) using an ultrasound probe. Both materials were characterized by common techniques such as X-ray diffraction (XRD), Transmission Electronic Microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). All of them revealed the formation of exfoliated graphene nanosheets with similar surface characteristics to the pristine graphite but with a decreased crystallite size and number of layers. An exhaustive study of the particle size distribution was carried out by different analytical techniques such as dynamic light scattering (DLS), nanoparticle tracking analysis (NTA) and asymmetric flow field flow fractionation (AF4). The results provided by these techniques have been compared. NTA and AF4 gave higher resolution than DLS. AF4 has shown to be a precise analytical technique for the separation of GNS of different sizes.

25 S-Adamantyl-23-yne-26,27-dinor-1α,25-dihydroxyvitamin D3: Synthesis, Tissue Selective Biological Activities, and X-ray Crystal Structural Analysis of Its Vitamin D Receptor Complex.

Both 25 R- and 25 S-25-adamantyl-23-yne-26,27-dinor-1α,25-dihydroxyvitamin D3 (4a and 4b) were stereoselectively synthesized by a Pd(0)-catalyzed ring closure and Suzuki-Miyaura coupling between enol-triflate 7 and alkenyl-boronic ester 8. The 25 S isomer (4b) showed high vitamin D receptor (VDR) affinity (50% of that of the natural hormone 1α,25-dihydroxyvitamin D3, 1) and transactivation potency (kidney HEK293, 90%). In endogenous gene expression, it showed high cell-type selectivity for kidney cells (HEK293, CYP24A1 160% of 1), bone cells (MG63, osteocalcin 64%), and monocytes (U937, CAMP 96%) over intestine (SW480, CYP24A1 8%) and skin (HaCaT, CYP24A1 7%) cells. The X-ray crystal structural analysis of 4b in complex with rat VDR-ligand binding domain (LBD) showed the highest Cα positional shift from the 1/VDR-LBD complex at helix 11. Helix 11 of the 4b and 1 VDR-LBD complexes also showed significant differences in surface properties. These results suggest that 4b should be examined further as another candidate for a mild preventive osteoporosis agent.

A comparative study of the suitability of different cereal straws for lignocellulose nanofibers isolation.

The aim of this work is to study the suitability of different soda cereal straw pulps (wheat, barley, corn and oats) to produce lignocellulose nanofibers (LCNF). For the study of the influence of the composition and physical characteristics, the pulps were characterized, observing that the physical characteristics do not influence the nanofibrillation process. However, the composition of the fibers plays a key role, mainly the hemicellulose content. The LCNF produced were characterized: chemical structure (FTIR), crystallinity (XRD), thermal stability (TGA), size (DLS) and colloidal stability (ZP). The TO-LCNF are those which presents higher nanofibrillation yields and lower nanofibers size, however presents low crystallinity, thermal stability and a further depolymerization compared to the others LCNF. The lignin contents allow a greater thermal stability (<330°C) than the same size CNF (<250°C). TO-LCNF present more stable suspensions (ZP<-25mV) due to their higher surface charge (COO- groups). AF4 technique was used to effectively determine the size of polydispersed samples of LCNF by avoiding the errors committed by conventional techniques. In addition, it is observed that wheat and barley straws present the most homogeneity in the LCNF samples, being the wheat which presents the best values in the production of LCNF under the three pretreatments.

A new approach to 19-nor-A-ring phosphine oxide for the convergent synthesis of 19-nor-calcitriol.

A new approach to 19-nor-A-ring phosphine oxide 5 together with a convergent synthesis of the vitamin D3 analogue 1α,25-dihydroxy-19-norvitamin D3 (3) have been developed. The 19-nor-A-ring is constructed from (S)-carvone. The triene system is assembled by a Wittig-Horner coupling.

Combined Effects of Non-Conforming Fly Ash and Recycled Masonry Aggregates on Mortar Properties.

This work evaluates the effects of using non-conforming fly ash (Nc-FA) generated in a thermoelectric power plant as filler material for mortars made with natural sand (NA) and recycled sand from masonry waste (FRMA). The incorporation of powdered recycled masonry filler (R-MF) is also tested as an alternative to siliceous filler (Si-F). Three families of mortars were designed to study: the effect of replacing Si-F with Nc-FA on mortars made with NA; the effect of replacing Si-F with Nc-FA on mortars made with 50% of NA and 50% of FRMA; and the effect of replacing Si-F with R-MF on mortars made with NA and FRMA. Replacing Si-F with Nc-FA is a viable alternative that increases the mechanical strength, the workability and durability properties and decreases the shrinkage. The use of FRMA and Nc-FA improved the mechanical strength of mortars, and it slightly increased the shrinkage. The replacement of Si-F with R-MF on mortars made with FRMA is not a good alternative, because it has a negative impact on all of the properties tested. This work can help both to reduce cement and natural resources' consumption and to increase the recycling rate of Nc-FA and FRMA.

Carborane-based design of a potent vitamin D receptor agonist.

The vitamin D nuclear receptor (VDR) is a potential target for cancer therapy. It is expressed in many tumors and its ligand shows anticancer actions. To combine these properties with the application of boron neutron capture therapy (BNCT), we design and synthesize a potent VDR agonist based on the skeleton of the hormone 1α,25-dihydroxyvitamin D3 (1,25D) and an o-carborane (dicarba-o-closo-1,2-dodecaborane) at the end of its side chain. The present ligand is the first secosteroidal analog with the carborane unit that efficiently binds to VDR and functions as an agonist with 1,25D-like potency in transcriptional assay on vitamin D target genes. Moreover it exhibits similar antiproliferative and pro-differentiating activities but is significantly less hypercalcemic than 1,25D. The crystal structure of its complex with VDR ligand binding domain reveals its binding mechanism involving boron-mediated dihydrogen bonds that mimic vitamin D hydroxyl interactions. In addition to the therapeutic interest, this study establishes the basis for the design of new unconventional vitamin D analogs containing carborane moieties for specific molecular recognition, and drug research and development.

An efficient convergent synthesis of 1α,25-dihydroxy-3-epi-vitamin D2.

The first synthesis of 1α,25-dihydroxy-3-epi-vitamin D2 is described. Key steps of the synthesis entail the construction of the triene unit by a Pd-catalyzed ring closure of an enol-triflate (A-ring fragment) followed by a Suzuki-Miyaura coupling with a boronate (upper fragment), and the installation of the methyl group at C-24 by an SN2'-syn displacement of an allylic carbamate. This article is part of a Special Issue entitled 'SI:17th Vitamin D Workshop'.