Synthesis of squalene epoxide and lanosterol analogues for a biosynthetic experiment

The syntheses of (21-¹⁴C)-2,3(RS)-oxide-2,6,10,15,19-pentamethyl-heneicosa-6E-10E, 14E,18Z-tetraene from squalene and of pure 20R and 20S 24,25,26,27-tetranorlanosteryl acetates from lanosteryl acetate are disclosed.     

The $$$$-means algorithm for 3D shapes with an application to apparel design

Clustering of objects according to shapes is of key importance in many scientific fields. In this paper we focus on the case where the shape of an object is represented by a configuration matrix of landmarks. It is well known that this shape space has a finite-dimensional Riemannian manifold structure (non-Euclidean) which makes it difficult to work with. Papers about clustering on this space are scarce in the literature. The basic foundation of the \(k\)-means algorithm is the fact that the sample mean is the value that minimizes the Euclidean distance from each point to the centroid of the cluster to which it belongs, so, our idea is integrating the Procrustes type distances and Procrustes mean into the \(k\)-means algorithm to adapt it to the shape analysis context. As far as we know, there have been just two attempts in that way. In this paper we propose to adapt the classical \(k\)-means Lloyd algorithm to the context of Shape Analysis, focusing on the three dimensional case. We present a study comparing its performance with the Hartigan-Wong \(k\)-means algorithm, one that was previously adapted to the field of Statistical Shape Analysis. We demonstrate the better performance of the Lloyd version and, finally, we propose to add a trimmed procedure. We apply both to a 3D database obtained from an anthropometric survey of the Spanish female population conducted in this country in 2006. The algorithms presented in this paper are available in the Anthropometry R package, whose most current version is always available from the Comprehensive R Archive Network.     

Multivariate optimisation and validation of a capillary electrophoresis method for the analysis of resveratrol in a nutraceutical

A rapid and simple method based on capillary electrophoresis was developed for the quality control of nutraceuticals containing resveratrol. Setting the UV detector at 280nm, the optimisation involved the separation of 11 effervescent tablet components, including the active compounds vitamin C, vitamin B(2), flavanones and hydroxycinnamic acids. Flufenamic acid was employed as internal standard. The effects of background electrolyte concentration, acetonitrile percentage and voltage were investigated by means of response surface methodology, considering as responses the critical resolution values and analysis time. The optimum conditions were found by Derringer desirability function. The background electrolyte consisted of 23mM borate buffer, adjusted to pH 10.0 with 1M sodium hydroxide, containing 7% (v/v) acetonitrile. Temperature and voltage were set at 25 degrees C and 26kV, respectively. Applying these conditions, the analysis time was below 7min. The performances of the method were tested in terms of selectivity, robustness, linearity and range, accuracy and precision and system suitability, following ICH guidelines.     

Optimization of hydroxyl radical formation using TiO2 as photocatalyst by response surface methodology

The determination of the optimum parameters for hydroxyl radicals (OH) formation by a TiO₂ solution has been investigated by measuring the emitted fluorescence after the reaction with terephthalic acid has occurred. After UV irradiation, the terephthalic acid was transformed into 2-hydroxyterephthalic acid whose fluorescence is directly proportional to the generated OH. Optimization of hydroxyl radicals’ formation using TiO₂ as catalyst was carried out by studying the effects of irradiation time, TiO₂ concentration and terephthalic acid concentration on the production of the fluorescent HTA with an experimental design. The aim of our research was to apply response surface methodology as a chemometric method for the optimization of the reaction conditions. The combination of irradiation time, TiO₂ concentration and terephthalic acid concentration was varied at designed points of a central composite rotatable design. The three factors were found to have a significant effect upon the reaction. The optimum conditions for the reaction achievement were estimated to be 10 min for the irradiation time, 25 μg mL⁻¹ TiO₂ concentration and 0.1 mmol L⁻¹ terephthalic acid concentration. Afterwards, using these parameters the method was applied for the determination of the ability of several plant extract samples to scavenge the formed OH.     

Europium(III) complexes containing organosilyldipyridine ligands grafted on silica nanoparticles

This work focuses on the grafting of transition metal complexes on silica surface nanoparticles. Nanoscale silica particles in aqueous sols are used as starting silicated materials. We have undertaken the synthesis of europium(III) complexes containing organosilyldipyridine ligands, (EtO)3Si(CH2)3NHCH2-bipy (1) and (EtO)(CH3)2Si(CH2) 3NHCH 2-bipy (2), in view of a direct grafting reaction on silica nanoparticles. Reaction of one molar equivalent of 1 and 2 with Eu(tmhd)3 (tmhd= 2,2,6,6-tetramethyl-3,5-heptanedionato), as precursor, leads to octacoordinated silylated europium(III) complexes [Eu(tmhd)3(1)] (3) and [Eu(tmhd)3(2)] (4) as white solids in 34-54% yields. Europium complexes were characterized by elemental analysis, mass spectrometry, FT-IR, UV, and luminescence spectroscopies. These new complexes are reacting in a 1:10 (v/v) water and ethanol mixture with silica nanoparticles colloidal sol. Elemental analysis and thermogravimetric data indicated grafting ratios of 0.41 and 0.26 mmol of europium(III) complexes per gram of silica. Functionalized silica nanoparticles were characterized by DRIFT spectroscopy and TEM microscopy. The first analysis shows that the chemical integrity of the complexes is retained on the silica surface together with the size and the monodispersity of the nanoscale particles. As expected for europium(III) complexes, luminescence is observed under UV irradiation. Emission and excitation spectra indicate that the metal coordination environment is not modified on the silica surface. Moreover, the sharpness of the luminescence bands and the strong antenna effect are maintained when complexes are covalently bonded to silica. New luminescent europium(III) complexes grafted on silica nanoparticles are therefore obtained from our approach.     

Structure and reactivity of a(n) and a(n) peptide fragments investigated using isotope labeling, tandem mass spectrometry, and density functional theory calculations

Extensive ¹⁵N labeling and multiple-stage tandem mass spectrometry were used to investigate the fragmentation pathways of the model peptide FGGFL during low-energy collision-induced-dissociation (CID) in an ion-trap mass spectrometer. Of particular interest was formation of a ₄ from b ₄ and a*₄ (a ₄-NH₃) from a ₄ ions correspondingly, and apparent rearrangement and scrambling of peptide sequence during CID. It is suggested that the original FGGF_oxa b ₄ structure undergoes b-type scrambling to form GGFF_oxa. These two isomers fragment further by elimination of CO and ¹⁴NH₃ or ¹⁵NH₃ to form the corresponding a ₄and a*₄ isomers, respectively. For (¹⁵N-F)GGFL and FGG(¹⁵N-F)L the a*₄ ion population appears as two distinct peaks separated by 1 mass unit. These two peaks could be separated and fragmented individually in subsequent CID stages to provide a useful tool for exploration of potential mechanisms along the a ₄ → a*₄ pathway reported previously in the literature (Vachet et al. J. Am. Chem. Soc. 1997, 119, 5481, and Cooper et al. J. Am. Soc. Mass Spectrom. 2006, 17, 1654). These mechanisms result in formally the same a*₄ structures but differ in the position of the expelled nitrogen atom. Detailed analysis of the observed fragmentation patterns for the separated light and heavy a*₄ ion fractions of (¹⁵N-F)GGFL indicates that the mechanism proposed by Cooper et al. is consistent with the experimental findings, while the mechanism proposed by Vachet et al. cannot account for the labeling data. In addition, a new rearrangement pathway is presented for a ₄*-CO ions that effectively transfers the former C-terminal amino acid residue to the N-terminus.     

One-step bioengineering of magnetic nanoparticles via a surface diazo transfer/azide-alkyne click reaction sequence

We have developed an efficient conversion of amino iron oxides to carbohydrate and protein derived nanoparticles with highly conserved bioactivity through a combination of diazo transfer and azide-alkyne click technology.