A new glucosidic phthalide from Helichrysum microphyllum subsp. tyrrhenicum from La Maddalena Island (Sardinia,Italy)

In this study, we reported the analysis of the medium polarity fraction obtained from an accession of Helichrysum microphyllum subsp. tyrrhenicum from La Maddalena Island. Besides several compounds already evidenced in this species and related genera, i.e. micropyrone (1), arzanol (2), helipyrone (3), acetyl-bitalin derivatives (4, 5), gnaphaliol (6), caffeic acid (7), ursolic acid (8), 7-O-β-(d-glucopyranosyl)-5-methoxy-1(3H)-isobenzofuranone (9), gnaphaliol-9-O-β-d-glucopyranoside (11) and gnaphaliol-3-O-β-d-glucopyranoside (12), the presence of a new glycosidic phthalide, 6-O-β-(d-glucopyranosyl)-4-methoxy-1(3H)-benzofuranone (10), was evidenced for the first time, which resulted in a structural isomer of compound (9). The occurrence of this new benzofuranone derivative is an additional evidence of the deep intraspecific variability expressed by this species, which was also stated for the non-volatile components, and may be a distinctive trait of the population growing on La Maddalena Island.     

N‐ and O‐linked glycosylation site profiling of the human basic salivary proline‐rich protein 3M

In the present study, we show that the heterogeneous mixture of glycoforms of the basic salivary proline‐rich protein 3M, encoded by PRB3‐M locus, is a major component of the acidic soluble fraction of human whole saliva in the first years of life. Reversed‐phase high‐performance liquid chromatography with high‐resolution electrospray ionization mass spectrometry analysis of the intact proteoforms before and after N‐deglycosylation with Peptide‐N‐Glycosidase F and tandem mass spectrometry sequencing of peptides obtained after Endoproteinase GluC digestion allowed the structural characterization of the peptide backbone and identification of N‐ and O‐glycosylation sites. The heterogeneous mixture of the proteoforms derives from the combination of 8 different neutral and sialylated glycans O‐linked to Threonine 50, and 33 different glycans N‐linked to Asparagine residues at positions 66, 87, 108, 129, 150, 171, 192, and 213.     

Pair distribution function and 71Ga NMR study of aqueous Ga3+ complexes

The atomic structures, and thereby the coordination chemistry, of metal ions in aqueous solution represent a cornerstone of chemistry, since they provide first steps in rationalizing generally observed chemical information. However, accurate structural information about metal ion solution species is often surprisingly scarce. Here, the atomic structures of Ga³⁺ ion complexes were determined directly in aqueous solutions across a wide range of pH, counter anions and concentrations by X-ray pair distribution function analysis and ⁷¹Ga NMR. At low pH (<2) octahedrally coordinated gallium dominates as either monomers with a high degree of solvent ordering or as Ga-dimers. At slightly higher pH (pH ≈ 2–3) a polyoxogallate structure is identified as either Ga₃₀ or Ga₃₂ in contradiction with the previously proposed Ga₁₃ Keggin structures. At neutral and slightly higher pH nanosized GaOOH particles form, whereas for pH > 12 tetrahedrally coordinated gallium ions surrounded by ordered solvent are observed. The effects of varying either the concentration or counter anion were minimal. The present study provides the first comprehensive structural exploration of the aqueous chemistry of Ga³⁺ ions with atomic resolution, which is relevant for both semiconductor fabrication and medical applications.

With changing pH four different structural regions in Ga³⁺ aqueous solutions are observed. In contrast the effects of different anions and concentrations are minimal.     

ICP-MS Determination of 23 Elements of Potential Health Concern in Liquids of e-Cigarettes. Method Development,Validation, and Application to 37 Real Samples

The lack of interest in the determination of toxic elements in liquids for electronic cigarettes (e-liquids) has so far been reflected in the scarce number of accurate and validated analytical methods devoted to this aim. Since the strong matrix effects observed for e-liquids constitute an exciting analytical challenge, the main goal of this study was to develop and validate an ICP-MS method aimed to quantify 23 elements in 37 e-liquids of different flavors. Great attention has been paid to the critical phases of sample pre-treatment, as well as to the optimization of the ICP-MS conditions for each element and of the quantification. All samples exhibited a very low amount of the elements under investigation. Indeed, the sum of their average concentration was of ca. 0.6 mg kg⁻¹. Toxic elements were always below a few tens of a μg per kg⁻¹ and, very often, their amount was below the relevant quantification limits. Tobacco and tonic flavors showed the highest and the lowest concentration of elements, respectively. The most abundant elements came frequently from propylene glycol and vegetal glycerin, as confirmed by PCA. A proper choice of these substances could further decrease the elemental concentration in e-liquids, which are probably barely involved as potential sources of toxic elements inhaled by vapers.     

Two‐photon microfabrication of poly(ethylene glycol) diacrylate and a novel biodegradable photopolymer—comparison of processability for biomedical applications

Two‐photon polymerization (2PP) is a versatile microfabrication tool for biomedical applications as it provides unparalleled resolution for accurate three‐dimensional (3D) replication of biological microstructures. To widen the selection of biomaterials suitable for 2PP, this paper presents the processing of a methacrylated poly(ε‐caprolactone)‐based oligomer (PCL‐o) and a poly(ethylene glycol) diacrylate (PEGda) hydrogel into microstructures. PCL‐o is a novel biodegradable photopolymer that has not been previously processed with 2PP, and the fabrication of both polymers with an Nd:YAG laser is reported here for the first time. The overall 2PP processability and achievable resolution were studied by polymerizing arbitrary microstructures on glass substrates. The samples were characterized with scanning electron microscopy. Additionally, the effect of photoinitiator concentration on the resolution was investigated. Also, a preliminary cell attachment test was performed with UV cured films in order to investigate the impact of the used material–initiator combination on cell viability and migration. As a result, laser‐induced polymerization of both PCL‐o and PEGda was successfully demonstrated, and the Nd:YAG laser was proven adequate for the 2PP processing of the novel biodegradable photoresist. Resolution in the order of 1 µm was achieved with PCL‐o. With the easy processing of both PEGda and PCL‐o, these materials have great potential for different biomedical applications. Copyright © 2011 John Wiley & Sons, Ltd.     

New class of aggregates in aqueous solution: an NMR, thermodynamic, and dynamic light scattering study

We investigated the aggregation properties of two classes of aromatic and hydrophobic compounds, namely chloroacetamides and ethyl 3-phenyl-2-nitropropionates, in moderately concentrated aqueous solution (millimolar range). The identification of all species present in solution under specific experimental conditions was performed by 1D and 2D NMR, pulsed gradient spin-echo NMR, and dynamic light scattering techniques. Some physical-chemical properties (viscosity, surface tension, and colligative properties) of the aqueous solutions were also determined. Both classes of compounds behave quite similarly: in solution, three distinct species, namely a monomeric species, small and mobile aggregates, and large and stiff aggregates, are observed. The results give insight into a new class of aggregates, held together by pi-pi interactions, which show an unusual associative behavior in water.     

HPLC-MS characterization of cyclo-statherin Q-37, a specific cyclization product of human salivary statherin generated by transglutaminase 2

In the present study the analytical potential of HPLC-MS/MS was utilized for the structural characterization of a post-translational modification of statherin. Human salivary statherin (M(av)5380.0 +/- 0.3 Da) is transformed by the action of transglutaminase 2 into a cyclic derivative with an average molecular mass of 5363.0 +/- 0.3 Da. The intra-molecular bridge is generated by the loss of an ammonia molecule between the unique Ione-pair donating nucleophile Lys-6 and one acceptor among the seven glutamine residues of statherin. Digestion of the cyclic derivative with chymotrypsin, proteinase K, and carboxypeptidase Y, monitored by HPLC-electrospray ionization-ion trap-mass spectrometric analysis, demonstrated that cyclization involved almost specifically Gln-37 (> 95%), with the percentage of Gln-39 implicated in the cross-linkiing being less than 5%. The main derivative was named cyclostatherin Q37. Guineapig transglutaminase 2 showed high affinity for statherin in vitro (Km = 0.65 +/- 0.06 microM). Cyclo-statherin was detected in vivo by HPLC-electrospray ionization ion trap-mass spectrometry analysis of whole human saliva and it accounted for about 1% of total statherin. Detection of cyclo-statherin in whole saliva is suggestive of a putative role of this molecule in the formation of the "oral protein pellicle".     

Bootstrap approximation for the exchange-correlation kernel of time-dependent density-functional theory

A new parameter-free approximation for the exchange-correlation kernel f(xc) of time-dependent density-functional theory is proposed. This kernel is expressed as an algorithm in which the exact Dyson equation for the response, as well as an approximate expression for f(xc) in terms of the dielectric function, are solved together self-consistently, leading to a simple parameter-free kernel. We apply this to the calculation of optical spectra for various small band gap (Ge, Si, GaAs, AlN, TiO(2), SiC), large band gap (C, LiF, Ar, Ne), and magnetic (NiO) insulators. The calculated spectra are in very good agreement with the experiment for this diverse set of materials, highlighting the universal applicability of the new kernel.