Influence of olive (cv Grignano) fruit ripening and oil extraction under different nitrogen regimes on volatile organic compound emissions studied by PTR-MS technique

Volatile organic compounds of extra virgin olive oils obtained from the local Italian cultivar Grignano were measured by proton transfer reaction–mass spectrometry (PTR-MS). Oils were extracted by olives harvested at different ripening stages across veraison, performing each extraction step and the whole extraction process in nitrogen atmosphere to observe the changes in the volatile profiles of the oils. Principal component analysis carried out on the full spectral signature of the PTR-MS measurements showed that the stage of ripening has a stronger effect on the global definition of volatile profiles than the use of nitrogen during oil extraction. The fingerprint-like chemical information provided by the spectra were used to construct a heat map, which allowed the dynamical representation of the multivariate nature of mass evolution during the ripening process. This provided the first evidence that some groups of volatile organic compounds displayed a time course of regulation with coordinated increasing or decreasing trends in association with specific stages of fruit ripening.     

Optimization of automated matrix deposition for biomolecular mapping using a spotter

Imaging mass spectrometry using matrix-assisted laser desorption/ionization allows the detailed mapping of biomolecules directly from tissue. Matrix deposition is the key step for successful imaging. The appropriate concentration and deposition of matrix is critical for extraction, desorption, and ionization of molecules from tissue without losing molecular localization. The main challenge to meet these criteria is to deposit matrix droplets homogeneously on the tissue section. This work shows how a chemical inkjet printer was used for this purpose resulting in the imaging of phosphatidylcholines and sulfatides. The intricacies involved in effective matrix deposition are discussed.     

Injection locking of mid‐infrared quantum cascade laser at 14 GHz,by direct microwave modulation

Compact laser sources operating in mid infrared spectral region with stable emission are important for applications in spectroscopy and wireless communication. Quantum cascade lasers (QCL) are unique semiconductor sources covering mid infrared frequency range. Based on intersubband transitions, the carrier lifetime of these sources is in the ps range. For this reason their frequency response to direct modulation is expected to overcome the limits of standard semiconductor lasers. In this work injection locking of the roundtrip frequency of a QCL emitting at 9 μm is reported. Inter modes laser frequency separation is stabilized and controlled by an external microwave source. Designing an optical waveguide embedded in a microstrip line a flat frequency response to direct modulation up to 14 GHz is presented. Injection locking over MHz frequency range at 13.7 GHz is demonstrated. Numerical solutions of injection locking theory are discussed and presented as tool to describe experimental results.     

Synergistic Action of Alginate Chemical Reduction and Laser Irradiation for the Formation of Au Nanoparticles with Controlled Dimensions

Freestanding natural polymeric films with homogeneous dispersion of gold nanoparticles (Au NPs) are obtained via in situ reduction of gold(III) chloride trihydrate by sodium alginate (SA) biopolymer matrix, during water evaporation without the use of additional reducing agents. The size and size distribution of the prepared Au NPs can be tuned by changing the concentration of the precursor and/or the procedure of the films’ preparation. The nanocomposite films after preparation are stable in ambient conditions and can be used without the need of further processing, or can be redissolved in water. In the case of water dissolution, the aqueous solutions are irradiated with UV laser pulses turning the previously formed Au NPs into smaller ones with narrow size distributions through photofragmentation. This technique is proposed as a green way of synthesizing Au NPs of tunable size in aqueous solution of alginate, or incorporated in alginate freestanding polymeric films, that due to their biocompatibility can be used as passive labels or active sensors in biomedical applications.     

Finite 2‐Geodesic Transitive Graphs of Prime Valency

We classify noncomplete prime valency graphs satisfying the property that their automorphism group is transitive on both the set of arcs and the set of 2‐geodesics. We prove that either Γ is 2‐arc transitive or the valency p satisfies , and for each such prime there is a unique graph with this property: it is a nonbipartite antipodal double cover of the complete graph with automorphism group and diameter 3.     

Molecular Recognition of Rosmarinic Acid from Salvia sclareoides Extracts by Acetylcholinesterase: A New Binding Site Detected by NMR Spectroscopy

Acetylcholinesterase (AChE) inhibition is one of the most currently available therapies for the management of Alzheimer’s disease (AD) symptoms. In this context, NMR spectroscopy binding studies were accomplished to explain the inhibition of AChE activity by Salvia sclareoides extracts. HPLC‐MS analyses of the acetone, butanol and water extracts eluted with methanol and acidified water showed that rosmarinic acid is present in all the studied samples and is a major constituent of butanol and water extracts. Moreover, luteolin 4′‐O‐glucoside, luteolin 3′,7‐di‐O‐glucoside and luteolin 7‐O‐(6′′‐O‐acetylglucoside) were identified by MS² and MS³ data acquired during the LC‐MSⁿ runs. Quantification of rosmarinic acid by HPLC with diode‐array detection (DAD) showed that the butanol extract is the richest one in this component (134 μg mg^?1 extract). Saturation transfer difference (STD) NMR spectroscopy binding experiments of S. sclareoides crude extracts in the presence of AChE in buffer solution determined rosmarinic acid as the only explicit binder for AChE. Furthermore, the binding epitope and the AChE‐bound conformation of rosmarinic acid were further elucidated by STD and transferred NOE effect (trNOESY) experiments. As a control, NMR spectroscopy binding experiments were also carried out with pure rosmarinic acid, thus confirming the specific interaction and inhibition of this compound against AChE. The binding site of AChE for rosmarinic acid was also investigated by STD‐based competition binding experiments using Donepezil, a drug currently used to treat AD, as a reference. These competition experiments demonstrated that rosmarinic acid does not compete with Donepezil for the same binding site. A 3D model of the molecular complex has been proposed. Therefore, the combination of the NMR spectroscopy based data with molecular modelling has permitted us to detect a new binding site in AChE, which could be used for future drug development.     

Column comparison and method development for the analysis of short‐chain carboxylic acids by zwitterionic hydrophilic interaction liquid chromatography with UV detection

Short‐chain carboxylic acids are relevant in pharmaceutical, food quality control, and biomedical analysis. In this study, 11 acids commonly found in drugs and in food products were selected. Wine was chosen as matrix for testing the method. The test compounds were used for comparing the selectivity of four 150 × 2.1 mm zwitterionic hydrophilic interaction LC (HILIC) columns (ZIC‐HILIC 5 μm, 200 Å, and 3.5 μm, 100 Å, ZIC‐pHILIC 5 μm, ZIC‐cHILIC 3 μm, 100 Å) while varying the conditions to optimize for low UV wavelength detection and achieve high sensitivity. Retention using potassium phosphate and ammonium carbonate as mobile‐phase components at pH 6.0, 7.5, and 8.5–8.9 was studied considering recent hypotheses on HILIC mechanism‐related with the Hofmeister series effect and ion hydration. An isocratic method with UV detection at 200 nm and mobile phase consisting of 75% acetonitrile and 10 mM potassium phosphate at pH 6.0 applied to a ZIC‐cHILIC column was found provisionally optimal and partially validated for the 11 analytes. Satisfactory results (R² from 0.9940 to >0.9999), and recoveries from 93–106% for all analytes evidenced the method as suitable for wine analysis. To the best of our knowledge, no previous study has reported on the direct ZIC‐HILIC separation and UV detection of the acids considered here in wine.     

Application of structural analogs of dimercaptosuccinic acid-functionalized silica nanoparticles (DMSA-[silica]) to adsorption of mercury, cadmium, and lead

In order to gain additional insight into mercury selectivity with nano-sized DMSA-[silica], we investigated a series of ligands related to DMSA, these are: monomercaptosuccinic acid; MMSA, 2-mercapto-4-methyl-5-thiazoleacetic acid; MCT, ortho-thiosalicylic acid; o-TSA and para-thiosalicylic acid; p-TSA. The MMSA chelate is structurally similar to DMSA except that it has only one thiol group. The chelates o-TSA and p-TSA each have one thiol and one carboxylic acid group. MCT includes neutral S and N atoms in close proximity to the thiolate binding site. MCT, o-TSA and p-TSA resemble each other in having equal numbers of carboxylic acid and thiol groups and formation of amide bonds with the linker on silica is expected to eliminate the carboxylate binding sites, making thiolates the only binding sites for Hg(II), Cd(II), and Pb(II) metals ions in the nano-sized; MMSA-[silica], MCT-[silica], o-TSA-[silica], and p-TSA-[silica]. Each of the nano-sized MMSA-[silica], MCT-[silica], o-TSA-[silica], and p-TSA-[silica], show a higher preference for Hg(II) over Cd(II) and Pb(II) compared to the same free chelates in solution, respectively. In addition, there are differences in the level of metal ion chelation for each functionalized silica nanoparticle. These differences in the degree of metal chelation for each functionalized silica nanoparticles surface are explained by the difference in thiolate/carboxylate ratio upon attachment to the surface and on steric reasons based on the orientation of the thiol groups on the surface. When attached via amide bond formation, the thiolate site in o-TSA-[silica] will face towards the silica surface, while for p-TSA-[silica], the thiolate site is expected to be pointed outwards and away from the silica surface. In comparing MMSA-[silica] to DMSA-[silica], the thiolate/carboxylate ratio decreases from 2/1 in DMSA-[silica] to 1/1 in MMSA-[silica] (assuming attachment via one amide bond in each case). This effect of increasing the ratio of thiolate to carboxylate upon attachment to the surface is believed to play a role in the selectivity enhancement towards Hg(II) over Cd(II) and Pb(II).     

Electrical neuroimaging evidence that spatial frequency-based selective attention affects V1 activity as early as 40-60 ms in humans

Background  

Karns and Knight (2009) [1] demonstrated by using ERP and gamma band oscillatory responses that intermodal attention modulates visual processing at the latency of the early phase of the C1 response (62-72 ms) thought to be generated in the primary visual cortex. However, the timing of attentional modulation of visual cortex during object-based attention remains a controversial issue.