Compound-Specific 14N/15N Analysis of Amino Acid Trimethylsilylated Derivatives from Plant Seed Proteins

Isotopic analyses of plant samples are now of considerable importance for food certification and plant physiology. In fact, the natural nitrogen isotope composition (δ¹⁵N) is extremely useful to examine metabolic pathways of N nutrition involving isotope fractionations. However, δ¹⁵N analysis of amino acids is not straightforward and involves specific derivatization procedures to yield volatile derivatives that can be analysed by gas chromatography coupled to isotope ratio mass spectrometry (GC-C-IRMS). Derivatizations other than trimethylsilylation are commonly used since they are believed to be more reliable and accurate. Their major drawback is that they are not associated with metabolite databases allowing identification of derivatives and by-products. Here, we revisit the potential of trimethylsilylated derivatives via concurrent analysis of δ¹⁵N and exact mass GC-MS of plant seed protein samples, allowing facile identification of derivatives using a database used for metabolomics. When multiple silylated derivatives of several amino acids are accounted for, there is a good agreement between theoretical and observed N mole fractions, and δ¹⁵N values are satisfactory, with little fractionation during derivatization. Overall, this technique may be suitable for compound-specific δ¹⁵N analysis, with pros and cons.     

Advances in Subcritical Hydro‐/Solvothermal Processing of Graphene Materials

Many promising graphene‐based materials are kept away from mainstream applications due to problems of scalability and environmental concerns in their processing. Hydro‐/solvothermal techniques overwhelmingly satisfy both the aforementioned criteria, and have matured as alternatives to wet‐chemical methods with advances made over the past few decades. The insolubility of graphene in many solvents poses considerable difficulties in their processing. In this context hydro‐/solvothermal techniques present an ideal opportunity for processing of graphenic materials with their versatility in manipulating the physical and thermodynamic properties of the solvent. The flexibility in hydro‐/solvothermal techniques for manipulation of solvent composition, temperature and pressure provides numerous handles to manipulate graphene‐based materials during synthesis. This review provides a comprehensive look at the subcritical hydro‐/solvothermal synthesis of graphene‐based functional materials and their applications. Several key synthetic strategies governing the morphology and properties of the products such as temperature, pressure, and solvent effects are elaborated. Advances in the synthesis, doping, and functionalization of graphene in hydro‐/solvothermal media are highlighted together with our perspectives in the field.     

MEMS Scanning Calorimeter With Serpentine-Shaped Platinum Resistors for Characterizations of Microsamples

We report a new design and operation of a microelectromechanical systems (MEMS) differential scanning calorimeter (DSC) for heat-capacity measurements. The sensor consists of a 500-nm silicon nitride membrane supported by four bridges on a silicon wafer. On one side of the membrane, a serpentine-shaped platinum layer is deposited and used as both a resistive heater and a thermometer during the DSC measurement. This MEMS design can provide a self-alignment between the DSC cell and the material to be analyzed in order to prevent its deposition on the sloping side walls of the silicon frame. According to FEM calculations, the system exhibits good thermal isolation and high uniformities in the temperature field in the sensing area of the device. To evaluate the use of this calorimetric device for liquid samples, we measure the heat of vaporization of nanoliter-scale water droplets with high preciseness using the calorimeter in both scanning and heat conduction modes.     

Polymeric Nanoparticles as a Self-Adjuvanting Peptide Vaccine Delivery System: The Role of Shape

Antigens incorporated in subunit vaccines are typically poorly immunogenic, so a strong immunostimulant (adjuvant) and/or delivery system is required to boost immunogenicity. In this work, the various functional polymer nanostructures, that is, rods, worms, spheres, and tadpoles are used to develop potent peptide antigen delivery systems. The antigen PADRE-J8 (PJ8), derived from Group A Streptococcus (GAS) M-protein, is either physically mixed or chemically conjugated to polymeric nanoparticles of different shapes. The physical mixture of polymeric nanoparticles and antigen is more effective in inducing antibody production than their chemical conjugates. Moreover, rod-shaped polymeric nanoparticles in physical mixture with PJ8 elicited higher and more opsonic antibody titers than powerful complete Freund's adjuvant (CFA)-adjuvanted antigen. Herein, for the first time it is demonstrated that a) the block copolymer, in nanoparticle form, can act as an immune adjuvant, b) nanoparticle shape plays a crucial role in their immunogenicity, and c) antigen conjugation is not required, nor is antigen encapsulation or absorption.     

Organic Conjugated Trimers with Donor–Acceptor–Donor Structures for Photocatalytic Hydrogen Generation Application

Organic donor–acceptor–donor (D–A–D) polymers or small molecules are widely investigated in organic solar cells due to their broad light absorption, narrow band gap, excellent charge mobility, and exciton seperation at the interface. However, studies of conjugated small molecules with D–A–D molecule structures as photocatalytically active materials are still rare. In this study, an unprecedented demonstration that photocatalytic activity can in fact be affected by tuning the D and A is given. Especially, the EBE trimer, comprising 3,4-ethylenedioxythiophene (E) and benzothiadiazole (B) units, exhibits the best photophysical, chemical, and photocatalytic properties compared to other D–A–D combinations of D and A. Detailed kinetic studies show that all trimers in organic solution present relatively long-lived and highly emissive photogenerated singlet excitons (τ = 4–13 ns; ϕ_em = 0.5–0.9) as judged by photoluminescence and transient absorption measurements, while in specific cases formation of long-lived triplet states can be identified. Organic microparticles of the trimers are efficiently formed in aqueous solution by nanoprecipitation, and rapid photoinduced electron release/injection to the solvent is evidenced spectroscopically. The results indicate that organic small molecule structures with D–A–D structures pave a new pathway for photocatalytic solar-to-chemical energy conversion of novel small organic molecules.     

Inclusion Complexes of Free Fatty Acids with Amylose

Spherocrystallite formation was observed when maize starch was gelatinized at temperatures greater than 120°C and the resultant paste stored at 75 – 95°C for defined time periods. Although the spherocrystals were of similar dimensions to native maize starch granules, and exhibited birefringent properties, Electron Microscope studies indicated quite different texture and morphology. Further evidence showed that the particles were formed from inclusion complexes of naturally occurring free fatty acids with the linear component of maize starch. Similar observations were made when the starch gelatinization was carried out at about 95°C in the presence of a specific α-amylase enzyme followed by similar storage conditions.     

Continuous flow photocatalytic reactor using TiO2-coated foams,modeling and experimental operating mode

This article aims to build a modeling and simulating tool of the operation of a continuous flow heterogeneous photocatalysis reactor. Continuous flow is well-known in reactor engineering for allowing advanced control of reactor and scaling-up with great confidence, but little research has addressed it's potential for this kind of application. In developing this model, particular attention was paid to the coupling which occurs at local scale between the radiative transfer and the reaction kinetics of advanced oxidation of a target organic micro-pollutant. The solution of the radiative transfer equation by Monte Carlo method was applied to a photocatalyst supported on a macroporous ceramic foam forming an efficient 3D support. After identification of the kinetic law of degradation, the dynamic simulation model was validated through comparison with a series of experiments performed for different but constant irradiations and for variable irradiations approaching, in term of intensity and dynamics, natural solar radiation.