Adlereaton3649

Gallotannins extracted from gallnuts are commonly added to wine to improve its properties. They consist of mixtures of galloylester derivatives of glucose. However, their composition and properties are not well established. In this study, methods based on liquid chromatography coupled to UV-visible detection and mass spectrometry, size exclusion chromatography and 1D (31P) and 2D (1H DOSY, 31P TOCSY, 1H/13C HSQC, HMBC) NMR spectroscopy have been implemented for extensive chemical characterization of three commercial gallnut tannin extracts. Differences in the proportions of the different constituents (gallic, digallic, trigallic acids, galloylglucose derivatives) and in the structure and molecular weight distributions of gallotannins were demonstrated between the three extracts, with chains containing 8.5, 12.2, and 12.4 galloyl groups in average for TAN A, B1, and B2, respectively. The antioxidant capacities of the extracts, evaluated using the ABTS method, were similar and related mostly to their total tannin content, with only limited impact of the tannin composition.Nuclear magnetic resonance (NMR) metabolomics profiling was evaluated as a new tool in sensory assessment of protein hydrolysates. Hydrolysates were produced on the basis of different raw materials (cod, salmon, and chicken), enzymes (Food Pro PNL and Bromelain), and hydrolysis time (10 and 50 min). The influence of raw material and hydrolysis parameters on sensory attributes was determined by traditional descriptive sensory analysis and 1H NMR spectroscopy. The raw material had a major influence on the attribute intensity and metabolite variation, followed by enzyme and hydrolysis time. However, the formation of bitter taste was not affected by the raw material. Partial least-squares regression (PLSR) on 1H NMR and sensory data provided good models (Q2 = 0.55-0.89) for 11 of the 17 evaluated attributes, including bitterness. Significant metabolite-attribute associations were identified. The study confirms the potential prediction of the sensory properties of protein hydrolysates from cod, salmon, and chicken based on 1H NMR metabolomics profiling.Herein, the mechanism of catalytic allylic C-H amination reactions promoted by Cp*Rh complexes is reported. Reaction kinetics experiments, stoichiometric studies, and DFT calculations demonstrate that the allylic C-H activation to generate a Cp*Rh(π-allyl) complex is viable under mild reaction conditions. The role of external oxidants in the catalytic cycle is elucidated. Quantum mechanical calculations, stoichiometric reactions, and cyclic voltammetry experiments concomitantly support an oxidatively induced reductive elimination process of the allyl fragment with an acetate ligand proceeding through a Rh(IV) intermediate. Stoichiometric oxidation and bulk electrolysis of the proposed π-allyl intermediate are also reported to support these analyses. Lastly, evidence supporting the amination of an allylic acetate intermediate is presented. We show that Cp*Rh(III)2+ behaves as a Lewis acid catalyst to complete the allylic amination reaction.The antisolvent precipitation method is widely applied to produce zein colloidal particles. The process involves dissolving zein in 55-90% (v/v) alcohol/water mixtures and then shearing such solutions into deionized water to lower the ethanol content. In the present work, on the basis of the preliminary result that gum arabic (GA) was able to well disperse in 70% (v/v) alcohol/water mixtures, a new way was created to produce zein-GA nanocomposites by simply mixing their aqueous alcohol solution with a high alcohol level of 70% (v/v) at pH 8.0. Findings showed that the multimodal size distribution of zein or GA alone was shifted to be the monomodal peak after zein and GA aqueous ethanol solution was mixed, indicating the successful formation of zein-GA nanocomposites. A core-shell structure was observed for zein-GA nanocomposites, with zein as a core and GA as a shell. In addition, the incorporation of GA caused the conformational and second structural changes of zein. A two-step mechanism was involved to explain the formation of zein-GA nanocomposites. The first step was that GA addition changed the polarity of zein aqueous ethanol solution and zein nanoparticles formed, and the second step was that hydrogen bonds and hydrophobic interactions promoted the adsorption of GA onto the particle surfaces. see more Results in this work would provide a new sight into the design of zein-based nanocomplexes, which may have potential applications, such as constructing delivery systems, for bioactive compounds.Non-platinum group metal (non-PGM) electrocatalysts for the oxygen reduction reaction (ORR) are generally composed of iron, nitrogen, and carbon synthesized through high-temperature pyrolysis. Among the various types of precursors, metal-organic frameworks (MOFs), zeolitic imidazolate framework (ZIF)-8 in particular, have often been used in the synthesis. The pyrolysis of ZIF-8 precursor relies on the use of Zn as a sacrificial metal (SM), and the optimal processing temperatures often exceed 1000 °C to generate active non-PGM catalysts. The high pyrolysis temperature tends to result in heterogeneous active moieties ranging from Fe single atoms to nanoparticles. In this study, we present the synthesis of non-PGM catalysts using Cd as the sacrificial metal instead of Zn. By using Cd, we were able to generate active non-PGM electrocatalysts from the MOF precursors at a low pyrolysis temperature of 750 °C, which helps preserve the single atomic iron active sites.Imidazolone (Iz) is one of the many products resulting from oxidative damage to DNA. Three pathways for the formation of Iz and related degradation products have been studied by density functional theory using the ωB97XD functional with the 6-31+G(d,p) basis set and SMD implicit water solvation plus a small number of explicit water molecules positioned to help stabilize charged species and facilitate reaction steps. The first pathway starts with guanine radical and the addition of superoxide at C5. Endoperoxide formation was calculated to have slightly lower barriers than diol formation. The next steps are pyrimidine ring opening and decarboxylation. Ring migration then proceeds via an acyclic intermediate rather than a bicyclic intermediate and is followed by formamide loss to yield Iz. The second pathway starts with 8oxoG and proceeds via C5 superoxide addition and diol formation to a relatively stable intermediate, oxidized guanidinohydantoin (Ghox). The barriers for hydroxide ion addition to Ghox are much lower than for water addition and should yield more Iz and parabanic acid at higher pH.