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Polyoxyethylene lauryl ether (POELE10)-NaH 2 PO 4 aqueous two-phase extraction system (ATPES) is coupled with HPLC to analyze chloramphenicol (CAP) in aquatic product. Response surface methodology (RSM) was adopted in the multi-factor experiment to determine the optimized conditions. The extraction efficiency of CAP ( E %) is up to 99.42% under the optimal conditions, namely, the concentration of NaH 2 PO 4 , the concentration of POELE10, pH and temperature were 0.186 g·mL −1 , 0.033 g·mL −1 , 3.8 and 25 °C respectively. The optimal value of enrichment factor of CAP (F) was 22.56 when the concentration of NaH 2 PO 4 was 0.192 g·mL −1 , the concentration of POELE10 was 0.024 g/ml, pH was 4.2 and temperature was 30 °C. The limit of detection (LOD) and limit of quantification (LOQ) of this method are 0.8 μg·kg −1 and 1 μg·kg −1 , which meet the needs of determining trace or ultratrace CAP in food. The E % and F of this technique are much better than other extraction methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Differences and similarities between two squids were investigated. • DG exhibited better MP stability than OB after 120 d of frozen storage. • NADP and malic enzyme initiated a rapid decrease in MP properties in OB. • Cytoskeletal proteins maintained the MP stability of DG during frozen storage. Neon flying squid (OB) and jumbo squid (DG) mantles were evaluated to reveal the similarities and differences in their physicochemical features and protein abundances. Microstructural results indicated that the OB mantle exhibited numerous myofibril fragments and disordered microstructures after frozen storage compared with DG tissues. Chemical analysis suggested that freezing resulted in a rapid decrease in myofibrillar protein (MP) content, Ca2+-ATPase activity, and total sulfhydryl content, and promoted the increase in carbonyl content of MPs in both OB and DG. While, DG presented better MP stability than OB muscle after 120 days of frozen storage. Label-free proteomic analysis detected 24 down- and 33 up-regulated differentially abundant proteins (DAPs) in OB and DG mantles. Identified DAPs including isocitrate dehydrogenase and malic enzyme initiated a rapid decrease in the MP properties in OB samples. Moreover, DAPs were related to cytoskeleton function, including paramyosin, tropomyosin, and troponin C, which improved the stability of DG in response to freezing-induced changes. [ABSTRACT FROM AUTHOR]

Abstract: Glutamate decarboxylase (EC 4.1.1.15, GAD) is a pyridoxal 5′-phosphate (PLP) dependent enzyme, which catalyses the irreversible α-decarboxylation of l-glutamic acid to γ-aminobutyric acid (GABA). GAD was purified 186-fold from rice germ. Ultraviolet–visible spectra showed that the rice germ holoGAD presented a weak peak at 420nm, but the inactivated apoGAD did not. The holoGAD also exhibited a strong peak at 308nm and a weak peak at 336nm in its fluorescence emission spectrum. The apoGAD led to a 20% increase in the fluorescence emission at 308nm. The contents of the secondary structure elements of the holoGAD and apoGAD were estimated from the values of the mean residue ellipticity based on the CD spectra. The holoGAD had a greater β-sheet content than the apoGAD (39% versus 27%), whereas both had a similar α-helix content (13% versus 14%). These findings confirmed that a slight conformational change had occurred when PLP bound to the apoGAD to form the holoGAD. Chemical modifications of the GAD by some selected reagents indicated that histidine residue(s) might be involved in the enzymatic functions, but were not essential for the enzyme activity. The study also suggested there was one arginine residue in the GAD active site, and most likely at the substrate-binding site. [Copyright &y& Elsevier]

Abstract: Glutamate decarboxylase (EC 4.1.1.15, GAD) is a pyridoxal 5′-phosphate (PLP) dependent enzyme, which catalyses the irreversible α-decarboxylation of l-glutamic acid to γ-aminobutyric acid. GAD was purified 186-fold from rice germ using a combination of ammonium sulfate fractionation, DEAE-Sepharose FF ion exchange chromatography, Superdex-200 gel filtration chromatography, and Glu-Sepharose CL 4B affinity chromatography. The purified preparation showed a single peak on SE-HPLC with an approximate molecular mass of 78kDa and a single band on SDS–PAGE with a subunit Mr of 40kDa. This indicated that the GAD from rice germ existed as a dimer of homological subunits. Rice germ GAD has an optimum pH range between 5.5 and 5.8, and an optimum temperature at 40°C. K m values for glutamic acid and PLP were determined at 32.3mM and 1.7μM, respectively. Chemicals reagents such as HgCl2, KI and AgNO3 decreased the enzyme activity by 68.5%, 44.9% and 32.4%, respectively, but 500μM of CaCl2 at the optimum pH could increase the activity by 145%. [Copyright &y& Elsevier]

• Morphology changes of MNPs were characterized in a quantitative braising process. • Compositions of MNPs were intrinsically rich in glycoconjugates and triglycerides. • MNPs initially formed were inclined to self-assemble into larger particles. • Mechanisms of MNP evolution were revealed from microcosmic-spatial perspectives. • A hypothesis that MNP might be a key factor of broth flavor regulation was proposed. The formation and transformation mechanisms of micro-nano particles (MNPs) in broth during meat braising were systematically investigated through a sophisticated controlled process. Dynamic changes in the morphology, composition and spatial distribution of MNPs were comprehensively characterized, and subsequently the mechanisms were visually uncovered from microcosmic-spatial perspectives. MNPs formed as circular-shape colloidal systems with an aggrandizing tendency for particle number and size and gradually stabilize eventually. Specifically, the major MNPs gradually increased the size from <400 nm to ~1500 nm and accumulated triglycerides and glycoconjugates resulting from lipid oxidation, Maillard reaction, etc. Continuous formation of MNPs in broth progressively facilitated the spatial coalescence and self-assembly of free substances driven by intermolecular interactions, and consequently principal nutrients and flavor compounds further accumulated in the MNPs by the braising process. Hence, this work not only revealed the MNP formation and transformation mechanisms but offered a foundation for investigating MNP-dependent effect on broth flavor. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three benzazole-based fluorophores show expectable dual-state emission as designed. • These fluorophores can selectively detect Hg2+/Cu2+ by regulating their skeletons. • Two probes based on benzimidazole or benzoxazole can ultrasensitively sense Hg2+. • The developed probes can detect and remove Hg2+ in real water and seaweed samples. • They also can be processed as a portable tool for Hg2+ visualization detection. Developing potentially toxic metal ion probes is significant for environment and food safety. Although Hg2+ probes have been extensively studied, small molecule fluorophores that can integrate two applications of visual detection and separation into one unit remain challenging to access. Herein, by incorporating triphenylamine (TPA) into tridentate skeleton with an acetylene bridge, 2,6-bisbenzimidazolpyridine-TPA (4a), 2,6-bisbenzothiazolylpyridine-TPA (4b) and 2,6-bisbenzothiazolylpyridine-TPA (4c) were first constructed, expectably showing distinct solvatochromism and dual-state emission properties. Since the diverse emission properties, the fluorescence detection of 4a - 4b can be achieved with an ultrasensitive response (LOD = 10−11 M) and efficient removal of Hg2+. More interestingly, 4a-4b can not only be developed into paper/film sensing platform, but also reliably detect Hg2+ in real water and seaweed samples, with recoveries ranging from 97.3% to 107.8% and a relative standard deviation of less than 5%, indicating that they have excellent application potential in the field of environmental and food chemistry. [ABSTRACT FROM AUTHOR]