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A capillary electrophoresis method with on-line inhibited chemiluminescence (CL) detection was first used to determine folic acid (FA). This method was established based on the quenching effect of FA on the CL reaction of luminol with a Ag(iii) complex in alkaline medium. The separation was conducted with a 20.0 mM sodium borate buffer containing 1.0 mmol L

In the present research, field-amplified sample injection-CZE (FASI-CZE) coupled with a diode array detector was established to determine trace level sulfa antibiotic. Sulfathiazole, sulfadiazine, sulfamethazine, sulfadimethoxine, sulfamethoxazole, and sulfisoxazole were selected as analytes for the experiments. The background electrolyte solution consisted of 70.0 mmol/L borax and 60.0 mmol/L boric acid (including 10% methanol, pH 9.1). The plug was 2.5 mmol/L borax, which was injected into the capillary at a pressure of 0.5 psi for 5 s. Then the sample was injected into the capillary at an injection voltage of -10 kV for 20 s. The electrophoretic separation was carried out under a voltage of +19 kV. The capillary temperature was maintained at 20˚C throughout the analysis, and six sulfonamides were completely separated within 35 min. Compared with pressure injection-CZE, the sensitivity of FASI-CZE was increased by 6.25-10.0 times, and the LODs were reduced from 0.2-0.5 to 0.02-0.05 μg/mL. The method was applied to the determination of sulfonamides in river water and particulate matter samples. The recoveries were 78.59-106.59%. The intraday and interday precisions were 2.89-7.35% and 2.77-7.09%, respectively. This provides a simpler and faster method for the analysis of sulfa antibiotic residues in environmental samples.

Caffeine (CA) is a common xanthine alkaloid found in tea leaves, coffee beans, and other natural plants, and is the most widely used psychotropic substance in the world. Accumulating evidence suggests that low plasma levels of CA and its metabolites may serve as reliable diagnostic markers for early Parkinson's disease (PD) patients. In this study, we demonstrated a new MEKC method for determining CA and its three main downstream metabolites, paraxanthine (PX), theobromine (TB), and theophylline (TP), in human plasma. Plasma samples were collected, and analyzed using MEKC, after SPE. The running buffer was composed of 35 mM phosphate, pH of 10.5, and 25 mM SDS. The separation voltage was 15 kV and the detection wavelength was at 210 nm. Under the optimum conditions, four distinct analytes were completely separated and detected in less than 12 min. Method limits of detection were as low as 7.5 ng/mL for CA, 5.0 ng/mL for TB, and 4.0 ng/mL for both PX and TP. The recoveries were between 88.0% and 105.9%. This method was successfully applied to 27 human plasma samples. The results indicate that the plasma concentrations of the four analytes are significantly lower in patients with early PD than in control subjects (p < 0.05). The area under curve was improved to 0.839 when CA and its three main metabolites were included, suggesting that MEKC testing of CA, TP, TB, and PX may serve as a potential method for early diagnosis of PD.

S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) play an important role in various biochemical reactions involving the maintenance of human health and disease prevention. In this study, ...

Herein, we report that Shroom3 knockdown, via Fyn inhibition, induced albuminuria with foot process effacement (FPE) without focal segmental glomerulosclerosis (FSGS) or podocytopenia. Interestingly, knockdown mice had reduced podocyte volumes. Human minimal change disease (MCD), where podocyte Fyn inactivation was reported, also showed lower glomerular volumes than FSGS. We hypothesized that lower glomerular volume prevented the progression to podocytopenia. To test this hypothesis, we utilized unilateral and 5/6th nephrectomy models in Shroom3-KD mice. Knockdown mice exhibited less glomerular and podocyte hypertrophy after nephrectomy. FYN-knockdown podocytes had similar reductions in podocyte volume, implying that Fyn was downstream of Shroom3. Using SHROOM3 or FYN knockdown, we confirmed reduced podocyte protein content, along with significantly increased phosphorylated AMPK, a negative regulator of anabolism. AMPK activation resulted from increased cytoplasmic redistribution of LKB1 in podocytes. Inhibition of AMPK abolished the reduction in glomerular volume and induced podocytopenia in mice with FPE, suggesting a protective role for AMPK activation. In agreement with this, treatment of glomerular injury models with AMPK activators restricted glomerular volume, podocytopenia, and progression to FSGS. Glomerular transcriptomes from MCD biopsies also showed significant enrichment of Fyn inactivation and Ampk activation versus FSGS glomeruli. In summary, we demonstrated the important role of AMPK in glomerular volume regulation and podocyte survival. Our data suggest that AMPK activation adaptively regulates glomerular volume to prevent podocytopenia in the context of podocyte injury.

After several decades of use, trimethoprim (TMP) remains one of the key access antimicrobial drugs listed by the World Health Organization. To circumvent the problem of trimethoprim resistance worldwide, a better understanding of drug-resistance mechanisms is required. In this study, we screened the single-gene knockout library of Escherichia coli, and identified mgrB and other several genes involved in trimethoprim resistance. Subsequent comparative transcriptional analysis between ΔmgrB and the wild-type strain showed that expression levels of phoP, phoQ, and folA were significantly upregulated in ΔmgrB. Further deleting phoP or phoQ could partially restore trimethoprim sensitivity to ΔmgrB, and co-overexpression of phoP/Q caused TMP resistance, suggesting the involvement of PhoP/Q in trimethoprim resistance. Correspondingly, MgrB and PhoP were shown to be able to modulated folA expression in vivo. After that, efforts were made to test if PhoP could directly modulate the expression of folA. Though phosphorylated PhoP could bind to the promotor region of folA in vitro, the former only provided a weak protection on the latter as shown by the DNA footprinting assay. In addition, deleting the deduced PhoP box in ΔmgrB could only slightly reverse the TMP resistance phenotype, suggesting that it is less likely for PhoP to directly modulate the transcription of folA. Taken together, our data suggested that, in E. coli, MgrB affects susceptibility to trimethoprim by modulating the expression of folA with the involvement of PhoP/Q. This work broadens our understanding of the regulation of folate metabolism and the mechanisms of TMP resistance in bacteria.

We reported that Shroom3 knockdown, via Fyn inhibition, induced albuminuria with foot process effacement (FPE) without glomerulosclerosis (FSGS) or podocytopenia. Interestingly, knockdown mice had reduced podocyte volumes. Human minimal change disease, where podocyte Fyn inactivation was reported, also showed lower glomerular volumes than FSGS. We hypothesized that lower glomerular volume prevented the progression to podocytopenia. To test this hypothesis, we utilized unilateral- and 5/6th nephrectomy models in Shroom3 knockdown mice. Knockdown mice exhibited lower glomerular volume, and less glomerular and podocyte hypertrophy after nephrectomy. FYN-knockdown podocytes had similar reductions in podocyte volume, implying Fyn was downstream of Shroom3. Using SHROOM3- or FYN-knockdown, we confirmed reduced podocyte protein content, along with significantly increased phosphorylated AMP-kinase, a negative regulator of anabolism. AMP-Kinase activation resulted from increased cytoplasmic redistribution of LKB1 in podocytes. Inhibition of AMP-Kinase abolished the reduction in glomerular volume and induced podocytopenia in mice with FPE, suggesting a protective role for AMP-Kinase activation. In agreement with this, treatment of glomerular injury models with AMP-Kinase activators restricted glomerular volume, podocytopenia and progression to FSGS. In summary, we demonstrate the important role of AMP-Kinase in glomerular volume regulation and podocyte survival. Our data suggest that AMP-Kinase activation adaptively regulates glomerular volume to prevent podocytopenia in the context of podocyte injury.

A novel magnetic solid-phase extraction (MSPE) material (Fe3O4@SiO2-NH2-G2) had been prepared and employed for adsorption and analysis of seven quaternary ammonium compounds (QACs) in infant fruit and vegetable products coupled with high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). In this paper, Fe3O4@SiO2-NH2-G2 was synthesized based on Fe3O4@SiO2-NH2 and dendrimer (G2) consisting of cyanuric chloride and imidazole. The morphology, configuration and magnetic behavior of the magnetic material were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). Critical parameters affecting extraction efficiency, such as the adsorbent amount, sample pH, extraction time, the type of eluent, and desorption time, were optimized. The proposed method provided good linearity with the correlation coefficients (R2) of 0.9992-0.9999, low limits of detection (LODs) (0.05-0.50 μg kg-1) and limits of quantitation (LOQs) (0.20-2.00 μg kg-1). The satisfactory method recoveries in three spiked infant fruit and vegetable products samples were between 80.12% and 101.35% with the relative standard deviations (RSDs) less than 12.04%. In summary, the established method was an effective sample preparation method and showed good prospect for the analysis of QACs in complex matrices.

Molybdenum (Mo) is a component of the Mo cofactor (Moco) of nitrate reductase (NR) and is therefore essential for nitrate metabolism. However, little is known about Mo deficiency phenotypes or about how physiological and molecular mechanisms of Mo uptake and transport influence nitrate uptake and utilization in strawberry. Here, we used physiological and cytological techniques to identify Mo deficiency phenotypes in strawberry. Seedlings cultured with MoO4 2- grew well and exhibited normal microstructure and ultrastructure of leaves and roots. By contrast, seedlings cultivated under Mo-deficient conditions showed yellow leaf blades and ultrastructural changes such as irregular chloroplasts and unclear membrane structures that were similar to the symptoms of nitrogen deficiency. We cloned and analyzed a putative molybdate transporter, FaMOT1, which may encode a molybdate transporter involved in the uptake and translocation of molybdate. Interestingly, the addition of the molybdate analog tungstate led to lower tissue Mo concentrations, reduced the translocation of Mo from roots to shoots, and increased the plants' sensitivity to Mo deficiency. Seedlings cultivated with MoO4 2- altered expression of genes in Moco biosynthesis. As expected, NR activity was higher under sufficient MoO4 2- levels. Furthermore, seedlings grown on Mo-deficient medium exhibited decreased 15NO3 - translocation and lower 15NO3 - use efficiency. These findings represent an important step towards understanding how molybdate transport, concentration, and deficiency symptoms influence nitrate uptake and utilization in strawberry.

Background LncRNAs are key regulators in cancer. The current study explored the role of lncRNA LINC00261 (LINC00261) in lung cancer (LC). Methods Expression of LINC00261 in LC tissues and cells was determined by quantitative real-time polymerase chain reaction (qRT-PCR). Pearson’s Chi square test and Kaplan–Meier analysis were performed to evaluate the correlations between LINC00261 expression and clinical characteristics, and overall survival time. A549 and SPC-A1 cells were transfected with LINC00261 overexpression plasmid, cell viability, cell number, and apoptosis were detected by CCK-8 assay, colony formation, and flow cytometry. Moreover, wound-healing and transwell assay were performed to detect cell metastasis and invasion. Expressions of proteins related to cell proliferation and metastasis were determined by Western blot. Xenograft was constructed, and tumor size and weight were measured and the effects of LINC00261 overexpression on tumor growth were detected. Bioinformatics analysis, dual-luciferase reporter assay, qRT-PCR, correlation analysis, and functional rescue experiments were conducted on clinical cases and LC cells to explore the molecular mechanism of LINC00261 in LC. Results In LC, LINC00261 expression was down-regulated, and was associated with more advanced TNM stage, metastasis and a shorter survival time. LINC00261 overexpression inhibited the growth and metastasis of LC cells in vitro and tumor growth in vivo. Furthermore, miR-1269a directly interacted with LINC00261 and FOXO1. The expressions of miR-1269a and FOXO1 were dysregulated by LINC00261 in LC. Additionally, miR-1269a promoted the progression of LC through targeting FOXO1. Conclusions Down-regulation of LINC00261 expression has a prognostic value in LC, and overexpression LINC00261 inhibits LC progression via targeting miR-1269a/FOXO1 axis.

A novel, simple and efficient chemiluminescence system has been developed for the determination of monoamine neurotransmitters and metabolites. By using the Ag (III)-luminol chemiluminescence system as a detector, a high performance liquid chromatography chemiluminescence method (HPLC-CL) was established and used to detect seven monoamine neurotransmitters. Under the optimized conditions, the detection limits (3S/N) of epinephrine (E), levodopa ( l -DOPA), dopamine (DA), serotonin (5-HT), 3-methoxy-4-hydroxyphenylglycol (MHPG), 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxypentylacetic acid (5-HIAA) were 20.0 μg dm−3,15.0 μg dm−3, 15.0 μg dm−3, 8.0 μg dm−3, 2.0 μg dm−3, 2.0 μg dm−3 and 3.0 μg dm−3, respectively. Moreover, they were well within the linear range of 50–1000 μg dm−3, 50–1000 μg dm−3, 50–1000 μg dm−3, 25–1000 μg dm−3, 5–25 μg dm−3, 5–25 μg dm−3 and 10–30 μg dm−3, respectively. The average recovery varied between 84.82% and 110.4%. The method has the attributes of simplicity, high sensitivity, and high efficiency. The sensitization and inhibition mechanisms for luminol-[Ag(HIO6)2]5–- analytes CL system were proposed by CL spectra and free-radical capture experiment.

Oxidations of hydrazine (H2NNH2) and substituted hydrazines (t-C4H9HNNH2 and c-C6H11HNNH2) by [IrCl6]2− are found to obey overall second-order kinetics: −d[IrCl62−]/dt = k′[RHNNH2]tot[IrCl62−], where k′ pertains to the observed second-order rate constants and [RHNNH2]tot stands for the total concentration of hydrazines. The k′ versus pH profiles have been established over a pH range from 3 to 10. Rapid scan spectra recorded for the reaction courses indicate that there are no fast substitutions on [IrCl6]2− and/or strong associations between [IrCl6]2− and hydrazines during the reactions. The determined ratios of Δ[Ir(IV)]/Δ[RHNNH2]tot clearly endow a 4:1 stoichiometry for all the hydrazines studied. The oxidation product has been identified by NMR spectroscopy in the case of t-C4H9HNNH2. The proposed reaction mechanisms involve parallel attack of [IrCl6]2− on RHNNH3+ and RHNNH2, forming the rate-determining steps and producing hydrazyl free radicals; these are followed by several fast reactions. Rate equations have been derived, and the rate constants of the rate-determining steps at 25.0 °C and 1.0 M ionic strength have been calculated. It is demonstrated that our kinetic analysis is a good approach for determination of the pKa values of hydrazines. Monoalkyl substitutions on hydrazine enhance the reactivity of substituted hydrazines significantly, but the reactivity has no correlation with the pKa values. All the kinetic and spectral attributes bestow that an outer-sphere electron transfer takes place in the rate-determining steps. Moreover, all the kinetic and mechanistic discrepancies for the hydrazine-[IrCl6]2− reaction remained in literature have been clarified in the present work.

Highlights • Ultrasound increases the DH of gelatin and antioxidant properties of hydrolysate. • Ultrasound facilitates the unfolding of protein structure. • Ultrasound accelerates the thermal degradation of the protein. • Ultrasound changes the morphology and interface characteristics of gelatin particles., This study primarily explored the internal mechanism underlying the ultrasonication-induced release of antioxidant peptides. An oxhide gelatin solution was treated ultrasonically (power = 200, 300, and 400 W), followed by enzymatic hydrolysis and structural and morphological analysis. The results showed that ultrasonication increased not only the degree of hydrolysis (DH) and protein recovery rate of the oxhide gelatin but also the ABTS radical scavenging, DPPH radical scavenging, ferrous chelating, and ferric reducing activities of its hydrolysate. The oxhide gelatin hydrolysate treated with 300-W ultrasonication had the maximum antioxidant activities. Ultrasonication inhibited hydrogen bond formation, reduced the crosslinking between collagen molecules, transformed part of the folded structure into a helical structure, and lowered the thermal stability of collagen molecules. The micromorphological analysis revealed that ultrasonication caused the gelatin surface to become loose and develop cracks, and as the power of the ultrasonication increased, the repetition interval distance (dÅ) also increased. Moreover, ultrasonication improved the solubilization, surface hydrophobicity, and interface characteristics and increased the content of basic and aromatic amino acids in the hydrolysate. In conclusion, ultrasonication modifies the protein structure, which increases the enzyme’s accessibility to the peptide bonds and further enhances antioxidant peptide release. These findings provide new insights into the application of ultrasonication in the release of antioxidant peptides.

Taint in grapes and wine following vineyard exposure to bushfire smoke continues to challenge the financial viability of grape and wine producers worldwide. In response, researchers are studying the chemical, sensory and physiological consequences of grapevine smoke exposure. However, studies involving winemaking trials are often limited by the availability of suitable quantities of smoke-affected grapes, either from vineyards exposed to smoke or from field trials involving the application of smoke to grapevines. This study compared the accumulation of volatile phenol glycosides (as compositional markers of smoke taint) in Viognier and Cabernet Sauvignon grapes exposed to smoke pre- vs. post-harvest, and found post-harvest smoke exposure of fruit gave similar levels of volatile phenol glycosides to fruit exposed to smoke pre-harvest. Furthermore, wines made from smoke-affected fruit contained similar levels of smoke-derived volatile phenols and their glycosides, irrespective of whether smoke exposure occurred pre- vs. post-harvest. Post-harvest smoke exposure therefore provides a valid approach to generating smoke-affected grapes in the quantities needed for winemaking trials and/or trials that employ both chemical and sensory analysis of wine.

5-hydroxytryptamine (5-HT) and its derivatives are endogenously active substances involved in multiple physiological and pathological processes. A novel method of detetermining 5-hydroxyindole ethanol (5-HTOL), 5-hydroxyindole acetic acid (5-HIAA), 5-hydroxytryptophan (5-HTP) and 5-HT in amniotic fluid by gas chromatography-mass spectrometry (GC-MS) was established based on a modified method of derivatization by silanization, in combination with solid-phase extraction pretreatment. Good linearity was achieved in the tested calibration range. The limits of detection (LOD) were 0.05, 0.08, 0.56, 0.43μg/L for 5-HTOL, 5-HIAA, 5-HTP and 5-HT, respectively. Accuracy (92.4-103.3) and precision (RSD5.4%) for all analytes was also determined. Then the method was used to analyze samples of amniotic fluid from 12 patients carrying foetuses with trisomy 21 and 12 healthy controls. Compared with normal fetuses, the levels of 5-HTOL, 5-HTP and 5-HT in the amniotic fluid were significantly altered in the fetuses with trisomy 21 (P0.01); the level of 5-HIAA showed no significant difference between the two groups (P0.05). This is a rapid, sensitive and reliable method for the determination of 5-HTOL, 5-HIAA, 5-HTP and 5-HT, and the study provide both potential trisomy 21 markers and elucidation of the physiological and pathological roles of 5-HT.

Pt(IV) anticancer active complexes are commonly regarded as prodrugs, and the reduction of the prodrugs to their Pt(II) analogs is the activation process. The reduction of a cisplatin prodrug cis-[Pt(NH3)2Cl4] and a carboplatin prodrug cis,trans-[Pt(cbdca)(NH3)2Cl2] by dl-homocysteine (Hcy) has been investigated kinetically in a wide pH range in this work. The reduction process follows overall second-order kinetics: −d[Pt(IV)]/dt = k′[Hcy]tot[Pt(IV)], where [Hcy]tot stands for the total concentration of Hcy and k′ pertains to the observed second-order rate constants. The k′ versus pH profiles have been established for both prodrugs. Spectrohotometric titrations reveal a stoichiometry of Δ[Pt(IV)]:Δ[Hcy]tot = 1:2; homocystine is identified as the major oxidation product of Hcy by high-resolution mass spectrometry. A reaction mechanism has been proposed, which involves all the four protolysis species of Hcy attacking the Pt(IV) prodrugs in parallel. Moreover, these parallel attacks are the rate-determining steps, resulting in a Cl+ transfer from the Pt(IV) prodrugs to the attacking sulfur atom. Rate constants of the rate-determining steps have been derived, indicating that the two prodrugs are reduced with a very similar rate in spite of the difference between the coordination ligands in their equatorial positions. The reactivity analysis in the case of cis,trans-[Pt(cbdca)(NH3)2Cl2] unravels that one species of Hcy (form III) is almost exclusively responsible for the reductions at the physiological pH (7.4), although it is existing only 5.2% of the total Hcy. On the other hand, the dominant existing form II of Hcy virtually does not make a contribution to the overall reactivity at pH 7.4.

Hydrogen sulfide (H2S) plays major functional and structural roles in diverse physiological functions and the pathogenesis of a variety of disorders in biological matrices. The significance of H2S has prompted the development of sensitive and selective methods to determine its concentration in biological samples. The fluorescent reagent monobromobimane (MBB) has been widely used to measure various thiol-containing species through alkylation. MBB may prevent the oxidation of sulfide and the reaction of sulfide with several different species (such as superoxide radicals, hydrogen peroxide and peroxynitrite). An isomers of MBB, 3-(bromomethyl)-2, 6, 7-trimethyl-1H, 5H-pyrazolo [1,2-a] pyrazole-1, 5-dione (MMB), is cheaper than MBB and its use in the analysis of H2S has not previously been reported. In the present study, we compared the derivatization reactions of hydrogen sulfide with MMB and MBB and developed a sensitive method to quantify H2S in blood. In our method, H2S was incubated in the dark with excess MMB in 0.1M Tris-HCl buffer (pH 10.1) at 50°C for 120min. 50μL aliquots of the derivatized product were analyzed using HPLC system with gradient elution of 0.1% (v/v) formic acid-acetonitrile. The limit of detection for the derivatized product was 0.03nmol/mL. The derivatization reaction was suitable for detecting low concentrations of H2S. The derivate product is stable over time, permitting batch storage and analysis.

Ascorbic acid (AA), uric acid (UA) and glutathione (GSH) are the most important water-soluble antioxidants. The concentrations of GSH and glutathione disulfide (GSSG) and their molar ratio are the indicators of oxidative stress. Little is known about the contents of UA, GSH and GSSG in human milk; a reliable and sensitive method to monitor the concentrations of the four compounds simultaneously in human milk is of critical importance. A new method for separation and quantification of these water-soluble antioxidants by HPLC coupled with Ag(III) chemiluminescence detector has been developed in this work with better recoveries. The antioxidants contents were determined in different times of lactation utilizing this method. The results show that the levels of AA, UA, GSH and GSH/GSSG of human colostrum are significantly higher than those of mature milk (P

Bisphenol A (BPA), as one of the environmental endocrine disruptors, is extensively existing and threatening to human health. To evaluate the environmental exposure level and protect human from the hazard of BPA, a precise and sensitive method is established. In this work, Graphene@ Fe3O4 (G@Fe3O4) is prepared by chemical coprecipitation method as magnetic dispersion solid phase extraction (MDSPE) material. The rapid and specific detection method of BPA is carried out by high-performance liquid chromatography (HPLC). Properties of G@Fe3O4 are identified by the fourier infrared spectrum and scanning electron microscopy. Conditions of solid phase extraction are optimized. Under the optimal extraction conditions, G@Fe3O4 has perfect enrichment effect on BPA. There is a good linear relationship in the range of 5.0~1000.0 μg/L with the correlation coefficient of 0.9997. The detection limit is 0.1 μg/L. This method is applied to water samples successfully, and recoveries of BPA are between 88.19% and 99.56% (RSDs

A solid phase membrane adsorbent&mdash, a nylon 6 nanofibers membrane coated by polypyrrole (PPy-PA6-NFsM)&mdash, was firstly synthesized and used for extraction of two &beta, lactam antibiotics (oxacillin and cloxacillin) in urban river water. Then the analytes were detected by capillary electrophoresis with a diode array detector (CE-DAD). The synthesized nanofibers membrane was characterized by scanning electron microscopy and a Fourier transform infrared spectrometer. The experimental conditions were optimized, including the amount used of PPy-PA6-NFsM, pH of the sample solutions, adsorption volume, and desorption conditions. Under the optimal extraction and separation conditions, the detection limits were found to be 2.0 ng/mL for both oxacillin and cloxacillin. The proposed method was applied to the determination of the two &beta, lactams in water samples of an urban river. The recoveries of these two &beta, lactams were found to be in the range 84.2&ndash, 96.4%, demonstrating that PPy-PA6-NFsM has a high extraction capability for these two antibiotics. The relative standard deviations, ranging from 2.26% to 5.29% for intraday measurements and from 2.38% to 7.02% for inter-day determinations, were derived respectively.

This study investigated the activity of adenosine monophosphate-activated protein kinase (AMPK), glycolysis, and meat quality index in three altitude bovines during postmortem aging process. Local cattle (altitude:1,500 m), Gannan yak (3,000 m), and Yushu yak (4,500 m) postmortem Longissimus Dorsi (LD) muscle were used. Results indicated that CaCl2 significantly increased the AMPK activity by increasing the calcium-regulated protein kinase kinase (CaMKKβ) activity. Besides, AMPK activation enhanced the activity of lactate dehydrogenase (LDH) and Ca2+ -ATPase and accelerated the rate of muscle maturation during postmortem aging. Moreover, the expression of HIF-1, PRKAA2, and GLUT4 genes in high-altitude Yushu yak was higher than that of low-altitude bovines. CaCl2 activates AMPK by activating CaMKKβ cascade and accelerates postmortem glycolysis affecting the intramuscular environment, color, and muscle protein degradation to accelerate postmortem muscle maturation, suggesting that AMPK has essential effects on postmortem muscle glycolysis and quality, and can regulate muscle quality by regulating postmortem muscle AMPK activity. PRACTICAL APPLICATIONS: Insufficient postmortem glycolysis usually leads to DFD (dark, firm, and dry) meat. Beef have relatively high incidences of DFD meat, which has an unattractive dark color and causes significant loss to the meat industry. Therefore, AMPK, which can regulate postmortem glycolysis to affect meat quality, is a valid research target.

A kinetic analysis of the oxidation of semicarbazide (SEM) by the single-electron oxidant [IrCl6]2− has been carried out by stopped-flow spectrometric techniques. The reaction proved to be first order each in [IrCl6 2−] and [SEM]tot, leading to overall second-order kinetics. The variation in the observed second-order rate constant k′ with pH was explored over the pH range of 0–7.11. Spectrophotometric titration revealed a stoichiometry of Δ[IrCl6 2−]/Δ[SEM]tot = 4:1 for the redox reaction. On the basis of the rate law, the redox stoichiometry, and the rapid scan spectra, a reaction mechanism is proposed which involves parallel attacks of [IrCl6]2− on both H2NCONHNH3 + and H2NCONHNH2 as rate-determining steps, followed by several rapid reactions. The rate expression, derived from the reaction mechanism, was utilized to simulate the k′–pH profile yielding a virtually perfect fit and indicating that the reaction path involving H2NCONHNH3 + does not make a significant contribution to the overall rate. The reaction between [IrCl6]2− and H2NCONHNH2 was further studied as a function of both temperature and ionic strength. From the temperature dependence, activation parameters were obtained as: ∆H 2 ‡ = 34.9 ± 1.5 kJ mol−1 and ∆S 2 ‡ = −78 ± 5 J K−1 mol−1. The observed ionic strength dependence suggests that the rate-determining step is between [IrCl6]2− and a neutral species of SEM. Hence, both the temperature and ionic strength dependency studies are in good agreement with the proposed reaction mechanism, in which the rate-determining step involves an outer sphere electron transfer.

A capillary electrophoresis method involving online indirect chemiluminescence (CL) detection was used to determine naphthol (NAP) isomers. The method was based on the quenching effect of 1- and 2-NAP on a new CL reaction of luminol with Ni(IV) complex in an alkaline medium. Separation was conducted with a 25.0 mM sodium borate buffer containing 0.8 mmol/L luminol. Under optimized conditions, 1- and 2-NAP were baseline separated and detected in less than 8 min. The limits of detection of 1- and 2-NAP were 3.1 and 2.7 μg/L, respectively (S/N = 3), with a linear range of 4.0-80.0 μg/L (r > 0.995). Analysis of real samples demonstrated that the spiked recoveries were in the range of 89.2-107.5% (n = 3). The proposed method was successfully used to determine 1- and 2-NAP contents in three environmental water samples and 14 human urine samples. No derivatization or tedious pretreatment was required in the analysis. The proposed method is a potential approach for routine tests of naphthol isomers in a facile CE-CL system.

A new, simple but efficient chemiluminescence system has been developed for determination of two β2-agonist drugs, ractopamine and fenoterol. The system is based on the chemiluminescence reaction of a Ni(IV) complex with luminol in alkaline media, while ractopamine or fenoterol can dramatically enhance chemiluminescence intensities. Under optimum conditions, chemiluminescence intensities are proportional to the concentrations of the drugs in the ranges of 1.0 × 10−8–1.0 × 10−6 mol dm−3 for ractopamine and of 1.0 × 10−9–1.0 × 10−7 mol dm−3 for fenoterol, respectively. The limits of detection (3σ) are 1.0 × 10−10 mol dm−3 for ractopamine and 1.0 × 10−11 mol dm−3 for fenoterol. Based on the kinetic characteristics of the chemiluminescence reaction, the chemiluminescence spectral change and free radical trapping experiment, a chemiluminescence reaction mechanism is proposed which involves free radicals in the Ni(IV)-luminol-ractopamine/fenoterol chemiluminescence systems. The mechanism of chemiluminescence enhancements by ractopamine/fenoterol to the Ni(IV)-luminol detection system is discussed.

In the present research, the application of a polypyrrole coating on Fe3O4 magnetic nanoparticles (PPy/Fe3O4 MNPs) as a sorbent was confirmed. The synthesized magnetic composites were characterized by TEM, FTIR spectroscopy, and XRD. Four β-lactams (oxacillin (OXA), cloxacillin (CLOX), dicloxacillin (DIC), and flucloxacillin (FLU)) were selected as analytes for the experiment. The extracted β-lactams were determined by micellar electrokinetic capillary chromatography-diode array detector (MEKC-DAD). The crucial parameters influencing the extraction efficiency and separation were studied and optimized. Under the optimal conditions, the limits of detection are 1.0 µg L−1 for OXA, CLOX, FLU, and 0.8 µg L−1 for DIC. The calibration curves are linear in the range of 2.5–200.0 µg L−1. The proposed method was applied for the determination of the β-lactams in water samples with satisfactory results. The intra-day relative standard deviations and the inter-day relative standard deviations range from 1.09% to 4.58% and from 2.95% to 7.80%, respectively. It can be concluded that this method is sensitive, convenient, and feasible for the determination of the β-lactams in water samples.

Veterinary drug residues, particularly traces of β2-agonists, can cause various kinds of harmful impact to the environment and public health. Here, a sensitive chemiluminescence (CL) method incorporated with a flow injection analysis is developed for the determination of two β2-agonists [i.e., salbutamol (SAL) and terbutaline (TEB)]. The system is based on the CL reaction of Ni(IV) complex with luminol in alkaline solutions, whereas SAL and TEB can significantly enhance CL intensities. Under optimum conditions, CL intensities are proportional to the SAL and TEB concentration in the range of 1.0 × 10−9 M to 5.0 × 10−7 M and 1.0 × 10−9 M to 1.0 × 10−7 M, respectively. The limits of detection (3σ) are 1.0 × 10−11 M for TEB, and 1.3 × 10−11 for SAL respectively. Relative standard deviations (n = 11) are less than 2% for 5.0 × 10−8 M SAL and TEB. Possible reaction mechanisms for the CL system are suggested based on the CL system spectra, Ni(IV) complex oxidation characteristics, and electron spin resonance (ESR) techniques. The proposed method has been applied to the analysis of urine and swine feed samples with satisfactory results.

The reaction mechanism of AgIII complex ([Ag(HIO6)2]5–) with ruthenium(II) bipyridine (Ru(bpy)32+) in acid medium was investigated. A novel flow injection chemiluminescence (CL) analysis method was developed for the detection of norfloxacin (NFLX) and ofloxacin (OFLX) in commercial drug, milk and human urine samples based on AgIII-ruthenium(II) bipyridine in acidic solution. Under optimal conditions, CL intensities were proportional to drug concentrations in the range of 1.6 × 10-9 to 8 × 10-6 g mL-1 for NFLX and 1.0 × 10-9 to 4 × 10-6 g mL-1 for OFLX. The detection limit was 1.0 × 10-9 g mL-1 for NFLX and 0.8 × 10-9 g mL-1 for OFLX. On the basis of the CL, UV and fluorescence spectra, possible reaction mechanisms were proposed.

Ormaplatin ([Pt(dach)Cl4]) is a prototypical of Pt(IV) anticancer prodrug; its reduction by 3,6-dioxa-1,8-octanedithiol (DODT, a model compound for the active site of thioredoxin), has been characterized at 25.0 °C and in a wide pH range by rapid scan spectral and kinetic analysis. The reduction follows overall second-order kinetics, being first-order each in [Pt(IV)] and in [DODT]; the observed second-order constant k′ versus pH profile has been established. A 1:1 reaction stoichiometry is obtained, indicating that DODT is oxidized to its intramolecular disulfide; these characteristics are consistent with the redox properties of thioredoxin. A reaction mechanism has been proposed which involves the three protolytic species of DODT attacking [Pt(dach)Cl4] in parallel as rate-determining steps. The rate equation is derived from the reaction mechanism and rate constants of the rate-determining steps have been evaluated. The thiol–thiolate and dithiolate forms of DODT are 105–106 times more reactive than the dithiol form. Comparisons of the rate constants highlight that the electron density of the sulfur atom plays a key role in determining the reactivity of DODT toward ormaplatin and similar Pt(IV) compounds. It is concluded that the reduced thioredoxin is a strong competitor to other thiol-containing compounds in the reduction processes of Pt(IV) anticancer prodrugs.

The kinetics of oxidation of l-asparagine by bis(hydrogenperiodato)argentate(III) complex anion ([Ag(HIO6)2]5−) has been studied in the temperature range of 10.0–25.0 °C in aqueous alkaline media. An overall second-order character is observed, the reaction being first order with respect to both Ag(III) and Asn. The observed second-order rate constants $$ k^{{\prime }} $$ are increased when [OH−] is increased, but are decreased with increasing total concentration of periodate, [IO 4 − ]tot. The oxidation results in both decarboxylation and deamination of Asn. A reaction mechanism is proposed which involves two pre-equilibria leading to an intermediate complex [Ag(HIO6)(Asn)(OH)]3−. This is followed by the collapse of the intermediate in two parallel reaction paths as the rate-determining steps; one path is independent of OH−, while the other involves OH−. The rate equation has been derived from the reaction mechanism, and the equilibrium constants and rate parameters have been evaluated. The mode of electron transfer is discussed. The reaction mechanism and electron transfer mode in the present system have no similarities to those derived for the oxidations of Asn by other oxidants reported previously, underlining the diverse nature of Asn oxidations.

The presence of sulfonamide (SA) residues in foods is largely due to the raising of animals with sulfonamide antibiotics added or polluted feedstuff. In this paper, a sensitive method was developed for the determination of the residues of three sulfonamides in animal-derived food; the SAs include sulfadimidine (SDD), sulfadiazine (SDZ), and sulfathiazole (STZ). The method is based on capillary zone electrophoresis (CE) with online chemiluminescence (CL) detection, using an Ag(III) complex as an oxidant. These SAs have an inhibiting effect on the Ag(III)-luminol CL reaction. The electrophoretic buffer is 12.0 mM sodium borate. Under a set of optimized conditions, the linear ranges for the detections were found to be 10.0-200 µg·mL-1 for SDD and SDZ, and 2.0-50.0 µg·mL-1 for STZ. The detection limits were 2.75, 3.14, and 0.65 µg·mL-1 for SDD, SDZ, and STZ, respectively. Relative standard deviations (RSD) for the peak heights were between 2.1% and 2.8% (n = 7). The proposed method was used in the analysis of the SAs in samples from pork meat, chicken meat, and milk, showing satisfactory detection results. A reaction mechanism was also proposed for the Ag(III)-luminol-SA CL reactions. The method has potential applications for the monitoring of residue levels of the three SAs in food, providing food safety data.

To study differentially expressed proteins on water-holding capacity (WHC) during postmortem aging of longissimus lumborum muscle, samples were classified according to drip loss into high and low drip loss groups. Fifty-five proteins were differentially abundant at days 0, 1 and 7 during postmortem aging and identified by MALDI TOF/TOF. The identified proteins can be divided into four main categories: metabolic enzymes, cell structural proteins, stress related proteins and transport proteins. Myosin light chain, heat shock protein 27 and triosephosphate isomerase showed a major difference between the two groups and may have the potential to be biological markers for WHC prediction. Furthermore, bioinformatics analysis revealed that the identified proteins were related to carbon metabolism, glycolysis and biosynthesis of amino acids and pyruvate metabolism. The functions of the identified proteins contribute to a more detailed molecular view of the processes behind WHC and are a valuable resource for future investigations.

The kinetics of oxidation of pyrrolidine by bis(hydrogenperiodato)argentate(III) complex anion ([Ag(HIO6)2]5−) was studied in alkaline medium, with reaction temperatures in the range of 15.0–30.0 °C. The experiments indicated that the oxidation follows an overall second-order reaction, being first-order in both Ag(III) and pyrrolidine. The observed second-order rate constants, k′, decreased with increasing [IO4 −] but increased slightly with increasing [OH−]. The influence of ionic strength on the reaction rate was also investigated. The oxidation resulted in oxidative deamination of pyrrolidine, giving 4-hydroxybutyrate as the product. A reaction mechanism is proposed which includes an equilibrium between [Ag(HIO6)2]5− and [Ag(HIO6)2(OH)(H2O)]2−; these two Ag(III) species are reduced by pyrrolidine in parallel rate-determining steps. The rate equation derived from the proposed mechanism can explain the experimental observations. The rate constants of the rate-determining steps, together with the associated activation parameters, were calculated accordingly.

A sensitive simple method is presented for the determination of three major catecholamines in human urine by capillary electrophoresis (CE) with on-line chemiluminescence (CL) detection. This was also the first time that the luminol-Ag(III) complex CL system was used for CE detection. This method was based on the enhancing effect of epinephrine (EP), norepinephrine (NE), and dopamine (DA) on the CL reaction between luminol and the Ag(III) complex in alkaline solution. The separations and determinations were performed with an electrophoretic buffer consisting of 20.0mM sodium borate and 1.0mM luminol. Under optimized conditions, the three catecholamines were baseline separated and detected in less than 8 min. Detection limits of 7.9 × 10(-8)M, 1.0 × 10(-7)M, and 6.9 × 10(-8)M were observed for EP, NE, and DA, respectively. Relative standard deviation (RSD) values for the peak height were 4.7% to 5.4% (n = 5). Our proposed method was applied to the determinations of the catecholamines in urine samples from 12 healthy individuals and 26 pheochromocytoma patients. Our results suggest that this method might be useful to monitor the catecholamine levels in routine screening and to diagnose pheochromocytoma.

A novel sensitive chemiluminescence (CL) system ([Ag(HIO6)2]5--luminol reaction system), coupled with a flow injection, is introduced for determination of d-penicillamine. The system is based on the enhancement effect of chemiluminescence reaction by penicillamine in alkaline medium. Under the optimum conditions, the CL intensity is proportional to the concentrations of d-penicillamine with a good linearity. The linear range covers 1.5-150 ng mL-1 and the limit of detection of the method is 0.8 ng mL-1. The relative standard deviation is 0.23% for 11 repeated measurements of 0.06 µg mL-1 d-penicillamine. The method has been successfully applied to the determinations of d-penicillamine in pharmaceutical preparations and urine samples, giving rise to satisfactory results. Based on the chemiluminescent spectra and free radical trapping experiment performed in this work, a possible reaction mechanism for this reaction system is suggested. Um novo sistema de quimioluminescência (CL), sensível, (reação [Ag(HIO6)2]5--luminol), acoplado com injeção em fluxo, é introduzido para determinação de d-penicilamina. O sistema é baseado no efeito do aumento da reação de quimioluminescência por penicilamina em meio alcalino. Sob condições ótimas, a intensidade de CL é proporcional às concentrações de d-penicilamina com uma boa linearidade. O intervalo linear é de 1,5-150 ng mL-1 e o limite de detecção do método, 0,8 ng mL-1. O desvio padrão relativo é 0,23% para 11 repetições de 0,06 µg mL-1 de d-penicilamina. O método tem sido aplicado com sucesso às determinações de d-penicilamina em preparações farmacêuticas e amostras de urina, proporcionando resultados satisfatórios. Com base nos espectros de quimioluminescência e no experimento de aprisionamento de radicais livres realizado neste trabalho, um possível mecanismo de reação para esse sistema reacional é sugerido.

The oxidation of N,N-dimethylethanolamine (DMEA) by bis(hydrogenperiodato) argentate(III) ([Ag(HIO6)2]5−) was studied in aqueous alkaline medium. Formaldehyde and dimethylamine were identified as the major oxidation products after the oxidation of DMEA. The oxidation kinetics was followed spectrophotometrically in the temperature range of 25.0 °C–40.0 °C. It was found that the reaction was first order in [Ag(III)]; the oberved first-order rate constants kobsd as functions of [DMEA], [OH−] and total concentration of periodate (\([\mathrm{IO}_{4}^{-}]_{\mathrm{tot}}\)) were analyzed and were revealed to follow a rate expression: \(k_{\mathrm{obsd}} = (k_{1} +k_{2}[\mathrm{OH}^{-}])K_{1}K_{2}[\mathrm{DMEA}]/\{f([\mathrm{OH}^{-}])[\mathrm{IO}_{4}^{-}]_{\mathrm{tot}}+ K_{1} + K_{1}K_{2}[\mathrm{DMEA}]\}\). Rate constants k1 and k2 and equilibrium constant K2 were derived; activation parameters corresponding to k1 and k2 were computed. In the proposed reaction mechanism, a peridato-Ag(III)-DMEA ternary complex is formed indirectly through a reactive intermediate species [Ag(HIO6)(OH)(H2O)]2−. In subsequent rate-determining steps as described by k1 and k2, the ternary complex decays to Ag(I) through two reaction pathways: one of which is spontaneous and the other is prompted by an OH−.

A novel flow injection analysis-direct chemiluminescence (FI-CL) method has been developed for determination of trace amounts of dopamine (DA) based on the enhancing effect of DA on the CL reaction of luminol with an Ag(III) complex in alkaline solution. Under optimum conditions, CL intensities are proportional to the concentration of DA in the range of 1.0 × 10−10 to 4.0 × 10−8 mol L−1. The detection limit is 3.0 × 10−11 mol L−1 for DA (3s), with a relative standard deviation (n = 13) of 2.3% for 1.0 × 10−8 mol L−1 DA. This method has also been applied for the determination of DA in commercial pharmaceutical injection samples. On the basis of the CL spectra and the results of the free-radical trapping experiment of this work, a reaction mechanism for this CL reaction is proposed and discussed. Copyright © 2010 John Wiley & Sons, Ltd.

Oxidation of N-methylethylamine by bis(hydrogenperiodato)argentate(III) ([Ag(HIO6)2]5−) in alkaline medium results in demethylation, giving rise to formaldehyde and ethylamine as the oxidation products. The oxidation kinetics has been followed spectrophotometrically in the temperature range of 20.0–35.0 °C, and shows an overall second-order character: being first-order with respect to both Ag(III) and N-methylethylamine. The observed second-order rate constants k′ increase with increasing [OH−] of the reaction medium, but decrease with increasing the total concentration of periodate. An empirical rate expression for k′ has been derived as: k′ = (k a + k b[OH−])K 1/{f([OH−])[IO4 −]tot + K 1}, where k a and k b are rate parameters, and K 1 is an equilibrium constant. These parameters have been evaluated at all the temperatures studied, enabling calculation of activation parameters. A reaction mechanism is suggested to involve two pre-equilibria, leading to formation of an intermediate Ag(III) complex, namely [Ag(HIO6)(OH)(MeNHEt)]2−. In the subsequent rate-determining steps, this intermediate undergoes inner-sphere electron transfer from the coordinated amine to the metal center via two distinct routes, one of which is spontaneous while the other is mediated by a hydroxide ion.

Kinetics of oxidation of dl-pipecolinate by bis(hydrogenperiodato)argentate(III) complex anion, [Ag(HIO6)2]5−, has been studied in aqueous alkaline medium in the temperature range of 25–40 °C. The oxidation kinetics is first order in the silver(III) and pipecolinate concentrations. The observed second-order rate constant, decreasing with increasing [periodate] is virtually independent of [OH−]. α-Aminoadipate as the major oxidation product of pipecolinate has been identified by chromatographic analysis. A reaction mechanism is proposed that involves a pre-equilibrium between [Ag(HIO6)2]5− and [Ag(HIO6)(H2O)(OH)]2−, a mono-periodate coordinated silver(III) complex. Both Ag(III) complexes are reduced in parallel by pipecolinate in rate-determining steps (described by k 1 for the former Ag(III) species and k 2 for the latter). The determined rate constants and their associated activation parameters are k 1 (25 °C) = 0.40 ± 0.02 M−1 s−1, ∆H 1 ≠ = 53 ± 2 kJ mol−1, ∆S 1 ≠ = −74 ± 5 J K−1 mol−1 and k 2 (25 °C) = 0.64 ± 0.02 M−1 s−1, ∆H 2 ≠ = 41 ± 2 kJ mol−1, ∆S 2 ≠ = −110 ± 5 J K−1 mol−1. The time-resolved spectra, a positive dependence of the rate constants on ionic strength of the reaction medium, and the consistency of pre-equilibrium constants derived from different reaction systems support the proposed reaction mechanism.

A new Ag(III) complex-luminol chemiluminescent system which was applied to the determination of epinephrine is firstly reported. Based on the enhancing effect of epinephrine on the chemiluminescence reaction of luminol with [Ag(HIO6)2]5− in alkaline solution, a highly sensitive chemiluminescence (CL) detection by flow injection analysis (FIA) was developed for epinephrine. Under the optimum conditions, CL intensity was proportional to concentration of epinephrine in the 1.0×10−9–1.0×10−7 mol·L−1 range. The limit of detection was 8.0×10−10 mol·L−1 for epinephrine (3δ), with a relative standard deviation (n=11) of 2.9% for 1.5×10−8 mol·L−1 epinephrine. The method validation was done with epinephrine determinations in commercial pharmaceutical products. The mechanism of the reactions was also discussed.

Oxidation of α-diols, namely ethylene glycol, 1,2-propanediol, and 1,2-butanediol, by [Ag(HIO6)2]5− is kinetically first-order with respect to the Ag(III) complex. The dependence of observed first-order rate constants k obs on [α-diol] can generally be expressed by: k obs = k x[α-diol] + k y[α-diol]2. Our experimental results demonstrate that the different rate laws derived in the oxidation reactions of ethylene glycol (J. H. Shan et al. Chin. J. Chem. 24:478, 2006) and 1,2-butanediol (J. H. Shan et al. Transition Met. Chem. 30:651, 2005) by the Ag(III) complex are probably not correct. In turn, the reaction mechanisms based on these rate laws should probably be treated with caution.

Oxidation of 3-(4-methoxyphenoxy)-1,2-propanediol (MPPD) by bis(hydrogenperiodato) argentate(III) complex anion, [Ag(HIO6)2]5− has been studied in aqueous alkaline medium by use of conventional spectrophotometry. The major oxidation product of MPPD has been identified as 3-(4-methoxyphenoxy)-2-ketone-1-propanol by mass spectrometry. The reaction shows overall second-order kinetics, being first-order in both [Ag(III)] and [MPPD]. The effects of [OH−] and periodate concentration on the observed second-order rate constants k′ have been analyzed, and accordingly an empirical expression has been deduced: $$ {{k^{\prime} = \left( {k_{\text{a}} + k_{\text{b}} \left[ {{\text{OH}}^{ - } } \right]} \right)K_{ 1} } \mathord{\left/ {\vphantom {{k^{\prime} = \left( {k_{\text{a}} + k_{\text{b}} \left[ {{\text{OH}}^{ - } } \right]} \right)K_{ 1} } {\left\{ {{\text{f}}\left( {\left[ {{\text{OH}}^{ - } } \right]} \right)\left[ {{\text{IO}}_{ 4}^{ - } } \right]_{\text{tot}} + K_{ 1} } \right\}}}} \right. \kern-\nulldelimiterspace} {\left\{ {{\text{f}}\left( {\left[ {{\text{OH}}^{ - } } \right]} \right)\left[ {{\text{IO}}_{ 4}^{ - } } \right]_{\text{tot}}\, +\, K_{ 1} } \right\}}}, $$ where [IO4 −]tot denotes the total concentration of periodate and k a = (0.19 ± 0.04) M−1 s−1, k b = (10.5 ± 0.3) M−2 s−1, and K 1 = (5.0 ± 0.8) × 10−4 M at 25.0 °C and ionic strength of 0.30 M. Activation parameters associated with k a and k b have been calculated. A mechanism is proposed, involving two pre-equilibria, leading to formation of a periodato–Ag(III)–MPPD complex. In the subsequent rate-determining steps, this complex undergoes inner-sphere electron-transfer from the coordinated MPPD molecule to the metal center by two paths: one path is independent of OH−, while the other is facilitated by a hydroxide ion.