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In this study, antioxidant peptides derived from sheep hemoglobin were prepared from fresh sheep blood. Sephadex G-25 chromatography, DEAE Sephadex A-50 chromatography, reverse phase high performance liquid chromatography (RP-HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to separate, purify, and identify peptides from the hydrolysate of sheep hemoglobin. The antioxidant activity of the obtained peptides was evaluated by their free radical scavenging capacity, stability against simulated gastrointestinal digestion and protective effect on H2O2-induced oxidative injury in Caco-2 cells. The results indicated that three novel antioxidant peptides, Ala-Tyr-Glu-Val-Asp (AYEVD), Phe-His-Thr-Met-Glu (FHTME) and Ser-Phe-Met-Tyr-Glu-Lys (SFMYEK), were purified and identified from the hydrolysate, with molecular masses of 595.60, 663.74 and 803.92 Da, respectively. Among them, AYEVD had the strongest scavenging capacity to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and AYEVD showed stronger antioxidant activity after simulated gastrointestinal digestion. In addition, AYEVD inhibited H2O2-induced oxidative injury in Caco-2 cells, significantly reduced the accumulation of reactive oxygen species (ROS), suppressed early cell apoptosis and the formation of malondialdehyde (MDA), and increased the activity of intracellular antioxidant enzymes. Therefore, this study could provide a theoretical basis for the application of novel antioxidant peptides from sheep hemoglobin in functional foods.

This study presents an ontology-based visualization support system for e-book learners which promotes both meaningful receptive learning and meaningful discovery learning. To examine the system effectiveness, two learning modes are used: (a) reception comparison mode, where at the outset learners are shown complete versions of expert-generated topic maps; and (b) "cache-cache comparison mode," where at the first stage of learning all information concerning relations is concealed, and at the second stage learners are encouraged to actively create those relations before comparing the learner-generated and expert-generated relations. The 50 control group participants studied in reception comparison mode while the 146 experimental group participants studied in cache-cache comparison mode. Differences in learning perception and achievement between the two groups are examined, as is the effect of learner expertise level on learning mode effectiveness. Although the control group reported significantly more pressure and less satisfaction than the experimental group, no significant learning achievement differences were found between the two groups. However, in cache-cache comparison mode, the performance of learners with low prior knowledge increased more than that of learners with high prior knowledge; on the other hand, for learners with high prior knowledge, no significant effect of learning mode on learning achievement was found.

BACKGROUND Hexavalent chromium Cr(Ⅵ) is one of the basic monitoring indicators of soil in construction land. It is of great significance to carry out soil hexavalent chromium monitoring in the prevention and control of environmental pollution. At present, the standard method of hexavalent chromium in soil is flame atomic absorption spectrometry (FAAS). The FAAS method has a high detection limit (0.5mg/kg), and serious matrix effect, and cannot meet the analysis of Cr(Ⅵ) in low-concentration soil samples. OBJECTIVES To establish a convenient and high sensitivity method for determination of low-concentration hexavalent chromium in soil. METHODS An ion-exchange-inductively coupled plasma-mass spectrometry (ICP-MS) method was developed to determine the content of hexavalent chromium in soil by extracting hexavalent chromium with alkali solution. The resin content, mixing speed, extraction temperature and extraction time were studied. The measurement results were compared with the flame atomic absorption spectrophotometry (FAAS) method. RESULTS The results showed that the total dissolved solids (TDS) mass fraction was reduced from 2.4% to 0.17% after the alkaline extraction solution was diluted 10 times and 3.5g of cation exchange resin was added, and the matrix interference was greatly reduced. At the same time, due to the dissolution of hydrogen ions in the ion exchange process, the pH reached a suitable detection range (7.5±0.5). The pretreatment conditions were optimized. When the extraction temperature was 90-95℃, the stirring speed was 300 rpm, and the heating time was 70 min, the extraction effect of Cr(Ⅵ) was the best, and the relative error was -1.7%. The relative standard deviation (RSD) was 3.1%-5.9%, and the average relative error was -3.8% to -1.1%. F test and t test were used to compare the test results of high, medium and low concentration standard substances by ICP-MS and FAAS, and there was no significant difference between the two methods. The method detection limit (MDL) was 0.061 mg/kg. CONCLUSIONS Since this method adopts dilution, ion exchange, internal standard method, to reduce matrix interference, combined with the high sensitivity and good accuracy of ICP-MS, the method detection limit (MDL) is significantly lower than the detection limit of FAAS method (0.5mg/kg). This method can be used for the determination of low-concentration soil Cr(Ⅵ) samples.

Early detection plays a critical role in mitigating mortality rates linked to gastric cancer. However, current clinical screening methods exhibit suboptimal efficacy. Methylation alterations identified from cell‐free DNA (cfDNA) present a promising biomarker for early cancer detection. Our study focused on identifying gastric cancer‐specific markers from cfDNA methylation to facilitate early detection. We enrolled 150 gastric cancer patients and 100 healthy controls in this study, and undertook genome‐wide methylation profiling of cfDNA using cell‐free methylated DNA immunoprecipitation and high‐throughput sequencing. We identified 21 differentially methylated regions (DMRs) between the gastric tumor and nontumor groups using multiple algorithms. Subsequently, using the 21 DMRs, we developed a gastric cancer detection model by random forest algorithm in the discovery set, and validated the model in an independent set. The model was able to accurately discriminate gastric cancer with a sensitivity and specificity of 93.90% and 95.15% in the discovery set, respectively, and 88.38% and 94.23% in the validation set, respectively. These results underscore the efficacy and accuracy of cfDNA‐derived methylation markers in distinguishing early stage gastric cancer. This study highlighted the significance of cfDNA methylation alterations in early gastric cancer detection. [ABSTRACT FROM AUTHOR]