Facial synthesis of dandelion-like g-C3N4/Ag with high performance of photocatalytic hydrogen production

Nowadays, energy shortage is one of the major problems in the world. Photocatalytic hydrogen production is a new type of energy technology with good application prospect. As a new type of photocatalytic semiconductor material, g-C₃N₄ has attracted much attention as a photocatalyst. By ultrasonic treatment of a mixed solution of g-C₃N₄ and bovine serum albumin, followed by adding a certain amount of silver nitrate solution and then directly hydrothermal treatment, a special dandelion-like g-C₃N₄/Ag (D-g-C₃N₄/Ag) was prepared. The scanning electronic microscopy, transmission electronic microscopy, X-ray diffraction, Fourier transform infrared, fluorescence and physicochemical adsorption methods were used to characterize the morphology and structure of D-g-C₃N₄/Ag. In addition, the photocatalytic H₂ production of D-g-C₃N₄/Ag with different Ag loadings or in different sacrificial agents and different pH conditions were investigated. The results indicated that when triethanolamine was used as sacrificial agent, photocatalytic hydrogen efficiency was the best, and the rate of photocatalytic hydrogen production reached 862 μmol g⁻¹ h^{− 1} as the Ag loading was 4%.     

A helium-filled time projection chamber for a neutron lifetime measurement

The design and performance of a⁴He-filled TPC, constructed to measure the neutron half-life, are described. Preliminary results obtained with radioactive sources and with a chopped neutron beam are discussed.     

龙须菜酸性多糖对H22荷瘤小鼠的抗肿瘤作用

本文主要研究龙须菜酸性多糖(GLSPs)对H22荷瘤小鼠的肿瘤抑制作用。通过流式细胞术检测GLSPs对小鼠体内肿瘤细胞的细胞凋亡和细胞周期的影响;MTT法检测GLSPs对荷瘤小鼠脾淋巴细胞增殖能力和NK细胞杀伤活性的影响;组织病理学方法检测GLSPs对荷瘤小鼠肿瘤和免疫器官(脾脏、胸腺)的影响。结果显示,GLSPs能够促进荷瘤小鼠体内H22肝癌细胞凋亡,显著抑制肿瘤生长。以200 mg/(kg?d)和600 mg/(kg?d)GLSPs灌胃管理荷瘤小鼠28 d,小鼠的平均体积抑瘤率分别为84.65%和94.58%。免疫学试验显示,GLSPs能够明显改善荷瘤小鼠脾脏肿大和胸腺萎缩的组织病变情况,增强荷瘤小鼠免疫器官的免疫功能,同时能够有效调节荷瘤小鼠白细胞和淋巴细胞的激增,显著增强荷瘤小鼠由ConA和LPS诱导的T、B细胞的增殖能力,提高脾NK细胞的杀伤活性,多方面提高荷瘤小鼠机体的免疫水平,提示GLSPs通过免疫调节作用达到体内抗肿瘤效果。     

量子点标记免疫层析试纸条快速检测谷物中赭曲霉毒素A

目的:根据竞争抑制免疫层析原理,构建一种基于量子点标记的免疫层析试纸条用于检测谷物中赭曲霉毒素A(Ochratoxin A,OTA)的残留量。方法:通过活化酯法将羧基功能化的量子点(Quantum dot,QD)与赭曲霉毒素A多克隆抗体(Antibody,Ab)偶联制备量子点抗体偶联物(QD-Ab);通过分别添加不同量的QD-Ab和工作液,优化量子点标记免疫层析试纸条的工作条件;通过商品化试剂盒验证该方法的有效性。结果:当QD与Ab的摩尔比为1:10时,QD-Ab荧光特性最佳;在QD-Ab和工作液添加量分别为1、10 μL时,量子点标记免疫层析试纸条结果最佳;量子点标记免疫层析试纸条的检测限为0.5 μg/L,谷物样品中的检测限为5 μg/kg,整个检测过程不超过10 min;量子点标记免疫层析试纸条特异性良好且具有有效性。结论:该方法操作简便、检测快速、结果准确灵敏,易于判断,可以满足谷物中赭曲霉毒素A残留量现场快速检测的要求。     

1-甲基环丙烯对不同脱涩程度冰温贮藏磨盘柿生理品质的影响

探讨1-甲基环丙烯对不同脱涩程度磨盘柿生理品质的调控效应,研究了1-甲基环丙烯对未脱涩和半脱涩冰温贮藏柿果的品质、生理代谢及软化相关指标的影响。结果表明:在冰温贮藏条件下(-0.5～-0.2℃)下,1-甲基环丙烯有效抑制不同脱涩程度柿果硬度的下降、乙醇的积累、呼吸强度和细胞膜透性的上升,减少了可滴定酸、总糖和Vc的损失,抑制可溶性单宁向不溶性单宁的转化,推迟PE活性峰的出现,降低PG活性峰的峰值。其中1-甲基环丙烯对半脱涩果实的作用效果更为明显。     

UV-C处理抑制马铃薯贮藏期发芽及相关机理研究

为提高马铃薯的食用安全性和贮藏品质,本实验研究了短波紫外线(ultraviolet C,UV-C)处理对马铃薯贮藏过程中发芽品质的影响。采用10 kJ/m2 UV-C对马铃薯进行一次处理(贮藏前),二次处理(贮藏前及中期),并测定发芽率、还原糖、苯丙氨酸解氨酶、多酚、赤霉素、α-茄碱等指标。结果表明,UV-C处理能够有效抑制马铃薯贮藏过程中的发芽,同时延缓赤霉素和α-茄碱的上升。二次处理组贮藏至90 d时,薯皮和肉质部分的α-茄碱含量仅为对照组的71.09%、65.75%;105 d时发芽率为68.78%,还原糖含量为0.40%,失重率为4.71%,贮藏品质均优于对照组和一次处理组。综上所述,当处理剂量和方式适宜时,UV-C可在马铃薯发芽控制及品质保持方面获得良好效果,其中二次处理更具优势。     

燕麦β-葡聚糖-槲皮素复合物的制备及其对秀丽隐杆线虫寿命的影响

为探究糖酚复合物的结构及功能特性,采用自由基催化、氢键吸附技术分别制备燕麦β-葡聚糖与槲皮素共价(COGQ)及非共价复合物(NOGQ),利用高效排阻色谱、红外光谱和核磁波谱等方法分析其结构特性,以秀丽隐杆线虫(简称线虫)为模型,研究复合物的抗衰老活性。高效排阻色谱显示,NOGQ和COGQ的相对分子质量分别为354、349kDa,两者相差不大;红外光谱显示,复合物在1660、1562、1243cm-1处有新的红外吸收峰,呈非晶态相,无定型状态;核磁波谱表明,复合物在化学位移为6.5~8.5处可产生3个属于苯基质子的新质子信号,有3个单糖残基;抗衰老活性研究表明,与空白组相比,COGQ与NOGQ均能显著提高秀丽隐杆线虫的平均寿命(P＜0.05),且两组中线虫体内的超氧化物岐化酶和过氧化氢酶活性均显著提高(P＜0.01),揭示两种复合物可能通过提高机体的抗氧化能力,进而发挥其延长寿命的功效。研究结果旨在为糖酚复合物的制备及新型食品抗氧化剂的开发提供参考。     

Interaction between rice bran albumin and epigallocatechin gallate and their physicochemical analysis

Epigallocatechin gallate (EGCG) is sensitive to heat thus its application in food industry is limited. In this work, rice bran albumin protein (RAP) was used as a carrier for EGCG. RAP-EGCG complexes (RAPE) were prepared with the binding number n of 0.0505:1 (EGCG: RAP, w/w) and binding constant K of (0.74?±?0.002)?×?10⁴ M^?1, which suggests that hydrogen bond/van der Waals forces played important roles in such binding. FTIR analysis demonstrated that EGCG could induce the secondary structure changes of RAP above the ratio of 1.92:1 (EGCG:RAP, w/w). Dynamic light scattering and scanning electron microscope results showed that EGCG could trigger RAP association. Furthermore, the EGCG stability in RAPE was significantly improved than that of free EGCG in 10–60 °C. The antioxidant ability of EGCG in RAPE was partially retained. These findings prove that RAP is a potential carrier for polyphenols and is beneficial for mechanism investigation between protein and polyphenols.     

Real-time TaqMan PCR for quantitative detection of cows’ milk in ewes’ milk mixtures

A real-time PCR based on the amplification of a fragment of the mitochondrial 12S ribosomal RNA gene was developed and evaluated for the detection and quantification of cows’ milk in raw and heat-treated cow/sheep milk mixtures. The method combines the use of cow-specific primers that amplify a 252 bp fragment from cow DNA, and mammalian-specific primers amplifying a 428 bp fragment from mammalian species DNA, which is used as an endogenous control. The method measures PCR product accumulation through a 6-carboxyfluorescein-labeled fluorogenic probe (TaqMan). A comparison of the cycle number at which mammalian and cow-specific PCR products were first detected, in combination with the use of reference standards of known bovine content, allowed the determination of the percentage of cows’ milk in mixtures. Experimental raw and heat-treated binary mixtures were analyzed, demonstrating the specificity and sensitivity of the assay for detection and quantification of cows’ milk in the range 0.5–10%.     

Inactivation of an indigenous transglutaminase inhibitor in milk serum by means of UHT-treatment and membrane separation techniques

An indigenous inhibitor in raw milk inhibits cross-linking by transglutaminase (TG). The enzymatic cross-linking of micellar casein, compared with sodium caseinate, taking thermal inactivation of the TG inhibitor in the milk serum into consideration, was investigated. Inhibitor-free micellar casein was prepared by membrane separation combined with heat treatment of the UF permeate. The inhibitor permeated through MF (nominal pore size 0.1 μm) and UF (cutoff 25 kDa) membranes. TG-catalyzed cross-linking of casein micelles was clearly enhanced by UHT-treatment of UF permeate. Variation of the enzyme concentration showed that the inhibitory effect could not be compensated by higher enzyme concentrations when the casein micelles were suspended in unheated milk serum. Sodium caseinate, however, underwent high degrees of cross-linking even in unheated milk serum. By mixing an unheated milk serum and a UHT-treated milk serum at different ratios, the relative TG inhibitor activity was analysed. High inactivation (>80%) of the TG inhibitor is necessary to achieve high degrees of protein cross-linking.