不同品种龙眼果肉酚类物质的抗氧化活性比较

为研究不同龙眼品种资源中酚类物质、黄酮类化合物含量及其抗氧化性差异,选取广东省农业科学院果树研究所龙眼资源圃的24个龙眼品种,分析其果肉中游离态和结合态总酚、总黄酮物质的含量,采用DPPH自由基清除能力、ABTS总抗氧化能力、FRAP抗氧化能力和氧自由基吸收能力ORAC四种不同方法评价其体外抗氧化能力差异;不同龙眼品种果肉总酚、总黄酮含量与DPPH、ABTS、FRAP、ORAC四种不同方法测定的抗氧化能力的变幅和变异系数较大,呈现出显著的基因型差异;不同品种龙眼果肉的多酚和黄酮的含量分别与ABTS自由基清除能力、FRAP和ORAC呈极显著(p<0.01)正相关关系,而与DPPH自由基清除能力的EC₅₀值呈极显著负相关关系(p<0.01)。采用快速聚类法将24个不同品种的龙眼聚成多酚及总黄酮含量和抗氧化能力差异显著的三大群类。不同品种龙眼果肉游离态和结合态酚类物质含量与其抗氧化活性均呈显著正相关关系,提示酚类物质是龙眼果肉抗氧化活性的主要成分;酚类物质和黄酮类物质在龙眼果肉中主要以游离态存在,其中结合态平均占总酚含量的17.45%。     

Association analyses of 249,796 individuals reveal 18 new loci associated with body mass index

Obesity is globally prevalent and highly heritable, but its underlying genetic factors remain largely elusive. To identify genetic loci for obesity susceptibility, we examined associations between body mass index and ～ 2.8 million SNPs in up to 123,865 individuals with targeted follow up of 42 SNPs in up to 125,931 additional individuals. We confirmed 14 known obesity susceptibility loci and identified 18 new loci associated with body mass index (P < 5 × 10??), one of which includes a copy number variant near GPRC5B. Some loci (at MC4R, POMC, SH2B1 and BDNF) map near key hypothalamic regulators of energy balance, and one of these loci is near GIPR, an incretin receptor. Furthermore, genes in other newly associated loci may provide new insights into human body weight regulation.     

活跃的汽车通信市场——进入了一个新的竞争舞台

汽车通信是最活跃的高技术市场之一。然而在由汽车电话中发出来的呼叫声的那种形象后面,无论是在技术上或生活方式方面都发生了惊人的变化。这种变化迅速地使汽车通信摆脱了只限少数人使用的状况,而将其推上了大规模市场的舞台。欧洲的汽车通信中的新想法都产生于英国。英国政府实行一种放宽对汽车通信的限制的政策已经数年了,并且将汽车通信当作一种优先发展的领域。     

南方波纹米粉丝的热泵-热风组合干燥工艺研究

以综合反映南方波纹米粉丝干燥过程中产品品质、能耗、干燥速率的干燥效果评价值为指标,研究了热泵-热风组合干燥工艺中热泵干燥温度、转换点含水量、热风干燥温度对南方波纹米粉丝干燥效果的影响,并采用完全析因设计进行了优化。结果表明,热泵干燥温度、转换点含水量及热风干燥温度对南方波纹米粉丝干燥效果均有极显著的影响,南方波纹米粉丝热泵-热风组合干燥优化工艺条件为:热泵温度48℃、转换点含水量23%及热风温度78℃。在此条件下所得南方波纹米粉丝干燥效果评价值为86.19,比热风干燥和热泵干燥分别提高了11.99%和13.15%。热泵-热风组合干燥方法是南方波纹米粉丝的较佳干燥方法。     

不同乳化稳定剂对全谷物糙米营养乳稳定性的影响及其配比优化

分析了影响全谷物糙米营养乳饮料稳定性的主要因素,筛选了合适的乳化稳定剂并对其配比进行了优化,探讨了蔗糖和三聚磷酸钠等品质改良剂对体系稳定性的影响。结果表明:全谷物糙米营养乳饮料的乳化剂蔗糖脂肪酸酯与蒸馏单硬脂酸甘油酯的优化复配比例为2∶8,复合乳化剂的添加量为0.20%；筛选出黄原胶、羧甲基纤维素和微晶纤维素为体系的稳定剂,其优化配方为黄原胶0.05%,羧甲基纤维素 0.15%,微晶纤维素 0.08%。进一步发现,蔗糖和三聚磷酸钠可以改善体系的稳定性,但当蔗糖添加量达到4%后,体系的离心悬浮比逐渐降低。     

Synthesis of macrocyclic natural products by catalyst-controlled stereoselective ring-closing metathesis

Many natural products contain a C = C double bond through which various other derivatives can be prepared; the stereochemical identity of the alkene can be critical to the biological activities of such molecules. Catalytic ring-closing metathesis (RCM) is a widely used method for the synthesis of large unsaturated rings; however, cyclizations often proceed without control of alkene stereochemistry. This shortcoming is particularly costly when the cyclization reaction is performed after a long sequence of other chemical transformations. Here we outline a reliable, practical and general approach for the efficient and highly stereoselective synthesis of macrocyclic alkenes by catalytic RCM; transformations deliver up to 97% of the Z isomer owing to control induced by a tungsten-based alkylidene. Utility is demonstrated through the stereoselective preparation of epothilone C (refs 3-5) and nakadomarin A (ref. 6), the previously reported syntheses of which have been marred by late-stage, non-selective RCM. The tungsten alkylidene can be manipulated in air, delivering the products in useful yields with high stereoselectivity. As a result of efficient RCM and re-incorporation of side products into the catalytic cycle with minimal alkene isomerization, desired cyclizations proceed in preference to alternative pathways, even under relatively high substrate concentration.     

油茶粕中茶皂素连续多级逆流水提工艺的建立

为提高油茶粕经济价值,充分利用油茶粕资源,以油茶粕为原料,采用热水连续多级逆流提取油茶粕中的茶皂素,优化了单级提取和连续多级逆流提取工艺参数。结果表明:单级提取的优化条件为提取时间85 min,提取温度80℃,料液比1:16 g/mL,油茶粕提取粒度60～100目。在单级提取基础上,确定连续多级逆流提取的优化提取级数为3级,每级优化的提取时间为20 min,此时得到的提取液中茶皂素的质量浓度为33.14 mg/mL,比单级提取质量浓度提高了1.23倍,提取时间缩短了29.41%,提高了提取效率。水溶液结合连续多级逆流提取,获得了质量浓度较高的茶皂素,并且缩短了提取时间,提取流程绿色环保,更易实现工业化生产。     

Regulation of cancer cell migration and bone metastasis by RANKL

Bone metastases are a frequent complication of many cancers that result in severe disease burden and pain. Since the late nineteenth century, it has been thought that the microenvironment of the local host tissue actively participates in the propensity of certain cancers to metastasize to specific organs, and that bone provides an especially fertile 'soil'. In the case of breast cancers, the local chemokine milieu is now emerging as an explanation for why these tumours preferentially metastasize to certain organs. However, as the inhibition of chemokine receptors in vivo only partially blocks metastatic behaviour, other factors must exist that regulate the preferential metastasis of breast cancer cells. Here we show that the cytokine RANKL (receptor activator of NF-kappaB ligand) triggers migration of human epithelial cancer cells and melanoma cells that express the receptor RANK. RANK is expressed on cancer cell lines and breast cancer cells in patients. In a mouse model of melanoma metastasis, in vivo neutralization of RANKL by osteoprotegerin results in complete protection from paralysis and a marked reduction in tumour burden in bones but not in other organs. Our data show that local differentiation factors such as RANKL have an important role in cell migration and the tissue-specific metastatic behaviour of cancer cells.