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排序方式: 共有71条查询结果,搜索用时 15 毫秒
1.
Hisao Tsukamoto Yoshihiro Kubo David L. Farrens Mitsumasa Koyanagi Akihisa Terakita Yuji Furutani 《The Journal of biological chemistry》2015,290(45):27176-27187
Melanopsins play a key role in non-visual photoreception in mammals. Their close phylogenetic relationship to the photopigments in invertebrate visual cells suggests they have evolved to acquire molecular characteristics that are more suited for their non-visual functions. Here we set out to identify such characteristics by comparing the molecular properties of mammalian melanopsin to those of invertebrate melanopsin and visual pigment. Our data show that the Schiff base linking the chromophore retinal to the protein is more susceptive to spontaneous cleavage in mammalian melanopsins. We also find this stability is highly diversified between mammalian species, being particularly unstable for human melanopsin. Through mutagenesis analyses, we find that this diversified stability is mainly due to parallel amino acid substitutions in extracellular regions. We propose that the different stability of the retinal attachment in melanopsins may contribute to functional tuning of non-visual photoreception in mammals. 相似文献
2.
分光光度法测定地骨皮中牛磺酸含量 总被引:7,自引:0,他引:7
用分光光度法测定地骨皮中是否含有牛磺酸。在一定条件下,牛磺酸与乙酰丙酮和甲醛反应生成带色的配合物,建立了测定牛磺酸含量的分光光度法。结果表明,地骨皮中含有牛磺酸,已测定样品1中牛磺酸的质量分数为3.124 mg.g-1,样品2中牛磺酸的质量分数为6.203 mg.g-1,且样品2中的牛磺酸质量分数极显著高于样品1(p<0.01)。研究结果表明,地骨皮中含有牛磺酸,而且分光光度法成本低,干扰少,是测定地骨皮中牛磺酸质量分数的较好方法。 相似文献
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Comparison of floral properties and breeding system in dimorphic Buddleja delavayi (Scrophulariaceae) 下载免费PDF全文
Gao CHEN Wei‐Chang GONG Jia GE Yang NIU Xin ZHANG Bruce L. DUNN Wei‐Bang SUN 《植物分类学报:英文版》2015,53(2):196-202
In this study, floral color, scent composition and emission rate, nectar property, pollinators, and breeding system of dimorphic Buddleja delavayi Gagnep. were investigated. Flower color of B. delavayi was determined using a standard color chart and spectrophotometer, and two distinct color polymorphisms were observed having purple or white flowers. Floral scents of B. delavayi were collected using dynamic headspace adsorption and identified with coupled gas chromatography and mass spectrometry. In total, 28 compounds were identified from the flowers of B. delavayi. The identified scents were divided into three chemical classes based on their biosynthetic origin: terpenes, fatty acid derivatives, and benzenoids. The scent profiles in all individuals were dominated by a few components, such as lilac aldehyde and alcohol, 4-oxoisophorone, benaldehyde, and oxoisophorone oxide. Floral scent composition (benzenoids and terpenes) showed a significant difference between white and purple flower morphs. Flower color–flower scent associations in B. delavayi were identified with two distinct scent profiles in the two color phenotypes. The studies of other floral characteristics (nectar, floral visitors, breeding system, and fruit set) indicated that floral scent emission rate, nectar volume, visitor visitation frequency, and natural fruit set were not significantly different between the two flower color morphs. Bagging experiments revealed that seed production of B. delavayi is dependent mainly on honeybee Apis cerana. Lastly, this study implies that dimorphic floral color in B. delavayi may have been maintained by floral visitors and nectar guide color. 相似文献
5.
分光光度法测定水母雪莲细胞培养物中的总黄酮 总被引:11,自引:2,他引:9
建立了测定水母雪莲细胞培养物中的总黄酮含量的分光光度法,该法操作简便,结果准确可靠。 相似文献
6.
Biochemical studies have shown that cardiolipin is essential for the integrity and activity of the cytochrome bc1 complex and many other membrane proteins. Recently the direct involvement of a bound cardiolipin molecule (CL) for proton uptake at center N, the site of quinone reduction, was suggested on the basis of a crystallographic study. In the study presented here, we probe the low frequency infrared spectroscopy region as a technique suitable to detect the involvement of the lipids in redox induced reactions of the protein. First the individual infrared spectroscopic features of lipids, typically present in the yeast membrane, have been monitored for different pH values in micelles and vesicles. The pKa values for cardiolipin molecule have been observed at 4.7 ± 0.3 and 7.9 ± 1.3, respectively. Lipid contributions in the electrochemically induced FTIR spectra of the bc1 complex from yeast have been identified by comparing the spectra of the as isolated form, with samples where the lipids were digested by lipase-A2. Overall, a noteworthy perturbation in the spectral region typical for the protein backbone can be reported. Interestingly, signals at 1159, 1113, 1039 and 980 cm− 1 have shifted, indicating the perturbation of the protonation state of cardiolipin coupled to the reduction of the hemes. Additional shifts are found and are proposed to reflect lipids reorganizing due to a change in their direct environment upon the redox reaction of the hemes. In addition a small shift in the alpha band from 559 to 556 nm can be seen after lipid depletion, reflecting the interaction with heme bH and heme c. Thus, our work highlights the role of lipids in enzyme reactivity and structure. 相似文献
7.
In an attempt to know whether highly consumed food might contribute to metal exposure, we analyzed cadmium, lead, and mercury
in 27 rice grain samples commonly consumed in Saudi Arabia by atomic absorption spectrometry after acid digestion. The mean
concentrations and ranges of cadmium, lead, and mercury in tested rice samples were 20.261 (range <DL-178.026 μg/kg), 134.819
(range 23.1–1529.0 μg/kg), and 3.186 (range <DL-43.573 μg/kg), respectively. The results showed high concentrations of metals
and in some cases exceeded the Provisional Tolerance Weekly Intake (PTWI) recommended by FAO/WHO. It was also noted that different
rice grain samples had varying concentrations of these metals. Because the bulk of literature warns against the cumulative
effects of prolonged heavy metal exposure, regular consumption of rice by local populations might pose potential health problems. 相似文献
8.
Drinking water contaminated with arsenic poses serious threat to the human health. The present study was aimed for quality assessment of the groundwater of Khairpur Mir's in respect with arsenic and other elemental contamination like Fe, Cu, Co, and Ni. The presence of the trace elements in groundwater from different sources in the study area was measured by using atomic absorption spectroscopy. For arsenic analysis hydride generation technique (MHS-15) was used with detection limit of 0.02 µg l?1. Elevated level of arsenic was observed in most of the samples as compared to recommended value of World Health Organization (WHO) guidelines (10 µg l?1). However, levels of Fe, Cu, Co, and Ni in hand pump (HP) water samples was found in the range of 4–1610 µg l?1, 0–556 µg l?1, 0–230 µg l?1, and 0–700 µg l?1, respectively. Whereas in tube well (TW) water samples the observed values are 5–1620 µg l?1, 0–50 µg l?1, 4–110 µg l?1, and 0–360 µg l?1 for Fe, Cu, Co, and Ni, respectively. Significant difference was observed between TW and HP water samples. It was concluded that the level of arsenic found was very high up to 13 fold more than the WHO recommended limit in study area. While the levels of other elements was noted within the safe limit. 相似文献
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10.
Ding ZC Zheng Q Cai B Ni FY Yu WH Teng XC Gao Y Liu F Chen D Wang Y Wu HM Sun HZ Zhang MJ Tan XS Huang ZX 《Journal of inorganic biochemistry》2008,102(11):1965-1972
Human metallothionein-3 (hMT3), also named as human neuronal growth inhibitory factor (hGIF), can inhibit the outgrowth of embryonic cortical neurons in the presence of brain extracts. In order to systematically study the structure-property-reactivity-function relationship of hGIF, our laboratory designed a series of mutants and studied their structure, property, reactivity and functions by a series of chemical and biological tools including UV spectroscopy, CD spectroscopy, NMR, chemical reaction and primary neuronal culture assays. In summary, we concluded that the bioactivity of hGIF was regulated by multiple factors, including the 6CPCP9 motif, an additional threonine insert at sequence position 5, domain-domain interactions, the structure and stability of the metal-thiolate cluster and the linker. Our studies provide more and more evidences which revealed that the bioactivity of hGIF is mainly related to the essential metal release and its characteristic conformation. 相似文献