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排序方式: 共有398条查询结果,搜索用时 156 毫秒
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Zheng Ling Andrew Harvey David McAteer Ian J. Godwin Beata Szydłowska Aideen Griffin Victor Vega‐Mayoral Yongchen Song Andrés Seral‐Ascaso Valeria Nicolosi Jonathan Coleman 《Liver Transplantation》2018,8(8)
Many promising supercapacitor electrode materials have high resistivity and require conductive additives to function effectively. However, the detailed role of the additive is not understood. Here, this question is resolved by applying a quantitative model for resistance‐limited supercapacitor electrodes to Co(OH)2‐nanosheet/carbon nanotube composites. Without nanotubes, theory predicts and experiments show that while the low‐rate capacitance increases linearly with electrode thickness, the high rate capacitance decreases with thickness due to slow charging. Experiments supported by theory show that nanotube addition has two effects. First, the nanotube network effectively distributes charge, increasing the intrinsic electrode performance to the limit associated with its accessible surface area. Second, at high‐rate, the increased electrode conductivity shifts the rate‐limiting resistance from electrode to electrolyte, thus removing the thickness‐dependent capacitance falloff. Furthermore, the analysis quantifies the out‐of‐plane conductivity of the nanotube network, identifies the cross‐over from resistance‐limited to diffusion‐limited behavior, and allows full electrode modeling, facilitating rational design. 相似文献
373.
A modern view of phenylalanine ammonia lyase. 总被引:6,自引:0,他引:6
Phenylalanine ammonia lyase (PAL; E.C.4.3.1.5), which catalyses the biotransformation of L-phenylalanine to trans-cinnamic acid and ammonia, was first described in 1961 by Koukol and Conn. Since its discovery, much knowledge has been gathered with reference to the enzyme's catabolic role in microorganisms and its importance in the phenyl propanoid pathway of plants. The 3-dimensional structure of the enzyme has been characterized using X-ray crystallography. This has led to a greater understanding of the mechanism of PAL-catalyzed reactions, including the discovery of a recently described cofactor, 3,5-dihydro-5-methyldiene-4H-imidazol-4-one. In the past 3 decades, PAL has gained considerable significance in several clinical, industrial, and biotechnological applications. The reversal of the normal physiological reaction can be effectively employed in the production of optically pure L-phenylalanine, which is a precursor of the noncalorific sweetener aspartame (L-phenylalanyl-L-aspartyl methyl ester). The enzyme's natural ability to break down L-phenylalanine makes PAL a reliable treatment for the genetic condition phenylketonuria. In this mini-review, we discuss prominent details relating to the physiological role of PAL, the mechanism of catalysis, methods of determination and purification, enzyme kinetics, and enzyme activity in nonaqueous media. Two topics of current study on PAL, molecular biology and crystal structure, are also discussed. 相似文献
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The effects of myiasis caused byBlepharipa pratensis (Meigen) on the pathogenicity of 3 dosages (1.00×104 PIB, 3.75×104 PIB and 7.50×104 PIB) of nucleopolyhedrosis virus (NPV) in stage V ofLymantria dispar (L.) were tested. When fed only NPV, 44% of the larvae fed the low dosage died, 67% of the larvae fed the mid-level dosage
died, and 73% of those fed the high-level dosage died. At the low dosage, mortality was significantly lower than at the other
dosages. The presence of the parasite significantly increased mortality due to NPV; 65% of the larvae fed the low dosage died,
77% of the larvae fed the mid-level dosage died, and 80% of the larvae fed the high-level dosage died. For biological control,
the combination of NPV and parasite would increase mortality, but at the expense of the parasite.
Résumé L'effet du parasitisme parBlepharipa pratensis sur la pathogénie de 3 doses (1.00×104 PIB, 3,75×104 PIB et 7,50×104 PIB) du virus de la polyédrie nucléaire (VPN) chez le 5ème stade deLymantria dispar a été étudié. Nourries avec seulement la dose faible du VPN, 44% des larves ont succombé, 67% sont mortes de la dose moyenne et 73% des larves de la dose forte. La différence de mortalité obtenue avec la dose faible était significative par rapport à la mortalité obtenue avec les 2 autres doses. La présence du parasite a augmenté significativement la mortalité par virose; avec la dose faible cette mortalité a atteint 65%, 77% avec la dose moyenne et 80% avec la dose forte. Pour la lutte biologique, la combinaison du virus avec le parasite augmenterait la mortalité, mais aux dépens du parasite.相似文献
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Cameron J. Nordell Samuel Haché Erin M. Bayne Péter Sólymos Kenneth R. Foster Christine M. Godwin Richard Krikun Peter Pyle Keith A. Hobson 《PloS one》2016,11(11)
Understanding bird migration and dispersal is important to inform full life-cycle conservation planning. Stable hydrogen isotope ratios from feathers (δ2Hf) can be linked to amount-weighted long-term, growing season precipitation δ2H (δ2Hp) surfaces to create δ2Hf isoscapes for assignment to molt origin. However, transfer functions linking δ2Hp with δ2Hf are influenced by physiological and environmental processes. A better understanding of the causes and consequences of variation in δ2Hf values among individuals and species will improve the predictive ability of geographic assignment tests. We tested for effects of species, land cover, forage substrate, nest substrate, diet composition, body mass, sex, and phylogenetic relatedness on δ2Hf from individuals at least two years old of 21 songbird species captured during the same breeding season at a site in northeastern Alberta, Canada. For four species, we also tested for a year × species interaction effect on δ2Hf. A model including species as single predictor received the most support (AIC weight = 0.74) in explaining variation in δ2Hf. A species-specific variance parameter was part of all best-ranked models, suggesting variation in δ2Hf was not consistent among species. The second best-ranked model included a forage substrate × diet interaction term (AIC weight = 0.16). There was a significant year × species interaction effect on δ2Hf suggesting that interspecific differences in δ2Hf can differ among years. Our results suggest that within- and among-year interspecific variation in δ2Hf is the most important source of variance typically not being explicitly quantified in geographic assignment tests using non-specific transfer functions to convert δ2Hp into δ2Hf. However, this source of variation is consistent with the range of variation from the transfer functions most commonly being propagated in assignment tests of geographic origins for passerines breeding in North America. 相似文献
379.
Rose M. McConnell Walter E. Godwin Amy Stefan Crystal Newton Nikki Myers Susan E. Hatfield 《Letters in Peptide Science》2003,10(2):69-78
Summary Cathepsin D, a lysosomal aspartic protease, has been suggested to play a role in the metastatic potential of several types
of cancer. A high activated cathepsin D level in breast tumor tissue has been associated with an increased incidence of relapse
and metastasis. High levels of active cathepsin D have also been found in colon cancer, prostate cancer, uterine cancer and
ovarian cancer. Hydroxyethyl isosteres with cyclic tertiary amine have proven to be clinically useful as inhibitors of aspartyl
proteases similar to cathepsin D in activity, such as the HIV-1 aspartyl protease. The design and the synthesis of (hydroxyethyl)amine
isostere inhibitors with cyclic tertiary amines is described. The IC50 and Ki(app) values for the six cathepsin D inhibitors and pepstatin are reported. Compounds7b,3(S)-[Acetyl-L-valyl-L-phenylalanylamino]-4-phenyl-1-N-piperidine-2(S)-butanol, and7c, 3(S)-[Acetyl-L-leucyl-L-phenylalanylamino]-4-phenyl-1-N-piperidine-2(S)-butanol, showed the most potent inhibition of cathepsin
D hydrolysis of hemoglobin with IC50 values of 3.5 nM and 4.5 nM, respectively. 相似文献
380.