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61.
Selective oxidation with dioxygen by gold nanoparticle catalysts derived from 55-atom clusters 总被引:1,自引:0,他引:1
Turner M Golovko VB Vaughan OP Abdulkin P Berenguer-Murcia A Tikhov MS Johnson BF Lambert RM 《Nature》2008,454(7207):981-983
Supported gold nanoparticles have excited much interest owing to their unusual and somewhat unexpected catalytic properties, but the origin of the catalytic activity is still not fully understood. Experimental work on gold particles supported on a titanium dioxide (110) single-crystal surface has established a striking size threshold effect associated with a metal-to-insulator transition, with gold particles catalytically active only if their diameters fall below approximately 3.5 nm. However, the remarkable catalytic behaviour might also in part arise from strong electronic interaction between the gold and the titanium dioxide support. In the case of industrially important selective oxidation reactions, explanation of the effectiveness of gold nanoparticle catalysts is complicated by the need for additives to drive the reaction, and/or the presence of strong support interactions and incomplete understanding of their possible catalytic role. Here we show that very small gold entities ( approximately 1.4 nm) derived from 55-atom gold clusters and supported on inert materials are efficient and robust catalysts for the selective oxidation of styrene by dioxygen. We find a sharp size threshold in catalytic activity, in that particles with diameters of approximately 2 nm and above are completely inactive. Our observations suggest that catalytic activity arises from the altered electronic structure intrinsic to small gold nanoparticles, and that the use of 55-atom gold clusters may prove a viable route to the synthesis of robust gold catalysts suited to practical application. 相似文献
62.
YunFei Bi J. Blanchard J. -F. Lambert Y. Millot P. P. Man ShuangQin Zeng Hong Nie DaDong Li MingFeng Li QingHe Yang XiaoXin Chen 《科学通报(英文版)》2010,55(23):2584-2588
In this paper, a new delaminated mesoporous material was prepared by swelling the lamellar phyllosilicate Magadiite using cetyltrimethylammonium bromide and tetrapropylammonium hydroxide solution, followed by delamination under the cavitation of ultrasonic treatment. Various characterization tools including XRD, N2 adsorption, NMR, IR, SEM and TEM were employed to observe its structure and morphology. XRD results show that the delaminated material has no long-range crystalline order. Fur-thermore, not only high surface area is obtained, but almost half of it is external surface. The observation for the morphology further reveals that it is made up of the random stacking of single or few layers. All these characters show that this delaminated mesoporous material meets the requirements for application as support in the hydrotreatment of heavy molecules. 相似文献
63.
Hollingworth P Harold D Sims R Gerrish A Lambert JC Carrasquillo MM Abraham R Hamshere ML Pahwa JS Moskvina V Dowzell K Jones N Stretton A Thomas C Richards A Ivanov D Widdowson C Chapman J Lovestone S Powell J Proitsi P Lupton MK Brayne C Rubinsztein DC Gill M Lawlor B Lynch A Brown KS Passmore PA Craig D McGuinness B Todd S Holmes C Mann D Smith AD Beaumont H Warden D Wilcock G Love S Kehoe PG Hooper NM Vardy ER Hardy J Mead S Fox NC Rossor M Collinge J Maier W Jessen F Rüther E Schürmann B 《Nature genetics》2011,43(5):429-435
We sought to identify new susceptibility loci for Alzheimer's disease through a staged association study (GERAD+) and by testing suggestive loci reported by the Alzheimer's Disease Genetic Consortium (ADGC) in a companion paper. We undertook a combined analysis of four genome-wide association datasets (stage 1) and identified ten newly associated variants with P ≤ 1 × 10(-5). We tested these variants for association in an independent sample (stage 2). Three SNPs at two loci replicated and showed evidence for association in a further sample (stage 3). Meta-analyses of all data provided compelling evidence that ABCA7 (rs3764650, meta P = 4.5 × 10(-17); including ADGC data, meta P = 5.0 × 10(-21)) and the MS4A gene cluster (rs610932, meta P = 1.8 × 10(-14); including ADGC data, meta P = 1.2 × 10(-16)) are new Alzheimer's disease susceptibility loci. We also found independent evidence for association for three loci reported by the ADGC, which, when combined, showed genome-wide significance: CD2AP (GERAD+, P = 8.0 × 10(-4); including ADGC data, meta P = 8.6 × 10(-9)), CD33 (GERAD+, P = 2.2 × 10(-4); including ADGC data, meta P = 1.6 × 10(-9)) and EPHA1 (GERAD+, P = 3.4 × 10(-4); including ADGC data, meta P = 6.0 × 10(-10)). 相似文献
64.
Zhang ZG Lambert CA Servotte S Chometon G Eckes B Krieg T Lapière CM Nusgens BV Aumailley M 《Cellular and molecular life sciences : CMLS》2006,63(1):82-91
The GTP-binding proteins RhoA, Cdc42 and Rac1 regulate the organization and turnover of the cytoskeleton and cell-matrix adhesions,
structures bridging cells to their support, and translating forces, external or generated within the cell. To investigate
the specific requirements of Rho GTPases for biomechanical activities of clonal cell populations, we compared side-by-side
stable lines of human fibroblasts expressing constitutively active (CA) RhoA, Cdc42 or Rac1. There was no marked effect of
any CA GTPase on cell adhesion to different extracellular matrix proteins. Cell spreading was CA Rho GTPase specific and independent
of the extracellular matrix proteins allowing adhesion. Mechanical properties were dramatically restricted by CA RhoA on bi-
and in tri-dimensional surroundings, were boosted by CA Rac1 on bi-dimensional surroundings only, and were not or marginally
affected by CA Cdc42. In conclusion, the action of Rho GTPases appears to depend on the task cells are performing.
Received 12 September 2005; received after revision 5 October 2005; accepted 1 November 2005 相似文献
65.
Daniel W. Lambert Nicola E. Clarke Anthony J. Turner 《Cellular and molecular life sciences : CMLS》2010,67(1):89-98
The renin-angiotensin system (RAS) is a critical regulator of blood pressure and fluid homeostasis. Angiotensin II, the primary
bioactive peptide of the RAS, is generated from angiotensin I by angiotensin-converting enzyme (ACE). A homologue of ACE,
ACE2, is able to convert angiotensin II to a peptide with opposing effects, angiotensin-(1-7). It is proposed that disturbance
of the balance of ACE and ACE2 expression and/or function is important in pathologies in which angiotensin II plays a role.
These include cardiovascular and renal disease, lung injury and liver fibrosis. The critical roles of ACE and ACE2 in regulating
angiotensin II levels have traditionally focussed attention on their activities as angiotensinases. Recent discoveries, however,
have illuminated the roles of these enzymes and of the ACE2 homologue, collectrin, in intracellular trafficking and signalling.
This paper reviews the key literature regarding both the catalytic and non-catalytic roles of the angiotensin-converting enzyme
gene family. 相似文献
66.
Yellow phenocopies of Drosophila melanogaster were produced by raising larvae on alpha-DMT contaminated media. Using a survivorship test, the sensitive period for phenocopy induction was found to occur during the third larval instar of development, with increased survivorship at 1% alpha-DMT compared with lower concentrations. It was also found that treatment with alpha-DMT significantly slowed development. These findings are related to the relevant morphological and behavioral developmental pathways and to phenocopy induction. 相似文献
67.
Summary Rabbit kidney cortex slices behave as osmometers when withstanding either hyperosmotic shocks or hypoosmotic shocks of amplitude up to P1/P2=1.25. For hypo-osmotic shocks of amplitude larger or equal to P1/P2=1.5 a volume regulation process occurs. Na+ is the main osmotic effector implicated in volume control.This work has been aided by a grant 1.5.422.82F from the FNRS to R.G. We wish to thank Mr J.M. Theate for his skilful assistance. 相似文献
68.
Synthesis and metabolism of vertebrate-type steroids by tissues of insects: A critical evaluation 总被引:2,自引:0,他引:2
Prof. L. Swevers J. G. D. Lambert A. De Loof 《Cellular and molecular life sciences : CMLS》1991,47(7):687-698
Summary This review covers the synthesis and the metabolism of vertebrate-type steroids (progesterone, testosterone, estradiol, corticosteroids) by insect tissues and discusses the significance of the reactions for insect physiology. Biosynthesis of vertebrate-type steroids from cholesterol hitherto has been demonstrated in only two insect species, i.e. the water beetleAcilius sulcatus (Coleoptera) and the tobacco hornwormManduca sexta (Lepidoptera). InAcilius, steroid synthesis is associated with exosecretion (chemical defense). Nothing, however, is known about a physiological role of the C21 steroid conjugate present in ovaries and eggs ofManduca. No synthesis of vertebrate-type steroids was observed in any other insect investigated to date. Most metabolic conversions of steroids by insects concerned oxidoreduction of oxygen groups (hydroxysteroid dehydrogenase activity) and (polar and apolar) conjugate formation. All important enzymatic steps involved in synthesis and catabolism, as known from studies with tissues of vertebrates, were not, or hardly observed. The conclusion is drawn that typical vertebrate-type (C21, C19 and C18) steroids probably do not act as physiologically active substances in insects. 相似文献
69.
70.
R. P. Duffley G. Lambert H. C. Dalzell R. K. Razdan 《Cellular and molecular life sciences : CMLS》1981,37(9):931-932
Summary The synthesis of (±)-211-dihydroxy-
9-THC, a difunctionalized metabolite of
9-THC, is presented.Acknowledgment. This work was carried out with the support of NIDA Grant No. DA 00574. We are grateful to Mr. J. Coe for assistance with some of the experiments. 相似文献