Incorporation of [14C] from acetoacetate, D(-)- and L(+)-3-hydroxybutyrate, glucose, glutamine, acetate and palmitate in cellular lipids were
studied in cultures in human diploid fibroblasts (HDF). The results showed that acetoacetate was 2–10 times more effective
as a lipogenic precursor than was either D- or L-3-hydroxybutyrate. Its extent of incorporation into lipids was 2- to 8-fold
more than the other precursors examined under conditions when the overall rates of nonsaponifiable and saponi-fiable lipogenesis
as measured by3H2O incorporation were essentially unchanged. Acetoacetate supported both saponifiable and nonsaponifiable lipid syntheses with
half-saturation values (Km app.) of 185 μM and 30 μM, respectively. Glucose stimulated acetoacetate incorporation into lipids whereas, conversely, acetoacetate
inhibited [14C] glucose incorporation into lipids. The presence of low density lipoproteins (LDL) cholesterol (@40 μg cholesterol/mL) inhibited
the incorporation of [14C] from acetoacetate 56% into nonsaponifiable lipids; the inhibition was consistently higher (75%) when [14C] glucose or glutamine were the precrusors. The loss of 3-hydroxy-3-methyl-glutaryl CoA (HMG CoA) reductase activity upon
addition of LDL-cholesterol was greater than the suppression of [14C] incorporation from acetoacetate or glucose into nonsaponifiable lipids. In the presence of glucose, [14C] acetoacetate was incorporated into 3-βOH sterols (digitonin precipitable). 7.7±1.1 times more effectively than was [14C] glucose. The results suggest that HDF would be a suitable model to investigate the effects of various precrusors of HMG
CoA on the rate of cholesterol biosynthesis. 相似文献
Machining of hard materials has become a great challenge for several decades. One of the problems in this machining process is early tool wear, and this affects the machinability of hard materials. In order to increase machinability, cutting tools are widely coated with nanostructured physical vapor deposition hard coatings. The main characteristics of such advanced hard coatings are high microhardness and toughness as well as good adhesion to the substrate. In this paper, the influence of hard coatings (nanolayer AlTiN/TiN, multilayer nanocomposite TiAlSiN/TiSiN/TiAlN, and commercially available TiN/TiAlN) and cutting parameters (cutting speed, feed rate, and depth of cut) on cutting forces and surface roughness were investigated during face milling of AISI O2 cold work tool steel (~61 HRC). The experiments were conducted based on 313 factorial design by response surface methodology, and response surface equations of cutting forces and surface roughness were obtained. In addition, the cutting forces obtained with the coated and uncoated tools were compared. The results showed that the interaction of coating type and depth of cut affects surface roughness. The hard coating type has no significant effect on cutting forces, while the cutting force Fz is approximately two times higher in the case of uncoated tool. 相似文献
While welcoming the European Landscape Convention and acknowledging the successes of conservation organizations such as the National Trust in Britain, the Czech Village Restoration Scheme and the French eco‐musées, this paper identifies some of the pitfalls that must be avoided if the fine words of the Convention are to be translated into effective action. These include problems with designation, conflicts between different types of conservation, and the side effects of gentrification and increased tourism. There is a call for more research to break down barriers to understanding between countries, between disciplines, and between academics and practitioners. 相似文献
This study investigates the influence of farm advisors on farmers’ decisions regarding ‘Multifunctional landscape commons’, a concept covering environmental and landscape values that benefit the public but which depend on farmers’ management practices. The influence of advisors is analysed by combining data about the source of advice with evidence of land use and landscape changes and participation in subsidy schemes. The study compares three agricultural areas in Denmark. Structured interviews were carried out with all farmers possessing more than 2 ha land in 1995–6 and in 2008. Vertical, production and business-oriented advisory services predominate, together with legal and organisational spatial competence networks. A new group of hobby farmers and pensioned farmers tend not to be included in traditional advisory networks, leaving them to carry out landscape changes and multifunctional landscape commons without professional guidance and consultancy. This means the horizontal coordination among farmers, that is, the territorial competences, decrease. 相似文献
This investigation explores the use of five‐parameter logistic curve fitting in quantifying turbidity robustness and risk scoring in clarification and filtrations stages of several surface water treatment works in the Anglian Water region of the United Kingdom. The approach taken reviews different scoring systems and addresses issues of weighting, averages and variability in robustness performance using turbidity robustness indices (TRIs). It also proposes an area‐based risk scoring profile to assess performance [relative area profile for T90 (RAP90)]. The metrics produced are considered to be a logical and rational way to help prioritise where resources for water treatment operation should be deployed. 相似文献
MIL-101@g-C3N4 nanocomposite was prepared by solvothermal synthesis and used for CO2 adsorption. The parent materials (MIL-101 and g-C3N4) and the MIL-101@g-C3N4 were characterized by X-ray diffraction, argon adsorption/desorption, Fourier transform infrared spectroscopy, thermal analysis (TG/DTA), transmission electronic microscopy, and Energy-dispersive X-ray spectroscopy. The results confirmed the formation of well-defined MIL-101@g-C3N4 with interesting surface area and pore volume. Furthermore, both MIL-101 and MIL-101@g-C3N4 were accomplished in carbon dioxide capture at different temperatures (280, 288, 273 and 298 K) at lower pressure. The adsorption isotherms show that the nanocomposite has a good CO2 adsorption affinity compared to MIL-101. The best adsorption capacity is about 1.6 mmol g?1 obtained for the nanocomposite material which is two times higher than that of MIL-101, indicating strong interactions between CO2 and MIL-101@g-C3N4. This difference in efficacy is mainly due to the presence of the amine groups dispersed in the nanocomposite. Finally, we have developed a simple route for the preparation of an effective and new adsorbent for the removal of CO2, which can be used as an excellent candidate for gas storage, catalysis, and adsorption. 相似文献
Novel soy protein/polystyrene nanoblends with core‐shell structures were successfully prepared by introducing nano‐sized PS into soy protein through emulsion polymerization. The nanoblends showed core‐shell structures, with the core being of PS and the shell of sodium dodecane sulfonate and soy protein polypeptides, when investigated by electron microscopy. Nanoblends containing high levels of PS (>30%) exhibited characteristic infrared spectrum bands, X‐ray diffraction peak, and glass transition, since PS microsphere aggregated to form independent PS domains. Mechanical strength and water resistance were effectively improved by introducing PS. An effective structure‐performance relationship was thereby established to describe the nanoblends.
De novo design and chemical synthesis of proteins and their mimics are central approaches for understanding protein folding and accessing proteins with novel functions. We have previously described carbohydrates as templates for the assembly of artificial proteins, so-called carboproteins. Here, we describe the preparation and structural studies of three alpha-helical bundle carboproteins, which were assembled from three different carbohydrate templates and one amphiphilic hexadecapeptide sequence. This heptad repeat peptide sequence has been reported to lead to 4-alpha-helix formation. The low resolution solution structures of the three carboproteins were analyzed by means of small-angle X-ray scattering (SAXS) and synchrotron radiation circular dichroism (SRCD). The ab initio SAXS data analysis revealed that all three carboproteins adopted an unexpected 3+1-helix folding topology in solution, while the free peptide formed a 3-helix bundle. This finding is consistent with the calculated alpha-helicities based on the SRCD data, which are 72 and 68 % for two of the carboproteins. The choice of template did not affect the overall folding topology (that is for the 3+1 helix bundle) the template did have a noticeable impact on the solution structure. This was particularly evident when comparing 4-helix carboprotein monomers with the 2x2-helix carboprotein dimer as the latter adopted a more compact conformation. Furthermore, the clear conformational differences observed between the two 4-helix (3+1) carboproteins based on D-altropyranoside and D-galactopyranoside support the notion that folding is affected by the template, and subtle variations in template distance-geometry design may be exploited to control the solution fold. In addition, the SRCD data show that template assembly significantly increases thermostability. 相似文献