Structural basis for substrate delivery by acyl carrier protein in the yeast fatty acid synthase     

Leibundgut M  Jenni S  Frick C  Ban N 《Science (New York, N.Y.)》2007,316(5822):288-290

In the multifunctional fungal fatty acid synthase (FAS), the acyl carrier protein (ACP) domain shuttles reaction intermediates covalently attached to its prosthetic phosphopantetheine group between the different enzymatic centers of the reaction cycle. Here, we report the structure of the Saccharomyces cerevisiae FAS determined at 3.1 angstrom resolution with its ACP stalled at the active site of ketoacyl synthase. The ACP contacts the base of the reaction chamber through conserved, charge-complementary surfaces, which optimally position the ACP toward the catalytic cleft of ketoacyl synthase. The conformation of the prosthetic group suggests a switchblade mechanism for acyl chain delivery to the active site of the enzyme.  相似文献   

Candidatus Chloracidobacterium thermophilum: an aerobic phototrophic Acidobacterium     

Bryant DA  Costas AM  Maresca JA  Chew AG  Klatt CG  Bateson MM  Tallon LJ  Hostetler J  Nelson WC  Heidelberg JF  Ward DM 《Science (New York, N.Y.)》2007,317(5837):523-526

Only five bacterial phyla with members capable of chlorophyll (Chl)-based phototrophy are presently known. Metagenomic data from the phototrophic microbial mats of alkaline siliceous hot springs in Yellowstone National Park revealed the existence of a distinctive bacteriochlorophyll (BChl)-synthesizing, phototrophic bacterium. A highly enriched culture of this bacterium grew photoheterotrophically, synthesized BChls a and c under oxic conditions, and had chlorosomes and type 1 reaction centers. "Candidatus Chloracidobacterium thermophilum" is a BChl-producing member of the poorly characterized phylum Acidobacteria.  相似文献   

Comparative metagenomics of microbial communities   总被引：1，自引：0，他引：1  

Tringe SG  von Mering C  Kobayashi A  Salamov AA  Chen K  Chang HW  Podar M  Short JM  Mathur EJ  Detter JC  Bork P  Hugenholtz P  Rubin EM 《Science (New York, N.Y.)》2005,308(5721):554-557

The species complexity of microbial communities and challenges in culturing representative isolates make it difficult to obtain assembled genomes. Here we characterize and compare the metabolic capabilities of terrestrial and marine microbial communities using largely unassembled sequence data obtained by shotgun sequencing DNA isolated from the various environments. Quantitative gene content analysis reveals habitat-specific fingerprints that reflect known characteristics of the sampled environments. The identification of environment-specific genes through a gene-centric comparative analysis presents new opportunities for interpreting and diagnosing environments.  相似文献   

Mental accounting and consumption of self-produced food          下载免费PDF全文

HUANG Jia-qi  Gerrit ANTONIDES  Christian H. KUHLGATZ  NIE Feng-ying 《农业科学学报》2021,20(9):2569-2580

This is an exploratory study on mental accounting and food budgeting of agricultural households, in which we assumed that agricultural households may have a mental account for consumption of their self-produced food. Accordingly, they may reserve a certain quantity of self-produced food as a set budget for own consumption, implying that they may keep on consuming their own produce until they have consumed the quantity set for the mental budget. By making the mental accounting assumption, we hypothesized that the consumption of self-produced food is independent of market price. Also, we hypothesized that the consumption of self-produced food is increasing in the quantity of production if production is lower than the set budget, and independent of the quantity of production if production exceeds the set budget. By applying a double-log demand model and using survey data from six poor rural counties in China, we tested these hypotheses for five food items, which are rice, flour, potatoes, pork, and eggs. We found that the hypothesis of no significant effect of price holds for flour, potatoes, and pork if production is lower than the set budget, and for rice, pork, and eggs if production is higher than the set budget. Production has a significant positive effect on consumption of selfproduced food but with a much greater influence when production is lower than the set budget for all five food items. These findings partly support our assumption of mental accounting of self-produced food. Limitations, policy implications, and possible future studies are discussed.  相似文献   

The development of soil organic carbon under young black locust (Robinia pseudoacacia L.) trees at a post-mining landscape in eastern Germany     

Kanzler  Michael  Böhm  Christian  Freese  Dirk 《New Forests》2021,52(1):47-68

The aim of this study was to evaluate the potential of short rotation alley cropping systems (SRACS) to improve the soil fertility of marginal post-mining sites in Brandenburg, Germany. Therefore, we annually investigated the crop alleys (AC) and black locust hedgerows (ABL) of a SRACS field trail under initial soil conditions to identify the short-term effects of tree planting on the storage of soil organic carbon (SOC) and its degree of stabilization by density fractionation. We detected a significant increase in SOC and hot-water-extractable organic C (HWEOC) at ABL, which was mainly restricted to the uppermost soil layer (0–10 cm). After 6 years, the SOC and HWEOC accumulation rates at ABL were 0.6 Mg and 46 kg ha^?1 year^?1, which were higher than those in the AC. In addition, comparatively high stocks of approximately 4.6 Mg OC and 182 kg HWEOC ha^?1 were stored in the ABL litter layer. Density fractionation of the 0–3 cm soil layer at ABL revealed that the majority of the total SOC (47%) was stored in the free particulate organic matter fraction, which was more than twice that of the AC. At the same time, a higher and steadily increasing amount of SOC was stored in the occluded particulate organic matter fraction at ABL, which indicated a high efficiency for SOC stabilization. Overall, our findings support the suitability of black locust trees for increasing the soil fertility of the reclaimed mining substrate and, consequently, the high potential for SRACS to serve as an effective recultivation measure at marginal sites.

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CIMMYT-selected derived synthetic bread wheats for rainfed environments: Yield evaluation in Mexico and Australia   总被引：1，自引：0，他引：1  

M. Fernanda Dreccer  M. Gabriela Borgognone  Francis C. Ogbonnaya  Richard M. Trethowan  Bruce Winter 《Field Crops Research》2007,100(2-3):218-228

Synthetic backcrossed-derived bread wheats (SBWs) from CIMMYT were grown in the Northwest of Mexico at Centro de Investigaciones Agrícolas del Noroeste (CIANO) and sites across Australia during three seasons. During three consecutive years Australia received “shipments” of different SBWs from CIMMYT for evaluation. A different set of lines was evaluated each season, as new materials became available from the CIMMYT crop enhancement program. These consisted of approximately 100 advanced lines (F7) per year. SBWs had been top and backcrossed to CIMMYT cultivars in the first two shipments and to Australian wheat cultivars in the third one. At CIANO, the SBWs were trialled under receding soil moisture conditions. We evaluated both the performance of each line across all environments and the genotype-by-environment interaction using an analysis that fits a multiplicative mixed model, adjusted for spatial field trends. Data were organised in three groups of multienvironment trials (MET) containing germplasm from shipment 1 (METShip1), 2 (METShip2), and 3 (METShip3), respectively. Large components of variance for the genotype × environment interaction were found for each MET analysis, due to the diversity of environments included and the limited replication over years (only in METShip2, lines were tested over 2 years). The average percentage of genetic variance explained by the factor analytic models with two factors was 50.3% for METShip1, 46.7% for METShip2, and 48.7% for METShip3. Yield comparison focused only on lines that were present in all locations within a METShip, or “core” SBWs. A number of core SBWs, crossed to both Australian and CIMMYT backgrounds, outperformed the local benchmark checks at sites from the northern end of the Australian wheat belt, with reduced success at more southern locations. In general, lines that succeeded in the north were different from those in the south. The moderate positive genetic correlation between CIANO and locations in the northern wheat growing region likely reflects similarities in average temperature during flowering, high evaporative demand, and a short flowering interval. We are currently studying attributes of this germplasm that may contribute to adaptation, with the aim of improving the selection process in both Mexico and Australia.  相似文献   

Biomimetic assembly of polyelectrolyte multilayers containing phosvitin monitored with reflectometric interference spectroscopy     

Grohmann S  Rothe H  Eisenhuth S  Hoffmann C  Liefeith K 《Biointerphases》2011,6(2):54-62

Coatings of biomaterials or implants that facilitate biomineralization possess a great potential for applications focused to the replacement, augmentation, and regeneration of bone tissue. Biomimetic approaches utilize biomolecules for either templating or supporting the crystallization process. One of these promising biomolecules is phosvitin (PV), an egg yolk protein known to transport and store inorganic phosphates and calcium ions. The incorporation of PV into polyelectrolyte multilayers is favorable due to PVs high degree of phosphorylation and thus a high acidity. Utilizing the reflectometric interference spectroscopy, the adsorption kinetics of this novel polyelectrolyte system composed of poly-L-lysine and the heavily phosphorylated phosvitin were monitored. The results demonstrate an unexpected nonregular growth regime called overshoot. Effective measures of shifting this irregular polyelectrolyte adsorption process back to a regular multilayer growth regime are reported in this paper.  相似文献   

Estimation of the Body Weight of Icelandic Horses     

Gundula Hoffmann  Annika Bentke  Sandra Rose-Meierhöfer  Christian Ammon  Petra Mazetti  Grétar H. Hardarson 《Journal of Equine Veterinary Science》2013

The body weight of horses is an interesting variable for horse owners, as well as for veterinarians. It is useful to have methods of estimation like weight tape or formula, rather than visual estimation, when a weight scale is not available. Different methods of weight estimation exist for adult horses, but to date, there has been no validation of these methods in Icelandic horses. Therefore, three different methods of weight determination (weight scale, weight tape, and weight formula) were compared in this study to investigate whether it is possible to obtain reliable weight measurements of Icelandic horses by using an estimation method. Both the weight pursuant to weight tape and pursuant to weight formula showed no significant differences (P = 1.00 and P = 0.37, respectively) from the actual weight. The correlation between estimated and actual weights was r = 0.94 for weight tape and r = 0.93 for weight formula. However, the differences between the estimated and actual weights were smallest when estimated using an adjusted weight formula: weight (kg) = girth² × length (both in cm)/11,400. In conclusion, the body weight of Icelandic horses can be estimated from the measurements of body girth and length, and weight tape also seems to be a suitable method.  相似文献   

Quantitative Glucose Metabolism in Lactating Mink ( Mustela vison ) - Effects of Dietary Levels of Protein,Fat and Carbohydrates     

Rikke Fink  Christian Friis Børsting 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(1):34-42

Glucose metabolism was measured during two consecutive years, 4 weeks postpartum, in a total of 36 yearling female mink, fitted with jugular vein catheters and raising litters of six to seven kits. The dams were fed ad libitum from parturition on diets with different ratios of metabolizable energy (ME) derived from protein:fat:carbohydrates (experiment 1: 61:37:2, 46:37:17, 31:37:32; experiment 2: 61:38:1, 47:52:1, 33:66:1). After 3 h fasting the dams were fed 210 kJ ME of the experimental diets. Two hours postprandially a single dose of 50 w Ci U- 14 C- and 2- 3 H-labelled glucose was administered to each dam and blood samples were drawn 5, 10, 20, 30, 45 and 60 min after the tracer administration. Glucose turnover rates were 4-5% min -1 in all dams, and the approximate daily glucose flux was 12-17 g day -1 ; however, these were not significantly affected by dietary treatment. In conclusion, the mink is able both to synthesize large amounts of glucose de novo and to utilize high levels of dietary digestible carbohydrates, and thereby to tolerate large variations in dietary carbohydrate supply.  相似文献   

Fatty Acid Metabolism in the Digestive Tract of Lactating Cows Fed Tallow in Increasing Amounts at Two Feed Levels     

Martin R. Weisbjerg  Christian F. Børsting  Torben Hvelplund 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(2):106-114

Abstract

Long-chain fatty acid metabolism in the digestive tract was studied in lactating cows fed at two levels of dry matter intake (L, 8.6 kg DM and H, 12.6 kg DM), with 0, 4 and 6% added tallow at low feed level (L0, L4 and L6), and 0, 2, 4 and 6% fat at high feed level (H0, H2, H4 and H6). Mean fatty acid balance from mouth to duodenum was about zero when corrected for endogenous fatty acids from bile. However, regression analysis showed a microbial synthesis of 68 g at zero fatty acid intake, and a trend which indicated declining de novo synthesis of fatty acids with increasing fat level in the diet. As a mean 68% of the unsaturated C18 fatty acids were hydrogenated in the rumen.

Fatty acid and crude fat true digestibilities decreased with increasing fat intakes owing to a decrease in stearic acid (C18:0) digestibility.  相似文献