Force-clamp spectroscopy monitors the folding trajectory of a single protein     

Fernandez JM  Li H 《Science (New York, N.Y.)》2004,303(5664):1674-1678

We used force-clamp atomic force microscopy to measure the end-to-end length of the small protein ubiquitin during its folding reaction at the single-molecule level. Ubiquitin was first unfolded and extended at a high force, then the stretching force was quenched and protein folding was observed. The folding trajectories were continuous and marked by several distinct stages. The time taken to fold was dependent on the contour length of the unfolded protein and the stretching force applied during folding. The folding collapse was marked by large fluctuations in the end-to-end length of the protein, but these fluctuations vanished upon the final folding contraction. These direct observations of the complete folding trajectory of a protein provide a benchmark to determine the physical basis of the folding reaction.  相似文献   

Effects of a diet enriched with eicosapentaenoic,docosahexaenoic and glutamine on cytokines as immunological markers for systemic inflammation in bitches before and after ovariohysterectomy     

Mariana Y. H. Porsani  Brana S. A. Bonder  Fabio A. Teixeira  Cristina O. M. S. Gomes  Lucas A. Gonçales  Julio K. Nagashima  Julio C. C. Balieiro  Denise T. Fantoni  Cristiana F. F. Pontieri  Juliana T. Jeremias  Marcio A. Brunetto 《Journal of animal physiology and animal nutrition》2021,105(Z2):79-88

The post-operative period can generate immunological stress and can be modulated through supplementation with the omega-3 series of polyunsaturated fatty acids. This study aimed to evaluate the effects of diets enriched with high doses of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids and glutamine on inflammatory mediators in dogs before and after ovariohysterectomy (OVH). Twelve female dogs were divided into two groups: group A was fed a commercial diet without the addition of EPA and DHA, and group B was fed an experimental diet enriched with EPA and DHA (0.2 g/100 kcal). Experimental diet intake initiated 21 days before surgery and continued until 30 days after OVH. Parameters measured were serum cytokines (TNF-α, IL-6 and IL-10), C-reactive protein (CRP), IGF-1, lymphoproliferation and body composition before and after surgery. Statistical analyses were performed with SAS software considering the effects of age and diet and their interactions, and means were compared by the Tukey test. There was no difference between groups in body weight (p = .682), lean mass (p = .101) and body fat (p = .103). There were no group differences in serum concentrations of TNF-α, IL-6, IL-10, IGF-1, CRP and the percentage of lymphocyte proliferation. However, a time effect for TNF-α was observed (p < .001), in which T_0P (10 days after the surgical procedure) presented lower values of this cytokine when compared to the other evaluation time points; and interaction effects between group and time were observed for serum concentrations of IL-6 (p < .001) and IL-10 (p = .002). OVH procedure was not considered invasive enough to increase inflammatory cytokines after 30 days of surgery, as well as the dosage of the EPA and DHA used before and after the surgery did not modulate the inflammatory markers.  相似文献   

Some chemical composition and biological activity of northern Argentine propolis   总被引：4，自引：0，他引：4  

Isla MI  Paredes-Guzman JF  Nieva-Moreno MI  Koo H  Park YK 《Journal of agricultural and food chemistry》2005,53(4):1166-1172

Twenty-five samples of propolis were collected from seven different regions in northern Argentina; ethanolic extracts of propolis were prepared from all samples, and the respective samples were examined for UV absorption spectra, RPHPTLC, RPHPLC, antimicrobial activity, antiradical activity, and total phenolic content. It was found that 16 of the 25 samples showed a phenolic profile similar to that found in samples from southern Brazil and corresponding to poplar-based propolis and that the rest of the samples showed a different profile and higher antimicrobial and antiradical activities.  相似文献   

Bound malondialdehyde in foods: bioavailability of N,N'-di-(4-methyl-1,4-dihydropyridine-3,5-dicarbaldehyde)lysine     

Girón-Calle J  Alaiz M  Millán F  Ruiz-Gutierrez V  Vioque E 《Journal of agricultural and food chemistry》2003,51(16):4799-4803

Reactions between lipid peroxidation products and proteins in foods have detrimental nutritional effects, most importantly, losses of essential amino acids. One of the major products of the reaction of malondialdehyde and alkanals with amino groups are 4-substituted 1,4-dihydropyridine-3,5-dicarbaldehyde derivatives. The product of the reaction of lysine with malondialdehyde and acetaldehyde, N,N'-di-(4-methyl-1,4-dihydropyridine-3,5-dicarbaldehyde)lysine (MDDL), has been synthesized and used for in vitro and in vivo bioavailability studies. Release of free lysine did not occur in incubations of MDDL with tissue homogenates. After oral administration of radioactively labeled MDDL, radioactivity was only recovered in feces. Radioactivity was not incorporated into hepatic microsomes after intraperitoneal administration, which would have indicated release of available lysine. These results show that MDDL is a form of unavailable lysine, because it is not metabolized to free lysine and cannot be absorbed from the gut. Thus, formation of this derivative in foods would result in loss of available lysine.  相似文献   

Temporal and spatial variations in dominance,diversity and biotic indices along a limestone stream receiving a trout farm effluent     

Julio A. Camargo 《Water, air, and soil pollution》1992,63(3-4):343-359

Benthic macroinvertebrate response to organic pollution generated by a trout farm, located in the upper Rio Tajuña (Central Spain), was evaluated by calculating Whittaker's and Camargo's dominance indices; Margalef s, Menhinick's, Camargo's, Shannon's and MacArthur's diversity indices; and several biotic indices, including the Trent Biotic Index (TBI), the Chandler Biotic Score (CBS), the Biological Monitoring Working Party (BMWP), the Average Score Per Taxon (ASPT) and the Overall Quality Rating (OQR). An upstream sampling site (S-1) and three downstream stations placed 10 (S-2), 150 (S-3) and 1000 (S-4) m below the fish farm outlet were selected along the study area. Site S-3 was situated just below a man-made waterfall (1.8 m in height). Winter, spring and summer macrobenthic surveys were conducted during 1986. Plecopterans, ephemeropterans, coleopterans, trichopterans, amphipods and planarians decreased in abundance or were basent at downstream sampling sites, whereas simuliids, leeches, chironomids and tubificid worms increased in abundance. All diversity and biotic indices had highest and lowest values at S-1 and S-2, respectively, and higher values at S-3 (below the waterfall) than at S-4. However, Shannon's and MacArthur's diversity indices and the TBI were less effective in quantifying differences among sampling sites, exhibiting the lowest positive coefficients of linear correlation with species richness and other diversity and biotic indices. Both dominance indices had highest values at S-2, but similar values at S-1, S-3 and S-4. Biotic indices (except the TBI) and Margalef s, Menhinick's and Camargo's diversity indices appear to be the most sensitive measures for assessing macroinvertebrate response to changes in environmental conditions downstream from the fish farm. In addition, temporal variation in species richness, Margalef s index and biotic indices was similar, exhibiting their highest coefficients of variation at S-4. It is concluded that small waterfalls may improve the streamns self-purification of organic pollution generated by trout farms.  相似文献   

Epistasis in the resistance of pepper to phytophthora stem blight (Phytophthora capsici L.) and its significance in the prediction of double cross performances     

Rafael Bartual  Alfredo Lacasa  Jose Ignacio Marsal  Julio Cèsar Tello 《Euphytica》1993,72(1-2):149-152

Summary Epistatic effects are present in the resistance to Phytophthora capsici in peppers (Capsicum annuum). Genetic statistical analysis shows that additive by additive epistasis as well as higher order epistatic effects contribute to the total variation of resistance, significantly. Higher order epistatic effects caused bias in the prediction of the performance of double crosses, the difference between observed and predicted performances being significant.The relative importance of higher order epistasis with respect to additive by additive epistasis seems to be correlated with the aggressiveness of the isolate of Phytophthora capsici.  相似文献   

Climate variability and trends in the reproductive habitat of the critically endangered hooded grebe     

Julio L. Lancelotti  Natalia L. Pessacg  Ignacio C. Roesler  Miguel A. Pascual 《水产资源保护:海洋与淡水生态系统》2020,30(3):554-564

1. The population of the critically endangered hooded grebe (Podiceps gallardoi) has decreased drastically during recent decades. The effects of climate change on their reproductive area (Southern Patagonia) have been proposed as one of the potential causes of their critical situation. However, there is much uncertainty about climate variability and climate trends at local scales in Patagonia, and their effects on the hooded grebe habitat.
2. Variability and trends in temperature, precipitation, and wind from 1960 to 2016 in one of the most important reproductive areas of hooded grebe – the Lake Strobel plateau – were analysed. A Landsat satellite image series (1973–2016) was used to evaluate changes in lake area in the region.
3. Generalized linear models were used to analyse the relationship between the variation in lake area and climatic variables, including the Antarctic Oscillation Mode (AAO) index, which is the most important year to year pattern in climate variability at high latitudes of the Southern Hemisphere.
4. High inter‐annual variability and increasing coefficients of variation in precipitation and wind were found, as well as a significant positive trend in temperature. Total lake area, as well as the area specifically used by hooded grebe to reproduce, decreased significantly over time, with high inter‐annual variability. Variation in lake area was significantly correlated with variation in precipitation, and with the AAO index.
5. The loss of reproductive habitat may force the hooded grebe to use sub‐optimal environments, such as lakes with lower food supply, lower macrophyte cover, and less protection from wind – a potential major handicap for this declining species.
6. Information on lake variation in response to climatic variability could be used to guide hooded grebe conservation strategies, directing more resources and special efforts to those reproductive lakes that are more resilient to the effects of climate fluctuations.

  相似文献   

Nutritive value of squid and hydrolyzed protein supplement in shrimp feed   总被引：4，自引：0，他引：4  

Julio Humberto Crdova-Murueta  Fernando Luis García-Carreo 《Aquaculture (Amsterdam, Netherlands)》2002,210(1-4):371-384

Though some protein sources like squid and protein hydrolysates are assumed as growth enhancers for shrimp, little is known about the biochemical basis of this phenomenon. Low, heat-dried squid (Dosidicus gigas) (SQ) and two commercial protein hydrolysates from fish (FH) and krill (Euphasia sp.) (KH) were assayed in feeding trials with Penaeus vannamei. Feeds were prepared with the tested proteins at 3%, 9%, and 15% of the total crude protein. A total of nine experimental feeds plus a commercial one as control (C32) were tried. Additionally, digestibility in vivo and in vitro was evaluated. Survival was not different among groups. Weight gain of shrimp and total and specific proteolytic activity for trypsin and chymotrypsin were affected by type and quantity of supplemented protein. In vivo and in vitro digestibilities were also influenced by the source and quantity of the protein supplement. Shrimp fed feed with FH at 3% protein supplementation grew more than those fed with higher supplementations. Groups fed SQ had similar results as those fed FH, and gained more weight when fed the lowest SQ quantity. SDS-PAGE showed a large concentration of small peptides in SQ, which may explain results similar to FH. KH enhanced shrimp growth at all supplementations and had a lower degree of hydrolysis (DH) than FH. SQ also demonstrated good growth performance, but better at the lower supplementation, probably because of the presence of small peptides and possibly free amino acids from protein hydrolyzed by endogenous enzymes in the squid mantle. We conclude that hydrolyzed protein is a good supplement for shrimp feeds, but it must meet specific requirements for adequate assimilation.  相似文献   

Growth Response and Resistance to Streptococcus iniae of Nile Tilapia, Oreochromis niloticus, Fed Diets Containing Distiller's Dried Grains with Solubles     

Chhorn  Lim  Julio C.  Garcia  Mediha  Yildirim-Aksoy  Phillip H.  Klesius  Craig A.  Shoemaker  Joyce J.  Evans 《Journal of the World Aquaculture Society》2007,38(2):231-237

This study was conducted to evaluate the effect of dietary levels of distiller’s dried grains with solubles (DDGS) on growth, body composition, hematology, and resistance of Nile tilapia, Oreochromis niloticus, to Streptococcus iniae challenge. Five isocaloric diets containing DDGS at levels of 0, 10, 20, and 40%, and 40% DDGS + lysine (Diets 1–5) as partial replacements of a combination of soybean meal (SBM) and corn meal (CM) on an equal protein basis were fed to juvenile Nile tilapia (9.41 ± 0.14 g) for 10 wk. Fish fed Diet 4 had the lowest weight gain (WG), feed efficiency ratio, protein efficiency ratio (PER), and whole‐body protein. Supplementation of lysine to the 40% DDGS diet (Diet 5) improved WG and PER. Hematological and immunological parameters were not affected by dietary treatment. There were no significant differences among the average number of days to first mortality after S. iniae challenge and cumulative mortality 14 d postchallenge among fish in various treatments. DDGS can be incorporated in tilapia diet at a level of 20% as a substitute for a combination of SBM and CM without affecting their growth performance, body composition, hematological parameters, immune response, and resistance to S. iniae infection.  相似文献   

Potential CO₂ emissions mitigation through forest prescribed burning: A case study in Patagonia, Argentina     

Guillermo E. Defossé  Gabriel Loguercio  Facundo J. Oddi  Julio C. Molina  P. Daniel Kraus 《Forest Ecology and Management》2011,261(12):2243-2254

Wildland fire is a natural force that has shaped most vegetation types of the world. However, its inappropriate management during the last century has led to more frequent and catastrophic fires. Wildland fires are also recognized as one of the sources of CO₂ and other greenhouse gases (GHG) that influence global climate change. As one of the techniques used to reduce the risk of destructive wildfires, prescribed burning has the potential of mitigating carbon emissions, and effectively contributes to the efforts proposed as part of the Clean Development Mechanism within the Kyoto protocol. In order to apply this concept to a real case, a simulation study was conducted in pine afforestation in the Andean region of Patagonia, Argentina, with the objective of evaluating the potential of prescribed burning for reducing GHG emissions. The scenario was established for a ten year period, in which simulated prescribed burning was compared to the traditional management scheme, which included the probability of annual average of wildfire occurrence based on available wildfire statistics. The two contrasting scenarios were: (1) managed afforestation, affected by the annual average rate of wildfires occurred in the same type of afforestation in the region, without prescribed burning, and (2) same as (1) but with the application of simulated prescribed burning. In order to estimate carbon stocks, and CO₂ removals and emissions, we followed the guidelines given for GHG inventories on the Agriculture, Forestry and Other Land Uses (AFOLU) sector of the International Panel on Climate Change (IPCC), while the terminology used was the established by IPCC (2003). Data of afforested area, thinnings, and biomass growth were taken from previous surveys in the study area. Downed dead wood and litter (forest fuel load, FFL) was estimated adjusting equations fitted to those fuels, based on field data. Results show that comparing the two scenarios, prescribed burning reduced CO₂ emissions by 44% compared to the situation without prescribed burning. The prescribed burning scenario represented about 12% of the total emissions (prescribed burning plus wildfires). Furthermore, avoided wildfires by simulated prescribed burning allowed an additional 78% GHG emissions mitigation due to extra biomass growth. Simulated prescribed burning in commercial afforestation of Patagonia appears to be an effective management practice not only to prevent wildfires, but also an efficient tool to mitigate GHG emissions. However, more studies in different scenarios would be needed to generalize these benefits to other ecosystems.  相似文献