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1.
J Dairy Sci ; 2024 Jul 19.
Artículo en Inglés | MEDLINE | ID: mdl-39033916

RESUMEN

Sweetened condensed milk (SCM) is a product widely used by both consumers and other food production branches. However, it contains a lot of sucrose. This study aimed to examine the effects provided by sugar substitutes, such as trehalose, isomaltulose, and polydextrose, upon the SCM sensory profile and valuable quality indicators, such as water activity, viscosity, acidity, crystals size, and Maillard reaction potential (browning index, color change, loss of free amino acids). The study was performed by making model systems of SCM (MSCMs) using the method of reconstitution of powdered ingredients. All the presented carbohydrate compositions in MSCMs provided Aw value typical of intermediate-moisture food, which contributes to the long-term shelf-life of the product. However, only 2 MSCMs with compositions consisted of isomaltulose, trehalose (22.55% and 22.55%); trehalose (28.19%), sucrose (5.64%), polydextrose (5.64%), isomaltulose (5.64%) showed the stability of Aw within 14-d storage period. Trehalose and polydextrose in MSCMs with mono-carbohydrate added fraction demonstrated their high structure-forming ability expressed in high values of dynamic viscosity (>30 Pa·s), provided not by crystallization. MSCMs containing trehalose in predominant amount in the carbohydrate compositions (≥50%) showed lower average crystal size (<16 µm) compared with other MSCMs with di- and tetra-carbohydrate added fractions with predominant amount of isomaltulose and polydextrose. Isomaltulose and polydextrose added to MSCMs led to pronounced browning, while trehalose and sucrose reduced this effect in MSCMs with di- and tetra-carbohydrate added fractions. Addition of 22.55% of polydextrose to carbohydrate fraction of MSCMs caused bitterness, while 5.64% didn't affect the taste. Based on the results of all the research conducted the most optimal carbohydrate compositions to produce SCM with lower calorie, sucrose contents and stable adequate values of processing and sensory properties were trehalose (22.55%) with isomaltulose (22.55%) and trehalose (28.19%) with sucrose (5.64%), polydextrose (5.64%), isomaltulose (5.64%).

2.
J Dairy Sci ; 106(10): 6741-6758, 2023 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-37236830

RESUMEN

Studies on the storage stability of milk powder are currently fragmented and mainly affect only the area of above-zero temperatures. At the same time, there are no studies that consider the load factor when milk powder is stored in bags on a pallet. The purpose of this study was to identify the influence of various factors of industrial storage (temperature, height or layer number, and time) on the change in quality and technological properties of powdered dairy products. We placed skim milk powder (SMP) and whole milk powder (WMP) in 10 × 14 × 2 cm resealable plastic bags on a model stand simulating an industrial layout on pallets. The samples were stored for 18 mo at temperatures -30 ± 1°C, 6 ± 1°C, and 25 ± 3°C and 40 to 80% relative humidity. Samples from the control (0), 5, and 10 (lower) layers of pallets were selected for analysis on 0, 3, 6, 9, 12, 15, and 18 mo of storage for each of the temperatures. As a result, we did not detect any changes in the storage process for water activity and mass fraction of moisture. The particle size distribution of all the SMP and WMP samples changed over time. The greatest changes were observed in the WMP samples placed on the 10th layer of pallets at 25 ± 3°C, from 0 to 18 mo of storage, the mean particle size (D[4,3]) increased from 120 to 258 µm (90% of all sample particle sizes ranging from 209 to 559 µm). We found significant clumping in the WMP samples (lumps up to 5 cm), correlating with the layer and storage time. The contact angle of the samples increased from 17° (SMP) and 53° (WMP) to 40° and 71°, respectively. The insolubility index and titratable acidity did not change only in the SMP samples stored with no load applied at -30 ± 1°C and 6 ± 1°C. The heat stability of all samples stored at 25 ± 3°C showed the lowest values. The data obtained allowed us to rank the factors as "layer - time - temperature." Only the temperature of 25 ± 3°C caused critical changes in the product properties. Thus, the possibility of industrial storage of the product for up to 15 mo over the entire temperature range is confirmed.


Asunto(s)
Leche , Agua , Animales , Polvos , Temperatura
3.
Georgian Med News ; (344): 6-12, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-38236091

RESUMEN

This article delves into a profoundly significant subject: competency modeling, now an imperative for maintaining high-quality professional standards in Armenia. The contemporary landscape, shaped by post-pandemic and post-war repercussions, alongside the prominence of online education, necessitates an exploration of new prerequisites for professional expertise. The article introduces a meticulously crafted three-level model (3/2) of professional psychosocial abilities, meticulously curated to guide the trajectory of professional development - from personal growth to a pinnacle of professionalism. This comprehensive model comprises upper, middle, and lower levels: the upper level encompasses general skills, the middle level intricately incorporates the specialist's activities, work orientation, and motivations, while the lower level intricately details the emotional and behavioral voluntary attributes of individuals. Through the nuanced reshaping of professional psychosocial competencies, the article culminates in the presentation of a three-level model tailored for several high-demand professions. This presentation is grounded in a foundation of theoretical studies, empirical research, expert insights, practical recommendations, and a thorough comparative analysis.


Asunto(s)
Emociones , Responsabilidad Legal , Humanos , Armenia , Investigación Empírica , Motivación
4.
J Dairy Sci ; 105(2): 1004-1013, 2022 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-34802731

RESUMEN

The development of molecular genetic and bioinformatic systems for identifying the species of milk and the raw material composition of dairy products is of great scientific and practical importance with the purpose of introducing developments in the system for controlling the turnover of falsified products. The aim of the research is to develop a method of PCR-RFLP analysis for species identification of milk and dairy products from agricultural ruminant animals by the κ-casein gene (CSN3) with the possibility of qualitative and relative quantitative assessment of species-specific DNA of the tested biomaterial. The objects of research were samples of raw milk and milk powder, pasteurized cream, and hard and semi-hard cheeses. The developed method of species identification of milk and dairy products includes sample preparation of the studied samples, nucleic acid extraction, combined PCR-RFLP technique, detection of obtained results by the method of horizontal electrophoresis in agarose gel and their analysis, including using the developed mathematical algorithms and software. The synergistic effect established in combined operation of 2 restriction enzymes ensured their application in a mix with increased performance in an ergonomic way in the context of DNA authentication of cow, goat, and sheep milk and dairy products based on them. The specificity and sensitivity of the proposed method is potentially suitable for implementing the development of a system to control the turnover of falsified and counterfeit goods.


Asunto(s)
Queso , Leche , Animales , Caseínas/genética , Bovinos , Femenino , Genotipo , Cabras/genética , Ovinos
5.
Ter Arkh ; 92(8): 86-94, 2020 Sep 03.
Artículo en Ruso | MEDLINE | ID: mdl-33346467

RESUMEN

AIM: Study of the current state of problems of treatment of patients with tuberculosis based on literature data and their own experience. MATERIALS AND METHODS: In the Russian Federation, the number and proportion of patients with co-infection with HIV/tuberculosis continues to increase against the background of improvement in the main epidemiological indicants for tuberculosis. In 2017, 20.9% of newly diagnosed tuberculosis patients had HIV infection. The combination of the two infections significantly complicates the further improvement of the situation with tuberculosis, and the appearance of drug-resistant strains of Mycobacterium tuberculosis sometimes completely neutralizes the results of chemotherapy. The article describes the schemes of modern tuberculosis chemotherapy taking into account HIV/tuberculosis co-infection, as well as MDR in combination with surgical treatment methods, as well as analyzes the data of epidemiological monitoring of treatment of 1115 tuberculosis patients newly diagnosed in 2017 in Moscow, 360 tuberculosis patients with MDR MBT (cohort 20132014), the results of treatment with the use of new chemotherapy regimens for tuberculosis (bedaquiline, linezolid, moxifloxacin) in 36 patients, the effectiveness and safety of surgical methods in 192 patients. RESULTS: The application of new individualized anti-TB chemotherapy schedules in patients with HIV co-infection/tuberculosis with MDR-MBT has allowed to improve the treatment efficacy. The surgical intervention combined with modern chemotherapy regimens in patients with HIV/tuberculosis co-infection with MDR MBT has been proved to be effective and safe, contributes to the improving the results of treatment for this category of patients. CONCLUSION: The confluence of two global problems of co-infection HIV/TB and MDR TB, significantly prevents from the end of the tuberculosis epidemic in the world. At the same time, advances in the development and implementation of new anti-TB drugs and surgical treatment methods give hope for significant progress for resolving this situation.


Asunto(s)
Infecciones por VIH , Mycobacterium tuberculosis , Tuberculosis , Antituberculosos/uso terapéutico , Infecciones por VIH/complicaciones , Infecciones por VIH/tratamiento farmacológico , Infecciones por VIH/epidemiología , Humanos , Moscú , Federación de Rusia/epidemiología , Tuberculosis/tratamiento farmacológico , Tuberculosis/epidemiología
6.
Vopr Pitan ; 89(5): 119-126, 2020.
Artículo en Ruso | MEDLINE | ID: mdl-33211924

RESUMEN

The article considers the guidelines of the choice of identification criteria, allowing to verify and confirm the geographical name of the origin of domestic primal wine production, thereby confirming their legal status. A priori the production of wine with protected designation of origin includes the use of certain raw materials with predetermined organoleptic and physical-chemical characteristics, which can be confirmed by respective tests. The aim of the work was to develop a robust differentiating criterion that allows one to determine the authenticity and origin of wine materials relative to the standard. Material and methods. The authors presented a clustering technique, which allows on the basis of test results and developed digital identification criteria to verify the origin of wine materials from Krasnodar and Rostov-on-Don regions. As a criterion, the data from the analysis of mineral and trace element composition of primal wine production in these regions have been used. Results. The article postulates following: the main concern of clustering, methods of identification from the perspective of food production using food regression model, information on fundamental clustering metrics, fields of appliance according to the approach of the identification of the product with indication of geographic place of origin. Based on the results of the analysis of the content of 21 mineral substances (10 in µg/l and 11 in mg/l), a regressive model of the primal wine production was built. Based on this model, cluster centers were identified. The resultant model allows us to distinguish the two mentioned wine regions and form a spatial digital discrimination criterion based on the proximity to one of the established cluster centers. Conclusion. The proposed model can be adapted to identify the production of different branches of the food industry.


Asunto(s)
Espectrometría de Masas , Modelos Químicos , Oligoelementos/análisis , Vino/análisis
7.
J Dairy Sci ; 102(12): 10779-10789, 2019 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-31606218

RESUMEN

Whole milk powder (WMP) is a universal raw material component that can overcome the problem of seasonality of raw milk. It can be used to provide high-nutritional products to remote areas experiencing a raw milk shortage. Its long shelf life depends on the conditions of storage and transportation, which are recommended to be carried out in a range from 0 to 10°C. At higher temperatures, the quality of WMP deteriorates because of a substantial increase in the degradation of fat and protein fractions. A range of low negative temperatures for storage have not been systematically investigated. Previous studies have shown that freezing WMP results in protein denaturation, crystallization of lactose, and extraction of free fat, all of which reduce the quality characteristics of the product, including deterioration of solubility, quick rancidification, and microbiological changes. However, these previous studies did not simulate the possible situations of transportation and storage of milk powder at low negative temperatures that occur in practice. Given the volume of transportation, distances and climatic characteristics of transportation routes play an important role in WMP preservation. In this study, we simulated storage and transport of WMP at -20°C. The samples were periodically thawed to 10 and 20°C and examined for physicochemical, functional-technological, thermodynamic, microbiological, and organoleptic parameters. Based on our results, storage of WMP at -20°C for 40 d did not have a significant effect on its qualitative characteristics. We observed some compaction of product structure and clustering or clumping, which was reversible by slight mechanical impact. Artificial contamination of the packaging surface with yeast and molds, followed by thawing of the samples, indicated the absence of the contaminants, which was explained by possible redistribution of moisture in the system.


Asunto(s)
Productos Lácteos , Almacenamiento de Alimentos , Leche , Animales , Bovinos , Congelación , Leche/química , Polvos , Temperatura
8.
Sci Total Environ ; 687: 839-848, 2019 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-31412487

RESUMEN

The adverse effects of air pollution have been long studied in the lung and respiratory systems, but the molecular changes that this causes at the central nervous system level have yet to be fully investigated and understood. To explore the evolution with time of protein expression levels in the brain of rats exposed to particulate matter of different sizes, we carried out two-dimensional gel electrophoresis followed by determination of dysregulated proteins through Coomassie blue staining-based densities (SameSpots software) and subsequent protein identification using MALDI-based mass spectrometry. Expression differences in dysregulated proteins were found to be statistically significant with p-value <0.05. A systems biology-based approach was utilized to determine critical biochemical pathways involved in the rats' brain response. Our results suggest that rats' brains have a particulate matter size dependent-response, being the mitochondrial activity and the astrocyte function severely affected. Our proteomic study confirms the dysregulation of different biochemical pathways involving energy metabolism, mitochondrial activity, and oxidative pathways as some of the main effects of PM exposure on the rat brain. SIGNIFICANCE: Rat brains exposed to particulate matter with origin in car engines are affected in two main areas: mitochondrial activity, by the dysregulation of many pathways linked to the respiratory chain, and neuronal and astrocytic function, which stimulates brain changes triggering tumorigenesis and neurodegeneration.


Asunto(s)
Contaminantes Atmosféricos/toxicidad , Encéfalo/metabolismo , Material Particulado/toxicidad , Proteoma/metabolismo , Contaminación del Aire/estadística & datos numéricos , Animales , Metabolismo Energético/efectos de los fármacos , Masculino , Estrés Oxidativo/fisiología , Proteómica , Ratas
9.
Vopr Pitan ; 87(2): 39-43, 2018.
Artículo en Ruso | MEDLINE | ID: mdl-30592867

RESUMEN

The article presents data on the frequency of consumption of carbohydrate-containing sweet carbonated drinks by the population of the Russian Federation and their contribution to the overall caloric intake of the diet. Questioning 11 850 people of different ages (from 12 to 60 years) and sex in all eight Federal Districts of Russia has been conducted. The frequency of food consumption has been studied, and in parallel dietary intake has been assessed using 24-hour recall method. The survey showed a fairly low frequency of consumption of sweet carbonated beverages and no significant differences in the frequency of their consumption by the population of various federal districts of Russia. With a certain frequency from 55.5 to 67.3% of the population consumed sweet carbonated drinks, while 18.1-20.9% of the respondents did not consume them more often 1-3 times a month, and 1.3% of the surveyed (from 0.3% in the North- West to 3.9% in the Southern Federal District) - 2 times a day or more often. Analysis of the data obtained showed that the contribution of the carbohydrate component contained in sweet carbonated beverages, even when consumed frequently (5-6 times a week) did not exceed 3.71% of the total diet calorie intake and not more than 7.1% of the caloric value of carbohydrates' intake.


Asunto(s)
Carbohidratos de la Dieta/administración & dosificación , Ingestión de Energía , Análisis de los Alimentos , Adolescente , Adulto , Bebidas Gaseosas , Niño , Femenino , Humanos , Masculino , Persona de Mediana Edad
10.
Vopr Pitan ; 86(6): 21-28, 2017.
Artículo en Ruso | MEDLINE | ID: mdl-30592850

RESUMEN

The article analyzes data on the safety of caffeine consumption by various population groups, mainly related to risk groups (pregnant and lactating women, adolescents and children), as well as the adult population, consumers of high doses of coffee. Based on the analysis of the data contained in the published studies, it was concluded that caffeine intake in the amount of 400 mg per day in healthy adults is not associated with obvious side effects in the cardiovascular system, significant changes in reproductive function, does not lead to any or any acute consequences and does not affect the exchange of calcium in bone tissue. In placebo-controlled studies it was found that caffeine, consumed in the range of 50 to 300 mg per day, did not cause serious side effects from the cardiovascular system and the cognitive functions of children and adolescents. In the study of a large group (3747) of children aged 15-16 years who consumed caffeine-containing beverages, according to the questionnaire surveyed, personal self-esteem increased and some behavioral disorders were observed. Studies by foreign authors confirm that consumption of caffeine by pregnant women also does not have side effects on fetal development.

11.
Vopr Pitan ; 86(6): 67-73, 2017.
Artículo en Ruso | MEDLINE | ID: mdl-30592855

RESUMEN

The article presents data on the technology of production of a fermented milk product based on camel milk and the evaluation of its immunotropic properties in еthe experiment on 60 male mice F1 (CBAxC57Bl/6) with an initial body weight 17.8±0.1 g. To simulate immune suppression, mice were injected cyclophosphamide intraperitoneally (125 mg/kg b.w.). The fermented milk product was daily administered orally in a volume of 0.5 ml/mouse for 30 days (n=30). The animals of the control group (n=30) received a similar amount of distilled water. The study of the immunotropic activity of a fermented milk drink on the model of immune deficiency showed that a 30-day administration to mice caused an increase in the number of antibody-plaque-forming cells (IgM-AFC) by 1.3 times in spleen of mice (32.4×103 vs 24.7×103 per organ in the control group). The analyzed drink strengthened the effector phase of the response of the cellular response to erythrocytes of the sheep. Thus, in mice treated with distilled water (control group), the reaction index was 7.80%, while in mice of the main group it increased by 70% and amounted to 13.26%. The use of a fermented dairy product in immune-deficient mice resulted in a significant (by 63%) increase of antioxidant activity of blood plasma. At the same time, the imbalance in the functioning of antiradical protection enzymes (catalase and superoxide dismutase) reduced sharply, indicating an increase in the adaptive capacity of the organism, disturbed by the introduction of an immune suppressive compound. The obtained data indicate a pronounced immune modulating and antioxidant effects of the fermented dairy product based on camel milk, which can be used in the prevention and in complex therapy of secondary immune deficiencies and inflammatory diseases.

12.
Vopr Pitan ; 86(3): 55-58, 2017.
Artículo en Ruso | MEDLINE | ID: mdl-30645863

RESUMEN

The article analyzes the frequency of consumption of sweet carbonated beverages by various age groups (from 12 to 60 years) of the population of all Federal districts of Russian Federation. The presence of general regularities in the frequency of consumption of these drinks, regardless of the region, was established. About 5-8% of the population of different age and sex groups consumed sweet carbonated drinks with a fairly high frequency (5-6 times a week). The analysis showed that there was no dependence of the body mass index on the frequency of consumption of carbonated beverages and the absence of gender and age differences.

13.
Vopr Pitan ; 86(2): 23-31, 2017.
Artículo en Ruso | MEDLINE | ID: mdl-30645875

RESUMEN

The purpose of the current scientific work was to study the condition of antioxidant status in sportsmen of different specializations and degree of training during measured physical training and recreational periods. 71 male sportsmen (18-25 years old) were studied. The control group included 15 practically healthy student volunteers of the same age who did not train. Physical loading was a cardiac stress test. Blood was taken by means of venipuncture in the condition of rest 5 and 30 minutes after work on a biological display stand in the volume of 13 500-27 000 kgf×m. Biochemical investigations were performed in blood plasma and erythrocytes. They included measuring of ascorbic acid, α-tocopherol, caeruloplasmin, antiradical activity, intensity of chemiluminescence in consider of general antioxidant activity, enzymatic activity of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase. Comprehensive analysis of lipoprotein fractions was performed taking into consideration diagnostic rates. Dependence of the antioxidant status of sportsmen on the degree of training and specializations was determined. Thus, at rest higher content of blood plasma ascorbic acid in well-trained sportsmen (more than 23.2% in acyclic kinds of sports and 11.9% in cyclic kinds of sports) was revealed. In highly qualified sportsmen the content of this vitamin was lower by 19.6%. Also the well-trained sportsmen have lower values of erythrocyte antioxidant enzyme activities. α-tocopherol blood plasma level and glutathione peroxidase activity as well as antioxidant enzyme activity in general corresponded with blood plasma content of ascorbic acid. Blood plasma decrease of ascorbic acid in all studied groups and α-tocopherol in nontrained group was noted after dosage physical loading and recreational periods. At the background of changes of various sorts of activity of enzyme antioxidants and indicators of deep analysis of lipoprotein spectrum protection was stressed. Recommendations on sport nutrition enrichment with vitamins and mineral substances of antioxidant action were developed.

14.
Vopr Pitan ; 85(5): 86-92, 2016.
Artículo en Ruso | MEDLINE | ID: mdl-29381306

RESUMEN

Food products are the objects of the consumer's market, and human's health and life are directly depended on these product's quality and safety. In this regard, the government is paying close attention to entrepreneurial activity aimed at the production and turnover of food products, including their realization to the final consumer. In the absence of proper state control, designed to ensure, first of all, the quality and safety of food products, the consequences may be more than the negative. A significant risk to public health can represent some of the falsification of food products. Typically, these are species of assortment counterfeiting, which may lead to the use of hazardous raw substitutes. In general, the falsification is divided into: assortment, qualitative, quantitative, informational, cost and complex. Herewith it should be noted that falsification in reality is consumer frand and it's necessary to fight against it on the State and social levels. Accordingly the ideology of the measures aimed at prevention and punishability of food products falsification has been proposed.


Asunto(s)
Embalaje de Alimentos , Calidad de los Alimentos , Fraude , Legislación Alimentaria , Humanos
15.
Vopr Pitan ; 85(5): 114-9, 2016.
Artículo en Ruso | MEDLINE | ID: mdl-29381317

RESUMEN

It is well known that aging is the natural growing multisection biological process inevitably leading to limitation of body adaptive capabilities. The body ageing is the result of self-regulation mechanism limitation, reduction of their potential capabilities at molecular-genetic, energetic, cellular and general-regulatory levels. It should be noted that due to lack of the unified theory of aging the importance of nutrition factor has been acknowladged particularly initiation and intensity of the process, and the role of antioxidants is discussed much in detail. As the result of long term investigations at model and natural objects the technologies of powder and condensed sterilized gerodietetic milk based preserved foods have been developed. The multicomponent receipts modules balanced by fatty-acid and amino-acid composition as well as enriched with lycopene have been theoretically substantiated and realized. The new gerodietetic products are characterized by the following coefficients of RL3/RL6 not less than for the products: powdered - 0.871/0.615 and condensed sterilized - 0.883/0.648. The following amino-acid balance of Rp/σ protein for the products: powdered - 0.46/15.00, condensed -0.44/15.76 has been obtained. The obtained velues of the balanced criteria of the protein-lipid composition of the product are higher comparing to similar values for milk fat and protein. Two lycopene dosages in the products are provided: prophylactic - 5 mg and antioxidant - 1.5 mg in 400 ml of the reconstituted milk. On the basis of the carried out studies two technologies of the manufacture of condensed milk gerodietetic products adapted to actual conditions of concentrated milk factories have been developed.


Asunto(s)
Culinaria , Conservación de Alimentos , Alimentos en Conserva/análisis , Leche/química , Esterilización , Animales
16.
Artículo en Inglés | MEDLINE | ID: mdl-26764761

RESUMEN

We study a mechanism of activity sustaining on networks inspired by a well-known model of neuronal dynamics. Our primary focus is the emergence of self-sustaining collective activity patterns, where no single node can stay active by itself, but the activity provided initially is sustained within the collective of interacting agents. In contrast to existing models of self-sustaining activity that are caused by (long) loops present in the network, here we focus on treelike structures and examine activation mechanisms that are due to temporal memory of the nodes. This approach is motivated by applications in social media, where long network loops are rare or absent. Our results suggest that under a weak behavioral noise, the nodes robustly split into several clusters, with partial synchronization of nodes within each cluster. We also study the randomly weighted version of the models where the nodes are allowed to change their connection strength (this can model attention redistribution) and show that it does facilitate the self-sustained activity.

17.
Solid State Nucl Magn Reson ; 34(1-2): 6-13, 2008.
Artículo en Inglés | MEDLINE | ID: mdl-18420387

RESUMEN

Human manganese superoxide dismutase (MnSOD) labeled with 3-fluorotyrosine (Tyf) was complexed with the (15)N-labeled inhibitor azide ([(15)N(3)(-)]). The sample was characterized by solid-state NMR (SSNMR) spectroscopy ((19)F-MAS and (15)N-CPMAS). Employing (19)F-(15)N-REDOR spectroscopy, we determined the distances between the fluorine label in Tyrosine-34 and the three (15)N-nuclei of the azide and the relative orientation of the azide in the binding pocket of the MnSOD. A distance of R(1)=4.85A between the (19)F-label of Tyf34 and the nearest (15)N of the azide and an azide-fluorotyrosine Tyf34 angle of 90 degrees were determined. These geometry data are employed as input for molecular modeling of the location of the inhibitor in the active site of the enzyme. In the computations, several possible binding geometries of the azide near the Mn-complex were assumed. Only when the azide replaces the water ligand at the Mn-complex we obtained a geometry of the azide-Mn-complex, which is consistent with the present NMR data. This indicates that the water molecule ligating to the Mn-complex is removed and the azide is placed at this position. As a consequence the azide forms an H bond with Gln143 instead with Tyf34, in contrast to non-(19)F-labeled MnSOD, where the azide is hydrogen bonded to the hydroxy group of Tyr34.


Asunto(s)
Azidas/química , Azidas/metabolismo , Modelos Moleculares , Superóxido Dismutasa/química , Superóxido Dismutasa/metabolismo , Simulación por Computador , Flúor , Humanos , Espectroscopía de Resonancia Magnética , Isótopos de Nitrógeno , Unión Proteica , Factores de Tiempo
18.
Artif Life ; 7(4): 375-93, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-11911788

RESUMEN

In this article, we present a macroscopic analytical model of collaboration in a group of reactive robots. The model consists of a series of coupled differential equations that describe the dynamics of group behavior. After presenting the general model, we analyze in detail a case study of collaboration, the stick-pulling experiment, studied experimentally and in simulation by Ijspeert et al. [Autonomous Robots, 11, 149-171]. The robots' task is to pull sticks out of their holes, and it can be successfully achieved only through the collaboration of two robots. There is no explicit communication or coordination between the robots. Unlike microscopic simulations (sensor-based or using a probabilistic numerical model), in which computational time scales with the robot group size, the macroscopic model is computationally efficient, because its solutions are independent of robot group size. Analysis reproduces several qualitative conclusions of Ijspeert et al.: namely, the different dynamical regimes for different values of the ratio of robots to sticks, the existence of optimal control parameters that maximize system performance as a function of group size, and the transition from superlinear to sublinear performance as the number of robots is increased.


Asunto(s)
Redes de Comunicación de Computadores/estadística & datos numéricos , Conducta Cooperativa , Modelos Teóricos , Robótica/métodos , Redes de Comunicación de Computadores/instrumentación , Robótica/instrumentación
19.
Bioelectrochemistry ; 51(2): 151-6, 2000 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-10910163

RESUMEN

Decrease of redox potential (Eh) down to -550-600 mV in the Escherichia coli culture is observed during growth in either anaerobic or aerobic conditions. The E. coli growth and survival under anaerobic fermentative conditions were found to be strongly inhibited by potassium ferricyanide in the concentration of 1 mM, when Eh was decreased to -50-100 mV. This oxidant also resulted in approximately 2-fold decrease of total and N,N'-dicyclohexylcarbodiimide (DCCD)-inhibited H+ efflux, 2.5-fold inhibition in K+ influx, 1.5-fold less K+ accumulation, and delayed a decrease in Eh to negative values by bacteria. K3[Fe(CN)6] was shown to block an ATP-dependent increase in the amount of accessible thiol groups of membrane vesicles that was inhibited by DCCD, and this inhibition by the oxidant could be recovered by dithiothreitol. These effects were not observed with cells growing under aerobic conditions. The effects of K3[Fe(CN)6], an impermeable oxidant, might be explained by the fact that redox potential is a determinant in the E. coli anaerobic fermentative growth and survival that has a regulatory role in maintaining H+ and K fluxes and the number of accessible thiol groups on membrane.


Asunto(s)
Escherichia coli/efectos de los fármacos , Ferrocianuros/farmacología , Oxidantes/farmacología , Diciclohexilcarbodiimida , Escherichia coli/crecimiento & desarrollo , Escherichia coli/metabolismo , Fermentación , Transporte Iónico , Oxidación-Reducción , Potasio/metabolismo , Protones , Compuestos de Sulfhidrilo/metabolismo
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