Domain structure of the Fib-1 and Fib-2 regions of human fibronectin. Thermodynamic properties of the type I finger module

The stability of the Fib-1 (29 kDa) and Fib-2 (19 kDa) fragments of human fibronectin as well as several different subfragments and isolated type I "finger" modules were studied under various solvent conditions by differential scanning calorimetry and fluorescence spectroscopy. It was established that all fibronectin fingers constitute independently folded domains whose melting temperatures range from 54 to 108 degrees C. The difference between heat capacities of the native and denatured states (delta Cp) is low, about 0.03 cal/K-g, which is consistent with the relatively low percentage of hydrophobic amino acids and the consequent small change in non-polar surface area exposed to the solvent upon denaturation. The free energy of unfolding at 25 degrees, as calculated from the calorimetric data or measured directly by titration with GdmSCN is also small, in the range of 2.4 to 6.7 kcal/mol. The small delta G value and its flat dependence on temperature (determined by delta Cp) translates the small variations in delta G between fingers into large variations in tm. The small value of delta G also indicates that finger modules are structurally rather fragile which may account for their sensitivity to proteolysis; almost any cleavage within either of the two disulfide loops destroys the cooperative structure and abolishes the corresponding melting transition. The fact that some fingers exhibit large decreases in tm upon separation from more stable neighbors with which they interact can also be viewed as a consequence of the low values of delta G and delta Cp.     

Photoelectric properties of the photoconducting film composites based on ferrocenyl‐ and carbazolyl‐containing oligomer doped with polymethine dye

New photosensitive polymeric film composites based on oligomer containing ferrocenyl and carbazolyl fragments doped with symmetric polymethine dye are synthesized. Their photoelectric properties are investigated. Photovoltaic properties of these composites are detected. The mechanisms and peculiarities of the photovoltaic and photodielectric effects are discussed.     

Primary structure of gene H of cattle plague virus strain K]

The paper analyzes the standard legal and methodological assurance of the quality and safety of animal food raw materials and foodstuffs (meat, meat products, fish, shellfish, crayfish and their processing products) by the parasitic purity rates according the requirements under the Russian Federation's laws "On Sanitary and Epidemiological Well-Being of the Population", "On Protection of Consumer's Rights", "On Certification of Products and Services", those of SanPiN, such as 2.3.2.560-96 "Sanitary Requirements for the Quality and Safety of Food Raw Materials and Foodstuffs" and 3.2.569-96 "Prevention of Parasitic Diseases in the Russian Federation".     

Parallel machine problems with equal processing times: a survey

The basic scheduling problem we are dealing with is the following. There are n jobs, each requiring an identical execution time. All jobs have to be processed on a set of parallel machines. Preemptions can be either allowed or forbidden. The aim is to construct a feasible schedule such that a given criterion is minimized. In this paper, we survey existing approaches for the problem class considered.     

Synthesis of the nitrogen-fixing enzyme system in oligonitrophilic bacteria

Oligonitrophilic bacteria were cultivated on a medium containing only 2.5--10.0 mg/litre of nitrogen compounds. They assimilated elementary nitrogen only after utilization of these nitrogen compounds during growth and formation of nitrogen-fixing enzyme system. Their cells grown on a medium containing high concentrations of bound nitrogen did not fix nitrogen during further incubation in the atmosphere of 15N; therefore, the enzymes involved in nitrogen fixation were induced. These organisms are characterized by diauxia during their growth on media containing "start" doses of nitrogen. Enzymes catalysing nitrogen fixation in azotobacter are also induced. But, contrary to oligonitrophilic bacteria, the azotobacter does not require nitrogen compounds in the medium in order to adapt to molecular nitrogen, and its growth curve is not of a biphasal character. These data and the evidence of other authors suggest that all nitrogen-fixing microorganisms are characterized by the induced, not constitutive, enzymes involved in reduction of molecular nitrogen.     

Biogenesis of cellulolytic enzymes by Trichoderma ligorum on media with "inductor"

Identical distribution of C2- and Cx-cellulase activities of enzyme complexes produced by Trichoderma lignorum on a medium with lactose, a soluble "inductor", and on a medium with cellulose was found by means of disc elestrophoresis in polyacrylamide gel. The maximum rate of synthesis of cellulases on the medium with lactose was registered during the highest deceleration, and even complete cessation, of the fungal growth. During this phase, only one electrophoretically homogeneous cellulase component with Rf of 0.44 possessing all types of the cellulase activity is present in the cultural broth. In the course of growth of the fungus on cellulose after 48 hours, also only one electrophoretically homogeneous component with Rf of 0.44 was found in the cultural broth when the rate of the substrate degradation was highest. The appearance of minor protein components with the activity of cellulase at later stages of cultivation after cessation of the fungal growth is supposed to be caused by modification of the main cellulase component with Rf of 0.44 by the growth medium.     

Influence of the dentate fascia on the sensory responses of neurons in hippocampal field CA3

In experiments with unanaesthetized rabbits the influences of electric stimulation of the dentate fascia (DF) on the extracellularly recorded spontaneous and evoked activity of the CA3 neurones were investigated. Stimulation of a fixed locus in the DF during recording in the CA3 by a microelectrode, shifted along the longitudinal axis of the hippocampus, supported the notion of the topical, "segmental" organization of connections between the DF and CA3. A relatively narrow "active zone" (approximately 700 nm) appeared in the CA3 during the threshold DF stimulation: it was bordered by zones with predominantly inhibitory responses to stimulation. The CA3 neurones in the "active zone" rapidly lost their reactivity to sensory stimuli. In the "inhibitory" and "zero" zones the normal level of reactivity to sensory stimuli was preserved.     

Determining the air excess in the heating of coke furnaces. 1. Adequacy of the chemical analysis

The traditional chemical framework for determining the air excess in the heating of coke furnaces is discussed. In determining the air excess, no account is taken of numerous chemical reactions associated with the combustion of the fuel gas in the heating channels. In fact, it is necessary to determine combustion products other than oxygen, carbon monoxide, and carbon dioxide: specifically, hydrogen, methane, nitrogen oxides, and sulfide. The formula for the air excess must therefore be corrected to include the content of those components.     

New constructions of 1D and 2D generalized Kravchenko-Kotel’nikov theorems on the basis of atomic function up(t)

New constructions of 1D and 2D generalized Kravchenko-Kotel’nikov sampling theorems based on atomic function up(t) are proposed and justified. The theorems are rigorously proved for both 2D and 1D cases. A simulation performed to analyze the construction and improvement of new series estimates shows their advantage over the classical Whittaker-Kotel’nikov-Shannon series.     

Relationship between effective and ideal separation factors for distillation and sublimation

General aspects of the relationship between the effective (β) and ideal (β_i) separation factors for the distillation and sublimation of elemental substances containing low-volatile impurities have been established. It has been shown that the difference between β and β_i may be both insignificant and extremely large: 4 to 16 orders of magnitude or even more. In host–impurity systems having the same host, the difference between β and β_i decreases as β_i approaches unity, all other factors being the same. The difference between β and β_i is moderate, within one order of magnitude, when βi differs from unity by no more than three orders of magnitude. In a given host–impurity system, the difference between β and β_i increases with decreasing impurity concentration. In individual systems, the difference between β and β_i increases with increasing yield at a given initial impurity concentration.