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101.
Modulation of stability properties of bovine trypsin after in vitro structural changes with a variety of chemical modifiers 总被引:4,自引:0,他引:4
Controlled chemical modification of enzymes, targeting groups not involvedin the active site, can lead to modified catalysts that are intrinsicallymore efficient and resistant to heat and denaturing agents. Bovinepancreatic trypsin was covalently modified up to 75-85% with monomericglutaraldehyde (MGA), polymeric glutaraldehyde (PGA), oxidized sucrose andoxidized sucrose polymers (OSP 70 and OSP 400). Virtually no loss inactivity occurred upon modification. Temperature optima of trypsin shiftsfrom 45-76 degrees C and T50 from 54-76 degrees C for the best modifiedsample made with OSP. The efficiency of the modifiers in stabilization wasranked in the order: OSP 400-T > OSP 70-T > PGA-T > MGA-T >Sucrose-T. Half-life of modified enzymes also followed the same trend. Bothstabilization factor and t1/2 decreased with increasing temperatures. Thefree energy of activation for inactivation delta(deltaG*) varies from 12-20kJ/mol and the activation enthalpy delta(deltaH*) of the modified trypsinby 80-120 kJ/mol indicating stabilization. Inactivation of modified trypsinby urea is less noticeable. The character of the two-step inactivationprocess of trypsin changes with the degree of stabilization in that theduration of phase I one increased noticeably as stabilization increases.Native trypsin fluoresces less intensely showing a red shift under theinfluence of denaturation. Such a fluorescence change is not so obvious forthe modified enzymes indicating conformational stability acquired bymodification. 相似文献
102.
Grigoriev S. N. Grechishnikov V. A. Volosova M. A. Kozochkin M. P. Pivkin P. M. Isaev A. V. Peretyagin P. Yu. Seleznev A. E. Minin I. V. 《Russian Engineering Research》2020,40(1):79-82
Russian Engineering Research - The cutting of high-temperature alloys is considered. The performance of solid ceramic end mills is assessed by experimental comparison of five different designs with... 相似文献
103.
Grechishnikov V. A. Grigoriev S. N. Pivkin P. M. Isaev A. V. Volosova M. A. Peretyagin P. Yu. 《Russian Engineering Research》2019,39(12):1084-1087
Russian Engineering Research - The possibility of designing solid ceramic end mills with different geometry is considered. A mathematical model is developed for the cutting section of the mill on... 相似文献
104.
P. Schroth T. Slobodskyy D. Grigoriev A. Minkevich M. Riotte S. Lazarev E. Fohtung D.Z. Hu D.M. Schaadt T. Baumbach 《Materials Science and Engineering: B》2012,177(10):721-724
Self-organized, buried InAs quantum dots covered by an AlAs diffusion barrier were investigated under UHV conditions using grazing incidence X-ray diffraction. The experimental data is compared to the simulated results obtained by Finite Element Method and Distorted Wave Born Approximation. We have found that the simulated data could be compared to the experimental one only after convolution by the resolution element which can be estimated from the experiment. By adjusting the simulation parameters we were able to find good agreement between the simulated and the measured data. 相似文献
105.
V. Yu. Fominski S. N. Grigoriev A. G. Gnedovets R. I. Romanov 《Technical Physics Letters》2013,39(3):312-315
We have studied factors influencing the formation of particles with the structure of a spherical metal W core inside a WSe2 shell during pulsed laser deposition (PLD) of thin films of tungsten diselenide under variable conditions (buffer gas (Ar) pressure, substrate temperature). It is established that the metal core is formed at the stage of laser ablation of a synthesized WSe2 target, while the shell grows as a result of condensation, migration, and redistribution of atoms during deposition of a laser-initiated atomic flow on the surface of a growing film. Retardation of the atomic flow by a buffer gas at pressures within 2–10 Pa does not ensure activation of the shell condensation process on the metal core in the gas phase. Increasing the substrate temperature from room temperature up to 250°C leads to transformation of the shell structure from amorphous into laminar. 相似文献
106.
The concept of precision standard for the domain of radiation measurements is formulated. In accordance with international recommendations for the quantitative expression of the precision of measurements, the concept of the uncertainty of results is used and its application to problems of radiation monitoring of objects is demonstrated. The basic principles underlying the application of criteria that define the conformance of results to safety standards are formulated. An example of a conformance criterion for a typical situation of radiation monitoring is given. 相似文献
107.
The limits of applicability of the SINAD method when measuring the signal-to-noise ratio, often used to estimate the sensitivity
of receivers, are investigated. It is shown that if the systematic component of the error in measuring the harmonic coefficients
of the generator being measured – the signal source – and of the high-frequency part of the receiver is ignored, there will
be an unlimited increase in the error in measuring the sensitivity when the signal-to-noise ratio approaches the limiting
value. The approach described enables the contribution to this error of components arising from distortions and noise of different
origin to be separated. 相似文献
108.
V. Yu. Fominskii S. N. Grigoriev A. G. Gnedovets R. I. Romanov 《Technical Physics Letters》2012,38(7):683-686
Experimental data and results of mathematical modeling have been used to determine the energy characteristics of an ion beam used to assist pulsed laser deposition (PLD) of MoSe2 layers under conditions of positive high-voltage pulses applied to a laser-ablated target. It is shown that PLD assisted by implantation of ions at energies up to 100 keV can be used to obtain MoSe2 coatings on 57Fe-containing substrates. Analysis of the concentration-depth profiles of Mo, Se, and 57Fe atoms and the phase composition of a near-surface layer in samples shows evidence for mass transfer domination in thermal spikes and a significant influence of ion impact on the structure of this layer at the nanoscale. These features are manifested by the formation of a nanocomposite structure with inclusions of a specific hexagonal FeSe phase. The obtained results demonstrate the existence of principally new possibilities of using the proposed modified PLD method for controlled formation of solid lubricant coatings with improved properties. 相似文献
109.
V. V. Zuev S. N. Grigoriev V. Yu. Fominski M. A. Volosova A. A. Soloviev 《Technical Physics Letters》2017,43(9):790-793
The possibility of detecting H2 by registering the thermal electromotive force signal, which arises between the surfaces of 6H-SiC plates with a thickness of 400 μm, is established. The working surface of the plates is modified by deposition of a WO x film and catalytic Pt. An ohmic contact (Ni/Pt) is created on the rear surface of the plate, and this surface is maintained at a stabilized temperature of 350°C. The temperature gradient through the plate thickness arises due to the cooling of the working surface with the air medium. The delivery of H2 into this medium up to a concentration of 2% gives rise to a 15-fold increase in the electric signal, which considerably exceeds the Pt/WO x /SiC/Ni/Pt system’s response registered in the usual way by measuring the current–voltage dependence. In this case, an additional power source for the registration of the thermal electromotive force is not required. 相似文献
110.
PV Rabins 《Canadian Metallurgical Quarterly》1997,277(24):1933-1934