How to improve nature: study of the electrostatic properties of the surface of alpha-lactalbumin

It was recently shown that alpha-lactalbumin interacts with histones and simple models of histone proteins such as positively charged polyamino acids, suggesting that some fundamental aspects of the protein surface electrostatics may come into play. In the present work, the energies of charge-charge interaction in apo- and Ca(2+)-loaded alpha-lactalbumin were calculated using a Tanford-Kirkwood algorithm with either solvent accessibility correction or using a finite difference Poisson-Boltzmann method. The analysis revealed two major regions of alpha-lactalbumin that possessed highly unfavorable electrostatic potentials: (a) the Ca(2+)-binding loop and its neighboring residues and (b) the N-terminal region of the protein. Several individual mutants were prepared to neutralize specific individual surface acidic amino acids at both the N-terminus and Ca(2+)-binding loop of bovine alpha-lactalbumin. These mutants were characterized by intrinsic fluorescence, differential scanning microcalorimetry and circular dichroism. The structural and thermodynamic data agree in every case with the theoretical predictions, confirming that the N-terminal region is very sensitive to changes in charge. For example, desMet D14N mutation destabilizes protein and decreases its calcium affinity. On the other hand, desMet E1M and desMet D37N substitutions increase the thermal stability and calcium affinity. The Met E1Q is characterized by a marked increase in protein stability, whereas desMet E7Q and desMet E11L display a slight increase in calcium affinity and thermal stability. Examination of the unfavorable energy contributed by Glu1 and the energetically favorable consequences of neutralizing this residue suggests that nature may have made an error with bovine alpha-lactalbumin from the viewpoint of stabilizing structure and conformation.     

Fuel elements based on spherical fuel pellets with a protective coating for enhanced-safety reactors

The principal investigations performed at the Scientific and Industrial Association Luch on the development of fuel elements based on spherical pellets of nuclear fuel with protective ceramic and metallic coatings for HTGR. VVéR, and other types of reactors are reviewed. The main solutions concerning the construction and technical and materials-science aspects of the fabrication of fuel micropellets, fuel microelements, and fuel elements of different modifications (spherical, rod-shaped) are examined. The characteristics of fuel elements and their components at the fabrication and preliminary and reactor testing stages are presented. It is shown that because of additional protective barriers the fuel elements which have been developed effectively confine the fission products and ensure safety. The directions of possible practical utilization of the fuel elements developed for improved enhanced-safety reactors are described. 7 figures, 6 tables, 42 references. Scientific and Industrial Association Luch, Translated from Atomnaya énergiya, Vol. 87, No. 6, pp. 451–462, December, 1999     

Changes in the properties and composition of cementite in the process of graphitization

Metal Science and Heat Treatment -     

Operation of gas pipe at working pressures up to 11.8 MPa

Full-scale hydraulic and pneumatic tests of spiral- and straight-seam gas pipe (diameter 1420 mm) produced by OAO Volzhskii Trubnyi Zavod are described. Satisfactory and equivalent resistance of different types of pipe to ductile failure is established. In terms of its operational characteristics, the pipe may be used in pipelines of working pressure up to 11.8 MPa in any Russian climatic zones, including the Far North.     

Hydraulic resistance of annular,and disperse-annular flow conditions of a two-phase mixture

Results of experimental research on hydraulic resistance in the case of annular and disperse-annular systems of movement of a two-phase mixture are given.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 18, No. 3, pp. 409–413, March, 1970.