Distinct stability of recombinant L and H subunits of human ferritin: calorimetric and ANS binding studies

Thermodynamic and pH stability of recombinant human L- and H-ferritins were probed by differential scanning calorimetry and 8-anilino-1- naphthalenesulfonate (ANS) binding in the pH range 2-7. At pH 2.0-2.8 they were dissociated into subunit monomers and in this pH interval the H-subunit displayed a single calorimetrically-revealed domain with properties of a molten globule-like state: low enthalpy (6.3-8.0 J/g or 169-172 kJ/mol) and Tm of thermal unfolding (approximately 50 degrees C), a wide transition range (approximately 20 degrees C) and high ANS binding. In contrast, at pH 2 the L-ferritin subunit showed two calorimetric domains with Tm of 35 and 40 degrees C with similar unfolding enthalpies and with moderate extent of interactions, as indicated by the ratio of calorimetric enthalpy (293.9 kJ/mol) and van't Hoff enthalpy (174.2 kJ/mol) for the thermal transition. A pH increase from 2.0 to 2.8 determined the coupling of the two domains into a single cooperative folding unit and drastic increase of the transition temperature (from 37 to 80 degrees C). The contacts between the two domains in the L-subunit appeared to contribute to about 30% of the total stabilization free energy. The unfolding enthalpies, heat capacity changes and pronounced ANS binding of the L-subunit at pH 2.0- 2.8 indicated that part of the structure lacked 'meltable' tertiary interactions. The results indicate that H- and L-subunits are stabilized by largely different intra-chain interactions with a critical contribution to L-subunit stability of embedded salt bridge(s) absent in the H-subunit.      

Thermal protection of an area from an incident gas jet

Results are offered from an experimental study of the decrease in thermal effect of a jet upon a normally oriented surface produced by introduction of cold air or water into the central portion of the jet.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 4, pp. 555–558, April, 1992.     

Mass spectrometry of chlorine monolayers on solid substrates

A new method is proposed for determining chlorine traces in monolayer films adsorbed on solid substrates. The method is based on secondary-ion mass spectrometry (SIMS) with the formation of positive chlorine-containing molecular ions. In contrast to the traditional method making use of inert gases, the secondary ions are generated by bombarding the chlorine-containing substrate with a beam of methane molecules. This leads to the formation of CCl ₂ ⁺ ions with molecular masses of 82, 84, and 85 amu. These peaks are reliably observed in the form of a doublet not masked by the peaks of ions of the substrate material and the other background reaction products.     

Properties of Passivating Coatings Based on Lead Borosilicate Glass

The charge distribution in passivating coatings based on lead borosilicate glass was studied by temperature-dependent flat-band voltage measurements. The results indicate the presence of two types of charge in the interfacial layer of the glass: a temperature-independent negative charge and a variable positive charge, which increases with temperature. The variable charge is shown to be associated with the donor states present in the interfacial layer, which exchange electrons with the semiconductor bulk.     

Physical and Mechanical Properties of Plasticized HMX under Effect of Mechanical Loadings, Temperature Drops and Shock Waves

During their life cycles, energetic materials (EM) can be subjected to various external effects, including non-authorized effects. Due to these effects, irreversible changes can occur in EM structures that, in turn, can be the reason for change of their physical and mechanical properties.     

Improving the technology for gzhel' porcelain decorated with underglaze cobalt pigments

Translated from Steklo i Kerainika, No. 8, pp. 20–22, August, 1991.     

Ellipsometric monitoring in label-free microarray biotechnologies

The surface of biochips prepared on the basis of silicon wafers for studies of reactions of pre-immobilized oligonucleotides and protein molecules was analyzed by high-resolution scanning ellipsometry. The hybridization interactions of nucleic acid (duplex formation in the reaction of an amplicon of the influenza A virus matrix protein gene with probe molecules), sorption of protein molecules, and protein-protein interactions on the surface of the biochip were detected. It was shown that pre-sorption of gold nanoparticles led to greater efficiency of immobilization of protein molecules on the biochip. The experimental data suggest that that ellipsometry is a highly sensitive, nondestructive and inexpensive label-free method for the detection of the biochip surface, which is suitable for quantitative analysis of reactions of biomolecules.