Some physico-chemical properties and structural changes of bovine beta-casein upon glycation

The studies on casein structure modification contribute to better understanding of the role of nonamino acid components in forming casein complexes and improving ways of protein functionality. The objective of the experiments was to explain the influence of bovine milk casein glycation on some physico-chemical properties and structural changes. From the the analysis of glycation rate curve the reaction of the first order range can be assumed during the first 24 h, turning to a mixed type afterwards. The isoelectric point and molecular weight of beta-casein increased after glycation and the electrophoretic mobility was slightly modified. The structural changes were also confirmed by different absorption spectra in UV and a better heat stability of the modified beta-casein. The findings showed higher solubility with modified beta-casein. The glycation caused changes in beta-casein, modifying its susceptibility to the trypsin hydrolysis.     

The assessment of DNA damage in lymphocytes of wooden furniture workers

Single-strand breaks (SSB) and DNA repair were detected in peripheral lymphocytes derived from workers of a furniture factory in a non-polluted region of Poland. The workers were exposed to wood dust (n = 19), or to the dust and varnishes or lacquers together (n = 5). Four groups were studied simultaneously: (a) exposed workers smokers of cigarettes (n = 14), (b) nonexposed smokers--control (n = 14), (c) exposed workers' nonsmokers (n = 14), (d) exposed nonsmokers (n = 10). In exposed workers DNA SSB and DNA repair were statistically significantly increased. DNA SSB was clearly higher in the smoking workers than in the smoking controls. Cigarette smoking itself has produced no evident increase in the frequency of DNA SSB in the control group. Occupational exposure had a significant effect on DNA repair in non stimulated lymphocytes both in smoking and nonsmoking workers.     

The technology of extrusion‐fusion welding of polythene and polypropylene butt and T joints

Abstract

Laser welding, regarded as one of the welding techniques for use with steel materials and employed in the fabrication of automobiles, has increasing applications in the manufacture of transmission systems and car bodies; however, there are not many examples of application to aluminium alloy components.¹ The reasons for this are thought to be as follows: aluminium alloys have a higher laser reflectivity compared with that of steel materials; consequently an even higher power laser is required to input energy to the material for welding and also, due to the low viscosity of molten aluminium alloy, stable welding is difficult.^2,3     

Effect of rapid thermally nitrided titanium films contacting silicided and nonsilicided junctions

The effect of rapid thermally nitrided titanium films contacting silicided (titanium disilicided) and nonsilicided junctions has been studied in the temperature range of 800 to 900°C. The rapid thermal nitridation of titanium films used as diffusion barriers between aluminum and silicon, has a major impact on shallow junction complementary metal oxide semiconductor technologies. During the process of rapid thermal nitridation, the dopants in the junctions undergo a redistribution and affect the electrical properties of shallow junction structures. This work focuses on using novel contact resistance structures to measure the variation in electrical parameters for rapid thermally nitrided titanium films annealed at different temperatures. The self-aligned silicide (salicide) junctions in this study were formed using rapid thermally annealed titanium films. Electrical contact resistance testers were used to measure the interface contact resistance between the salicide and silicon, as well as between the metal and the salicide. The results show that the interface contact resistance to the p⁻ diffused salicided junctions increases with rapid thermal nitridation of the additional titanium film, whereas the interface contact resistance to the n⁻ diffused salicided junction shows a decrease. Further, as a function of the rapid thermal annealing temperature (for fixed titanium thickness), the nonsalicided diffusions show an increase in the interface contact resistance. The boron profiles at the TiSi₂/Si interface obtained using secondary ion mass spectroscopy show an excellent qualitative agreement with the electrical results for each of the conditions discussed. The films were also characterized using Rutherford back-scattering spectrometry and transmission electron microscopy and the results show good agreement with the measured variation in electrical parameters. These results also show that as the anneal temperature is increased, the TiN thickness increases, further the change in the silicide/silicon interface position with the nitridation of the additional titanium layer was verified. This work was carried out when the author was working at AT&T Bell Labs     

Composition of proteins in wheat grain streams obtained by sieve classification

Sieve classification was used to prepare grain streams of distinct protein content and composition. Both reverse‐phase high‐performance liquid chromatography and two‐dimensional electrophoresis revealed differences in protein composition between large (F1), medium (F2–F3), and small (F4) kernel fractions of three Polish cultivars: Sukces and Tonacja (winter wheats) and Nawra (spring wheat). Statistical analysis indicated that grain protein composition is affected by the cultivar and kernel size, as well as by interaction of these traits. The albumin/globulin and glutenin fractions showed a tendency to decrease with diminishing kernel size. The gliadin content was affected to a greater extent by the kernel size than by the wheat genotype. The highest content of gliadins was observed in the smallest and the largest kernel fractions. Copyright © 2007 Society of Chemical Industry     

A laboratory model for evaluating the behavior of heavy metals in an aquatic environment

A dynamic biological system capable of simultaneously distinguishing between bioaccumulation and biomagnification through successive trophic levels in an aquatic ecosystem is described. The organisms used in the system were algae, predominantly Scenedesmus sp., Daphnia magna, fresh water mussels (Ligumia sp. and Margaritifera sp.) and the fathead minnow, Pimephales promelas.Thiosulfate complexed mercury and silver were each studied at two concentrations. The water and organisms were analyzed for the metals periodically during the 10-week tests. Both mercury and silver can be bioaccumulated by fish. The concentration factors for mercury are greater than for silver. Further, mercury is biomagnified by fish whereas silver is not. Fresh water mussels were found to be poor indicator species for metal contamination.     

A Genetically Encoded Diazirine Analogue for RNA–Protein Photo-crosslinking

Ultraviolent crosslinking is a key experimental step in the numerous protocols that have been developed for capturing and dissecting RNA–protein interactions in living cells. UV crosslinking covalently stalls dynamic interactions between RNAs and the directly contacting RNA-binding proteins and enables stringent denaturing downstream purification conditions needed for the enrichment and biochemical analysis of RNA–protein complexes. Despite its popularity, conventional 254 nm UV crosslinking possesses a set of intrinsic drawbacks, with the low photochemical efficiency being the central caveat. Here we show that genetically encoded photoreactive unnatural amino acids bearing a dialkyl diazirine photoreactive group can address this problem. Using the human iron regulatory protein 1 (IRP1) as a model RNA-binding protein, we show that the photoreactive amino acids can be introduced into the protein without diminishing its RNA-binding properties. A sevenfold increase in the crosslinking efficiency compared to conventional 254 nm UV crosslinking was achieved using the diazirine-based unnatural amino acid DiAzKs. This finding opens an avenue for new applications of the unnatural amino acids in studying RNA–protein interactions.     

Database of biologically active peptide sequences

Proteins are sources of many peptides with diverse biological activity. Such peptides are considered as valuable components of foods with desired and designed biological activity. Two strategies are currently recommended for research in the area of biological activity of food protein fragments. The first strategy covers investigations on products of enzymic hydrolysis of proteins. The second one is synthesis of peptides identical with protein fragments and investigations using these peptides. It is possible to predict biological activity of protein fragments using sequence alignments between proteins and biologically active peptides from database. Our database contains currently 527 sequences of bioactive peptides with antihypertensive, opioid, immunomodulating and other activities. The sequence alignments can give information about localization of biologically active fragments in protein chain, but not about possibilities of enzymic release of such fragments. The information is thus equivalent with this obtained using synthetic peptides identical with protein fragments. Possibilities offered by the database are discussed using wheat α/β-gliadin, bovine β-lactoglobulin and bovine β-casein (including influence of genetic polymorphism and genetic engineering on amino acid sequences) as examples.     

The Ampere and Electrical Standards

This paper describes some of the major contributions to metrology and physics made by the NIST Electricity Division, which has existed since 1901. It was one of the six original divisions of the National Bureau of Standards. The Electricity Division provides dc and low-frequency calibrations for industrial, scientific, and research organizations, and conducts research on topics related to electrical metrology and fundamental constants. The early work of the Electricity Division staff included the development of precision standards, such as Rosa and Thomas standard resistors and the ac-dc thermal converter. Research contributions helped define the early international system of measurement units and bring about the transition to absolute units based on fundamental principles and physical and dimensional measurements. NIST research has helped to develop and refine electrical standards using the quantum Hall effect and the Josephson effect, which are both based on quantum physics. Four projects covering a number of voltage and impedance measurements are described in detail. Several other areas of current research at NIST are described, including the use of the Internet for international compatibility in metrology, determination of the fine-structure and Planck constants, and construction of the electronic kilogram.