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The precursors that appear when geological disasters occur are geotechnical deformations. This paper studies the TDR (Time Domain Reflection) measurement technology for the distributed measurement of geotechnical deformation using parallel spiral wire as a sensor, which is used for monitoring and early warning detection of geological disasters. Based on the mechanism of the electromagnetic field distribution parameters of the parallel spiral sensing wire, the relationship between the stretching amount of the parallel spiral wire and the change in its characteristic impedance is analyzed. When the parallel spiral wire is buried in the soil, the geotechnical deformation causes the parallel spiral wire to be stretched, and according to its characteristic impedance change, the stretching position and the stretching degree can be obtained, thus realizing the distributed measurement of geotechnical deformation. Based on this principle, the TDR measurement system is developed, and a local single-point stretching amount and stretching positioning experiment are designed for the parallel spiral sensing line to verify the effectiveness of the sensing technology and the usability of the measurement system.

Because the insolubility of the scrapie prion protein (PrPSc) has frustrated structural studies by x-ray crystallography or NMR spectroscopy, we used electron crystallography to characterize the structure of two infectious variants of the prion protein. Isomorphous two-dimensional crystals of the N-terminally truncated PrPSc(PrP 27-30) and a miniprion (PrPSc106) were identified by negative stain electron microscopy. Image processing allowed the extraction of limited structural information to 7 Å resolution. By comparing projection maps of PrP 27-30 and PrPSc106, we visualized the 36-residue internal deletion of the miniprion and localized the N-linked sugars. The dimensions of the monomer and the locations of the deleted segment and sugars were used as constraints in the construction of models for PrPSc. Only models featuring parallel β-helices as the key element could satisfy the constraints. These low-resolution projection maps and models have implications for understanding prion propagation and the pathogenesis of neurodegeneration.

The complex topologies of large multi-domain globular proteins make the study of their folding and assembly particularly demanding. It is often characterized by complex kinetics and undesired side reactions, such as aggregation. The structural simplicity of tandem-repeat proteins, which are characterized by the repetition of a basic structural motif and are stabilized exclusively by sequentially localized contacts, has provided opportunities for dissecting their folding landscapes. In this study, we focus on the Erwinia chrysanthemi pectin methylesterase (342 residues), an all-β pectinolytic enzyme with a right-handed parallel β-helix structure. Chemicals and pressure were chosen as denaturants and a variety of optical techniques were used in conjunction with stopped-flow equipment to investigate the folding mechanism of the enzyme at 25 °C. Under equilibrium conditions, both chemical- and pressure-induced unfolding show two-state transitions, with average conformational stability (ΔG° = 35 ± 5 kJ·mol−1) but exceptionally high resistance to pressure (Pm = 800 ± 7 MPa). Stopped-flow kinetic experiments revealed a very rapid (τ < 1 ms) hydrophobic collapse accompanied by the formation of an extended secondary structure but did not reveal stable tertiary contacts. This is followed by three distinct cooperative phases and the significant population of two intermediate species. The kinetics followed by intrinsic fluorescence shows a lag phase, strongly indicating that these intermediates are productive species on a sequential folding pathway, for which we propose a plausible model. These combined data demonstrate that even a large repeat protein can fold in a highly cooperative manner.

This chapter contains sections titled: Properties of Base Pairing The Double Helix

The histone octamer core of the nucleosome is a protein superhelix of four spirally arrayed histone dimers. The cylindrical face of this superhelix is marked by intradimer and interdimer pseudodyad axes, which derive from the nature of the histone fold. The histone fold appears as the result of a tandem, parallel duplication of the \"helix-strand-helix\" motif. This motif, by its occurrence in the four dimers, gives rise to repetitive structural elements-i.e., the \"parallel β bridges\" and the \"paired ends of helix I\" motifs. A preponderance of positive charges on the surface of the octamer appears as a left-handed spiral situated at the expected path of the DNA. We have matched a subset of DNA pseudodyads with the octamer pseudodyads and thus have built a model of the nucleosome. In it, the two DNA strands coincide with the path of the histonepositive charges, and the central 12 turns of the double helix contact the surface of the octamer at the repetitive structural motifs. The properties of these complementary contacts appear to explain the preference of histones for double-helical DNA and to suggest a possible basis for allosteric regulation of nucleosome function.

This chapter contains sections titled: Interaction of Human Body and GNSS Antennas Effects of Human Body on GNSS Mobile Terminal Antennas in Difficult Environments References