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  • (1998) Thomas, Torsten; Cavicchioli, Ricardo
    Journal Article
    To identify structural features important for low temperature activity in archaeal proteins, elongation factor 2 (EF-2) genes (aef2) were sequenced from psychrophilic, mesophilic and thermophilic methanogens. Scatter plots were used to compare evolutionary distances for EF-2 amino acid sequences vs. 16S-rRNA sequences from methanogens growing at diverse temperatures. The absence of a temperature bias for the rate of protein vs. nucleic acid evolution demonstrated the importance of comparing closely related proteins in order to identify changes indicative of thermal adaptation. Three-dimensional modelling of the new EF-2 sequences enabled the identification of amino acid residues that may be important for conferring low temperature activity and included greater structural flexibility produced by fewer salt bridges, less packed hydrophobic cores and the reduction of proline residues in loop structures.

  • (1999) Gosbell, Iain; Ross, Alfred; Turner, Ian
    Journal Article

  • (1997) Choi, Caroline; Han, Shaowei; Andrikidis, C; Zhao, Yong
    Journal Article
    Flux pinning force and irreversible line of the melt-textured-growth (MTG) YBa2Cu3O7−y (Y-123) crystals with various sizes of secondary phase particles have been investigated by measuring the magnetization of the samples under a series of magnetic fields up to 55 kOe. The magnetic Jc and the pinning force are found to increase as the particle size decreases. A linear relationship between Jc and 1/D has been obtained where D is the average size of the precipitates. The highest Jc value has reached 4×104 A/cm2 at 77 K and 40 kOe in a sample with a high density of the precipitates in nanometre size. Two peaks are observed in the Fp(H) curve in which the position of the first peak is independent of the particle size. The height and the location of the second peak is sensitive to the particle size, indicating that the peak is associated with the small particles.