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  • 1
    Electronic Resource
    Electronic Resource
    System for electron paramagnetic resonance measurements at high pressure and low temperature (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3877-3882 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Major improvements have been made on the sensitive high pressure electron paramagnetic resonance (EPR) system developed previously in 1978 at this laboratory. These changes allow low temperature measurements and provide a more stable signal. The high pressure EPR cell is placed inside a vacuum chamber to provide thermal isolation, so that the system may be cooled by a closed cycle refrigerator to temperatures between 45 and 60 K, depending on the energy input to the modulation coil. The combination of high pressure and low temperature greatly expands the thermodynamic range over which EPR measurements can be made. An improved and effective method of forming a conductive surface to define the microwave cavity is presented. This method successfully avoids the deterioration of the sapphire's polished surface which causes premature breaking of the sapphire high pressure anvil, and therefore significantly improves the reliability of the system at high pressure. Other modifications to the system, such as the microwave coupling method, the modulation coil, and selecting of a hydrostatic pressure fluid, are discussed. EPR measurements on BaTiO3 have been made at temperatures ranging from 233 to 353 K and pressures from 0 to 4.4 GPa. High quality signals can be realized in the entire pressure and temperature range. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148041
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  • 2
    Electronic Resource
    Electronic Resource
    Functional Analyses of Natural Variation in Sp1 Binding Sites of a TATA-Less Promoter (1999)
    Springer
    Journal of molecular evolution 49 (1999), S. 736-749 
    Details
    ISSN: 1432-1432
    Keywords: Key Words: Binding affinities — phylogeny — evolutionary adaptation — transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Within the lactate dehydrogenase-B (LdhB) proximal promoter is a region with multiple in vivo footprinted sites that resembles the binding site for the transcription factor SP1. Like many sequences that regulate transcription rate, these Sp1 binding sites are well conserved among species of the teleost fish Fundulus. The only exception is in the northern population of F. heteroclitus, where there are many changes in the Sp1 binding sites. These changes affect footprinting patterns, measures of promoter strength, and are associated with the adaptive increase in Ldh-B transcription rates. Reported here is data that demonstrates that Fundulus hepatocyctes have an SP1-like protein; in comparison to human SP1 protein, it has similar specificity and size and a greater affinity for the consensus Sp1 site. This Fundulus hepatocyte SP1-like protein as well as the human SP1 protein binds the Ldh-B Sp1 sites. Sequence variation in the northern Sp1 region eliminates the ``preferred'' Sp1 binding site, yet these northern Sp1 sites have significantly greater affinity for the SP1 protein than either the Sp1 sites from southern F. heteroclitus (∼ 1.6-fold) or the consensus Sp1 site (GGGCGG; ∼ 1.8-fold). Furthermore, the Ldh-B Sp1 sites also bind non-SP1 proteins, and the extent of binding is affected by the sequence variation in the proximal promoter. These data suggest that natural variation in Sp1 sites affect binding of transcription factors and may effect a modest change in transcription rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006596
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  • 3
    Electronic Resource
    Electronic Resource
    Cortical microtubule involvement in bordered pit formation in secondary xylem vessel elements ofAesculus hippocastanum L. (Hippocastanaceae): A correlative study using electron microscopy and indirect immunofluorescence microscopy (1997)
    Springer
    Protoplasma 197 (1997), S. 64-75 
    Details
    ISSN: 1615-6102
    Keywords: Aesculus hippocastanum L ; Microtubules ; Indirect immunofluorescence microscopy ; Vascular cambium ; Secondary xylem vessel elements ; Bordered pits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A correlative study, using indirect immunofluorescence microscopy (IIF) of anti-α-tubulin stained sections and transmission electron microscopy (TEM), gave details of the involvement of cortical microtubules (CMTs) in the development of bordered pits in secondary xylem vessel elements ofAesculus hippocastanum L. In addition, aspects of wall cytochemistry were studied during this process using the Thiéry (PATAg) test, immunolocalization with the monoclonal antibodies JIM5 and JIM7, and a range of other cytochemical procedures. IIF showed that the alternately-arranged pits are pre-figured as perforations within a reticulum of randomly-oriented CMTs before any secondary wall thickening is obvious. Each incipient pit border is subsequently delimited by a circle of CMTs whose diameter decreases as deposition of secondary wall takes place around the perforation. These IIF observations are corroborated by a parallel TEM study. During the period of bordered pit formation, the secondary walls of the cell are lignifying. At maturity, however, the pit membrane is unlignified and continues to stain strongly with the monoclonal antibody JIM5, a marker of primary, “juvenile” wall. The results are discussed in terms of the relationship of the CMT cytoskeleton with development of bordered pits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279885
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