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71.
Solution NMR approaches for establishing specificity of weak heterodimerization of membrane proteins
Solution NMR provides a powerful approach for detecting complex formation involving weak to moderate intermolecular affinity. However, solution NMR has only rarely been used to detect complex formation between two membrane proteins in model membranes. The impact of specific binding on the NMR spectrum of a membrane protein can be difficult to distinguish from spectral changes that are induced by nonspecific binding and/or by changes that arise from forced cohabitation of the two proteins in a single model membrane assembly. This is particularly the case when solubility limits make it impossible to complete a titration to the point of near saturation of complex formation. In this work experiments are presented that provide the basis for establishing whether specific complex formation occurs between two membrane proteins under conditions where binding is not of high avidity. Application of these methods led to the conclusion that the membrane protein CD147 (also known as EMMPRIN or basigin) forms a specific heterodimeric complex in the membrane with the 99-residue transmembrane C-terminal fragment of the amyloid precursor protein (C99 or APP-βCTF), the latter being the immediate precursor of the amyloid-β polypeptides that are closely linked to the etiology of Alzheimer's disease. 相似文献
72.
Denis A. Brosnan John P. Sanders Stephanie A. Hart 《Journal of Thermal Analysis and Calorimetry》2011,106(1):109-115
Thermal analysis techniques have been used in characterizing building materials from significant historic properties in the
Charleston, South Carolina area. Determining the chemical and physical effects of deterioration resulting from long periods
of exposure is a first step in formulating preservation strategies. In this regard, simultaneous thermal analysis coupled
with evolved gas analysis has been used to study reactions between air, seawater, and masonry materials. Further, the traditional
petrographic identification of mortar composition is greatly facilitated through use of thermal analysis. Simultaneous thermal
analysis allows for an exact determination of the calcium carbonate content in mortars as an alternative to the use of an
inferred value based on chemical analysis data. The partial dissolution of calcium carbonate in the presence of sea salt is
a major deterioration process. Further, natural cements manufactured in the United States are identified, in part, based on
their thermogravimetric (TG) traces and their evolved gases. The data indicates that natural cements form some carbonate phases
in addition to the major hydrate phases. Clay bricks are found to exhibit interaction with sea water, with uptake of bicarbonate
suggested. Additionally, there is evidence of re-hydroxylation in the 160 year old bricks. The bricks made in coastal zones
contain a considerable free silica fraction that is composed of a small percentage of cristobalite. The silica content of
the clay bricks is seen to result in very high thermal expansion coefficients in the area of 10 × 10−6 to 12 × 10−6 K−1. These studies provide guidance in restoration efforts where authenticity of cements is important. In the event that replacement
bricks are required, matching the thermal expansion coefficient of the original bricks is a requirement for preservation of
the masonry structure. 相似文献
73.
Clifton LA Sanders MR Castelletto V Rogers SE Heenan RK Neylon C Frazier RA Green RJ 《Physical chemistry chemical physics : PCCP》2011,13(19):8881-8888
The self-assembly in solution of puroindoline-a (Pin-a), an amphiphilic lipid binding protein from common wheat, was investigated by small angle neutron scattering, dynamic light scattering and size exclusion chromatography. Pin-a was found to form monodisperse prolate ellipsoidal micelles with a major axial radius of 112 ± 4.5 ? and minor axial radius of 40.4 ± 0.18 ?. These protein micelles were formed by the spontaneous self-assembly of 38 Pin-a molecules in solution and were stable over a wide pH range (3.5-11) and at elevated temperatures (20-65 °C). Pin-a micelles could be disrupted upon addition of the non-ionic surfactant dodecyl-β-maltoside, suggesting that the protein self-assembly is driven by hydrophobic forces, consisting of intermolecular interactions between Trp residues located within a well-defined Trp-rich domain of Pin-a. 相似文献
74.
75.
A spectrophotometric method has been employed to measure the surface acidities of stoichiometric and nonstoichiometric B-P-O catalysts. Three phosphorus/boron ratios, 0.7, 1.0, 1.3, and three pretreatment temperatures, 200, 375, and 600°C, were employed. The data obtained appear to be consistent with earlier measurements of surface acidity by the Hammett indicator method and by infrared spectroscopy and with the results of studies of probe reactions. 相似文献
76.
Fluorescence lifetime imaging of oxygen in living cells 总被引:1,自引:0,他引:1
H. C. Gerritsen R. Sanders A. Draaijer C. Ince Y. K. Levine 《Journal of fluorescence》1997,7(1):11-15
The usefulness of the fluorescent probe ruthenium tris(2,2′-dipyridyl) dichloride hydrate (RTDP) for the quantitative imaging
of oxygen in single cells was investigated utilizing fluorescence lifetime imaging. The results indicate that the fluorescence
behavior of RTDP in the presence of oxygen can be described by the Stem-Volmer equation. This shows that fluorescence quenching
by oxygen is a dynamic quenching process. In addition, it was demonstrated that the fluorescence lifetime of RTDP is insensitive
to pH, ion concentration, and cellular contents. This implies that a simple calibration procedure in buffers can be used to
quantify oxygen concentrations within cells. First fluorescence imaging experiments on J774 macrophages show a nonuniform
fluorescence intensity and a uniform fluorescence lifetime image. This indicates that the RTDP is heterogeneously partitioned
throughout the cells, while the oxygen concentration is constant. 相似文献
77.
Ultraviolet broadband light spanning 337–405 nm was produced in a single-mode optical fiber primarily by stimulated Raman scattering. Pulses of 4 ns duration at 337 nm were coupled into a 50 m long ultraviolet-grade fiber featuring single-mode operation in the 320–450 nm range. Significant spectral broadening was achieved with pulses of only ∼10 W peak power. Our experiments demonstrate the potential for a source with ∼104 times the spectral radiance of a quartz tungsten halogen lamp, which is currently used for many applications in this wavelength range. PACS 42.65.Ky; 42.81.Wg 相似文献
78.
79.
It is proved that any one-to-one edge map f from a 3-connected graph G onto a graph G′, G and G′ possibly infinite, satisfying f(C) is a circuit in G′ whenever C is a circuit in G is induced by a vertex isomorphism. This generalizes a result of Whitney which hypothesizes f(C) is a circuit in G′ if and only if C is a circuit in G. 相似文献
80.