37 research outputs found
The pH-dependent conformational transition of beta-lactoglobulin modulates the binding of protoporphyrin IX.
We have investigated the interaction between PPIX and beta-lactoglobulin (beta-lg) as a function of the pH of the solution. beta-Ig is a small globular protein (MW approximate to 18 kDa) with a very well characterized structure that reveals several possible binding sites for ligands. The interaction with beta-lg affects the photophysical properties of PPIX. The shift of PPIX emission maximum, excitation maximum and the increase of the fluorescence intensity is an indicator that binding between the porphyrin and beta-lg occurs. The binding constant appears to be modulated by the pH of the solution. Spectroscopic measurements do not reveal any significant energy transfer between the Trp residues of beta-lg and PPIX, however, fluorescence anisotropy decay measurements confirm the binding and the modulation introduced by the pH of the solution. Since beta-lg has been shown to be stable within the range of pH adopted in our experiments (5.0-9.0), the results suggest that PPIX binds a site affected by the pH of the solution. Because of the crystallographic evidence an obvious site is near the aperture of the interior beta-barrel however an alternative (or concurrent) binding site may still be present
Influence of repeated lyophilization on the survival ofDeinococcus proteolyticus, Micrococcus luteus andEscherichia coli
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High-resolution calorimetry: limitations of doped semiconductor thermometers
Small thermal calorimeters operating at cryogenic temperatures have achieved an energy resolution for single X-ray photons that is a factor of 20 better than the theoretical limit for a silicon ionization detector. To determine the potential for further improvements and decide on likely routes for achieving them, we discuss detector design optimization, first for an ideal calorimeter, and then for the case where components exhibit non-ideal behavior. Two serious non-ideal properties of doped semiconductor thermometers are electron–phonon decoupling and excess noise. These have been characterized over a range of sensitivity and operating temperature, and their effects on design optimization and ultimate performance can be evaluated
Rural Accessibility of General Practitioners: the Case of Bruce and Grey Counties, ONTARIO, 1901–1981
Technical note: A rapid enzyme-linked immunosorbent assay blood test for pregnancy in dairy and beef cattle
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The next-generation microcalorimeter array of XRS on Astro-E2
The square-format 32-pixel microcalorimeter array at the focal plane of the high-resolution X-ray spectrometer on the Astro-E2 X-ray Observatory is the first of a new generation of silicon-based microcalorimeters. This array has numerous advantages over its predecessor, the bilinear array that was launched on Astro-E. Foremost among its benefits are: (1) the energy resolution is improved by a factor of two at 6keV (now 6eV FWHM), (2) the thermal time constant is a factor of two faster, and (3) each pixel has a Gaussian line response. We will discuss the design changes that have led to these and other advantages