β-Lactoglobulin, a protein belonging to the lipocaline family, is studied by Photon correlation spectroscopy and small angle X-ray scattering in acidic solutions (pH = 2.3) and at ionic strengths in the range 7−507 mM. Both experiments give a clear evidence of a protein monomer−dimer equilibrium affected by the ionic strength of the solution. The interparticle interactions are determined by means of Photon correlation spectroscopy by following the trend of the protein diffusion coefficient versus concentration (from 0.2 to 25 g/L) at ionic strengths of 7 and 107 mM. From a detailed analysis, estimates of the protein charge, hydrodynamic radius, and dimeritazion fraction have been obtained. Small angle X-ray scattering measurements performed versus ionic strength (from 7 to 507 mM) in dilute solutions (10 g/L) allow an independent estimate of the dimerization fraction. A global fit of the SAXS scattered intensities at different salt concentrations using a simple electrostatic model for the aggregation mechanism is presented. As a result, the dissociation free energy has been obtained as a function of the ionic strength, yielding an excellent agreement with photon correlation spectroscopy data.

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We report on a case of reversible Pisa syndrome developed after treatment with galantamine in a patient with Alzheimer's disease without previous exposure to neuroleptic or other cholinesterase inhibitors. Complete and persistent resolution of the syndrome was achieved several weeks after botulinum toxin type-A injection.

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The effect of GuHCl and of NaCl on the structural properties of the hemocyanin (Hc) from Carcinus aestuarii has been studied by small angle x-ray scattering (SAXS) using synchrotron radiation. SAXS data collected as a function of perturbant concentration have been used to analyze conformational states of hexameric holo and apoHc as well as the holo and apoforms of the monomeric subunit CaeSS2. In the case of the holoprotein in GuHCl, two concentration domains were identified: at lower concentration, the perturbant induces aggregation of Hc molecules, whereas at higher concentration the aggregates dissociate with concomitant denaturation of the protein. In contrast, with apoHc the denaturation occurs at rather low GuHCl, pointing to an important effect of the active site bound copper for the stabilization of Hc tertiary structure. The effects of NaCl are similar to those of GuHCl as far as CaeSS2 is concerned, namely oligomerization precedes denaturation, whereas in the case of the hexameric form no aggregation occurs. To improve data analysis, on the basis of the current models for Hc monomers and oligomers, the fraction of each aggregation state and/or unfolded protein has been determined by fitting experimental SAXS curves with form factors calculated from Monte Carlo methods. In addition, a global analysis has been carried out on the basis of a thermodynamic model involving an equilibrium between a monomer in a nativelike and denatured form as well as a class of equilibria among the monomer and other aggregates.