PubMed · 874707
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J R Poley. 1977. Bile acid malabsorption, ileal dysfunction, and protracted diarrhea.. https://doi.org/10.1016/s0022-3476(77)80864-0
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Emulsification of aqueous protein solutions in methylene chloride triggered the formation of water-insoluble aggregates at a water/methylene chloride interface. As a result, the amounts of beta-lactoglobulin and ovalbumin recovered in water were 36 and 44%, respectively. Addition of 5 mM: CHAPS in the aqueous phase raised the degree of beta-lactoglobulin recovery to 96%. Sodium taurocholate, however, failed to improve protein recovery. The stabilizing effect of CHAPS was also protein-specific and concentration-dependent: at >or=5 mM: , the surfactant caused unfolding of ovalbumin to make a water-soluble oligomer. CHAPS thus stabilizes proteins at an interface.
The dynamics of DMPC in different isotropic bicelles have been investigated by NMR and EPR methods. The local dynamics were obtained by interpretation of 13C NMR relaxation measurements of DMPC in the bicelles, and these results were compared to EPR spectra of spin-labeled lipids. The overall size of the bicelles was investigated by PFG NMR translational diffusion measurements. The dynamics and relative sizes were compared among three different bicelles: [DMPC]/[DHPC] = 0.25, [DMPC]/[DHPC] = 0.5, and [DMPC]/[CHAPS] = 0.5. The local motion is found to depend much more strongly on the choice of the detergent, rather than the overall size of the bicelle. The results provide an explanation for differences in apparent dynamics for different peptides, which are bound to bicelles. This in turn determines under what conditions reasonable NMR spectra can be observed. A model is presented in which extensive local motion, in conjunction with the overall size, affects the spectral properties. An analytical expression for the size dependence of the bicelles, relating the radius of the bilayer region with physical properties of the detergent and the lipid, is also presented.
The crystal structures of six new crystals of oxo-cholic acids (oxo-CA) are reported: (I) 3alpha,12alpha-dihydroxy-7-oxo-5beta-cholan-24-oic acid; (II) 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholan-24-oic acid; (III) 7alpha-hydroxy-3,12-dioxo-5beta-cholan-24-oic acid; (IV-alpha) and (IV-beta) 12alpha-hydroxy-3,7-dioxo-5beta-cholan-24-oic acid; (V) 3,7,12-trihydroxy-5beta-cholan-24-oic acid. (IV-beta) is a pseudopolymorphic solvated form of (IV-alpha) and contains small channels which can trap disordered water molecules. In all the structures the four saturated cycles, forming the common alicyclic skeleton, have the same conformation, while the carboxylic side chain adopts flexible conformations in order to produce the most efficient crystal aggregations. The structures display a variety of supramolecular architectures dominated by networks of cooperative O-H...O hydrogen bonds forming different packing motifs often supported by weaker C-H...O interactions.