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The sedimentation half-times t s of suspensions of polydisperse titania particles in aqueous Triton X-100 (TX100) solutions with concentrations c TX 100 ranging from 0.05 to 250 mM were measured. Three regions of TX100 concentrations with different settling behavior were observed. In region A, or for c TX 100 below its cmc (ca. 0.24 mM in water at 25 °C), the t s -values increase with increasing surfactant concentration. In region B, or for cmc ≤ c TX 100 < c * * , where c * * was determined to be 30 mM experimentally, the t s -values do not vary with the surfactant concentration. In region C, or for c TX 100 ≥ c * * , as c TX 100 increases, the t s -values increase. In regions A and B, little or no viscosity effect on the sedimentation was observed. By contrast, in region C, the viscosity of the micellar solution increases with increasing c TX 100 and accounts partially for the slower particle sedimentation rate. The surface densities of adsorbed TX100 molecules on the particle surfaces were measured to probe their effects on the steric interactions, which are responsible for the increase in the t s -values in region A. The maximum adsorbed densities on the particle surfaces, which are presumed to be hydrophilic, were found to be much smaller than those on other hydrophobic surfaces, as expected. Nonetheless, the adsorbed densities are high enough to induce strong steric interactions in region B, preventing the particles from agglomerating. In region C, the increase in viscosity slows down not only the particle sedimentation, but also the particle agglomeration, resulting in an apparently weaker micellar depletion effect. Our inference is that depletion-induced flocculation in region C is masked by the high solution viscosity. This inference is supported by several different lines of evidence. First, the once corrected half-times, t s I , which are the measured half-times divided by the relative viscosities, start to decrease at c TX 100 ≅ 160 mM, suggesting the formation of particle clusters, and reveals a micelle-induced depletion effect. The twice corrected half-times, t s II , which are t s I divided by the viscosity of the solution to account for the effect of viscosity on the agglomeration rate, are consistent with these inferences. In addition, the DLS data support our inference that the clusters in region C are flocs, which can be de-agglomerated with some mild agitation. A recently published model of agglomeration and sedimentation (Yang et al., 2016) is used to fit the data for estimating the effective Fuchs-Smoluchowski stability ratio W for flocculation. W -values are inferred to be over 10 6 at c TX 100 < 160 mM, but only ca. 500–1000 at higher concentrations, supporting the hypothesis of a depletion-induced flocculation that is masked by the solution viscosity. [ABSTRACT FROM AUTHOR]

The linear peptide gramicidin A (gA) forms prototypical ion channels specific for monovalent cations and has been extensively used to study the organization and dynamics of membrane channels. This polymorphic peptide can adopt two different types of structures, the helical dimer β6.3 ('channel state') and the double helical structure with two intertwined monomers. The structure of gA in micelles of detergent Triton X-100 has been studied using CD, Fourier transform infrared, and fluorescence spectroscopy. The results obtained demonstrate that only one thermodynamically stable gA structure, the antiparallel left-handed double helix β5.6, is formed in this membrane-mimetic environment. The position of the tryptophan fluorescence maximum at 332 nm is the same as that in phospholipid membranes. The causative factors governing the double helix formation in the micellar medium are discussed on the basis of known physicochemical properties of Triton X-100. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: UV–vis spectra, fluorescence emission spectra and cyclic voltammetric measurements were used to study the influence of Vitamin C on the antioxidant of rutin in Triton X-100 micelles. Rutin can be located in Triton X-100 micelles spontaneously through hydrophobic force, and the binding constant K between rutin and Triton X-100 increases with the rutin concentration. The embedment of two hydroxyl groups on rutin into the more hydrophobic micellar microenvironment makes the oxidation of rutin harder and the radical scavenging activity decrease. With low concentration of Vitamin C, the antioxidant capacity of rutin against hydroxyl radical is enhanced, while that capacity is partly inhibited when the concentration of Vitamin C become higher. [Copyright &y& Elsevier]