An influenza epidemic is still a problem despite the development of vaccines and anti-influenza drugs. Preventive measures such as handwashing are fundamental and important for counteracting influenza virus infection. In this study, we clarified the anti-influenza virus effects of surfactants, which are the main components of hand soaps for hand washing: potassium oleate (C18:1), sodium laureth sulfate (LES) and sodium lauryl sulfate (SDS). For a human influenza virus strain (H3N2), C18:1 reduced the infectivity by 4 logs or more, whereas LES and SDS reduced the infectivity by 1 log or less. Similar results were obtained when an avian influenza virus strain (H5N3) was used. The interaction between the surfactant and virus was then investigated by isothermal titration calorimetry. The LES-virus system showed a positive value of enthalpy changes (ΔH), meaning an exothermic interaction that indicated a hydrophobic interaction. In contrast, both the C18:1-virus system and the SDS-virus system showed negative values of ΔH, meaning an endothermic interaction that indicated an electrical interaction. The ΔH value of the C18:1-virus system was much higher than that of the SDS-virus system. A mixture of C18:1 and HA proteins similarly showed negative values of ΔH. These results indicate that influenza virus inactivation by a hydrophobic interaction of a surfactant with the viral envelope is insufficient to prevent infection, whereas inactivation by an electrical interaction of a surfactant with HA proteins is sufficient to prevent influenza virus infection.
Anomalous small-angle X-ray scattering (ASAXS) near the absorption edge of bromine has been used to investigate the internal structure of polymer micelles comprising poly(4-bromostyrene)-block-poly(ethylene glycol)block-poly(4-bromostyrene) (PBrS-b-PEG-b-PBrS) in aqueous solution. The ASAXS analysis revealed that the hydrophobic core composed of PBrS can be regarded as a homogeneous sphere with a radius of 10.2 nm and a decaying electron density at the surface. The aggregation number of micelle directly estimated on the basis of ASAXS analysis well agreed with that determined by field-flow fractionation coupled with multiangle light scattering, confirming the reliability of ASAXS analysis. The small-angle X-ray scattering (SAXS) profile from whole PBrS-b-PEG-b-PBrS micelle was further analyzed by using the result of ASAXS analysis. The micelles could be well described by a core−corona model in which the monomer concentration of PEG in the shell decreased as R −4.2/3 , where R is the distance from the center of micelle. The index 4.2/3 is very close to that predicted by theory for star polymers (R −4/3 ), indicating that the PEG chains in the shell can be well described by the blob model in which chains are modeled as strings of blobs that extend radially. Thus, combination of ASAXS and conventional SAXS analyses permit to reveal precisely the internal structure and nature of the tethered chains of polymer micelles, and it could become a powerful tool for exploring internal structures of multiphase systems when they contain a probe atom for ASAXS.
Anomalous small‐angle X‐ray scattering with two marker elements was applied to the structural analysis of poly(4‐vinylphenol rubidium salt)‐block‐poly(4‐bromostyrene) (RbPVPh‐b‐PBrS) micelles, where Br and Rb were the markers for the hydrophobic core and the hydrated corona, respectively. By using two different markers for the hydrophobic core and the hydrated corona, the form factors of the core and corona were extracted separately from the scattering profile of the whole RbPVPh‐b‐PBrS micelles. The form factor of the hydrophobic core (the spatial distribution of Br) revealed that the core was regarded as a solid sphere with a smooth surface and a radius of 47 nm. Conversely, the form factor of the spatial distribution of Rb+ indicated that the shell of the RbPVPh‐b‐PBrS micelles was 15 nm thick.
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