A Green Analytical Method Using Polyurethane Foam for The Extraction and Determination of Lauryl Ether Sulfate in Personal Care Hygiene Products

A green methodology was developed for the extraction and determination of lauryl ether sulfate in raw materials and commercial liquid soap and shower gel samples. The method avoids the use of organic solvents, offering a simple, cheap, and safe analysis. The methodology is based on the sorption of an ionic pair consisting of a cationic dye and an anionic surfactant onto polyurethane foam. The experimental variables were optimized by chemometry to obtain the conditions that maximized extraction of the ionic pair. Digital imaging and spectrophotometry were used for quantification in the linear concentration range from 10.0 to 100 mg L-1. The limits of detection and quantification were, respectively, 2.71 and 9.28 mg L-1 for digital imaging, and 1.74 and 5.83 mg L-1 for spectrophotometry. The methods showed good results when applied to commercial samples, with recoveries in the range 96.8-103%.

Effect of Phenolic Acids on Temperature-sensitive Property of Self-assembly of Ionic Pair of Poly(ethylene imine)/(phenylthio)Acetic Acid

The ionic pair self-assembly (IPSAM) composed of poly(ethyleneimine) (PEI) and (phenylthio)acetic acid (PTA) was prepared and the effect of phenolic acids (PAs) (e.g. cinnamic acid (CA), hydroxycinnamic acid (HCA), and dihydroxycinnamic acid (DHCA)) on the upper critical solution temperature (UCST) and the temperature-responsive releasing property of IPSAM were investigated. PEI/PTA ionic pair showed a UCST behavior and the PAs decreased the UCST effective in the order of DHCA > HCA > CA. The PAs were thought to attach to the PEI chain of PEI/PTA ionic pair as pendants. According to the interfacial tensiometry, PEI/PTA(3/7) ionic pair was found to be air/water interface-active due to their amphiphilic property. CA had little effect on the interfacial activity of the ionic pair. HCA and HDCA significantly decreased the interfacial activity possibly because they are more polar than CA thus the hydrophilic and lipophilic balance of PEI/PTA ionic pair could be broken by their attachment to PEI chains. IPSAM was found as nanoparticles whose diameter was tens of nanometer and PAs had little effect on the shape and the size of IPSAM, once the UCST of PEI/PTA/PA ionic pair was above room temperature where the TEM micrographs were taken. If the UCST of PEI/PTA/PA ionic pair was below room temperature, no particulate matters were found on the TEM micrographs. The release degree of cargo loaded in IPSAM increased slowly with time lapse below UCST. Whereas, the release degree increased rapidly with time lapse above UCST, possibly because of the thermally-induced disintegration of IPSAM.

Prediction of Sodium Substitution Sites in Octacalcium Phosphate: The Relationships of Ionic Pair Ratios in Reacting Solutions

Octacalcium phosphate (OCP) is widely used in biomaterial fabrication by virtue of its unique crystal structure and low environmental loading. Although various ion and molecule substitution methods into the OCP unit lattice have been introduced, it remains unclear which factors and mechanisms dominate the substitution process. Experimental studies have indicated that Na alkali metal ions are substituted at the P3 PO4 conjugated site in acidic to weakly acidic conditions and the P5 PO4 conjugated site in neutral to weak basic conditions. Ionic species calculation methods have indicated that the pair ratios of Na and HPO42− (NaHPO4−) are small in acidic reacting solutions but large under weakly basic conditions. Consequently, the roles played by NaHPO4− and ionic pair formation processes are thought to dominate ion and molecule substitution into the OCP unit lattice. Such ionic pair formation strongly inhibits dicarboxylic acid substitution into the OCP unit lattice due to the replacement of the Ca ion, which conjugates P5 PO4 as an anchor of dicarboxylic acid.

Common architecture of Tc toxins from human and insect pathogenic bacteria

Tc toxins use a syringe-like mechanism to penetrate the membrane and translocate toxic enzymes into the host cytosol. They are composed of three components: TcA, TcB, and TcC. Low-resolution structures of TcAs from different bacteria suggest a considerable difference in their architecture and possibly in their mechanism of action. Here, we present high-resolution structures of five TcAs from insect and human pathogens, which show a similar overall composition and domain organization. Essential structural features, including a trefoil protein knot, are present in all TcAs, suggesting a common mechanism of action. All TcAs form functional pores and can be combined with TcB-TcC subunits from other species to form active chimeric holotoxins. We identified a conserved ionic pair that stabilizes the shell, likely operating as a strong latch that only springs open after destabilization of other regions. Our results provide new insights into the architecture and mechanism of the Tc toxin family.

Conserved architecture of Tc toxins from human and insect pathogenic bacteria

Tc toxin complexes use a syringe-like mechanism to penetrate the membrane and translocate a toxic enzyme into the host cytosol. They are composed of three components: TcA, TcB and TcC. Until recently, low-resolution structures of TcA from different bacteria suggested that Tc toxins differ considerably in their architecture and possibly in their mechanism of action. Here, we present high-resolution structures and functional studies of five TcAs from different insect and human pathogenic bacteria. Contrary to previous expectations, their overall composition and domain organization is almost identical. The TcAs assemble as a pentamer with a central α-helical channel surrounded by a shell composed of conserved α-helical domains and variable β-sheet domains. Essential structural features, including a conserved trefoil protein knot, are present in all five TcAs, suggesting a common mechanism of action. All TcAs form functional pores and can be combined with TcB-TcC subunits from other species resulting in chimeric holotoxins. We have identified a conserved ionic pair that stabilizes the shell, likely operating as a strong latch that only springs open after the destabilization of other regions. Our results lead to new insights into the architecture and host specificity of the Tc toxin family.