Rhodamine 6G-Anionic Surfactant System Modified by Triton X-100 for Fluorescence Determination of Albumin

The influence of sodium hexadecyl sulfate on the nature of the fluorescence spectra of rhodamine 6G in an aqueous solution and a solution of nonionic Triton X-100 was investigated. The change in the nature of the emission spectra is explained by the formation of hydrophobic stoichiometric and sub-stoichiometric reagent-surfactant associates. Stabilization of the colloid-chemical state and reduction of the total turbidity of rhodamine 6G-anionic surfactant associate solutions with the addition of nonionic surfactant as a modifier were registered. The method of modification of the rhodamine 6G-sodium hexadecyl sulfate system with a nonionic surfactant was used in the development of conditions for the fluorescence determination of protein substances in physiological solutions. The concentration conditions for the use of the modified reagent system rhodamine 6G-anionic surfactant-nonionic surfactant for the fluorescence determination of albumin in urine were optimized.

Elimination of light chain tailing in reducing capillary electrophoresis with sodium dodecyl sulfate analysis of a monoclonal antibody

Capillary electrophoresis with sodium dodecyl sulfate (CE-SDS) is a common analytical technique for investigating the purity and molecular size heterogeneity of monoclonal antibody (mAb) drugs. In reducing CE-SDS analysis of mAb-A, the light chain (LC) peak exhibited severe tailing, seriously affecting the purity analysis. The purposes of this investigation are to clarify the source of tailing and develop a more appropriate CE-SDS method to eliminate LC tailing. The degree of LC tailing was closely related to the mAb concentration, SDS concentration, and injection amount, and more hydrophobic detergents, such as sodium hexadecyl sulfate (SHS) and sodium tetradecyl sulfate (STS), could be used instead of SDS to obtain better peak shapes. The results also indicated that the tailing was caused by the binding problem associated with SDS, and SHS/STS could provide a more stable and uniform complexation for the LC. In summary, the method we developed successfully eliminated the LC tailing and provided a robust characterization of mAb-A in reducing CE-SDS analysis.

Sodium hexadecyl sulfate as an interfacial substance adjusting the adsorption of a protein on carbon nanotubes

Carbon nanotubes (CNTs) were functionalized with sodium hexadecyl sulfate (SHS). The lysozyme adsorbed on the SHS-CNTs exhibited a higher activity than that immobilized on the nonfunctionalized CNTs. To explain the experimental results and explore the mechanism of lysozyme adsorption, large-scale molecular dynamics simulations have been performed for a four-component system, including lysozyme, SHS, CNTs in explicit water. It has been found that the assembled SHS molecules form a soft layer on the surface of CNTs. The interactions between lysozyme and SHS induce the rearrangement of SHS molecules, forming a saddle-like structure on the CNT surface. The saddle-like structure fits the shape of the lysozyme, and the active-site cleft of the lysozyme is exposed to the water phase. Whereas, for the lysozyme adsorbed on the nonfunctionalized CNT, due to the hydrophobic interactions, the active-site cleft of the enzyme tends to face the wall of the CNT. The results of this work demonstrate that the SHS molecules as the interfacial substance have a function of adjusting the lysozyme with an appropriate orientation, which is favorable for the lysozyme having a higher activity.