Influence of counterion on the interaction of dodecyl sulfates and cellulose ethers.

Fluorescence probe techniques together with microcalorimetry and dye solubilization were used to study the interaction between nonionic polymers and anionic surfactants with different monovalent counterions in order to examine the effects of the counterion. The polymers used were the cellulose ethers hydroxypropyl methyl cellulose (HPMC) and ethyl hydroxyethyl cellulose (EHEC). The surfactants were dodecyl sulfates with potassium, sodium, and lithium as counterions (KDS, NaDS, LiDS).

Interaction between lactate dehydrogenase and Tween 80 in aqueous solution.

Purpose: The weak aqueous interaction between the protein lactate dehydrogenase (LDH) and the nonionic surfactant Tween 80 has been investigated, because weak protein-amphiphile interactions are of significant importance in pharmaceutical formulations, but are experimentally hard to determine. The system LDH/sodium dodecyl sulphate (SDS) was used as reference because SDS, by its strong protein binding, denatures LDH completely.

Methods: Fluorescence spectroscopy with pyrene and 1,3-bis(lphenyl)propane (P3P) as probes, intrinsic protein fluorescence and NMR spectroscopy have been used.