Interaction between Starburst Dendrimers and SDS micelles studied by continuous-wave and pulsed electron spin resonances

Abstract

A computer aided analysis of both cw-and pulsed-Electron Paramagnetic Resonance (EPR) spectra of 5doxylstearic acid (5DXSA) as a probe was carried out to compare the aggregation process of Sodium Dodecyl Sulfate (SDS) surfactants in the absence and in the presence of Starburst Dendrimers (SBDs), and to provide information on the interactions between SDS and SBDs. Mobility and polarity parameters were extracted from the cw-EPR analysis, whereas the analysis of the Eleetron Spin Echo Envelope Modulation (ESEEM) signal provided details about the doxyl environment in the SDS mieeUes. In the absence of SBDs, the formation of SDS mieelles was revealed by the decrease in mobility of the probes inserted in the micelles. The high packing of SDS chains in the rniceUes prevented the water permeability at the doxyl site. In the presence of the dend¡ the analysis of the EPR spectra suggested the formation of SDS aggregates at the dendfimer surface (cooperative interaction). The larger the size of the dendrimers and the protonation of their surface, the stronger the interactions resulted between the SDS surfactants and the SBD surface. The analysis of the ESEEM pattern indicated that the cooperative interaction of the surfaetant with the SBD surface led to a less packed structure of the aggregates. A schematic view was proposed to describe the local structure of the doxyl group and its environment in the absenee and in the presence of the dendrimers.

Prediction of EPR Spectra of Lyotropic Liquid Crystals using a Combination of Molecular Dynamics Simulations and the Model‐Free Approach

“…Micro‐aggregate states of lyotropics have been modelled using SDS molecules. Previous experimental studies have suggested that due to the hydrophobic nature of the 5DSA spin probe, limited aggregation centred around the probe can occur below the critical micelle concentration …”

“…Previouse xperimental studies have suggested that due to the hydrophobic nature of the 5DSA spin probe, limited aggregation centred around the probe can occur below the critical micelle concentration. [74] By starting MD simulations with ar andom dispersion of up to five SDS molecules and one probe in as imulation box filled with water molecules, the formation of flexible micro-aggregates aroundt he spin probe was observed in < 10 ns (Figure 3a). In fact, SDS molecules did not form stable micro-aggregatese xcept in the presenceo f5 DSA.…”

Effect of the preparation procedure on the structural properties of oligonucleotide/cationic liposome complexes (lipoplexes) studied by electron spin resonance and Zeta potential

“…Amphiphilic probes, bearing the paramagnetic unit along the alkyl chain, have been extensively employed to obtain information on the dynamics and ordering at the molecular level within aggregates such as micelles and natural or synthetic lipid membranes [18,19,[21][22][23][24][25][29][30][31][32][33][34][35][36][43][44][45][46][47][48]. Here, we used CAT-12, i.e.…”

Modulation of Guest Partitioning Within Dendrimer–Surfactant Supramolecular Assemblies

“…[7] The interactions of a cationic surfactant at the dendrimer=water interface of half-generation dendrimers [6] and an anionic surfactant with the surface of full-generation dendrimers have been shown to be feasible. [3,4,8] In contrast to previous studies that have observed surfactant aggregation on dendrimer surfaces, [8][9][10][11][12] in this work we focus on supramolecular structures with electrostatic interactions involving a maximum of one surfactant per dendrimer terminal group. Also, in contrast with earlier studies, [4] we show that the positioning of a guest molecule within the dendrimer-surfactant supramolecular complex can be modulated by using surfactants of varying alkyl chain length, varying dendrimer generation, and varying surfactant concentration.…”