title: Location of TEMPO derivatives in micelles: subtle effect of the probe orientation.
abstract: Partition coefficients for six 4-substituted derivatives of the 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) derivatives in aqueous solutions of reduced Triton X-100 (RTX-100) were determined by measurements of the probe EPR g-factor and of the fluorescence quenching of pyrene by the radical in the micelle. The partition constant attained a maximum value and then decreased with increasing probe hydrophobicity. Simulation of the probes inside the micelle showed that this trend could be rationalized by a change in the orientation of the 4-substituted TEMPO derivatives with the increasing substituent chain-length. The use of the EPR g-factor for the determination of partition constants of radicals in micellar systems was thus validated as a reliable and sensitive method, capable of describing the probe orientation in its microenvironment.
authors: Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40 Correo 33, Santiago de Chile, Chile; Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Chile. Electronic address: carolina.aliaga@usach.cl.
authors: Carolina
authors: C
authors: Aliaga
authors: Center for Bioinformatics and Integrative Biology, Facultad de Ciencias Biológicas, Universidad Andres Bello, Chile.
authors: Felipe
authors: F
authors: Bravo-Moraga
authors: Center for Bioinformatics and Integrative Biology, Facultad de Ciencias Biológicas, Universidad Andres Bello, Chile.
authors: Danilo
authors: D
authors: Gonzalez-Nilo
authors: Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40 Correo 33, Santiago de Chile, Chile.
authors: Sebastián
authors: S
authors: Márquez
authors: Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40 Correo 33, Santiago de Chile, Chile.
authors: Susan
authors: S
authors: Lühr
authors: Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40 Correo 33, Santiago de Chile, Chile.
authors: Geraldine
authors: G
authors: Mena
authors: Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40 Correo 33, Santiago de Chile, Chile.
authors: Marcos Caroli
authors: MC
authors: Rezende
mesh_terms: D005453:Fluorescence; D057927:Hydrophobic and Hydrophilic Interactions; D008823:Micelles; D056004:Molecular Dynamics Simulation / Q000706:statistics & numerical data*; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D008823:Micelles
keywords: 4-AcyloxyTEMPO; EPR g-factor; Molecular dynamics simulation; Partition constants; Reduced Triton X-100 micelle