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Self-Assembly of Pyridine-Modified Lipoic Acid Derivatives on Gold and Their Interaction with Thyroxine (T4)
VTT Technical Research Centre of Finland, Sinitaival 6, 33720 Tampere, Finland & Metallimiehenkuja 8, Espoo, 02044 VTT, Finland
NFMLab-DCMIC "Giulio Natta", Politecnico di Milano, Via Mancinelli 7, I-20131 Milano, Italy
Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, Via Giovanni Pascoli, 70/3, I-20133 Milano, Italy
* Authors to whom correspondence should be addressed.
Received: 26 December 2012; in revised form: 30 January 2013 / Accepted: 31 January 2013 / Published: 6 February 2013
Abstract: Pyridyl derivatives of lipoic acid were prepared as ligands for the study of the interaction with thyroxine (T4). Thin self-assembled films of the ligands were prepared in 70% ethanol on gold and their interaction with T4 was studied by titration experiments in an aqueous buffer solution using Surface Plasmon Resonance (SPR). The thickness and refractive index of the ligand layers were calculated from SPR spectra recorded in two media, also allowing for surface coverage and the density of the layers to be estimated. Two ligands, a 4-pyridyl and a bis(2-hydroxyethyl) derivative of lipoic acid, were selected to investigate the feasibility for producing molecularly imprinted self-assembled layers on gold for T4. The methodology was to co-assemble T4 and the ligand onto the gold surface, elute the T4 from the layer under alkaline conditions, and study the rebinding of T4 to the layer. Multiple elution/rebinding cycles were conducted in different buffer solutions, and rebinding of T4 could be observed, with a moderate binding affinity that depended greatly on the solvent used. More optimal binding was observed in HBS buffer, and the affinity of the interaction could be slightly increased when the 4-pyridyl and bis(2-hydroxy-ethyl) derivatives of lipoic acid were combined in the imprinted layer.
Keywords: thyroxine; self-assembly; imprinting; noncovalent interactions; Surface Plasmon Resonance (SPR)
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Albers, W.M.; Milani, R.; Tappura, K.; Munter, T.; Resnati, G.; Metrangolo, P. Self-Assembly of Pyridine-Modified Lipoic Acid Derivatives on Gold and Their Interaction with Thyroxine (T4). Int. J. Mol. Sci. 2013, 14, 3500-3513.
Albers WM, Milani R, Tappura K, Munter T, Resnati G, Metrangolo P. Self-Assembly of Pyridine-Modified Lipoic Acid Derivatives on Gold and Their Interaction with Thyroxine (T4). International Journal of Molecular Sciences. 2013; 14(2):3500-3513.
Albers, Willem M.; Milani, Roberto; Tappura, Kirsi; Munter, Tony; Resnati, Giuseppe; Metrangolo, Pierangelo. 2013. "Self-Assembly of Pyridine-Modified Lipoic Acid Derivatives on Gold and Their Interaction with Thyroxine (T4)." Int. J. Mol. Sci. 14, no. 2: 3500-3513.