A novel column based on silica containing immobilized carbon nanotubes (CNTs) was developed and evaluated in terms of its binding efficiency and resolution. First, CNT functionalized with amino groups (CNT-NH(2)) were prepared via chemical modification of carboxylic groups introduced on the CNT surface. Secondly the covalent immobilization of CNT-NH(2) was carried out by using glutardialdehyde activating agent on aminopropyl (AP)-silica surface. This CNT stationary phase was applied to the HPLC separation of two molecule series, i.e. polychlorinated biphenyl (PCB) isomers with different degrees of substitution in the ortho-position (non-ortho to tetra-ortho substituted) and terpenes (linalool, geraniol, thymol, alpha-terpineol). The retention behavior of these solute molecules was measured under isocratic conditions with different mobile phase compositions, ranging from 0.05-0.70 v/v of toluene in cyclohexane. The retention factors of the solute molecule do not depend linearly on the toluene fraction but follow a quadratic relationship. This CNT stationary phase was a very useful column for the separation of PCB congeners and terpenes. It was demonstrated that a planar conformation of the solute molecule enhanced the solute retention on this CNT stationary phase. As well, a quantitative structure relationship derived, demonstrated the significant input to retention was due to the structurally selective dipole-dipole and charge transfer interactions with the solutes. These results were compared with those obtained on the AP stationary phase. The proposed CNT stationary phase for the separation possess distinctive and interesting retentive properties, and chemometric analysis of retention data of appropriate designed series of test solutes appears to be a convenient, objective and quantitative method to prove a new phase specificity.
The aggregation of alpha-synuclein in the dopaminergic neurons of the substantia nigra is a critical step in the Parkinson's disease (PD). The etiology of the disease is unknown but recent epidemiological and experimental studies have renewed interest in the hypothesis that environmental factors, especially herbicides and metals, have a role on the pathogenesis of PD. For the first time, the association constants of alpha-synuclein with five herbicides have been calculated using a capillary electrophoresis (CE) method. In addition, the effect of a number of metals on this binding has been investigated. It appears that the herbicides preferentially bind to a partially folded intermediate conformation of alpha-synuclein induced by manganese, aluminium, cadmium, copper and zinc. Then, metal increases the synuclein-herbicide association. However, this study shows contrasting actions with the antibiotic rifampicin and magnesium addition leading to a decrease of the alpha-synuclein-herbicide interaction even if other metals are present in the bulk solvent. Considering epidemiological studies, all these results suggest an underlying molecular basis for PD and related body diseases.
The retention mechanism of a series of peptides on a single-wall carbon nanotube (SWCNT) stationary phase inside an HPLC column was investigated over a wide range of mobile phase compositions. While the similar size C18 column exhibited an efficiency of 11.5 μm, the SWCNT column increased the efficiency, i.e. 7.10 μm at a flow rate of 0.8 mL/min, and significantly affected the separation quality of the peptides. The values of enthalpy (ΔH) and entropy (ΔS(*)) of transfer of the peptides from the mobile to the SWCNT stationary phase were determined. The method studied each factor, i.e. ACN fraction x in the ACN/water mixture and column temperature. The changes in retention factor, ΔH and ΔS(*) as a function of the ACN fraction in the mobile phase were examined. These variations are explained using the organization of ACN in clusters in the ACN/water mixture and on the steric and electronic forces implied in the retention process. The information obtained in this work makes this SWCNT stationary phase useful for peptide research and demonstrated the role of ACN to improve the separation quality.
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