Saccharose effects on surface association of phenol derivatives with porous graphitic carbon

André, Carl; Guillaume, Yves Claude

doi:10.1016/j.chroma.2003.12.017

Cited by 11 publications

(8 citation statements)

References 26 publications

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“…Hence, if the phase ratioˇis known, van't-Hoff plots yield information about enthalpic and entropic contributions to the free energy of adsorption of the analytes on PGC. The phase ratio of Hypercarb ® was reported in literature [17].…”

Section: Introductionmentioning

confidence: 87%

Solvent effects on the retention of oligosaccharides in porous graphitic carbon liquid chromatography

Melmer

Stangler

Premstaller

et al. 2010

Journal of Chromatography A

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Section: Introductionmentioning

confidence: 87%

Solvent effects on the retention of oligosaccharides in porous graphitic carbon liquid chromatography

Melmer

Stangler

Premstaller

et al. 2010

Journal of Chromatography A

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“…The k′ retention factor of each TTR form can be also expressed by the well known equation (André and Guillaume, 2004) ln k ′ ¼ ÀΔH°=RT þ ΔS°*…”

Section: Thermodynamic Approachmentioning

confidence: 99%

Thermodynamic study of transthyretin association (wild‐type and senile forms) with heparan sulfate proteoglycan: pH effect and implication of the reactive histidine residue

Geneste

André

Magy-Bertrand

et al. 2014

Biomedical Chromatography

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The tetramer destabilization of transthyretin into monomers and its fibrillation are phenomena leading to amyloid deposition. Heparan sulfate proteoglycan (HSPG) has been found in all amyloid deposits. A chromatographic approach was developed to compare binding parameters between wild-type transthyretin (wtTTR) and an amyloidogenic transthyretin (sTTR). Results showed a greater affinity of sTTR for HSPG at pH 7.4 compared with wtTTR owing to the monomeric form of sTTR. Analysis of the thermodynamic parameters showed that van der Waals interactions were involved at the complex interface for both transthyretin forms. For sTTR, results from the plot representing the number of protons exchanged vs pH showed that the binding mechanism was pH-dependent with a critical value at a pH 6.5. This observation was due to the protonation of a histidine residue as an imidazolium cation, which was not accessible when TTR was in its tetrameric structure. At pH >6.5, dehydration at the binding interface and several contacts between nonpolar groups of sTTR and HSPG were also coupled to binding for an optimal hydrogen-bond network. At pH <6.5, the protonation of the His residue from sTTR monomer when pH decreased broke the hydrogen-bond network, leading to its destabilization and thus producing slight conformational changes in the sTTR monomer structure.

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“…For the charged pesticide at pH 7 (i.e., chlordimeform and paraquat), the plots could be divided into three domains (Figure ). The complexation phenomena seemed to be an association of two effects additive to the change of water activity classically attributed to the NaCl and the HA conformation change. At a low salt concentration ( x < x x ‘ = 0.3 M), the Cl - anion and the amino group of the charged pesticides formed a ion pair noted PCl.…”

Section: Resultsmentioning

confidence: 96%

“…Therefore, at a low salt concentration (x < x x′ ), the salt effect can change the pesticide binding with HA by these two mechanisms, leading to an increase in the pesticide complexation thermodynamic data (Figure 10). 36 Assuming that salt can react at n independent sites, this salt dependence on the k′ can be described by the following equation derived from the one of Aune and Tanford: 37 where λ is the average binding constant between the salt and the binding site (pesticide and HA) and ∆n is the difference in the number of salt molecules bound in the HA-pesticide interface between the two states in equilibrium (unbound and bound to HA). At a high salt concentration (x x′ < x < x c ) 0.6 M), as previously observed with the neutral pesticides, the change in the water activity led to a favorable pesticide-HA association and a decrease of the thermodynamic data.…”

Section: Resultsmentioning

confidence: 99%

Construction and Evaluation of a Humic Acid Column: Implication for Pesticide Risk Assessment

André

Truong

et al. 2005

Anal. Chem.

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In this paper, humic acid (HA), known to play a large role in the binding and transport of pesticides in soil, was immobilized on a chromatographic support. Then, the association of some herbicides and rodenticides with the main soil component HA was examined using this novel chromatographic column. It appeared that HA has a lower affinity for neutral than for charged pesticides. Moreover, the influence of various parameters was investigated on the pesticide retention in order to providevaluable information about both the binding mechanism and the utilization conditions of the HA column. For all the pesticides studied, a change was clearly vizualized in the HA-pesticide association mechanism at a critical value of the Na+ concentration in the bulk solvent, x(c), equal to 0.6 M. Around this value, the HA structure balanced between a flexible linear conformation for x < x(c) and a random coil form for x > x(c). This work confirmed the conformation change on HA immobilized on silica. As well, only for the charged pesticides, it was clearly pointed out that below a Na+ concentration equal to 0.3 M, the pesticide binding to HA decreased when the salt concentration was enhanced due to an ion pair formation and a competition effect between the sodium cation and pesticide to bind to the HA molecule. Furthermore, it was established that the HA column was stable during an extended period of time, indicating that the HA column could soon become very attractive to determine the risk assessment of pesticides.

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Saccharose effects on surface association of phenol derivatives with porous graphitic carbon

Cited by 11 publications

References 26 publications

Solvent effects on the retention of oligosaccharides in porous graphitic carbon liquid chromatography

Solvent effects on the retention of oligosaccharides in porous graphitic carbon liquid chromatography

Thermodynamic study of transthyretin association (wild‐type and senile forms) with heparan sulfate proteoglycan: pH effect and implication of the reactive histidine residue

Construction and Evaluation of a Humic Acid Column: Implication for Pesticide Risk Assessment

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