Supercoiled circular DNA retention in nonequilibrium chromatography: viscosity and velocity dependence--behavior difference with proteins.

This study demonstrates that the retention behavior of various circular double-stranded DNA molecules (3, 5, and 10 kb) increases over the entire flow-rate range (0.02-1.8 mL/min) at all the mobile phase viscosities (h). The transition between the two well-known nonequilibrium chromatography methods (slalom and hydrodynamic chromatography) is clearly visualized for proteins and does not appear for plasmids because of their strong compact structure. Also, the optimal conditions for F and h are determined to obtain the most efficient separation of these three plasmids in a minimum analysis time.

A biochromatographic framework to evaluate the calcium effect on the antihypertensive molecule-human serum albumin binding.

The Ca(2+) cation effect on the antihypertensive molecule binding on human serum albumin (HSA) was studied by biochromatography. The thermodynamic parameters corresponding to this binding were determined for a wide range of Ca(2+) concentration (x). For the two antihypertensive molecules under study, their binding to HSA can be divided into two Ca(2+) cation concentration regions due to a HSA phase transition. This result was confirmed by an enthalpy-entropy investigation. For a low x value (below x(c)=1.6 mmol l(-1)), the HSA cavity was in an ordered solid-like state leading to an increase in the interactions between the antihypertensive drugs and the HSA cavity and consequently, a solute-HSA affinity increase. For x above x(c), the HSA cavity was in a disordered solid-like state, implying a decrease in the antihypertensive drug-HSA binding.

Triazine-human serum albumin association: thermodynamic approach and sodium effect.

Human serum albumin (HSA) serves as a carrier protein to transport triazine herbicides to molecular targets. In this paper, a theoretical treatment was developed to describe the HSA-triazine herbicides association. A determination of the association constant, K, as well as the degree of complexation n(c) (the percent of complex guest) was carried out. Enthalpy-entropy compensation was also analyzed in relation to this mathematical model to confirm the herbicide complexation behavior with HSA. The role of the sodium cation (Na(+)) on this association was investigated. It was expected that the sodium ion would act on the herbicide-HSA association process by modifying the surface tension of the bulk solvent and increase the K and n(c) values. The results showed that for patients who suffer from Na(+) desequilibrium, the triazine-HSA binding would change and as well the toxicological effect of these herbicides.

Role of the Na+ ion on phenol derivatives/hydroxypropyl-beta-cyclodextrin complex formation on porous graphitic carbon phase.

The reversed-phase liquid chromatography retention of phenol derivatives was investigated over a concentration range of sodium chloride (0-10(-2) M) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) (0-35x10(-3) M) using a porous graphitic carbon (PGC) stationary phase and a methanol/water mixture (50:50 (v/v)) as the mobile phase. A theoretical treatment was developed to investigate the effect of the sodium chloride and hydroxypropyl-beta-cyclodextrin on the equilibrium between the solutes with the PGC surface and the aqueous medium, respectively. The thermodynamic parameter variations were calculated using van't Hoff plots. It was expected that the sodium ion acted on the solute-PGC association process by modifying the surface tension of both the bulk solvent and the PGC surface. The phenol derivative/HP-beta-cyclodextrin complexation was shown to be entropically controlled for all the solutes except for the one which contained the -NO2 group in its structure, i.e. the nitro phenol derivative. A comparison of the compensation temperature of the solute-PGC association process when sodium chloride and HP-beta-CD concentration changed in the mobile phase led to the conclusion that these two modifiers acted via a variation in the hydrophobic effect.

Supercoiled circular DNA and protein retention in non-equilibrium chromatography temperature and velocity dependence: testimony of a transition.

Non-equilibrium chromatography (NEC) is a chromatographic mode for the rapid separation of polymers. The retention behavior of various proteins (human, chicken, bovine serum albumin) and supercoiled circular double-stranded DNA (plasmids) was investigated using a phosphate buffer as a mobile phase at different velocities and column temperatures with a C1 column with very low-packing particle diameter as a stationary phase. It was shown that the two factors (temperature and velocity) constituted important parameters in the retention mechanism of plasmids and proteins in NEC. The protein was retained more than the plasmid. At all the temperatures (5, 10, 15, 20, 25 degrees C) the plasmid retention increased over the entire flow-rate range (0.02-1.8 ml/min). For the protein, the retention curve presented a decrease in the relative retention time until a critical value of the mobile phase flow-rate, followed by an increase. The transition between the two well known NEC methods, slalom chromatography and hydrodynamic chromatography was clearly visualized for proteins at the lowest temperature, but did not appear for plasmids due to their strong compact structure.

Separation in slalom chromatography: stretching and velocity dependence.

Slalom chromatography (SC) is used for the separation of large double-stranded DNA molecules. In this technique, the progression of the DNA fragments through the closed column packing follows the flow direction and is like a snake edging is way into long grass. A novel mathematical model is developed in this paper to describe this hydrodynamic phenomenon. The results obtained provided a model for the resolution between two adjacent peaks on a chromatogram. As well, a chromatographic response function was used to obtain the most efficient separation conditions for a mixture of DNA fragments with sizes higher than 15 kbp in a minimum analysis time.