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Neville G Pinto

Publications and source records attributed to Neville G Pinto.

10 recordsLinked to original sources
PubMed2006

Incorporating water-release and lateral protein interactions in modeling equilibrium adsorption for ion-exchange chromatography.

The equilibrium adsorption of two albumin proteins on a commercial ion exchanger has been studied using a colloidal model. The model accounts for electrostatic and van der Waals forces between proteins and the ion exchanger surface, the energy of interaction between adsorbed proteins, and the contribution of entropy from water-release accompanying protein adsorption. Protein-surface interactions were calculated using methods previously reported in the literature. Lateral interactions between adsorbed proteins were experimentally measured with microcalorimetry. Water-release was estimated by applying the preferential interaction approach to chromatographic retention data. The adsorption of ovalbumin and bovine serum albumin on an anion exchanger at solution pH>pI of protein was measured. The experimental isotherms have been modeled from the linear region to saturation, and the influence of three modulating alkali chlorides on capacity has been evaluated. The heat of adsorption is endothermic for all cases studied, despite the fact that the net charge on the protein is opposite that of the adsorbing surface. Strong repulsive forces between adsorbed proteins underlie the endothermic heat of adsorption, and these forces intensify with protein loading. It was found that the driving force for adsorption is the entropy increase due to the release of water from the protein and adsorbent surfaces. It is shown that the colloidal model predicts protein adsorption capacity in both the linear and non-linear isotherm regions, and can account for the effects of modulating salt.

Adsorption↗
PubMed2006

Synthesis of ordered large pore SBA-15 spherical particles for adsorption of biomolecules.

The synthesis of spherical particles of mesoporous silicates (SBA-15) with mesopore diameter upto 127A, and particle diameter of 4-10 microm has been achieved. The SBA-15 spheres were obtained using pluronics P123 (EO20PO70EO20) as a surfactant coupled with cetyltrimethylammonium bromide (CTAB) as a co-surfactant. Ethanol played a very important role in the formation of silica spheres, as it delays the reaction rate of the SBA-15 synthesis. A wide range of pore diameters (28-127 A) of these spherical SBA-15 materials with large surface area >700 m2/g has been synthesized. The effects of temperature, ethanol, CTAB and swelling agent have also been studied. The SBA-15 samples were characterized using small angle X-ray scattering (SAXS), N2 adsorption-desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The spherical SBA-15 after mechanical grinding was used for protein adsorption, and adsorption capacity was compared with that of conventional fibrous SBA-15. The spherical SBA-15 particles with pore diameter of 127 A have a very high capacity of 700 mg/g for lysozyme at pH 7.

Adsorption↗
PubMed2005

Determination of adsorption isotherms of proteins by H-root method: comparison between open micro-channels and conventional packed columns.

This communication compares the accuracy of a micro open parallel plate system (microOPPS) with a conventional packed column for predicting isotherm data by using the H-root method (HRM). HRM is restricted to compounds obeying the Langmuir isotherm model. The performance of the two chromatographic systems was simulated by using comprehensive mathematical models. Operating conditions were varied and their effects on the accuracy of predictions was evaluated. Better accuracy in the isotherm predictions was obtained with the packed column due to its higher efficiency. However, good predictions can be obtained with the microOPPS with the advantage of significantly lower sample consumption.

Proteins↗
PubMed2005

Protein adsorption on the mesoporous molecular sieve silicate SBA-15: effects of pH and pore size.

A mesoporous molecular sieve silicate, SBA-15, with three pore sizes (38.1 A, 77.3 A, and 240 A) has been synthesized using a non-ionic, tri-block copolymer as a template in a sol-gel method. The effects of synthesis conditions on the pore size and pore-size distribution of this adsorbent have been described. The adsorption of proteins on these crystalline, ordered, materials has been studied. The kinetics of adsorption and equilibrium capacity have been probed with three proteins of different dimensions. The effects of electrostatic interactions and protein size are illustrated. It has been shown that SBA-15 materials can be tailored to show size selectivity for proteins, and very high capacities (450 mg/g) can be obtained. Furthermore, the rates of adsorption are shown to be dependent on the pore size, protein structure and solution pH.

Adsorption↗
PubMed2004

Effectiveness of the H-root method for determining adsorption isotherms of protein-salt systems in open micro-channels.

The application of the H-root method (HRM) for predicting isotherm data for protein-salt systems in open-channel chromatographs is presented. HRM mainly consists of performing a regression of the chromatographic response of a system in order to predict the isotherms of the solutes. The method is applicable to proteins with Type I (Langmuir) isotherms. HRM enables a quick determination of the effects of salt on protein isotherms, to facilitate the development of preparative separation protocols of trace proteins in open micro-channel systems. Two configurations were investigated: micro open parallel plate system (microOPPS) and micro open tubular system (microOTS). The effectiveness of HRM was evaluated by simulating the behavior of these open-channel systems with mass-transfer effects included. The influence of operating and geometrical parameters was determined with a detailed parametric study. It was found that HRM can give good estimates of the adsorption isotherms in both micro-channel systems. This is primarily attributed to efficient mass transfer, which ensured correspondence to the equilibrium assumption of HRM. In general, the microOTS was found to give more accurate predictions than the microOPPS. This is attributed to the smooth circular perimeter of flow. Nevertheless, the difference in accuracy is generally insignificant, and with the proper selection of operating conditions, both systems are well suited for HRM.

Adsorption↗
PubMed2004

Calorimetric investigation of the adsorption of nitrogen bases and nucleosides on a hydrophobic interaction sorbent.

Heats of adsorption for nitrogen bases and nucleosides on Sepharose CL-6B, a hydrophobic interaction adsorbent, were collected through flow microcalorimetry in order to ascertain the thermodynamic driving force for adsorption in each case. It was determined that enthalpy changes associated with base stacking self-interactions can contribute significantly to the observed heats of adsorption. Accordingly, the observed heats were the net effect of the adsorbate/adsorbent interactions and the adsorbate stacking self-interactions. Since base stacking proceeds beyond the dimer stage, multi-layer adsorption of these compounds is possible, even at low solution concentrations.

Calorimetry↗
PubMed2004

On the potential of electrochemically modulated liquid chromatography of proteins in a micro open parallel plate separator.

Electrochemically Modulated Liquid Chromatography (EMLC) is a technique in which an electrical potential is applied to the stationary phase in order to alter its adsorptive properties. The micro Open Parallel Plate Separator (microOPPS) is an open-channel micro-chromatographic system with the unique characteristic of an adjustable rectangular flow cross-section. In this publication, the performance of the microOPPS in the EMLC mode was simulated using a comprehensive mathematical model. The separation of two proteins was analyzed by performing a parametric study for the effects of the potential applied to the stationary phase, the dimensions of the device, and the operating conditions. It is shown that the combination of the microOPPS and EMLC is promising for protein separations. These separations can be optimized by carefully selecting the applied potential and the geometry of the microOPPS. The marriage of the microOPPS and EMLC adds two additional dimensions for control, to improve the separation efficiency in analytical applications and in preparative separations of trace compounds.

Chromatography, Liquid↗
PubMed2003

Comparison of preparative characteristics of micro open parallel plate separators and microbore columns for concentration of trace species by displacement chromatography.

The potential for preparative concentration of trace species by displacement chromatography in a micro open parallel plate separator (microOPPS) has been explored. A comparison of the performance of the microOPPS with micro open tubular columns (microOTC) has been presented. Using simulation models, the effects of operating and equilibrium parameters on throughput and yield have been determined. It is shown that the microOPPS can offer considerable advantages over the traditional microOTCs. Most significantly, throughputs can be enhanced by more than an order of magnitude in many cases. This is primarily due to the higher loading per cycle in the microOPPS, made possible by the ability to change the depth of the channel independent of the width. While yield is generally lower in the microOPPS, this effect can be overcome by the proper selection of operating conditions.

Chromatography, Liquid↗
PubMed2002

Characterization of enthalpic events in overloaded ion-exchange chromatography.

Protein adsorption can be either endothermic or exothermic depending upon the protein, the sorbent and process conditions. In the case of protein adsorption onto ion-exchange surfaces exothermic adsorption heats are usually characterized as representing the electrostatic interaction between two oppositely charged surfaces. Endothermic adsorption heats are typically characterized as representing protein reconfiguration and/or repulsive interactions between adsorbed molecules. In certain segments of the literature surface dehydration and solution non-idealities have been suggested as possible sources of endothermic heats of adsorption. Each of these phenomena was investigated during studies concerning the adsorption of bovine serum albumin and ovalbumin onto an anion-exchange sorbent. The results demonstrated that electrostatic repulsive interactions between adsorbed molecules appears to be a larger contributor to endothermic heats of adsorption than surface dehydration or solution non-idealities. The presence of mobile phase cations can reduce the magnitude of endothermic adsorption heats by screening repulsive interactions between adsorbed molecules. Although water release was not found to be a major contributor to endothermic adsorption heats, it is likely to be a contributor to the entropic driving force associated with the adsorption of bovine serum albumin.

Calorimetry↗