Separation of macromolecules by ultrafiltration: removal of poly(ethylene glycol) from human albumin

A Review on Membrane Fouling Prediction Using Artificial Neural Networks (ANNs)

Membrane fouling is a major hurdle to effective pressure-driven membrane processes, such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). Fouling refers to the accumulation of particles, organic and inorganic matter, and microbial cells on the membrane's external and internal surface, which reduces the permeate flux and increases the needed transmembrane pressure. Various factors affect membrane fouling, including feed water quality, membrane characteristics, operating conditions, and cleaning protocols. Several models have been developed to predict membrane fouling in pressure-driven processes. These models can be divided into traditional empirical, mechanistic, and artificial intelligence (AI)-based models. Artificial neural networks (ANNs) are powerful tools for nonlinear mapping and prediction, and they can capture complex relationships between input and output variables. In membrane fouling prediction, ANNs can be trained using historical data to predict the fouling rate or other fouling-related parameters based on the process parameters. This review addresses the pertinent literature about using ANNs for membrane fouling prediction. Specifically, complementing other existing reviews that focus on mathematical models or broad AI-based simulations, the present review focuses on the use of AI-based fouling prediction models, namely, artificial neural networks (ANNs) and their derivatives, to provide deeper insights into the strengths, weaknesses, potential, and areas of improvement associated with such models for membrane fouling prediction.

Precipitation of proteins with polyethylene glycol

Polyethylene glycol is a nondenaturing water-soluble polymer whose ability to precipitate protein from aqueous solution can be qualitatively understood in terms of an excluded volume mechanism. The increment in PEG concentration required to effect a given reduction in solubility is unique for a given protein-polymer pair, being insensitive to solution conditions and primarily dependent on the size of the protein and polymer. Selective manipulation of the solubility of specific proteins through control of their state of association or ligand environment can potentially remove some of the empiricism otherwise involved in fractional precipitation. Adequate methods for removing the polymer are available.

Synthesis, isolation, and characterization of conjugates of ovalbumin with monomethoxypolyethylene glycol using cyanuric chloride as the coupling agent

The experimental conditions for the preparation of conjugates of ovalbumin (OA) and monomethoxypolyethylene glycol (mPEG) of a preselected average degree of conjugation, n, using cyanuric chloride as the coupling agent, have been investigated with emphasis on purification and characterization of the products. These conjugates served as prototypes of tolerogenic mPEG derivatives of antigenic proteins which were capable of suppressing in mammals the immunological response to the corresponding unmodified antigens. In other studies in this laboratory, the tolerogenicity of OA(mPEG)n conjugates was found to be a function of n. The reproducibility of the reaction leading to the production of OA(mPEG)n conjugates was shown to depend primarily on the reactivity of the mPEG-cyanuric chloride intermediate, which--for best results--had to be synthesized under completely anhydrous conditions. Isolation of the OA(mPEG)n conjugates was optimized by the use of ion-exchange chromatography whereby rapid removal of large amounts of uncoupled intermediate from the conjugate was achieved; the conditions of fractionation were affected by the degree of conjugation. This method of purification was superior to dialysis, ultrafiltration, and gel filtration. Furthermore, by the application of analytical hydrophobic interaction HPLC it was possible to differentiate among conjugates of different degrees of conjugation and to establish the absence of any detectable free OA in any of the preparations. The quantity of mPEG in the conjugates was determined directly by NMR.

Protein precipitation with polyethylene glycol

Polyethylene glycol is a nondenaturing water-soluble polymer whose ability to precipitate protein from aqueous solution can be qualitatively understood in terms of an excluded volume mechanism. The increment in PEG concentration required to effect a given reduction in solubility is unique for a given protein-polymer pair, being insensitive to solution conditions and primarily dependent on the size of the protein and polymer. Selective manipulation of the solubility of specific proteins through control of their state of association or ligand environment can potentially remove some of the empiricism otherwise involved in fractional precipitation. Adequate methods for removing the polymer are available.

The influence of poly(ethylene glycol) 6000 on the properties of skeletal-muscle actin

Poly(ethylene glycol) 6000 affected many of the properties of skeletal-muscle actin. It accelerated the rate and increased the extent of actin polymerization as measured by light-scattering and sedimentation studies respectively. Moreover, intrinsic-fluorescence measurements showed that addition of poly(ethylene glycol) 6000 decreased the rate of EDTA-induced denaturation of actin monomer and increased the temperature at which irreversible conformational changes occur in actin monomer. These effects occurred without any apparent direct binding interaction and are postulated to be a consequence of the effect of excluded volume on the thermodynamic activity of actin. A relationship based on spherical geometry was formulated which described the co-volume increment that occurs upon addition of a monomer to a long linear polymer in the presence of a space-filling macromolecule. The application of this relationship to the poly(ethylene glycol) 6000-actin system was not without assumption, but it permitted quantitative estimation of the co-volume increment which proved to be of the sign and magnitude required to explain the increased extent of actin polymerization found experimentally in the presence of various concentrations of poly(ethylene glycol) 6000. It is suggested that, in vivo, excluded volume may play a role in actin-filament formation and in the maintenance of the native G-actin structure.

A new method for the large scale preparation of antitoxic antibodies exhibiting high specific protective activities

A method using polyethylene-glycol and immobilized pepsin for purifying heterologous antitoxic antibodies is described. Using horse antitetanus plasma or sera, F(ab')2 fragments exhibiting specific activities in the range of 150 IU per mg protein were repeatedly isolated with a yield around 80%. The procedure was scaled up from 200 ml up to 201.

Removal of polyethylene glycol from proteins by salt-induced phase separation

The use of poly(ethylene glycol) in the purification of plasma and cellular protein is somewhat complicated by the difficulty of removing it from the protein product. The method presented here, quickly and efficiently removes over 95% of the PEG by the simple addition of salts to induce an aqueous two-phase separation with the PEG in the upper phase and greater than 90% of the protein in the lower phase.