Protein precipitation by uncharged water-soluble polymers

Extruded collagen‐polyethylene glycol fibers for tissue engineering applications

“…These observations are in accord with other work, where it was mentioned that flocs formed under polymer overdosing conditions are larger than flocs formed under polymer under‐dosing conditions 57. Bearing in mind that (a) PEG20, 21, 58 can precipitate collagen; (b) the in vitro self‐assembly of collagen molecules into fibrils with periodic patterns59 is analogous to the precipitation of collagen56; (c) precipitation (bulky result occurring at low temperatures) and self‐assembly (structural, highly organised result occurring at around 37°C) are processes driven by forces, which are mainly electrostatic attraction plus hydrogen and hydrophobic bonding57; and (d) taking as particle size the diameter of the fiber produced, the same results obtained from these experiments; the fiber diameter was decreased as the amount of PEG was increased from 5 to 20% (under‐dosing conditions), and the fiber diameter was increased as the amount of PEG was increased from 20 to 40% (overdose conditions) in the FFB. Furthermore, since at 20% PEG the highest correlation between stress at break and fiber diameter was obtained, we tend to believe that the 20% PEG in the FFB comprises the optimum amount of PEG required for the production of reproducible extruded collagen fibers.…”

Concentration of Rous Sarcoma Virus from Tissue Culture Fluids with Polyethylene Glycol

“…PEG has been reported to be effective in concentrating proteins from solutions (5,9,16,23), and it was considered probable that proteinaceous material from medium supplements may VOL. 30, 1975 on July 4, 2020 by guest http://aem.asm.org/ Downloaded from be responsible for aggregation and subsequent losses of RSV(RAV-1).…”

Gels mimicking antibodies in their selective recognition of proteins

“…It should be emphasized that continuous addition of a polymer (or a saturated ammonium sulfate solution) to a mixture of proteins does not give rise to a precipitate where all the different proteins have the same concentrations as in the original mixture. Instead, a stepwise precipitation occurs: each protein precipitates at a certain polymer (ammonium sulfate) concentration, characteristic of each particular protein [19][20][21]. The underlying selectivity mechanism could perhaps~dperate also in the proposed, alternative protein-protein interaction.…”

“…Can this finding be explained by specific protein-protein interactions? One cannot at present exclude completely this possible adsorption mechanism, since proteins can be precipitated in the presence of polymers, such as polyacrylamide, dextran, polyethyleneglycol, etc., i.e., the proteins have a tendency to aggregate in contact with polymers [19][20][21] and also when they are cross-linked to form a gel [22][23]. It should be emphasized that continuous addition of a polymer (or a saturated ammonium sulfate solution) to a mixture of proteins does not give rise to a precipitate where all the different proteins have the same concentrations as in the original mixture.…”