Subject(s)
Biotechnology/methods , Proteins/isolation & purification , Biotechnology/economics , Polymers , Salts , Solutions , Thermodynamics , WaterABSTRACT
A general model for the phase behavior of polymer-polymer aqueous two-phase systems containing small amounts of added inorganic salts has been developed from statistical thermodynamics. The model is based on the solution theory of Hill and new electrolyte solution model based on Fluctuation Solution Theory. It includes the effect of polymer molecular weight with scaling expressions from the Renormalization Group theory of polymer solutions. The model has been used to calculate the phase diagram and the partitioning of salt for an aqueous two-phase system containing polyethylene glycol (MW = 8000) and dextran (MW = 28,700) with 0.1 mole/kg of added Na2SO4. The calculations have been compared to experimental results with good agreement.
Subject(s)
Models, Chemical , Polymers/isolation & purification , Ions , Models, Statistical , Solubility , ThermodynamicsABSTRACT
Microgravity research includes investigations designed to gain insight on methods of separating living cells. During a typical separation certain real-time measurements can be made by optical methods, but some materials must also be subjected to subsequent analyses, sometimes including cultivation of the separated cells. In the absence of on-orbit analytical or fraction collecting procedures, some means is required to "capture" cells after separation. The use of solutions that form gels was therefore investigated as a means of maintaining cells and/or macromolecules in the separated state after two types of simple ground-based experiments. Microgravity electrophoresis experiments were simulated by separating model cell types (rat, chicken, human and rabbit erythrocytes) in a vertical density gradient containing low-conductivity buffer, 1.7%-6.5% Ficoll, 6.8-5.0% sucrose, and 1% SeaPrep low-melting temperature agarose and demonstrating that, upon cooling, a gel formed in the column, and cells could be captured in the positions to which they had migrated. Two-phase extraction experiments were simulated by choosing two-polymer solutions in which phase separation occurs in normal saline at temperatures compatible with cell viability and in which one or both phases form a gel upon cooling. Suitable polymers included commercial agaroses (1-2%), maltodextrin (5-7%) and gelatin (5-20%).
Subject(s)
Cell Separation/methods , Erythrocytes/cytology , Gels , Weightlessness Simulation , Animals , Chickens , Culture Media , Electrophoresis/methods , Gelatin , Humans , Polysaccharides , Rabbits , Rats , SepharoseABSTRACT
This study examined gel filtered rat platelet activation by Walker 256 rat carcinoma cells and characterized fibronectin release. Using aggregometry measurements, a biphasic platelet response was characterized and the timing of alpha granule release was determined. The localization and association of released platelet fibronectin with tumor cell-platelet aggregates was determined by immunofluorescent and immunocytochemical methods. The immunofluorescent studies showed that the platelet fibronectin was released and became associated with the peripheries of the tumor cells following alpha granule discharge. The ultrastructural immunocytochemical data revealed that this fibronectin was associated with a fibrin-like material, enmeshing the tumor cell-platelet aggregates. The significance of the release and localization of platelet fibronectin to tumor cell metastasis is discussed.
