title: A sensitive and accurate gel osmometer.
abstract: 1. A bilayer strip, cut from a thin layer of cross-linked polyacrylamide gel cast on to cellulose tissue, forms an open circular loop whose ends are close together. Shrinkage of the gel, in response to the osmotic pressure of a non-penetrating solution, causes a proportional separation of the ends of the loop. This is measured with a microscope and micrometer eyepiece. 2. The resulting effective sensitivity is about 30 times that of the Sephadex-bead osmometer (Ogston & Wells, 1970), i.e. of the order of 5Pa, comparable with that of a membrane osmometer. Use of gel up to 70% (w/v) allows the measurement of molecular weights, as low as 1500 in favourable cases, with an accuracy of 1-2%. The useful range of osmotic pressure is up to 5kPa. A single measurement requires 0.5ml of solution. Equilibration is completed in 20-30min. 3. The method is illustrated by measurements on human serum albumin, ovalbumin, cytochrome c, samples of dextrans, polyvinyl alcohol, and polyethylene glycols 6000 and 1000.
mesh_terms: D000178:Acrylamides; D002627:Chemistry, Physical / Q000295:instrumentation; D003574:Cytochrome c Group / Q000032:analysis; D003911:Dextrans / Q000032:analysis; D005069:Evaluation Studies as Topic; D005782:Gels; D006018:Glycols / Q000032:analysis; D006801:Humans; D008433:Mathematics; D008722:Methods; D008970:Molecular Weight; D009995:Osmosis; D009997:Osmotic Pressure; D010047:Ovalbumin / Q000032:analysis; D010539:Permeability; D011095:Polyethylenes / Q000032:analysis; D011134:Polysaccharides; D011142:Polyvinyl Alcohol / Q000032:analysis; D012709:Serum Albumin / Q000032:analysis; D012965:Sodium Chloride; D013696:Temperature
chemical_list: D000178:Acrylamides; D003574:Cytochrome c Group; D003911:Dextrans; D005782:Gels; D006018:Glycols; D011095:Polyethylenes; D011134:Polysaccharides; D012709:Serum Albumin; D012965:Sodium Chloride; D011142:Polyvinyl Alcohol; D010047:Ovalbumin