Osmotic stress (OS) is an experimental strategy originally developed to measure hydration and other forces between phospholipid bilayers. It is now being used to study the energetics of other macromolecular assemblies and of single macromolecular conformational changes.

Some references here describe the application of OS to membrane and macromolecular interactions, to membrane channel gating, and to small molecule binding and enzyme function.

An Art Gallery provides conceptual views of how it works in several specific applications. Here we are looking specifically at hexokinase and actin.

We provide here a Data Base of Measured Osmotic Pressures, seen below, of several solutes or osmolytes which can be used by those interested in doing osmotic stress experiments.

For more news on osmotic stress, and macromolecular forces check out the Laboratory of Structural Biology page at NIH in Washington.

OS-niks

Here is a list of people, who are either using osmotic stress experimentally, or have closely connected interests somehow.

• whom you can contact by e-mail by clicking on their name
• or see what they are doing through their web site

Osmotic Pressure Data

Osmotic pressure measurements are given here for several different osmolytes, of different molecular weights. They are for the stated polymer dissolved in pure water.

The osmotic pressures were measured several different ways:

1. measured DIRECTLY by determining the pressure required on the solution side of a semipermeable membrane to prevent water flow into that solution.
2. measured using the relationship between osmotic pressure and REPEAT SPACING of the phospholipid lamellar phase of SOPC (1-Stearoyl-2-Oleoyl- sn -Glycero-3-Phosphocholine)
3. measured through the VAPOUR PRESSURE of the solutions using a vapour pressure osmometer.
4. measured using light scattering
5. measured using Sedimentation Equilibrium Ultracentrifugation

All measurements were done at 20 degrees C, UNLESS otherwise stated. The temperature coefficient is low but some measurements can be found in Methods of Enzymology 127: p400-416 (1986) and recent measurements at different temperatures have been completed for PEG 400 and PEG 8000 (Stanley and Strey, Department of Polymer Science and Engineering, University of Massachusetts)

The Data

The following individual tables provide the measured osmotic pressures for the indicated weight percent osmolyte in water.

Polyethylene Glycols of the Follwing Molecular Weights

300, 400, 400 at various temperatures, 600, 1,000, 1,500, 2,000, 3,000, 4,000, 6,000, 8,000, 8000 at various temperatures, 10,000, 20,000, and 20,000 at 7 degrees.

Methylated Polyethylene Glycol, MW 2000

Polyvinylpryrrolidone

Polyvinylalchol

Dextrans of the Molecular Weights

40,000, from 0.1 to20 wt%

10,000, from 14 to 34 wt%

100,000, from 0.1 to 5 wt%

3 to 15 wt%

16.6 to 28.4 wt %

all fitted from 0.2 to 40 wt%

Triethylene glycol

Sucrose

Betaine

Sodium chloride

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