Water and ion permeability of a native collagen membrane

With the help of a ribonucleoprotein it is possible to precipitate collagen in a layer of fibers with a 700 Å period. As collagen is a constituent of many membrane systems in the body, it seemed interesting to investigate the permeability of ions and water through a native collagen membrane.The experiments were carried out with the help of an acryl glass apparatus, where an osmotic pressure, a hydrostatic pressure difference or both can be maintained between the two bulk phases separated by the membrane. The diffusion coefficients for NaCl and KCl were found to be comparable with those in other biological membranes (D_s = 9 · 10⁻⁷cm² · s⁻¹) whereas there is difference of more than three orders of magnitude in the hydraulic permeability (L_p = 6 cm⁴ · J⁻¹ · s⁻¹).Volume flow measurements caused by an osmotic gradient indicated that the reflection coefficient for NaCl and KCl is very small. In hydrostatic pressure experiments, the membrane shows a preferred direction for volume flows which seems to have something to do with the mode of preparation of the membrane.