UPHILL TRANSPORT OF SACCHARIDES ACROSS AN ANION-EXCHANGE MEMBRANE

Unmodified carbohydrates were transported across an anion-exchange mem brane from a neutral solution cell (Part O) to a basic solution cell ( Part A) against their concentration gradients. The amount of each suga r transported across the membrane tended to decrease along with an inc rease in the pK(a) value of the sugar. The transportation was dependen t on the presence of a hydroxide-ion concentration gradient. These res ults suggest the uphill transport of sugars based on a coupled counter -transport of hydroxide ion through the anion-exchange membrane. A com parison of the transportation of monosaccharides with that of disaccha rides showed that the steric bulkiness of the sugar molecules affected the amount of each sugar transported. Among the water-soluble organic solvents which have a membrane swelling effect, acetonitrile, having the larger dielectric constant, was found to be a highly effective cos olvent to facilitate uphill transport. When aqueous KOH (10 mM) contai ning D-fructose (2 mM) was added to Part A and a solution of D-fructos e (2 mM) in a 3:7 mixture of water and acetonitrile was added to Part O, the dialysis at 20 degrees C for 3 h changed the ratio of the amoun t of D-fructose in Part A to the amount of D-fructose in Part O from 5 0:50 to 72:28.