Supramolecular Structures Generated by a p-tert-Butylphenylamide Derivative of Deoxycholic Acid. From Planar Sheets to Tubular Structures through Helical Ribbons

The formation of supramolecular structures initiated by a p-tert-butylphenylamide derivative of deoxycholic acid (Na-t-butPhDC) is investigated. At 1.18 mM concentration of Na-t-butPhDC and 37 degrees C, initial flat ribbons are observed which sell-transform into helical ribbons (with a mean pitch angle of 47 +/- 6) which finally originate molecular tubes with an external diameter of 241 +/- 28 inn. Most of the molecular tubes show helical markings with a pitch angle value of 45 +/- 4 degrees, in full agreement with predictions of simple models based on chiral elastic properties of the membrane. A lateral association mechanism is proposed to account or the growth of the external diameter (from 225 +/- 32 to 546 +/- 59 nm) of tubes with time at 3.99 mM.