Use of 'soluble lipids' for biochemical processes: linoleic acid-cyclodextrin inclusion complexes in aqueous solutions.

The equilibria of linoleic acid (LA)-cyclodextrin (CD) complexes were studied to investigate the behaviour of 'soluble lipids' in solution as a function of factors that typically affect biochemical processes, such as pH, temperature and CD structure. The above complexes are formed with a stoicheiometry of 1:2 in solution. The first CD molecule interacts with LA through hydrogen bonds when the pH is below the fatty acid pK; hydrophobic interactions may also play an important role at high pH. The second CD molecule makes only hydrophobic contact with the LA hydrocarbon chain. The formation of hydrogen bonds is dependent on the inner diameter of the CD whereas the strength of the hydrophobic interactions between CD and LA can be related to the presence of hydrophobic groups in the CD. The first CD molecule interacts more strongly with LA at increased temperatures. The quantitative description of the LA-CD interaction allows absolute control of the effects produced by the lipid on biochemical processes.