Project Details


The goal of this work is to describe specific ion and pH effects on the
apparent pKa's of micellized surfactants with head groups that model those
of membrane phospholipids. Potentiometric titrations will be carried out
on four different micellized subfactants with increasingly complex head
groups using a variety of counterion concentrations and types. Specific
ion electrodes will be used to monitor the distribution of each counterion
and micellar bound spectrophotometric indicators to distinguish between
site bound protons and the proton "concentration-in-the-immediate-vicinity"
of the micelle surface. The experimental results should provide crucial
tests of current models for the structure of charged aqueous interfaces.
If successful, it will be possible to describe, quantitatively, the
observed shifts in the apparent pKa's of the titratable phosphate, carboxyl
and amino functional groups attached to the surfactant head group and the
apparent pKa's of micellar bound indicators over a wide range of
experimental conditions, using a single value for the intrinsic pKa's of
the functional groups and bound indicators and independently verifiable
constants for the distribution of counterions between the micellar and
aqueous phase.

These results should provide a clearer picture of the structure of the
electrical double layer around functionalized micelles as a function of
surface charge density; a more detailed understanding of the relationship
between head group structure, specific ion binding and surface pH; aid in
the interpretation of the catalytic activity of functional micelles;
increase the utility of spectrophotometric indicators as probes of surface
pH of membranes and membrane mimetic agents; and clarify how the electrical
double layer influences structural properties of phospholipid vesicle such
as phase transition temperature, fusion and domain formation. The dynamic
response of bilayer structure to its environment mediates a number of
important functions of biological membranes such as excitability, active
and passive transport, fluidity, the absorption of anesthetics and the
activity of membrane bound enzymes. A clear picture of the specific
interactions between the components of biological membranes may be
important in understanding diseases, such as Tay-Sachs, which are caused
bydefects in the catabolism of certain classes of phospholipids.
Effective start/end date1/1/901/1/90


  • National Institute of General Medical Sciences
  • National Institute of General Medical Sciences
  • National Institute of General Medical Sciences


  • Catalysis


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