required to close the channel pore the system is at the threshold value. Following cessation of ion
movement and concomitant neutralization of membrane ethenes, the channel protein relaxes to
the a-helix conformation which restores hydro- phobic matching Leuchtag, 1994. In this man-
ner, microdomain dynamics regulate the duration of channel opening, a model consistent with in
vitro experimental manipulation of ion channel activity by variations in concentration of unsatu-
rated membrane lipids Vreugdenhil et al., 1996. We describe the above process in terms of
biomolecular computing Wallace and Price, 1999, i.e. as a mechanism by which the frequency
coding of classical neural networks is regulated by molecular minimum potential energy searches
Conrad, 1992. Finally, we propose experiments involving Raman and fluorescence resonance en-
ergy transfer FRET spectroscopy as a means of investigating the above features in a liposomal
system.
2. Computational modeling of membrane ethene system stability and polarization
2
.
1
. Rationale Our primary objective was to construct a com-
putational model of ethene polarization. We in- vestigated dipole and quadrupole moments, and
polarizability in the adjacent double bonds of a monomer, dimer, and trimer. The electrical per-
manent moments dipole, quadrupole represent derivatives of the energy E with respect to the
applied electric field vector E
a . Specifically, dipole moment is given as − dEdE
a and quadrupole moment is given as
1 2
d
2
EdE a . Similarly, polariz-
ability is given as − d
2
EdE a
2
and varies with the oscillation of an applied electric field Dykstra,
1997. This latter feature is consistent with the complex, interacting fields with time-dependent
variation in strength that are encountered in actual membranes. The use of a polymer model
stabilized by methylene linkages was justified by computational pragmatics. When ab initio meth-
ods are applied to disconnected model compo- nents,
radical changes
in system
geometry frequently result. We further wished to demon-
strate that systematically increasing the number of aligned ethenes would produce a dramatic in-
crease in the observed polarization.
2
.
2
. Method Calculations were performed on an ethene
monomer, dimer, and trimer using Hyperchem v. 4.5 Hypercube Inc., 1995 and Gaussian 95 W
Frisch et al., 1995. The latter two components were stabilized by methylene linkages Fig. 2.
The 4-31G basis set was used to optimize all structures. Dipole and quadrupole moments and
polarizability values were then calculated on the optimized system using the same basis set.
2
.
3
. Results Sensitivity of the aligned ethenes to an applied
electric field was indicated by our analysis of dipole and quadrupole moments, and polarizabil-
ity Table
1. Proceeding
from the
ethene monomer to the trimer, total dipole moment in-
creases from 0.0000 to 0.6538 Debye. Examina- tion of the quadrupole moments reveals a
consistent 5-fold increase in the axial moments i.e. xx, yy, zz from monomer to trimer. These
cumulative increases suggest a progressive mobi- lization of p electrons. Pronounced fluctuation of
the p electronic structure in the applied field is indicated by component increases in polarizability
from monomer to trimer a
xx
from 7.672 to 93.644, a
yy
from 19.226 to 125.284, a
zz
from 30.875 to 91.345 J
− 1
C
2
m
2
. These increases in turn produced an increase in mean polarizability
a from 19.258 to 103.424 [where a = a
xx
+ a
yy
+ a
zz
3]. Together these results indicate an overall increase in the stability of the aligned
ethenes, as well as a pronounced increase in the mobilized electron polarizability.
3. Ethene polarization and neuromolecular computing
