Transmembrane Protein Function Evaluated in Biomimetic Environments
The scientists can now perform optical fluorescence and electrochemical
studies, isolating a single protein on these microspheres.
Prototype drawing of a
microfluidic instrument
for simultaneous optical
and electrochemical
measurements on a single
transmembrane protein.
Many cell membrane functions — such
as regulation of cellular potential, selective
filtration, molecular recognition, and regulation
of nutrient and waste movement — are
mediated by transmembrane proteins.
Despite decades of intensive research about
the relationship of these proteins’ structure to
function, there is much to be learned.
Now, Sandia researchers, led by Susan
Brozik in collaboration with scientists at the
University of New Mexico, are developing
artificial biomimetic structures, where they
can place transmembrane proteins, eliminating
the complications of the cell and cell
membrane during study.
This approach — borrowing design from
nature — allows scientists to isolate individual
proteins for study, while retaining their
native structure and function. This team of
researchers is also adapting optical and
electrochemical techniques to probe the
structure and function. The goal is the
creation of a body of knowledge that could
benefit drug development, medical treatment,
and biosensing technologies.
Initial work focused on the thermodynamics
of gramicidin ion channel formation (see
above) in supported lipid bilayers, investigated
through single molecule fluorescence
imaging. More recently, lipid-coated nanoporous
silica beads have shown promise as
convenient platforms for the study of transmembrane
proteins.
Scanning electron microscope
images of nanoporous silica
microspheres used to help understand
transmembrane proteins. Image at
the left is a 10,000 times enlargement
of a 10-micrometer bead with
10-nanometer-diameter pores.
Images enlarged to 100,000 times
actual size in right column show
beads (from the top) of 10-, 50-, and
100-nanometer pores.
Team members, including Gabriel Lopez,
Ryan Davis, and James Brozik from UNM,
have learned that the proteins can be correctly
oriented in these artificial substrates,
have near-native diffusion characteristics,
and retain their functions in the biomimetic
environment. To date, the beads have been
the most stable biomimetic platform reported.
The scientists can now perform optical
fluorescence and electrochemical studies,
isolating a single protein on these microspheres.
Ultimately, the goal is to produce new
microfluidic instruments, in which single
transmembrane proteins can be simultaneously
measured with electrochemical and
optical probes. These single-molecule
spectroscopic measurements would offer a
unique opportunity for obtaining a dynamic
view of structural/functional relationships on
transmembrane proteins.
For more information:
Susan Brozik, Ph.D., 505-844-5105, smbrozi@sandia.gov
