Source:
JOURNAL OF PHYSICAL CHEMISTRY B, Volume 107, Number 51, p.14537-14544 (2003)
Abstract:
The application of dielectric spectroscopy (DS) to the study of
bacteriorhodopsin (bR)-containing purple membrane films is presented in
this paper. Two types of bR membrane films, oriented and nonoriented,
were investigated in a wide frequency range (10(-2) - 3 x 10(9) Hz) and
temperature interval (5 -70 degreesC). Four relaxation processes were
observed in this frequency range and ascribed to different mechanisms,
related to the structural units of the system. A large nonreversibility
of the dielectric response as a result of heating and cooling has been
observed in the slow processes implicating a change in the structure of
the membrane stacking depending on the history of cooling and heating
of the sample. Significant changes as large as 3 orders of magnitude in
the mobility have been observed in this time scale. Comparison of the
oriented and nonoriented bR membrane films was performed, and it was
found that the oriented purple membrane has a unique liquid
crystal-like ferroelectric behavior.
