ABSTRACT
The nature of charge transfer (CT) in biological matter is a
subject of outstanding interest both for fundamental knowledge
and applications. Indeed, organic/biological devices are the new
frontiers of technology, due to their potential characteristics of low
cost, small size, and high specificity [BOND (2009-2011); SPOT-
NOSED (2003-2005)]. In general, biological matter is not easy
to be investigated, mostly because a standard (i.e., reliable and
reproducible) way of preparation is still not available in most cases
[Hou et al. (2006, 2007)]. Nevertheless, there are some relevant
exceptions, such as monolayers of purple membrane (PM), a part
of the cell membrane of the halophile Halobacterium salinarum, which is easy to be prepared and suitable for direct electrical
measurements. PM is constituted by a single type of protein, the
light receptor bacteriorhodopsin (bR), organized in trimers (see
Fig. 1.10) and stabilized by lipids [Lozier et al. (1975); Luecke
et al. (1999)]. For this reason, bR is chosen as a relevant prototype
to investigate the correlation between its molecular structure
and electrical properties as measured by different experimental
techniques and theoretically interpreted within the impedance
network protein analogue (INPA) model widely illustrated in
Chapter 4.
