Biology Reference
In-Depth Information
variations in the fluorescence intensity, which can be correlated with partner
association.
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However, if cargo proteins possess one or several tryptophan
residues, the intrinsic fluorescence approach can no longer be applicable.
In this case, an extrinsic probe is clearly required to determine peptide/
protein affinity and characterize the formation of carrier/cargo complexes.
Whatever be the location of the probe, on the cargo protein/peptide or on
the carrier, its fluorescence emission can be monitored to gain insight into
carrier/cargo interactions. As shown for several carrier peptides and various
cargoes, this fluorescence approach allows for the comparison of the affinity
between different carrier/cargo combinations.
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4. FLUORESCENCE FOR PROTEIN/MEMBRANE
INTERACTIONS
Biological membranes constitute important components of living
cells. Constituting a physical barrier between the cytosol and the extracel-
lular environment, lipid membranes also compose the architecture of several
intracellular compartments such as the Golgi, the endoplasmic reticulum,
mitochondria, or the different types of endosomal/lysosomal vesicles
involved in intracellular traffic. Membrane studies are often associated with
analyses of specific proteins or peptides that are able to interact with, or are
especially localized through, the lipid bilayer or the surface of membranes.
From the role of membrane proteins to the translocating properties of some
peptides, the protein/membrane interactions have been widely investigated.
Among the different strategies for deciphering the nature and strength of
protein/membrane interactions, the use of fluorescent probes as well as
the involvement of new fluorescence technologies provides a better insight
into protein/lipid affinity. In this section, the focus is on fluorescence
approaches
for protein or peptide/membrane interactions,
from lipid
bilayer insertion to direct phospholipid interactions.
4.1. Probing membrane interactions with tryptophan
solvatochromism
Membrane insertion of a molecule may be easily correlated with its ability to
be partially or fully embedded through fatty acyl chains that maintain phos-
pholipid bilayer integrity. The development of membrane models has led to
different systems that can mimic the natural membrane. Indeed, biological
membranes are usually composed of numerous compounds. From phospho-
lipids to membrane proteins, there are clearly too many components to study
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