Chemistry Reference
In-Depth Information
polymer micelles have been shown to be noncovalent hosts for hydrophobic guest
molecules and these can bind to proteins. If these guest molecules can be varied to
be fluorescent dyes, a variety of receptors with different fluorescent transducers
can be achieved very rapidly. We hypothesized (Sandanaraj, Demont et al. 2007)
that this strategy will work, because factors such as the relative frontier orbital ener-
getics of different fluorescent transducers and the distance between the transducer and
the protein will vary for each fluorophore. These variations should provide different
responses and therefore result in a fingerprint for different metalloproteins. This was
demonstrated to be the case using four different metalloproteins and eight different
dye molecules.
2.3.4. Recognition and Detection of Peptides
One of the interesting aspects of amphiphilic homopolymer assemblies is that they
are kinetically trapped in the solvents in which they are initially assembled.
Therefore, we envisioned the possibility of utilizing inverse micelles in apolar
solvents and utilizing electrostatic interactions to selectively remove molecules
with complementary charges from aqueous solutions into the organic phase
(Combariza et al. 2007). It is particularly interesting to be able to achieve such a
separation with peptides based on their isoelectric points (pIs). Peptide detection
is capable of ultimately providing information on proteins, especially in mass
spectrometry based proteomics (Karas and Hillenkamp 1988; Tanaka et al. 1988;
Aebersold and Mann 2003). We hypothesized that 1) the anionic carboxylate
interiors are capable of recognizing positively charged peptides and sequestering
them through electrostatic interactions and 2) because the interactions are mainly
due to electrostatics, the selective separation of proteins can be achieved at different
pH values based on the different pI values of protein. This strategy is schematically
represented in Figure 2.10.
A toluene solution of polymer 15 was added to an aqueous mixture of peptides.
After effective equilibration, the heterogeneous mixture was allowed to separate
and the organic layer was analyzed by matrix assisted laser desorption ionization
mass spectrometry analysis. Because the pH of the aqueous solution was 7.1, the
peptides with pIs above 7.1 were extracted and the peptides with pIs below 7.1
Figure 2.10 Selective extraction of peptides utilizing amphiphilic homopolymeric micelles.
