3 research outputs found
Polymer Nanoparticle–Protein Interface. Evaluation of the Contribution of Positively Charged Functional Groups to Protein Affinity
Cationic-functionalized polymer nanoparticles (NPs) show
strikingly distinct affinities to proteins depending on the nature
of the cationic functional group. <i>N</i>-Isopropylacrylamide
(NIPAm) polymer NPs incorporating three types of positively charged
functional groups (guanidinium, primary amino, and quaternary ammonium
groups) were prepared by precipitation polymerization. The affinities
to fibrinogen, a protein with an isoelectric point (pI) of 5.5, were
compared using UV–vis spectrometry and a quartz crystal microbalance
(QCM). Guanidinium-containing NPs showed the highest affinity to fibrinogen.
The observation is attributed to strong, specific interactions with
carboxylate groups on the protein surface. The affinity of the positively
charged NPs to proteins with a range of pIs revealed that protein-NP
affinity is due to a combination of ionic, hydrogen bonding, and hydrophobic
interactions. Protein affinity can be modulated by varying the composition
of these functional monomers in the acrylamide NPs. Engineered NPs
containing the guanidinium group with hydrophobic and hydrogen bonding
functional groups were used in an affinity precipitation for the selective
separation of fibrinogen from a plasma protein mixture. Circular dichroism
(CD) revealed that the protein was not denatured in the process of
binding or release
Light-Triggered Charge Reversal of Organic–Silica Hybrid Nanoparticles
A functional nanoparticle with light-triggered charge
reversal
based on a protected amine-bridged polysilsesquioxane was designed.
An emulsion- and amine-free sol–gel synthesis was developed
to prepare uniform nanospheres. Photolysis of suspensions of these
nanoparticles results in a reversal of the ζ potential. This
behavior has been used to trigger nanoparticle self-assembly, nanocomposite
hydrogel formation, and nanoparticle release, showing the potential
of this material in nanoscale manipulation and nanoparticle therapy
Epitope Discovery for a Synthetic Polymer Nanoparticle: A New Strategy for Developing a Peptide Tag
We describe a novel epitope discovery
strategy for creating an
affinity agent/peptide tag pair. A synthetic polymer nanoparticle
(NP) was used as the “bait” to catch an affinity peptide
tag. Biotinylated peptide tag candidates of varied sequence and length
were attached to an avidin platform and screened for affinity against
the polymer NP. NP affinity for the avidin/peptide tag complexes was
used to provide insight into factors that contribute NP/tag binding.
The identified epitope sequence with an optimized length (tMel-tag)
was fused to two recombinant proteins. The tagged proteins exhibited
higher NP affinity than proteins without tags. The results establish
that a fusion peptide tag consisting of optimized 15 amino acid residues
can provide strong affinity to an abiotic polymer NP. The affinity
and selectivity of NP/tMel-tag interactions were exploited for protein
purification in conjunction with immobilized metal ion/His6-tag interactions
to prepare highly purified recombinant proteins. This strategy makes
available inexpensive, abiotic synthetic polymers as affinity agents
for peptide tags and provides alternatives for important applications
where more costly affinity agents are used