2 research outputs found
Bicyclic Peptide Ligands Pulled out of Cysteine-Rich Peptide Libraries
Bicyclic peptide
ligands were found to have good binding affinity
and target specificity. However, the method applied to generate bicyclic
ligands based on phage-peptide alkylation is technically complex and
limits its application to specialized laboratories. Herein, we report
a method that involves a simpler and more robust procedure that additionally
allows screening of structurally more diverse bicyclic peptide libraries.
In brief, phage-encoded combinatorial peptide libraries of the format
X<sub><i>m</i></sub>CX<sub><i>n</i></sub>CX<sub><i>o</i></sub>CX<sub><i>p</i></sub> are oxidized
to connect two pairs of cysteines (C). This allows the generation
of 3 Ă— (<i>m</i> + <i>n</i> + <i>o</i> + <i>p</i>) different peptide topologies because the fourth
cysteine can appear in any of the (<i>m</i> + <i>n</i> + <i>o</i> + <i>p</i>) randomized amino acid
positions (X). Panning of such libraries enriched strongly peptides
with four cysteines and yielded tight binders to protein targets.
X-ray structure analysis revealed an important structural role of
the disulfide bridges. In summary, the presented approach offers facile
access to bicyclic peptide ligands with good binding affinities
Genetic, Structural, and Phenotypic Properties of MS2 Coliphage with Resistance to ClO<sub>2</sub> Disinfection
Common water disinfectants
like chlorine have been reported to
select for resistant viruses, yet little attention has been devoted
to characterizing disinfection resistance. Here, we investigated the
resistance of MS2 coliphage to inactivation by chlorine dioxide (ClO<sub>2</sub>). ClO<sub>2</sub> inactivates MS2 by degrading its structural
proteins, thereby disrupting the ability of MS2 to attach to and infect
its host. ClO<sub>2</sub>-resistant virus populations emerged not
only after repeated cycles of ClO<sub>2</sub> disinfection followed
by regrowth but also after dilution-regrowth cycles in the absence
of ClO<sub>2</sub>. The resistant populations exhibited several fixed
mutations which caused the substitution of ClO<sub>2</sub>-labile
by ClO<sub>2</sub>-stable amino acids. On a phenotypic level, these
mutations resulted in a more stable host binding during inactivation
compared to the wild-type, thus resulting in a greater ability to
maintain infectivity. This conclusion was supported by cryo-electron
microscopy reconstruction of the virus particle, which demonstrated
that most structural modification occurred in the putative A protein,
an important binding factor. Resistance was specific to the inactivation
mechanism of ClO<sub>2</sub> and did not result in significant cross-resistance
to genome-damaging disinfectants. Overall, our data indicate that
resistant viruses may emerge even in the absence of ClO<sub>2</sub> pressure but that they can be inactivated by other common disinfectants