2 research outputs found
Neat Protein–Polymer Surfactant Bioconjugates as Universal Solvents
Solvents,
particularly those having low volatility, are of great
interest for the biocatalytic synthesis of utility chemicals and fuels.
We show novel and universal solvent-like properties of a neat and
water-less polymer surfactant–bovine serum albumin (BSA) conjugated
material (WL-PS<i>p</i>BSA). This highly viscous, nonvolatile
material behaves as a liquid above its solid–liquid transition
temperature (∼25–27 °C) and can be used as a solvent
for variety of completely dry solutes of different sizes and surface
chemistries. We show using a combination of optical microscopy and
steady -state and time-resolved fluorescence spectroscopy that dry
and powdered dyes (hydrophobic Coumarin 153 (C153)), enzymes (α-chymotrypsin
(α-Chy)), or even 1 μm microparticles (diffusion coefficient
ca. three orders slower than C153), can be solubilized and completely
dispersed in the WL-PS<i>p</i>BSA solvent above 25 °C.
While C153, irrespective of its mode of addition to WL-PS<i>p</i>BSA, binds similarly to BSA, α-Chy can be stabilized and activated
to perform its hydrolysis function, even at 100 °C. This work
therefore provides insights into the form of universal solvent characteristic
property for this new class of nonaqueous, nonvolatile, biodegradable
protein–polymer surfactant-based conjugated materials and suggests
potential new avenues that can have a huge impact on biocatalysis,
bionanotechnology, drug delivery, and other applications
Isolation of a Highly Reactive β‑Sheet-Rich Intermediate of Lysozyme in a Solvent-Free Liquid Phase
The
thermal denaturation of solvent-free liquid lysozyme at temperatures
in excess of 200 °C was studied by synchrotron radiation circular
dichroism spectroscopy. Temperature-dependent changes in the secondary
structure were used to map the equilibrium denaturation pathway and
characterize a reactive β-sheet-rich unfolding intermediate
that was stable in the solvent-free liquid phase under anhydrous conditions
but which underwent irreversible aggregation in the presence of water.
The unfolding intermediate had a transition temperature of 78 °C
and was extremely stable to temperature, eventually reaching the fully
denatured state at 178 °C. We propose that the three-stage denaturation
pathway arises from the decreased stability of the native state due
to the absence of any appreciable hydrophobic effect, along with an
entropically derived stabilization of the reactive intermediate associated
with molecular crowding in the solvent-free liquid