3 research outputs found
Hydrogen Abstraction of Camphor Catalyzed by Cytochrome P450<sub>cam</sub>: A QM/MM Study
A combined
quantum mechanics and molecular mechanics (QM/MM, QM
= UB3LYP-D3, MM = AMBER) method is used to study the hydrogen abstraction
reaction in P450<sub>cam</sub> catalyzed hydroxylation of camphor
in the quartet state. Compared to QM/MM calculations in the literature,
this study uses larger basis sets for the most important atoms at
the active site and QM/MM Hessian harmonic frequency calculations
to determine the standard Gibbs free energy of activation and kinetic
isotope effect. The QM/MM covalent boundary is treated with a capping
hydrogen atom method, which is simple and robust. An energy barrier
of 21.3 kcal/mol and a standard free energy of activation of 16.8
kcal/mol are obtained for this hydrogen abstraction reaction. These
values are similar to those reported in the literature, suggesting
that when a general protocol is followed, QM/MM results are reproducible.
It is found that using a sufficiently large basis set is important
to minimize basis set errors
The 8-Silyloxyquinoline Scaffold as a Versatile Platform for the Sensitive Detection of Aqueous Fluoride
Utilizing a novel 8-silyloxyquinoline
scaffold, we demonstrate
the ability to synthesize fluorogenic probes for the sensitive and
selective detection of inorganic fluoride (NaF) in aqueous samples.
Our initial probe design (<b>2</b>) is capable of detecting
inorganic fluoride at levels as low as 3.8 μM (72 ppb) in aqueous
solutions, well below PHS recommended levels for drinking water (0.7–1.2
ppm), placing this probe among the most sensitive fluoride sensors
reported to date. Furthermore, our results highlight the utility of
the readily modifiable 8-silyloxyquinoline scaffold for the design
of tailored fluoride sensing platforms. We demonstrate the ability
to rationally tune the fluorescence and physical properties of the
8-silyloxyquinoline scaffold, producing a red-shifted fluoride probe
(<b>4</b>) capable of detecting 50 μM (0.95 ppm) NaF in
aqueous samples using a straightforward test-strip-based assay format.
Taken together this work provides a template for the design of fluoride
sensors capable of reporting on relevant concentrations of fluoride
in the laboratory and in the field
Improved Photoinduced Fluorogenic Alkene–Tetrazole Reaction for Protein Labeling
The
1,3-dipolar cycloaddition reaction between an alkene and a
tetrazole represents one elegant and rare example of fluorophore-forming
bioorthogonal chemistry. This is an attractive reaction for imaging
applications in live cells that requires less intensive washing steps
and/or needs spatiotemporal resolutions. In the present work, as an
effort to improve the fluorogenic property of the alkene–tetrazole
reaction, an aromatic alkene (styrene) was investigated as the dipolarophile.
Over 30-fold improvement in quantum yield of the reaction product
was achieved in aqueous solution. According to our mechanistic studies,
the observed improvement is likely due to an insufficient protonation
of the styrene–tetrazole reaction product. This finding provides
useful guidance to the future design of alkene–tetrazole reactions
for biological studies. Fluorogenic protein labeling using the styrene–tetrazole
reaction was demonstrated both in vitro and in vivo. This was realized
by the genetic incorporation of an unnatural amino acid containing
the styrene moiety. It is anticipated that the combination of styrene
with different tetrazole derivatives can generally improve and broaden
the application of alkene–tetrazole chemistry in real-time
imaging in live cells