Recently, defect engineering has been used to intruduce half‐metallicity into selected semiconductors, thereby significantly enhancing their electrical conductivity and catalytic/electrocatalytic performance. Taking inspiration from this, we developed a novel bifunctional electrode consisting of two monolayer thick manganese dioxide (δ‐MnO2) nanosheet arrays on a nickel foam, using a novel in‐situ method. The bifunctional electrode exposes numerous active sites for electrocatalytic rections and displays excellent electrical conductivity, resulting in strong performance for both HER and OER. Based on detailed structure analysis and density functional theory (DFT) calculations, the remarkably OER and HER activity of the bifunctional electrode can be attributed to the ultrathin δ‐MnO2 nanosheets containing abundant oxygen vacancies lead to the formation od Mn3+ active sites, which give rise to half‐metallicity properties and strong H2O adsorption. This synthetic strategy introduced here represents a new method for the development of non‐precious metal Mn‐based electrocatalysts for eddicient energy conversion.
Overprediction is a major limitation of current crystal structure prediction (CSP) methods. It is difficult to determine whether computer-predicted polymorphic structures are artefacts of the calculation model or are polymorphs that have not yet been found. Here, we reported the well-known vitamin nicotinamide (NIC) to be a highly polymorphic compound with nine solved single-crystal structures determined by performing melt crystallization. A CSP calculation successfully identifies all six Z′ = 1 and 2 experimental structures, five of which defy 66 years of attempts at being explored using solution crystallization. Our study demonstrates that when combined with our strategy for cultivating single crystals from melt microdroplets, melt crystallization has turned out to be an efficient tool for exploring polymorphic landscapes to better understand polymorphic crystallization and to more effectively test the accuracy of theoretical predictions, especially in regions inaccessible by solution crystallization.
One
of the most popular strategies of the optimization of drug
properties in the pharmaceutical industry appears to be a solid form
changing into a cocrystalline form. A number of virtual screening
approaches have been previously developed to allow a selection of
the most promising cocrystal formers (coformers) for an experimental
follow-up. A significant drawback of those methods is related to the
lack of accounting for the crystallinity contribution to cocrystal
formation. To address this issue, we propose in this study two virtual
coformer screening approaches based on a modern cloud-computing crystal
structure prediction (CSP) technology at a dispersion-corrected density
functional theory (DFT-D) level. The CSP-based methods were for the
first time validated on challenging cases of indomethacin and paracetamol
cocrystallization, for which the previously developed approaches provided
poor predictions. The calculations demonstrated a dramatic improvement
of the virtual coformer screening performance relative to the other
methods. It is demonstrated that the crystallinity contribution to
the formation of paracetamol and indomethacin cocrystals is a dominant
one and, therefore, should not be ignored in the virtual screening
calculations. Our results encourage a broad utilization of the proposed
CSP-based technology in the pharmaceutical industry as the only virtual
coformer screening method that directly accounts for the crystallinity
contribution.
We
demonstrate the successful application of the state-of-the-art
AstraZeneca in-house and XtalPi cloud-based virtual polymorph screening
workflows in support of stable form selection of crystalline oxabispidine AZD1305, a pharmaceutical compound. Experimental solid form
screening had found two polymorphic forms, A and B, with physical
stabilities that appeared to be extremely close at ambient temperature.
Such observation may make experimental and in silico support of the
solid form selection a challenging task. Both computational approaches
correctly predicted the ranking and geometry of the stable form B
at 0 K. This level of information would be important and sufficient
for project support at the late discovery stage. However, metastable
form A was predicted by both workflows to be considerably less stable
than form B, separated by multiple virtual forms in the lattice energy
landscapes. In order to account for the experimentally observed close
physical stabilities of forms A and B at ambient temperature, calculation
of the free-energy landscape was performed using pseudo-supercritical
path method. This allowed the demonstration that, while form B is
significantly more stable at 0 K, the two forms display a very close
physical stability at ambient temperature. The current work highlights
the importance of using advanced virtual polymorph screening to get
a more comprehensive insight into identifying the most stable form
of a pharmaceutical compound under different experimental conditions.
Terahertz
(THz) waves show nontrivial interactions with living
systems, but the underlying molecular mechanisms have yet to be explored.
Here, we employ DNA origami as a model system to study the interactions
between THz waves and DNA structures. We find that a 3-min THz illumination
(35.2 THz) can drive the unwinding of DNA duplexes at ∼10 °C
below their melting point. Computational study reveals that the THz
wave can resonate with the vibration of DNA bases, provoking the hydrogen
bond breaking. The cooperation of thermal and nonthermal effects allows
the unfolding of undesired secondary structures and the THz illumination
can generate diverse DNA origami assemblies with the yield (>80%)
∼ 4-fold higher than that by the contact heating at similar
temperatures. We also demonstrate the in situ assembly of DNA origami
in cell lysate. This method enables remotely controllable assembly
of intact biomacromolecules, providing new insight into the bioeffects
of THz waves.
In situ synthesis of DNA origami
structures in living systems is
highly desirable due to its potential in biological applications,
which nevertheless is hampered by the requirement of thermal activation
procedures. Here, we report a photothermal DNA origami assembly method
in near-physiological environments. We find that the use of copper
sulfide nanoparticles (CuS NPs) can mediate efficient near-infrared
(NIR) photothermal conversion to remotely control the solution temperature.
Under a 4 min NIR illumination and subsequent natural cooling, rapid
and high-yield (>80%) assembly of various types of DNA origami
nanostructures
is achieved as revealed by atomic force microscopy and single-molecule
fluorescence resonance energy transfer analysis. We further demonstrate
the in situ assembly of DNA origami with high location precision in
cell lysates and in cell culture environments.
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