The outbreak of coronavirus disease 2019 (COVID-19) due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed significant threats to international health. The genetic traits as ...well as evolutionary processes in this novel coronavirus are not fully characterized, and their roles in viral pathogenesis are yet largely unknown. To get a better picture of the codon architecture of this newly emerging coronavirus, in this study we perform bioinformatic analysis, based on publicly available nucleotide sequences of SARS-CoV-2 along with those of other members of human coronaviruses as well as non-human coronaviruses in different hosts, to take a snapshot of the genome-wide codon usage pattern of SARS-CoV-2 and uncover that all over-represented codons end with A/U and this newly emerging coronavirus has a relatively low codon usage bias, which is shaped by both mutation pressure and natural selection. Additionally, there is slight variation in the codon usage pattern among the SARS-CoV-2 isolates from different geo-locations. Furthermore, the overall codon usage pattern of SARS-CoV-2 is generally similar to that of its phylogenetic relatives among non-human betacoronaviruses such as RaTG13. Taken together, we comprehensively analyze the characteristics of codon usage pattern in SARS-CoV-2 via bioinformatic approaches. The information from this research may not only be helpful to get new insights into the evolution of SARS-CoV-2, but also have potential value for developing coronavirus vaccines.
A photoelectrochemical method for the C−H alkylation of heteroarenes with organotrifluoroborates has been developed. The merger of electrocatalysis and photoredox catalysis provides a chemical ...oxidant‐free approach for the generation and functionalization of alkyl radicals from organotrifluoroborates. A variety of heteroarenes were functionalized using primary, secondary, and tertiary alkyltrifluoroborates with excellent regio‐ and chemoselectivity.
A radical approach: A photoelectrochemical method has been developed for the C−H alkylation of heteroarenes with organotrifluoroborates under oxidant‐free conditions. A variety of heteroarenes can be functionalized with primary, secondary, and tertiary alkyl groups with excellent regio‐ and chemoselectivity.
The recent confirmation of the muon
g
-
2
anomaly by the Fermilab
g
-
2
experiment may harbinger a new era in
μ
and
τ
physics. In the context of general two Higgs doublet model, the discrepancy can ...be explained via one-loop exchange of sub-TeV exotic scalar and pseudoscalars, namely
H
and
A
, that have flavor changing neutral couplings
ρ
τ
μ
and
ρ
μ
τ
at
∼
20
times the usual tau Yukawa coupling,
λ
τ
. Taking
ρ
ℓ
ℓ
′
∼
λ
m
i
n
(
ℓ
,
ℓ
′
)
, we show that the above solution to muon
g
-
2
then predicts enhanced rates of various charged lepton flavor violating processes, which should be accessible at upcoming experiments. We cover muon related processes such as
μ
→
e
γ
,
μ
→
e
e
e
and
μ
N
→
e
N
, and
τ
decays
τ
→
μ
γ
and
τ
→
μ
μ
μ
. A similar one-loop diagram with
ρ
e
τ
=
ρ
τ
e
=
O
(
λ
e
)
induces
μ
→
e
γ
, bringing the rate right into the sensitivity of the MEG II experiment. The
μ
e
γ
dipole can be probed further by
μ
→
3
e
and
μ
N
→
e
N
. With its promised sensitivity range and ability to use different nuclei, the
μ
N
→
e
N
conversion experiments can not only make discovery, but access the extra diagonal quark Yukawa couplings
ρ
qq
. For the
τ
lepton, we find that
τ
→
μ
γ
would probe
ρ
τ
τ
down to
λ
τ
or lower, while
τ
→
3
μ
would probe
ρ
μ
μ
to
O
(
λ
μ
)
.
We study electroweak baryogenesis driven by the top quark in a general two Higgs doublet model with flavor-changing Yukawa couplings, keeping the Higgs potential CP invariant. With Higgs sector ...couplings and the additional top Yukawa coupling ρtt all of O(1), one naturally has sizable CP violation that fuels the cosmic baryon asymmetry. Even if ρtt vanishes, the favor-changing coupling ρtc can still lead to successful baryogenesis. Phenomenological consequences such as t→ch, τ→μγ electron electric dipole moment, h→γγ, and hhh coupling are discussed.
C−H/N‐H cross‐coupling is an ideal strategy to synthesize various amines but remains challenging owing to the requirement for sacrificial chemical oxidants and the difficulty in controlling the ...regio‐ and chemo‐selectivity. Herein we report a site‐selective electrochemical amination reaction that can convert benzylic C−H bonds into C‐N linkages via H2 evolution without need for external oxidants or metal catalysts. The synthetic strategy involves anodic cleavage of benzylic C−H to form a carbocation intermediate, which is then trapped with an amine nucleophile leading to C−N bond formation. Key to the success is to include HFIP as a co‐solvent to modulate the oxidation potentials of the alkylbenzene substrate and the aminated product to avoid overoxidation of the latter.
An electrooxidative C−H/N−H cross‐coupling reaction with excellent site selectivity for benzylic positions is presented. The electrochemical C−H amination reaction employs easily available starting materials and proceeds under mild conditions without need for transition‐metal catalysts and external chemical oxidants.
An electrochemical electrophilic bromination/spirocyclization of N -benzyl-acrylamides with 2-bromoethan-1-ol as the brominating reagent has been developed. The paired electrolysis employs low ...concentrations of bromine produced from both cathodic reduction and anodic oxidation as an electrophile, and realizes an H 2 O-involved electrophilic spirocyclization. A number of unexplored brominated 2-azaspiro4.5decanes are obtained with satisfactory yields under mild conditions, and the reaction exhibits good efficiency at the gram-scale synthesis. In addition, this approach is further highlighted by late-stage transformations and synthetic applications in constructing cyclohepta c pyrrole-1,6-diones via debromination tandem cyclization of brominated 2-azaspiro4.5decanes.
Electrochemistry, which employs electrons as reagents and avoids the use of traditional redox reagents, becomes a powerful tool in oxidative dehydrogenation cross-coupling reactions. 1,3-Dicarbonyl ...derivatives are common and easily available synthetic blocks and are widely used for the construction of active molecules in organic synthesis. 1,3-Dicarbonyl radicals can be generated by direct anodic oxidation or indirect anodic oxidation with the assistance of a redox reagent and can undergo addition to arenes, double bonds or triple bonds to build multifarious organic molecules. In this review, we succinctly summarize the recent advances in the electrochemical generation of 1,3-dicarbonyl radicals from C–H-based 1,3-dicarbonyl derivatives and focus on the mechanistic insights and synthetic applications of these methods and transformations.
Three-dimensional (3D) laser nanoprinting allows maskless manufacturing of diverse nanostructures with nanoscale resolution. However, 3D manufacturing of inorganic nanostructures typically requires ...nanomaterial-polymer composites and is limited by a photopolymerization mechanism, resulting in a reduction of material purity and degradation of intrinsic properties. We developed a polymerization-independent, laser direct writing technique called photoexcitation-induced chemical bonding. Without any additives, the holes excited inside semiconductor quantum dots are transferred to the nanocrystal surface and improve their chemical reactivity, leading to interparticle chemical bonding. As a proof of concept, we printed arbitrary 3D quantum dot architectures at a resolution beyond the diffraction limit. Our strategy will enable the manufacturing of free-form quantum dot optoelectronic devices such as light-emitting devices or photodetectors.
Photoprinting nanoparticles
Nanoparticle assembly often requires tailored selection of the ligands so that they can selectively bond, as with complementary DNA strands. Alternately, they can be linked together at specified locations using photopolymerization to connect ligands at desired places. However, this process adds to the complexity of making the nanoparticles and is limited by the fidelity of the ligand attachment. Liu
et al
. show that light can be used to desorb surface thiolate ligands from cadmium selenide/zinc sulfide core shell quantum dots (see the Perspective by Pan and Talapin). The resulting trapped holes drive bonding between the particles through the remaining surface ligands. The authors reveal photoprinting of arbitrary three-dimensional architectures at a resolution beyond the diffraction limit and for a range of nanocrystals. Printing can be optically selected based on the size and/or bandgap of the quantum dots. —MSL
Photoexcitation-induced chemical bonding enables high-resolution three-dimensional printing of semiconductor quantum dots.
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