51 research outputs found
The SARS-CoV-2 SSHHPS Recognized by the Papain-like Protease
Viral proteases are highly specific and recognize conserved cleavage site sequences of
∼6–8 amino acids. Short stretches of homologous host–pathogen
sequences (SSHHPS) can be found spanning the viral protease cleavage sites. We
hypothesized that these sequences corresponded to specific host protein targets since
>40 host proteins have been shown to be cleaved by Group IV viral proteases and one
Group VI viral protease. Using PHI-BLAST and the viral protease cleavage site sequences,
we searched the human proteome for host targets and analyzed the hit results. Although
the polyprotein and host proteins related to the suppression of the innate immune
responses may be the primary targets of these viral proteases, we identified other
cleavable host proteins. These proteins appear to be related to the virus-induced
phenotype associated with Group IV viruses, suggesting that information about viral
pathogenesis may be extractable directly from the viral genome sequence. Here we
identify sequences cleaved by the SARS-CoV-2 papain-like protease (PLpro) in
vitro within human MYH7 and MYH6 (two cardiac myosins linked to several
cardiomyopathies), FOXP3 (an X-linked Treg cell transcription factor), ErbB4
(HER4), and vitamin-K-dependent plasma protein S (PROS1), an anticoagulation protein
that prevents blood clots. Zinc inhibited the cleavage of these host sequences
in vitro. Other patterns emerged from multispecies sequence
alignments of the cleavage sites, which may have implications for the selection of
animal models and zoonosis. SSHHPS/nsP is an example of a sequence-specific
post-translational silencing mechanism
Conversion of Bilayers of PS‑<i>b</i>‑PDMS Block Copolymer into Closely Packed, Aligned Silica Nanopatterns
Block copolymer (BCP) self-assembly is an effective and versatile approach for the production of complex nanopatterned interfaces. Monolayers of BCP films can be harnessed to produce a variety of different patterns, including lines, with specific spacings and order. In this work, bilayers of cylinder-forming polystyrene-<i>block</i>-polydimethylsiloxane block copolymer (PS-<i>b</i>-PDMS) were transformed into arrays of silica lines with half the pitch normally attained for conventional monolayers, with the PDMS acting as the source for the SiO<sub><i>x</i></sub>. The primary hurdle was ensuring the bilayer silica lines were distinctly separate; to attain the control necessary to prevent overlap, a number of variables related to the materials and self-assembly process were investigated in detail. Developing a detailed understanding of BCP film swelling during solvent annealing, blending of the PS-<i>b</i>-PDMS with PS homopolymer, utilization of a surface brush layer, and adjustment of the plasma exposure conditions, distinct and separate silica lines were prepared. On the microscale, the sample coverage of PS-<i>b</i>-PDMS bilayers was investigated and maximized to attain >95% bilayers under defined conditions. The bilayer BCP structures were also amenable to graphoepitaxy, and thus, dense and highly ordered arrays of silica line patterns with tightly controlled width and pitch were fabricated and distributed uniformly across a Si surface
Density doubling of block copolymer templated features
Block copolymers can be used to template large arrays of nanopatterns with periodicities equal to the characteristic spacing of the polymer. Here we demonstrate a technique capitalizing on the multilayered arrangement of cylindrical domains to effectively double the pattern density templated by a given polymer. By controlling the initial thickness of the film and the solvent annealing conditions, it was possible to reproducibly create density doubled lines by swelling the film with solvent until bilayers of horizontal cylinders were obtained. This process was also demonstrated to be compatible with graphoepitaxy.Peer reviewed: YesNRC publication: Ye
Sequential Nanopatterned Block Copolymer Self-Assembly on Surfaces
Bottom-up self-assembly of high-density
block-copolymer nanopatterns is of significant interest for a range
of technologies, including memory storage and low-cost lithography
for on-chip applications. The intrinsic or native spacing of a given
block copolymer is dependent upon its size (<i>N</i>, degree
of polymerization), composition, and the conditions of self-assembly.
Polystyrene-<i>block</i>-polydimethylsiloxane (PS<i>-b</i>-PDMS) block copolymers, which are well-established for
the production of strongly segregated single-layer hexagonal nanopatterns
of silica dots, can be layered sequentially to produce density-doubled
and -tripled nanopatterns. The center-to-center spacing and diameter
of the resulting silica dots are critical with respect to the resulting
double- and triple-layer assemblies because dot overlap reduces the
quality of the resulting pattern. The addition of polystyrene (PS)
homopolymer to PS<i>-b</i>-PDMS reduces the size of the
resulting silica dots but leads to increased disorder at higher concentrations.
The quality of these density-multiplied patterns can be calculated
and predicted using parameters easily derived from SEM micrographs
of corresponding single and multilayer patterns; simple geometric
considerations underlie the degree of overlap of dots and layer-to-layer
registration, two important factors for regular ordered patterns,
and clearly defined dot borders. Because the higher-molecular-weight
block copolymers tend to yield more regular patterns than smaller
block copolymers, as defined by order and dot circularity, this sequential
patterning approach may provide a route toward harnessing these materials,
thus surpassing their native feature density
Density Doubling of Block Copolymer Templated Features
Block copolymers can be used to template large arrays
of nanopatterns
with periodicities equal to the characteristic spacing of the polymer.
Here we demonstrate a technique capitalizing on the multilayered arrangement
of cylindrical domains to effectively double the pattern density templated
by a given polymer. By controlling the initial thickness of the film
and the solvent annealing conditions, it was possible to reproducibly
create density doubled lines by swelling the film with solvent until
bilayers of horizontal cylinders were obtained. This process was also
demonstrated to be compatible with graphoepitaxy
Hydroxyapatite extracted by animal bone image analysis in ionic liquid choline chloride-glycerol
Three-Terminal Nanoelectromechanical Field Effect Transistor with Abrupt Subthreshold Slope
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