304 research outputs found
Semiconducting Monolayer Materials as a Tunable Platform for Excitonic Solar Cells
The recent advent of two-dimensional monolayer materials with tunable
optoelectronic properties and high carrier mobility offers renewed
opportunities for efficient, ultra-thin excitonic solar cells alternative to
those based on conjugated polymer and small molecule donors. Using
first-principles density functional theory and many-body calculations, we
demonstrate that monolayers of hexagonal BN and graphene (CBN) combined with
commonly used acceptors such as PCBM fullerene or semiconducting carbon
nanotubes can provide excitonic solar cells with tunable absorber gap,
donor-acceptor interface band alignment, and power conversion efficiency, as
well as novel device architectures. For the case of CBN-PCBM devices, we
predict the limit of power conversion efficiencies to be in the 10 - 20% range
depending on the CBN monolayer structure. Our results demonstrate the
possibility of using monolayer materials in tunable, efficient, polymer-free
thin-film solar cells in which unexplored exciton and carrier transport regimes
are at play.Comment: 7 pages, 5 figure
Binding hotspots of BAZ2B bromodomain: Histone interaction revealed by solution NMR driven docking.
Bromodomains are epigenetic reader domains, which have come under increasing scrutiny both from academic and pharmaceutical research groups. Effective targeting of the BAZ2B bromodomain by small molecule inhibitors has been recently reported, but no structural information is yet available on the interaction with its natural binding partner, acetylated histone H3K14ac. We have assigned the BAZ2B bromodomain and studied its interaction with H3K14ac acetylated peptides by NMR spectroscopy using both chemical shift perturbation (CSP) data and clean chemical exchange (CLEANEX-PM) NMR experiments. The latter was used to characterize water molecules known to play an important role in mediating interactions. Besides the anticipated Kac binding site, we consistently found the bromodomain BC loop as hotspots for the interaction. This information was used to create a data-driven model for the complex using HADDOCK. Our findings provide both structure and dynamics characterization that will be useful in the quest for potent and selective inhibitors to probe the function of the BAZ2B bromodomain.This is the final published version of the article. It has been published by the American Chemical Society in Biochemistry. The article can be accessed on their website here: http://pubs.acs.org/doi/abs/10.1021/bi500909d. It is freely available under a CC BY licence
Nanocarbon-Based photovoltaics
Carbon materials are excellent candidates for photovoltaic solar cells: they
are Earth-abundant, possess high optical absorption, and superior thermal and
photostability. Here we report on solar cells with active layers made solely of
carbon nanomaterials that present the same advantages of conjugated
polymer-based solar cells - namely solution processable, potentially flexible,
and chemically tunable - but with significantly increased photostability and
the possibility to revert photodegradation. The device active layer composition
is optimized using ab-initio density functional theory calculations to predict
type-II band alignment and Schottky barrier formation. The best device
fabricated is composed of PC70BM fullerene, semiconducting single-walled carbon
nanotubes and reduced graphene oxide. It achieves a power conversion efficiency
of 1.3% - a record for solar cells based on carbon as the active material - and
shows significantly improved lifetime than a polymer-based device. We calculate
efficiency limits of up to 13% for the devices fabricated in this work,
comparable to those predicted for polymer solar cells. There is great promise
for improving carbon-based solar cells considering the novelty of this type of
device, the superior photostability, and the availability of a large number of
carbon materials with yet untapped potential for photovoltaics. Our results
indicate a new strategy for efficient carbon-based, solution-processable, thin
film, photostable solar cells
Chaperoning of the histone octamer by the acidic domain of DNA repair factor APLF
Nucleosome assembly requires the coordinated deposition of histone complexes H3-H4 and H2A-H2B to form a histone octamer on DNA. In the current paradigm, specific histone chaperones guide the deposition of first H3-H4 and then H2A-H2B. Here, we show that the acidic domain of DNA repair factor APLF (APLF AD) can assemble the histone octamer in a single step and deposit it on DNA to form nucleosomes. The crystal structure of the APLF AD-histone octamer complex shows that APLF AD tethers the histones in their nucleosomal conformation. Mutations of key aromatic anchor residues in APLF AD affect chaperone activity in vitro and in cells. Together, we propose that chaperoning of the histone octamer is a mechanism for histone chaperone function at sites where chromatin is temporarily disrupted
Genetic and Physiological Analysis of Iron Biofortification in Maize Kernels
BACKGROUND: Maize is a major cereal crop widely consumed in developing countries, which have a high prevalence of iron (Fe) deficiency anemia. The major cause of Fe deficiency in these countries is inadequate intake of bioavailable Fe, where poverty is a major factor. Therefore, biofortification of maize by increasing Fe concentration and or bioavailability has great potential to alleviate this deficiency. Maize is also a model system for genomic research and thus allows the opportunity for gene discovery. Here we describe an integrated genetic and physiological analysis of Fe nutrition in maize kernels, to identify loci that influence grain Fe concentration and bioavailability. METHODOLOGY: Quantitative trait locus (QTL) analysis was used to dissect grain Fe concentration (FeGC) and Fe bioavailability (FeGB) from the Intermated B73 × Mo17 (IBM) recombinant inbred (RI) population. FeGC was determined by ion coupled argon plasma emission spectroscopy (ICP). FeGB was determined by an in vitro digestion/Caco-2 cell line bioassay. CONCLUSIONS: Three modest QTL for FeGC were detected, in spite of high heritability. This suggests that FeGC is controlled by many small QTL, which may make it a challenging trait to improve by marker assisted breeding. Ten QTL for FeGB were identified and explained 54% of the variance observed in samples from a single year/location. Three of the largest FeGB QTL were isolated in sister derived lines and their effect was observed in three subsequent seasons in New York. Single season evaluations were also made at six other sites around North America, suggesting the enhancement of FeGB was not specific to our farm site. FeGB was not correlated with FeGC or phytic acid, suggesting that novel regulators of Fe nutrition are responsible for the differences observed. Our results indicate that iron biofortification of maize grain is achievable using specialized phenotyping tools and conventional plant breeding techniques
The Cryo-EM Structure of a Complete 30S Translation Initiation Complex from Escherichia coli
Formation of the 30S initiation complex (30S IC) is an important checkpoint in regulation of gene expression. The selection of mRNA, correct start codon, and the initiator fMet-tRNAfMet requires the presence of three initiation factors (IF1, IF2, IF3) of which IF3 and IF1 control the fidelity of the process, while IF2 recruits fMet-tRNAfMet. Here we present a cryo-EM reconstruction of the complete 30S IC, containing mRNA, fMet-tRNAfMet, IF1, IF2, and IF3. In the 30S IC, IF2 contacts IF1, the 30S subunit shoulder, and the CCA end of fMet-tRNAfMet, which occupies a novel P/I position (P/I1). The N-terminal domain of IF3 contacts the tRNA, whereas the C-terminal domain is bound to the platform of the 30S subunit. Binding of initiation factors and fMet-tRNAfMet induces a rotation of the head relative to the body of the 30S subunit, which is likely to prevail through 50S subunit joining until GTP hydrolysis and dissociation of IF2 take place. The structure provides insights into the mechanism of mRNA selection during translation initiation
An effective method to prepare polymer/nanocrystal composites with tunable emission over the whole visible light range
Phytophthora Nicotianae: Host Range Studies on the Pathogen of Zebra Disease of Agave Hybrid No. 11648
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