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Highly Efficient Perovskite Solar Cells Enabled by Multiple Ligand Passivation
Get PDFIn the past decade, the efficiency of perovskite solar cells quickly increased from 3.8% to 25.2%. The quality of perovskite films plays vital role in device performance. The films fabricated by solution-process are usually polycrystalline, with significantly higher defect density than that of single crystal. One kind of defect in the films is uncoordinated Pb2+, which is usually generated during thermal annealing process due to the volatile organic component. Another detrimental kind of defect is Pb-0, which is often observed during the film fabrication process or solar cell operation. Because the open circuit voltage has a close relation with the defect density, it is thus desirable to passivate these two kinds of defects. Here, a molecule with multiple ligands is introduced, which not only passivates the uncoordinated Pb2+ defects, but also suppresses the formation of Pb-0 defects. Meanwhile, such a treatment improves the energy level alignment between the valence band of perovskite and the highest occupied molecular orbital of spiro-OMeTAD. As a result, the performance of perovskite solar cells significantly increases from 19.0% to 21.4%.journal articl
Deeply conserved synteny resolves early events in vertebrate evolution
Get PDFAlthough it is widely believed that early vertebrate evolution was shaped by ancient whole-genome duplications, the number, timing and mechanism of these events remain elusive. Here, we infer the history of vertebrates through genomic comparisons with a new chromosome-scale sequence of the invertebrate chordate amphioxus. We show how the karyotypes of amphioxus and diverse vertebrates are derived from 17 ancestral chordate linkage groups (and 19 ancestral bilaterian groups) by fusion, rearrangement and duplication. We resolve two distinct ancient duplications based on patterns of chromosomal conserved synteny. All extant vertebrates share the first duplication, which occurred in the mid/late Cambrian by autotetraploidization (that is, direct genome doubling). In contrast, the second duplication is found only in jawed vertebrates and occurred in the mid-late Ordovician by allotetraploidization (that is, genome duplication following interspecific hybridization) from two now-extinct progenitors. This complex genomic history parallels the diversification of vertebrate lineages in the fossil record.journal articl
ARE-binding protein ZFP36L1 interacts with CNOT1 to directly repress translation via a deadenylation-independent mechanism
Get PDFEukaryotic gene expression can be spatiotemporally tuned at the post-transcriptional level by cis-regulatory elements in mRNA sequences. An important example is the AU-rich element (ARE), which induces mRNA destabilization in a variety of biological contexts in mammals and can also mediate translational control. Regulation is mediated by trans-acting factors that recognize the ARE, such as Tristetraprolin (TTP) and BRF1/ZFP36L1. Although both proteins can destabilize their target mRNAs through the recruitment of the CCR4-NOT deadenylation complex, TTP also directly regulates translation. Whether ZFP36L1 can directly repress translation remains unknown. Here, we used an in vitro translation system derived from mammalian cell lines to address this key mechanistic issue in ARE regulation by ZFP36L1. Functional assays with mutant proteins reveal that ZFP36L1 can repress translation via AU-Rich elements independent of deadenylation. ZFP36L1-mediated translation repression requires interaction between ZFP36L1 and CNOT1, suggesting that it might use a repression mechanism similar to either TPP or miRISC. However, several lines of evidence suggest that the similarity ends there. Unlike, TTP, it does not efficiently interact with either 4E-HP or GIGYF2, suggesting it does not repress translation by recruiting these proteins to the mRNA cap. Moreover, ZFP36L1 could not repress ECMV-IRES driven translation and was resistant to pharmacological eIF4A inhibitor silvestrol, suggesting fundamental differences with miRISC repression via eIF4A. Collectively, our results reveal that ZFP36L1 represses translation directly and suggest that it does so via a novel mechanism distinct from other translational regulators that interact with the CCR4-NOT deadenylase complex.journal articl
Design Integrin-targeted Molecular Self-assembling Peptides for Studying Cancer Migration Inhibition
Get PDFOkinawa Institute of Science and Technology Graduate UniversityDoctor of PhilosophyCancer metastasis, the ability of cancer cell to change position within the tissue through migration and invasion represents the most deadly aspect of cancer. As one of the ongoing challenges in cancer therapy, it’s failed in most treatments. For example, cell surface receptor-integrin that functions as adhesion molecule is well-recognized drug target for anti-metastatic drug development. By targeting the integrin-ligand binding site, antibody, and small molecule antagonists have been commonly used. But these treatments only offer modest response rates on limited cancer types. Therefore, nanotechnology that has been widely applied in biomedical engineering is desired in the cancer metastasis treatment. Inspired by the facts that integrin density, clustering, and redistribution on cell surface are the key spatial features influencing cell motility, we intend to develop a molecular self-assembly (MSA) technology that suppresses cancer metastasis by regulating integrin spatial distribution. To achieve the goal, we designed and synthesized a library of self-assembling integrin ligands composed of 29 peptides made via conjugation of phenylalanine based hydrophobic peptide and various integrin ligands. After confirming that they self-assemble in aqueous solution, we examined these peptides in multiple cancer cell lines and screened out five peptides that exert caner-cell-specific migration. We further examined peptide 5 among the 5 peptides and observed the peptide shows inhibition on cancer invasion, spheroid growth and spreading. We explored the molecular mechanism of the peptide on migration inhibition and found the the self-assembly of the peptide forms nanostructured microdomain as nano-biointerface on cancer cell membrane. We examined the molecular consequences of the bio-nanointerface on mechanotransduction-related proteins, especially the Hippo signaling related ones. Finally, the peptide is applied in xenograft tumor models in mice to examine the efficacy of tumor suppression effect and the molecular consequences in vivo. The research work presented in the thesis is intend to establish an easy and practical strategy for anti-metastatic drug development, and illustrate how basic biochemical insights can be exploited as the basis for a nano-biointerface fabrication technology which links nanoscale protein activities to molecular biological activities to suppress metastasis.doctoral thesi
More on quantum chiral higher spin gravity
Get PDFChiral higher spin gravity is unique in being the smallest higher spin extension of gravity and in having a simple local action both in flat and (anti-)de Sitter spaces. It must be a closed subsector of any other higher spin theory in four dimensions, which makes it an important building block and benchmark. Using the flat space version for simplicity, we perform a thorough study of quantum corrections in chiral theory, which strengthens our earlier results [E. Skvortsov, T. Tran, and M. Tsulaia, Phys. Rev. Lett. 121, 031601 (2018)]. Even though the interactions are naively nonrenormalizable, we show that there are no UV divergences in two-, three-, and four-point amplitudes at one loop thanks to the higher spin symmetry. We also give arguments that the AdS chiral theory should exhibit similar properties. It is shown that chiral theory admits Yang-Mills gaugings with U(N), SO(N), and USp(N) groups, which is reminiscent of the Chan-Paton symmetry in string theory.journal articl
Passive microwave radiometry in biomedical studies
Get PDFPassive microwave radiometry (MWR) measures natural emissions in the range 1–10 GHz from proteins, cells, organs and the whole human body. The intensity of intrinsic emission is determined by biochemical and biophysical processes. The nature of this process is still not very well known. Infrared thermography (IRT) can detect emission several microns deep (skin temperature), whereas MWR allows detection of thermal abnormalities down to several centimeters (internal or deep temperature). MWR is noninvasive and inexpensive. It requires neither fluorescent nor radioactive labels, nor ionizing or other radiation. MWR can be used in early drug discovery as well as preclinical and clinical studies.journal articl
Armored eyes of the whale shark
Get PDFThis report elaborates on adaptations of the eyes of the whale shark Rhincodon typus (Elasmobranchii, Rhincodontidae), including the discovery that they are covered with dermal denticles, which is a novel mechanism of eye protection in vertebrates. The eye denticle differs in morphology from that of the dermal denticles distributed over the rest of the body, consistent with a different function (abrasion resistance). We also demonstrate that the whale shark has a strong ability to retract the eyeball into the eye socket. The retraction distance was calculated to be approximately half the diameter of the eye, which is comparable to those of other vertebrates that are known to have highly retractable eyes. These highly protective features of the whale shark eye seem to emphasize the importance of vision for environmental perception, which contradicts the general, though poorly established, notion of low reliance on vision in this species.journal articl
Top-down approach using supercritical carbon dioxide ball milling for producing sub-10 nm Bi2Te3 grains
Get PDFWe compare Bi2Te3 powders prepared by conventional ball milling to powders milled in supercritical carbon dioxide (scCO2). We demonstrate that scCO2 milling overcomes size-reduction limitations reported for conventional milling. XRD and TEM reveal nanograins with smaller average sizes (< 10 nm) and narrower grain size distributions in the scCO2 milled case. scCO2 milling also preserves the crystallinity and shows less oxidation than conventional milling. This is the first report of Bi2Te3 with a sub-10 nm grain size whilst conserving high quality crystallinity, made using a top-down approach. Our study offers a route for developing unprecedentedly fine bulk nanostructured Bi2Te3-based thermoelectric materials.journal articl
Constructing Cross-Linked Nanofibrous Scaffold via Dual-Enzyme-Instructed Hierarchical Assembly
Get PDFTo explore the potential of step-by-step assembly in the fabrication of biological materials, we designed and synthesized two peptide-based molecules for enzyme-instructed hierarchical assembly. Upon the treatment of alkaline phosphatase, one molecule undergoes enzyme-instructed self-assembly forming uniformed nanofibers. The other one that can self-assemble into vesicles undergoes enzyme-induced transformation of self-assembly converting vesicles into irregular aggregates upon the treatment of carboxylesterase. Coadministration of two enzymes to a mixture of these two molecules in a stage-by-stage fashion leads to a physically knotted nanofibrous scaffold that is applicable as a nanostructured matrix for cell culture.journal articl
Epigenetic regulation of spurious transcription initiation in Arabidopsis
Get PDFIn plants, epigenetic regulation is critical for silencing transposons and maintaining proper gene expression. However, its impact on the genome-wide transcription initiation landscape remains elusive. By conducting a genome-wide analysis of transcription start sites (TSSs) using cap analysis of gene expression (CAGE) sequencing, we show that thousands of TSSs are exclusively activated in various epigenetic mutants of Arabidopsis thaliana and referred to as cryptic TSSs. Many have not been identified in previous studies, of which up to 65% are contributed by transposons. They possess similar genetic features to regular TSSs and their activation is strongly associated with the ectopic recruitment of RNAPII machinery. The activation of cryptic TSSs significantly alters transcription of nearby TSSs, including those of genes important for development and stress responses. Our study, therefore, sheds light on the role of epigenetic regulation in maintaining proper gene functions in plants by suppressing transcription from cryptic TSSs.journal articl