Search

Low-dimensional lead halide perovskites with broadband emission hold great promise for single-component white-light-emitting (WLE) devices. The origin of their broadband emission has been commonly attributed to self-trapped excitons (STEs) composed of localized electronic polarization with a distorted lattice. Unfortunately, the exact electronic and structural nature of the STE species in these WLE materials remains elusive, hindering the rational design of high-efficiency WLE materials. In this study, by combining ultrafast transient absorption spectroscopy and ab initio calculations, we uncover surprisingly similar STE features in two prototypical low dimensional WLE perovskite single crystals: 1D (DMEDA)PbBr 4 and 2D (EDBE)PbBr 4 , despite of their different dimensionalities. Photoexcited excitons rapidly localize to intrinsic STEs within ∼250 fs, contributing to the white light emission. Crucially, STEs in both systems exhibit characteristic absorption features akin to those of Pb + and Pb 3+ . Further atomic level theoretical simulations confirm photoexcited electrons and holes are localized on the Pb 2+ site to form Pb + - and Pb 3+ -like species, resembling transient photoinduced Pb 2+ disproportionation. This study provides conclusive evidence on the key excited state species for exciton self-trapping and broadband emission in low dimensional lead halide WLE perovskites and paves the way for the rational design of high-efficiency WLE materials.

With recent emergence of huge number of long noncoding RNAs (lncRNAs), purification of lncRNA-protein (lncRNP) complexes is fundamental to understand the role of lncRNA and its biological function. However, lncRNP purification is still a daunting challenge. Here we describe a protocol to purify lncRNP formed in vivo with MS2-MBP-based affinity purification. Inducible lncRNA tagged with MS2 RNA hairpins is introduced into cells of interest, and RNP on tagged lncRNA is formed in vivo. MS2-MBP fusion protein is expressed in Escherichia coli and purified with amylose resin and HiTrap heparin column. The MS2 part of MS2-MBP fusion protein binds to the hairpins, and MBP part binds to amylose resin. We also describe a protocol to separate the nucleus and the cytoplasm so that lncRNP localized in the nucleus or cytoplasm can be individually purified. The amount of lncRNP purified is well sufficient for mass spectrometry analysis., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

RNA localization is involved in multiple biological processes. Recent advances in subcellular fractionation-based sequencing approaches uncovered localization pattern on a global scale. Most of existing methods adopt relative localization ratios (such as ratios of separately normalized transcripts per millions of different subcellular fractions without considering the difference in total RNA abundances in different fractions), however, absolute ratios may yield different results on the preference to different cellular compartment. Experimentally, adding external Spike-in RNAs to different fractionation can be used to obtain absolute ratios. In addition, a spike-in independent computational approach based on multiple linear regression model can also be used. However, currently, no custom tool is available. To solve this problem, we developed a method called subcellular fraction abundance estimator to correctly estimate relative RNA abundances of different subcellular fractionations. The ratios estimated by our method were consistent with existing reports. By applying the estimated ratios for different fractions, we explored the RNA localization pattern in cell lines and also predicted RBP motifs that were associated with different localization patterns. In addition, we showed that different isoforms of same genes could exhibit distinct localization patterns. To conclude, we believed our tool will facilitate future subcellular fractionation-related sequencing study to explore the function of RNA localization in various biological problems., (© The Author(s) 2021. Published by Oxford University Press on behalf of Genetics Society of America.)

RNA-protein complexes are essential for the function of different RNAs, yet purification of specific RNA-protein complexes can be complicated and is a major obstacle in understanding the mechanism of regulatory RNAs. Here we present a protocol to purify RNA-protein complexes assembled in vitro based on biotin-streptavidin affinity. In vitro transcribed RNA is labeled with (32)P and biotin, ribonucleoprotein particles or RNPs are assembled by incubation of RNA in nuclear extract and fractionated using gel filtration, and RNP fractions are pooled for biotin-streptavidin affinity purification. The amount of RNA-protein complexes purified following this protocol is sufficient for mass spectrometry.