分类: 材料科学 >> 电子、光学、磁材料 提交时间: 2022-03-07
摘要: In this paper, we reported a method to modify the crystallization of CZTSSe films by changing the microstructures of the precursor films. Precursor films with different microstructures were prepared and their crystallization processes were analyzed. We find even tiny differences in microstructures of the precursor films can result in significant alteration of the crystallization processes and the properties of CZTSSe films. Moreover, we found the S-to-Se substitution can be delayed to higher temperature depending on the microstructure of the precursor. This process plays critical roles in enhanceing the crystallization of CZTSSe films and can be used to eliminate the multi-layer crystallization in CZTSSe films. The detailed analysis on the crystallization processes revealed that different mechanism may dominate the crystallization of the films, which can determine the properties of CZTSSe films and solar cells. Moreover, a hybrid structure for precursor film was proposed which has different microstructures in different part of the film. In such a precursor film, different crystallization mechanism can work synergically during the preparation of the film. As the results, the comprehensive properties of the films were improved and solar cells with efficiencies up to 12.6% was prepared.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-18
摘要: Photo-induced electron transfer (PET) is ubiquitous for photosynthesis and fluorescent sensor design. However, genetically coded PET sensors are underdeveloped, due to the lack of methods to site-specifically install PET probes on proteins. Here we describe a family of acid and Mn(III) turn-on fluorescent protein (FP) sensors, named iLovU, based on PET and the genetic incorporation of superior PET quenchers in the fluorescent flavoprotein iLov. Using the iLovU PET sensors, we monitored the cytoplasmic acidification process, and achieved Mn(III) fluorescence sensing for the first time. The iLovU sensors should be applicable for studying pH changes in living cells, monitoring biogentic Mn(III) in the environment, and screening for efficient manganese peroxidase, which is highly desirable for lignin degradation and biomass conversion. Our work establishes a platform for many more protein PET sensors, facilitates the de novo design of metalloenzymes harboring redox active residues, and expands our ability to probe protein conformational dynamics.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-12
摘要: While a conserved tyrosine (Tyr) is found in oxidases, the roles of phenol ring pK(a) and reduction potential in O-2 reduction have not been defined despite many years of research on numerous oxidases and their models. These issues represent major challenges in our understanding of O-2 reduction mechanism in bioenergetics. Through genetic incorporation of unnatural amino acid analogs of Tyr, with progressively decreasing pKa of the phenol ring and increasing reduction potential, in the active site of a functional model of oxidase in myoglobin, a linear dependence of both the O-2 reduction activity and the fraction of H2O formation with the pKa of the phenol ring has been established. By using these unnatural amino acids as spectroscopic probe, we have provided conclusive evidence for the location of a Tyr radical generated during reaction with H2O2, by the distinctive hyperfine splitting patterns of the halogenated tyrosines and one of its deuterated derivatives incorporated at the 33 position of the protein. These results demonstrate for the first time that enhancing the proton donation ability of the Tyr enhances the oxidase activity, allowing the Tyr analogs to augment enzymatic activity beyond that of natural Tyr.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-11
摘要: Lysine formylation is a newly discovered post-translational modification (PTM) in histones and other nuclear proteins; it has a well-recognized but poorly defined role in chromatin conformation modulation and gene expression. To date, there is no general method to site-specifically incorporate N-epsilon-formyllysine at a defined site of a protein. Here we report the highly efficient genetic incorporation of the unnatural amino acid N-epsilon-formyllysine into proteins produced in Escherichia coli and mammalian cells, by using an orthogonal N-epsilon-formyllysine tRNAsynthetase/tRNA(CUA) pair. This technique can be applied to study the role of lysine formylation in epigenetic regulation.