A new strategy is performed to fabricate conjugated polymer microarray with the assistance of protein in this work.The water-soluble cationic conjugated polymer employed in the present work is capable of absorbing light at 510 nm,which makes it compatible with a variety of commercial microarray scanners.It is demonstrated that the protein-assisted conjugated polymer microarray exhibits higher fluorescence signal and better stability in comparison with the case without protein.The conjugated polymer microarray can be used for sensitive detection of picric acid(PA).A major advantage of our approach is its simplicity and chemical linking is not required between the conjugated polymer and microarray substrate.Considering the simplicity of the preparation of the conjugated polymer microarray,it is anticipated that novel sensing platforms will be constructed by employing this versatile method.
Histone H2A methylation at Glnl04 （H2AQ104Me） is a new type of histone post-translational modification （PTM） discovered recently. This modification has been found to have significant influence on gene transcription. However, the structural and fimctional consequence of glutamine methylation on nucleosome remains to be further elucidated. Obtaining of histones with site-specific methylation at glutamine residues might facilitate the studies towards a better understanding of this new PTM. In the present work, total chemical synthesis of H2AQ 104Me was carried out through use of the hydrazide-based native chemical ligation. Synthetic histone H2AQ104Me could be successfully incorporated into nucleosomes in vitro and showed a negative influence on the nucleosome stability.
Qiaoqiao HeJiabin LiYunkun QiZhipeng WangYong HuangLei Liu
原子力显微术(Atomic force microscopy,AFM)的力学成像模式可在高分辨成像的同时,定量测量材料的力学性质。然而,对尺度小、质地薄而软的生物分子的弹性模量的测量仍然是一个挑战。本文以脱氧核糖核酸(Deoxyribonucleic acid,DNA)折纸为检测样品,将峰值力定量纳米力学模式(Peak Force Quantitative Nanomechanical Mapping,PF-QNM)作为测量手段研究了DNA分子的力学性质,探索不同作用力对DNA折纸弹性模量的影响。结果表明,当峰值力控制在80-100 p N时,峰值力成像稳定,获得的杨氏模量维持在约10 MPa。与传统力曲线阵列模式(Force volume mapping,FV)相比较,在小力区(<100 p N),两种方法符合性较好。这种峰值力定量纳米力学模式为DNA分子定量力学性质研究提供了一种简便而有效的研究方法。
Mercury is one of the major toxic pollutants and has many adverse effects on human health. The main mercury species in the environment or in living organisms are inorganic mercuric ion （Hg2＋） and organic methylmercury （CH3Hg＋）. Detection of the two mercury ions is a particularly active topic in the molecular sensing field during the past decade. However, efficient sensors that can sensitively detect and discriminate the two species are rare. In this work, we adopt the concept of restriction of intramolecular rotations which is the basis of aggregation induced emission, and design a molecular probe with pyridyl group as the chelating unit and 1,8-naphthalimide as the fluorescent unit for the detection of both Hg2＋ and CH3Hg＋. When the probe is free in solution, it exhibits weak fluorescence because free intramolecular rotations of the 1,8-naphthalimide moieties non-radiatively annihilate its excited state. However, upon coordination with Hg2＋ or CH3Hg＋, the rotation of 1,8-naphthalimide moieties would be restricted due to the chelation between 1,8-naphthalimide and Hg2＋ or CH3Hg＋, leading to significantly enhanced fluorescent emission. The response induced by Hg2＋ is much stronger than CH3Hg＋; but for specific detection of CH3Hg＋, we introduced a T-rich DNA fragment which could completely mask Hg2＋ in solution. Furthermore, we have employed the sensor for confocal imaging of rig2＋ and CH3Hg＋in immobilized cells. We expect the probe design tactics can be generally useful for sensing many other analytes.
The DNA i-motif is a quadruplex structure formed in tandem cytosine-rich sequences in slightly acidic conditions. Besides being considered as a building block of DNA nano-devices, it may also play potential roles in regulating chromo- some stability and gene transcriptions. The stability of i-motif is crucial for these functions. In this work, we investigated the mechanical stability of a single i-motif formed in the human telomeric sequence 51-（CCCTAA）3CCC, which revealed a novel pH and loading rate-dependent bimodal unfolding force distribution. Although the cause of the bimodal unfolding force species is not clear, we proposed a phenomenological model involving a direct unfolding favored at lower loading rate or higher pH value, which is subject to competition with another unfolding pathway through a mechanically stable inter- mediate state whose nature is yet to be determined. Overall, the unique mechano-chemical responses of i-motif-provide a new perspective to its stability, which may be useful to guide designing new i-motif-based DNA mechanical nano-devices.
We studied the synthesis of mesoporous silica from cetyltrimethyl ammonium bromide（CTAB） and so- dium dodecyl sulfate（SDS） at different molar ratios（R）. X-ray diffraction（XRD）, scanning electron spectroscopy （SEM）, transmission electron spectroscopy（TEM） and nitrogen sorption analysis were then used to further investigate the internal relationship among different morphologies and structures, as well as the mechanism of the transition from hexagonal to vesicular structure. The results reveal that as R increased, a consistent and gradual transition occurred via a concentric circular secondary structure formed. The antagonistic effect between the decreasing curvature of surfactant micelle and increasing curvature of secondary structures may be the reason for the complex morphologies synthesized, and the increasing bending energy AGb is the main driving force for the transition.
Nanopore has been developed to be a powerful,single-molecule analytical tool for sensing ions,small organic molecules and biomacromolecules such as proteins and DNAs.Generally,the identity of the analyte can be revealed by current amplitude changes and mean dwell time of the analyte binding events.In some cases,generation of highly characteristic current events affords an alternative way of analyte determination with high confidence level.However,we found that secondary structures in DNA/RNA hybrids might severely hinder the generation of signature events during their translocation through?-hemolysin nanopore.In this report,we propose a strategy to add a certain concentration of urea in the buffer solution for single channel recordings and validate that low concentration of urea can effectively denature the secondary structures in DNA hybrids and recover the generation of signature events.This finding might be useful in other secondary structure-related nanopore sensing activities.
