Planar oligomerization of reconfigurable gold nanorod dimers.

Reconfigurable chiral plasmonic complexes are fabricated by planar assembly of multiple individual gold nanorod dimers using DNA origami templates. Additionally, each chiral center can be controlled to switch among achiral, left-handed, and right-handed states. We demonstrate that their overall circular dichroism is determined by the coupling of individual chiral centers and is heavily influenced by the precise number and arrangement of these centers. Our study offers a novel self-assembly method for constructing intricate and dynamic chiral plasmonics as well as investigating the interactions among several plasmonic chiral centers.

Finite Assembly of Three-Dimensional DNA Hierarchical Nanoarchitectures through Orthogonal and Directional Bonding.

Reliable orthogonal bonding with precise and flexible orientation control would be ideal for building finite complex nanostructures via self-assembly. Employing a three-dimensional (3D) DNA origami, hexagonal prism DNA origami (HDO), as building block, we demonstrate it is practical to construct finite hierarchical nanoarchitectures with complicated conformations through orthogonal and directional bonding. The as-designed HDO building block has twelve prescribed directional valences in 3D space and each of them supports two opposite orientations, yielding the capability to generate abundant directional bonding. Meanwhile, we minimize the thorny non-specific interactions among HDOs and enable the orthogonal bonding between any two valences based on self-similar designing. Consequently, various hierarchical nanostructures are prepared at will simply by the combination of HDOs with appropriate valences. We believe this route towards hierarchically assembly is inspiring and hope it will facilitate the fabrication of functional superstructures.

Pb-Doped Ag2 Se Quantum Dots with Enhanced Photoluminescence in the NIR-II Window.

Ag2 Se quantum dots (QDs) as an effective biological probe in the second near-infrared window (NIR-II, 1000-1700 nm) have been widely applied in bioimaging with high tissue penetration depth and high spatiotemporal resolution. However, the ions deficiency and crystal defects caused by the high Ag+ mobility in Ag2 Se crystals are mainly responsible for the inefficient photoluminescence (PL) of Ag2 Se QDs. Herein, a tailored route is reported to achieve controllable doping of Ag2 Se QDs in which Ag is exchanged by Pb via cation exchange (CE), which is unattainable by direct synthetic methods. The Pb-doped Ag2 Se QDs (denoted as Pb:Ag2 Se QDs) present fire-new optical features with significantly enhanced PL intensity of 4.2 folds. Photoelectron spectroscopy confirms that Pb acts as an n-type dopant for Ag2 Se QDs and therefore the electronic impurities provide additional carriers to fill the traps. Moreover, the general validity of this method is demonstrated to convert different sized Ag2 Se into Pb:Ag2 Se QDs, so that a wide range of NIR-II PL with high intensity is obtained. The bright NIR-II emission of Pb:Ag2 Se QDs is further successfully performed in lymphatic system mapping.

Using exosomal miRNAs extracted from porcine follicular fluid to investigate their role in oocyte development.

BACKGROUND: Follicular development is crucial to normal oocyte maturation, with follicular size closely related to oocyte maturation. To better understand the molecular mechanisms behind porcine oocyte maturation, we obtained exosomal miRNA from porcine follicular fluid (PFF). These miRNA samples were then sequenced and analyzed regarding their different follicular sizes, as described in the methods section. RESULTS: First, these results showed that this process successfully isolated PFF exosomes. Nearly all valid reads from the PFF exosomal sequencing data were successfully mapped to the porcine genome database. Second, we used hierarchical clustering methods to determine that significantly expressed miRNAs were clustered into A, B, C, and D groups in our heatmap according to different follicle sizes. These results allowed for the targeting of potential mRNAs genes related to porcine oocyte development. Third, we chose ten, significantly expressed miRNAs and predicted their target genes for further GO analysis. These results showed that the expression levels of neurotransmitter secretion genes were greatly changed, as were many target genes involved in the regulation of FSH secretion. Notably, these are genes that are very closely related to oocyte maturation in growing follicles. We then used pathway analysis for these targeted genes based on the originally selected ten miRNAs. Results indicated that the pathways were mainly related to the biosynthesis of TGF-beta and its signaling pathway, which are very closely related to reproductive system functions. CONCLUSIONS: Finally, these exosomal miRNAs obtained from PFF may provide a valuable addition to our understanding of the mechanism of porcine oocyte maturation. It is also likely that these exosomal miRNAs could function as molecular biomarkers to choose high-quality oocytes and allow for in vitro porcine embryo production.

DNA-Based Adaptive Plasmonic Logic Gates.

Self-assembled plasmonic logic gates that read DNA molecules as input and return plasmonic chiroptical signals as outputs are reported. Such logic gates are achieved on a DNA-based platform that logically regulate the conformation of a chiral plasmonic nanostructure, upon specific input DNA strands and internal computing units. With systematical designs, a complete set of Boolean logical gates are realized. Intriguingly, the logic gates could be endowed with adaptiveness, so they can autonomously alter their logics when the environment changes. As a demonstration, a logic gate that performs AND function at body temperature while OR function at cold storage temperature is constructed. In addition, the plasmonic chiroptical output has three distinctive states, which makes a three-state molecular logic gate readily achievable on this platform. Such DNA-based plasmonic logic gates are envisioned to execute more complex tasks giving these unique characteristics.

Toward Precise Manipulation of DNA-Protein Hybrid Nanoarchitectures.

Nucleic acids and proteins are the two primary building materials of living organisms. Over the past decade, artificial DNA-protein hybrid structures have been pursued for a wide range of applications. DNA nanotechnology, in particular, has dramatically expanded nanoscale molecule engineering and contributed to the spatial arrangement of protein components. Strategies for designing site-specific coupling of DNA oligomers to proteins are needed in order to allow for precise control over stoichiometry and position. Efforts have also been focused on coassembly of protein-DNA complexes by engineering their fundamental molecular recognition interactions. This Concept focuses on the precise manipulation of DNA-protein nanoarchitectures. Particular attention is paid to site-selectivity within DNA-protein conjugates, regulation of protein orientation using DNA scaffolds, and coassembly principles upon unique structural motifs. Current challenges and future directions are also discussed in the design and application of DNA-protein nanoarchitectures.

Modular Assembly of Plasmonic Nanoparticles Assisted by DNA Origami.

Arraying noble metal nanoparticles with nanoscale features is an important way to develop plasmonic devices with novel optical properties such as plasmonic chiral metamolecules, optical waveguides, and so forth. Along with top-down methods of fabricating plasmonic nanostructures, solution-based self-assembly provides an alternative approach. There are mainly two routes to organizing metal nanoparticles via self-assembly. One is directly linking nanoparticles through linker molecules, and the other is using nanoparticles to decorate a preformed template. We combine these two routes and herein report a strategy for the DNA origami-assisted modular assembly of gold nanoparticles into homogeneous and heterogeneous plasmonic nanostructures. For each module, we designed W-shaped DNA origami with two troughs as two domains. One domain is used to host a gold nanoparticle, and the other domain is designed to capture another gold nanoparticle hosted on a different module. By simply tuning the sequences of capture DNA strands on each module, gold nanoparticles including spherical and rod-shaped gold nanoparticles (denoted as AuNPs and AuNRs) could be well organized in a predefined manner to form versatile plasmonic nanostructures. Since the interparticle distances could be precisely controlled at the nanoscale, we also studied the plasma coupling among the assembled plasmonic nanostructures. This modular assembly strategy represents a simple yet general and effective design principle for DNA-assembled plasmonic nanostructures.

Assembling gold nanobipyramids into chiral plasmonic nanostructures with DNA origami.

Herein, we report the assembly of gold nanobipyramids (AuNBPs) into static and dynamic chiral plasmonic nanostructures via DNA origami. Compared with conventional chiral dimers of gold nanorods (AuNRs), AuNBP dimers exhibit more intriguing chiroptical responses, suggesting that they could be a superior alternative for constructing chiral plasmonic nanostructures for biosensing.

[Evaluating the growth status and threatened factors for old trees in China]. / æˆ‘å›½å¤æ ‘èµ„æºçš„ç”Ÿå­˜çŽ°çŠ¶è¯„ä¼°åŠå¨èƒå› ç´ åˆ†æž.

Old trees are critical components of ecosystems, with important ecological function and high genetic diversity. To strengthen the protection and management of old trees, we analyzed the distribution, survival and protection status of old trees and their threatened factors in China. The results showed there were a total of 10.66 million old trees in China. The Inner Mongolia Autonomous Region and Yunnan Province had more than one million trees, respectively. For 440000 old trees in 102 counties, 94.3% grew normally, 5.5% in a weak or endangered status, and 0.2% had been dead. The main factors threatened to old trees included natural disasters (e.g., elevated temperature, drought, fire), urbanization, land use, pests and diseases, and cutting and stealing. Among those factors, damage from pests and diseases was the most serious, which was found in 83 counties (81.4%). The second important threatened factor was natural disasters, which occurred in 68 regions (66.7%). In addition, most of the old trees (around 89%) grew in remote countryside, lacking of enough protection. Modern technologies should be used to protect old trees, such as using unmanned aerial vehicles to monitor the growth status of old trees, strengthening pest and disease control, and avoiding natural disasters. Establishing a database of old tree resources is important to update and share information timely to avoid stealing and felling old trees.

Chloroplast and Nuclear Genetic Diversity Explain the Limited Distribution of Endangered and Endemic Thuja sutchuenensis in China.

Narrow-ranged species face challenges from natural disasters and human activities, and to address why species distributes only in a limited region is of great significance. Here we investigated the genetic diversity, gene flow, and genetic differentiation in six wild and three cultivated populations of Thuja sutchuenensis, a species that survive only in the Daba mountain chain, using chloroplast simple sequence repeats (cpSSR) and nuclear restriction site-associated DNA sequencing (nRAD-seq). Wild T. sutchuenensis populations were from a common ancestral population at 203 ka, indicating they reached the Daba mountain chain before the start of population contraction at the Last Interglacial (LIG, ∼120-140 ka). T. sutchuenensis populations showed relatively high chloroplast but low nuclear genetic diversity. The genetic differentiation of nRAD-seq in any pairwise comparisons were low, while the cpSSR genetic differentiation values varied with pairwise comparisons of populations. High gene flow and low genetic differentiation resulted in a weak isolation-by-distance effect. The genetic diversity and differentiation of T. sutchuenensis explained its survival in the Daba mountain chain, while its narrow ecological niche from the relatively isolated and unique environment in the "refugia" limited its distribution.

Towards Active Self-Assembly Through DNA Nanotechnology.

Self-assembly, which is ubiquitous in living systems, also stimulates countless synthetic molecular self-assembling systems. Most synthetic self-assemblies are realized by passive processes, going from high-energy states to thermodynamic equilibrium. Conversely, living systems work out of equilibrium, meaning they are energy-consuming, dissipative and active. In recently years, chemists have made extensive efforts to design artificial active self-assembly systems, which will be pivotal to emulating and understanding life. Among various strategies, emerging approaches based on DNA nanotechnology have attracted a lot of attention. Structural- as well as dynamic-DNA-nanotechnology offer diverse tools with which to design building blocks and to shape their assembly behaviors. To achieve active self-assembly, a synergy of diverse DNA techniques is essential, including structural design, controllable assembly-disassembly, autonomous assembly, molecular circuits, biochemical oscillators, and so on. In this review, we introduce progress towards, or related to, active assembly via DNA nanotechnology. Dynamic DNA assembly systems ranging from passive assembly-disassembly systems, to autonomous assembly systems to sophisticated artificial metabolism and time-clocking oscillation systems will be discussed. We catalogue these systems from the perspective of free energy change with the reaction process. We end the review with a brief outlook and discussion.

Reconfigurable Plasmonic Diastereomers Assembled by DNA Origami.

Herein, we report self-assembled reconfigurable plasmonic diastereomers based on DNA nanotechnology. Up to three plasmonic chiral centers were organized by dynamic DNA origami platforms. Meanwhile, each chiral center could be individually controlled to switch between left-handed and right-handed states. Thus, complex and reconfigurable chiral plasmonic diastereomers with eight plasmonic stereoisomers were achieved, driven by programmed DNA reactions. With these plasmonic diastereomers, we demonstrated the existence of strong cross-talk near-field coupling among chiral centers, and the coupling of chiral centers could substantially contribute to the overall CD signals. Our work provides an important bottom-up approach for building complex and dynamic chiral plasmonics and for probing the interactions of plasmonic chiral centers.

[Determination of chlorophyll a and b using absorption spectrum].

Chlorophyll a and chlorophyll b play a significant role in the plant growth process. Precise determination of its content could provide the scientific basis for the corps growth state, the plant pathology diagnosis and so on, and is the key point of implementing accurate agriculture. The authors transfered the absorption spectrum experiment data of chlorophyll a and chlorophyll b determined by predecessor into a transmission spectrum. Observing the transmission spectrum using human eyes, the color of chlorophyll a and chlorophyll b was obtained. Thus, according to the predecessor's experiment curve of absorption spectrum of chlorophyll a and chlorophyll b, combining the three primary color principles of colorimetry, and choosing a standard light source with spectrum power distribution similar to D65 as the illumination, the authors determined their chromaticity coordinates in the 1931CIE-x, y chromaticity diagram: Chlorophyll a is (0.198 1, 0.334 1), which falls in the cyan color region; Chlorophyll b is (0. 270 4, 0. 566 3), which falls in the yellowish green region. The main point of above processing is: reducing the spectrum curves of chlorophyll a and the chlorophyll b to coordinates on the chromaticity diagram, and the result could offer the essential theoretical support for a new non-contact, long-distance and non-damage technology to determine the pigment content in single leaf or mass.