Chiral three-dimensional supramolecular assemblies: colloidal onions, cubosomes, and hexosomes.

Amphiphilic molecules can self-assemble in solution into a variety of supramolecular assemblies, ranging from simple micelles, ribbons, and tubes to complex cubosomes with bicontinuous cubic nanostructures. It is well known that the self-assembly of chiral building blocks into one-dimensional (1D) twisted fibers, helical ribbons, and tubes enables chiral transfer from the molecular scale to super-assemblies. In this study, we investigate the chirality of three-dimensional (3D) supramolecular assemblies, such as colloidal onions, cubosomes, and hexosomes, formed from the same chiral heteroclusters. Unlike supramolecular 1D helical ribbons, these assemblies do not have chiral external shapes or chiral internal nanostructures, but they do exhibit circular dichroism, suggesting that they are chiral. Structural studies revealed that the ordered arrangement of the chiral units in curved superstructures is the origin of the supramolecular chirality of these 3D assemblies. Therefore, this study provides insights for enriching the diversity and complexity of supramolecular chiral assemblies.

Symmetry and Topology of Twin Boundaries and Five-Fold Twin Boundaries in Soft Crystals.

Heteroclusters constructed by tethering dissimilar nanoclusters using organic linkers resemble lipids and self-assemble into cubosomes, namely, microparticles of soft crystals composed of unique nanochannel lattices with a defined symmetry and topology. The internal porous crystal structures can be accurately characterized using transmission electron microscopy. We herein describe twin boundaries and five-fold twin boundaries in cubosomes with a double-diamond Pn3̅m structure. Our analysis indicates a clear distinction in the conformation of the skeletal unit: a centrosymmetric staggered conformation with point group D3d for the normal skeletal unit and a mirror-symmetric eclipsed one with point group D3h for the skeletal unit on the twin boundary. This symmetry distinction causes the channels to change direction and elongate slightly as they pass through the twin boundary, but the topology is maintained. For cubosomes containing five-fold twin boundaries, one of the channels is in the center of the particles seamlessly connecting the five blocks. Our conclusion is that the two distinct channel systems are still continuous. This fundamental understanding will contribute to the development of soft crystals with defined shapes and special inner nanostructures for advanced applications.

Toward Cluster Materials with Ordered Structures via Self-Assembly of Heterocluster Janus Molecules.

Cluster materials have attracted much attention because of their unique chemical and physical properties, hitherto unseen in bulk materials. Inspired by the lipid self-assembly principle, a series of heterocluster Janus molecules (HCJMs) with atomic precision have been rationally designed and synthesized by connecting different clusters via covalent bonds for the construction of nanomaterials and nano-objects. Due to their amphiphilicity, HCJMs self-assemble into cluster-containing nanomaterials or nano-objects with versatile ordered structures beyond those observed in conventional crystals. Their hybrid composition and nanoscale size are also greatly advantageous in the study of their fine structure by electron microscopy techniques, and enable their formation mechanisms to be unraveled. Finally, the influence of the characteristics of the HCJMs on the structure and properties of the self-assembled nano-objects are explored comprehensively. This synthesis strategy will promote further development of cluster materials with advanced functions via rational molecular design toward the construction of hierarchical nanostructures via molecular self-assembly.

Archaeal community succession with fine root growth in poplar plantation.

The archaeal community structure in the rhizosphere soils might change with root growth, which is of great importance for understanding the interaction between roots and microbes. According to root colors, three groups of rhizosphere soils from first-order fine roots of poplar trees (Populus × euramericana) were sampled, including rhizosphere soils surrounding newly born roots (white color, WR), mature roots (yellow color, YR) and aged roots (brown color, BR). Total microbial DNA was extracted from the soils associated with poplar fine roots. The specific primers were used to amplify the 16S rDNA V4-V5 region of soil archaea, and the Illumina MiSeq platform was used for high-throughput sequencing analysis. The results showed that the observed OTU (operational taxonomic unit) abundance of archaeal community in WR and BR rhizosphere soils were similar, while the OTU abundance in YR rhizosphere soil were lower. The WR and BR shared 134 OTUs of archea, the YR and BR shared 87 OTUs, and the WR and BR shared 90 OTUs. The Chao1 index and the ACE index of archaeal community in YR rhizosphere soil were significantly lower than those of WR and BR, while the Simpson index and the Shannon index of BR were significantly lower than WR to YR. Results from the PERMANOVA analysis showed that archaeal community compositions in WR and BR rhizosphere soils were significantly different. Species annotation showed that there were 12 genera of archea in three rhizosphere soils, five genera in WR, 10 genera in YR, and six genera in BR, respectively. The similarity of the archaeal community composition in poplar rhizosphere soils gradually decreased from WR to BR, with large differences among different growth stages of fine roots. The dominant genus was Candidatus_Nitrososphaera, with a relative abundance of more than 70%, indicating this archaea group might be closely related to poplar fine roots development.

Unraveling the Self-Assembly of Heterocluster Janus Dumbbells into Hybrid Cubosomes with Internal Double-Diamond Structure.

Cubosomes are bicontinuous cubic-phase particles generated by amphiphile self-assembly with bicontinuous cubic phases, which creates an intricate network of interconnected nanochannels that endow these materials with special functions for advanced applications. On the other hand, clusters are an attractive class of molecules that exhibit intriguing functions and properties that differ from those of atoms and nanoparticles. Inspired by lipid self-assembly and attracted to the new functionalities of clusters, we prepared special heterocluster Janus dumbbells (HCJDs) composed of dissimilar nanoclusters: namely, a polyoxometalate and a polyhedral oligomeric silsesquioxane. HCJDs resemble conventional amphiphiles and, as such, they self-assemble in solution into faceted hybrid cubosomes via the transformation of vesicles into spongelike aggregates. Multiple mechanisms that lead to equilibrium, including molecular self-assembly, vesicle accumulation, membrane fusion, inner-structure reorganization, and cubic crystal growth, contributed to the overall process. On the basis of these results, we proposed a strategy for self-assembly-from basic molecular design that goes beyond traditional amphiphiles to the construction of micro- or nanomaterials with hierarchical structures and advanced functions.

Generic tags for Mn(ii) and Gd(iii) spin labels for distance measurements in proteins.

High-affinity chelating tags for Gd(iii) and Mn(ii) ions that provide valuable high-resolution distance restraints for biomolecules were used as spin labels for double electron-electron resonance (DEER) measurements. The availability of a generic tag that can bind both metal ions and provide a narrow and predictable distance distribution for both ions is attractive owing to their different EPR-related characteristics. Herein we introduced two paramagnetic tags, 4PSPyMTA and 4PSPyNPDA, which are conjugated to cysteine residues through a stable thioether bond, forming a short and, depending on the metal ion coordination mode, a rigid tether with the protein. These tags exhibit high affinity for both Mn(ii) and Gd(iii) ions. The DEER performance of the 4PSPyMTA and 4PSPyNPDA tags, in complex with Gd(iii) or Mn(ii), was evaluated for three double cysteine mutants of ubiquitin, and the Gd(iii)-Gd(iii) and Mn(ii)-Mn(ii) distance distributions they generated were compared. All three Gd(iii) complexes of the ubiquitin-PyMTA and ubiquitin-PyNPDA conjugates produced similar and expected distance distributions. In contrast, significant variations in the maxima and widths of the distance distributions were observed for the Mn(ii) analogs. Furthermore, whereas PyNPDA-Gd(iii) and PyNPDA-Mn(ii) delivered similar distance distributions, appreciable differences were observed for two mutants with PyMTA, with the Mn(ii) analog exhibiting a broader distance distribution and shorter distances. ELDOR (electron-electron double resonance)-detected NMR measurements revealed some distribution in the Mn(ii) coordination environment for the protein conjugates of both tags but not for the free tags. The broader distance distributions generated by 4PSPyMTA-Mn(ii), as compared with Gd(iii), were attributed to the distributed location of the Mn(ii) ion within the PyMTA chelate owing to its smaller size and lower coordination number that leave the pyridine nitrogen uncoordinated. Accordingly, in terms of distance resolution, 4PSPyNPDA can serve as an effective generic tag for Gd(iii) and Mn(ii), whereas 4PSPyMTA is efficient for Gd(iii) only. This comparison between Gd(iii) and Mn(ii) suggests that PyMTA model compounds may not predict sufficiently well the performance of PyMTA-Mn(ii) as a tag for high-resolution distance measurements in proteins because the protein environment can influence its coordination mode.

Ethylene-induced changes in lignification and cell wall-degrading enzymes in the roots of mungbean (Vigna radiata) sprouts.

As an important regulator, ethylene inhibits root growth and development in plants. To determine the mechanism of ethylene on root elongation growth and lateral root formation, ethylene-induced lignification and cell wall-degrading enzymes in the roots of mungbean sprouts were tested. We initially observed that primary root elongation and lateral root numbers were inhibited, while lignin content was enhanced by ethephon (ETH). Cell wall remolding proteins, polygalacturonase (PG) and carboxymethyl cellulose (Cx) activities were reduced, but α-expansins and xyloglucan endotransglucosylases/hydrolases (XTH) were enhanced by ETH. The promotion in lignin production was correlated with changes in activities of key lignin biosynthesis enzymes and hydrogen peroxide (H2O2) content. These actions induced by ETH were altered via treatment with an ethylene perception antagonist (Ag+). We subsequently demonstrated that the role of endogenous ethylene in regulating root elongation growth and lateral root formation were correlated with lignification and cell wall-degrading enzymes, respectively. These results suggested that the ethylene-regulated inhibition of primary root elongation growth was caused by an increase in lignification that reinforced the cell wall and shortened root length, and the suppression of lateral root formation was linked to activities of PG, Cx, α-expansins and XTH.

[Effects of p,p'-dDE on the expression of androgen-binding protein, transferrin and inhibin B mRNA in rat sertoli cells].

OBJECTIVE: To explore effects of p, p'DDE on the expression of androgen binding protein (ABP), transferrin (Tf) and inhibin B (INH B) mRNA in testis Sertoli cells of Sprague Dawley rats. METHODS: A method has been set up to obtain a large number of viable Sertoli cells from SD rats of 18-20 days of age. With a series of concentration p,p'-DDE (10, 30, and 50 micromol/L) co-incubating the Sertoli cells in vitro, the expression of ABP, Tf and INH B mRNA were determined by RT-PCR. RESULTS: a) With increase of the incubated p, p'-DDE, the expression of ABP mRNA in Sertoli cells went up while that of Tf and INH B dropped in a dose-dependent manner (P < 0. 05). b) The correlation analysis among ABP, Tf and INH B showed that negative relationships were found between ABP and Tf or INH B, respectively (r = - 0. 391 3, P = 0. 032 5; r = - 0.235 2, P = 0.0158), and that positive correlation was indicated between Tf and INH B (r =0.4516, P =0.0047). CONCLUSION: p,p'-DDE is a reproductive toxicant which disrupts the transcription of ABP, Tf and INH B in rat Sertoli cells so as to result in reproductive dysfunction.