Biological encapsulants such as ferritin, [1] lumazine synthase, [2] and viral capsids [3] achieve their selective separation and sequestration of substrates by providing: 1) a guest microenvironment isolated from the surroundings, 2) favorable interactions complementing a size and shape match with the encapsulated guests, and 3) sufficient flexibility to allow guests to be incorporated and released.[4] These biological hosts self-assemble from multiple copies of identical protein subunits, the symmetries and connection properties [5] of which dictate the hollow polyhedral structures of the encapsulant. In order to create abiological molecular systems that are capable of expressing functions of similar complexity to biological systems and to explore new applications of synthetic hosts, [6] there is a need to create synthetic capsules capable of tightly and selectively binding large substrates.Taking inspiration from natural systems [1][2][3] and from other previously reported metal-organic capsules, [7] we report the design and synthesis of a series of metallo-supramolecular cage molecules capable of selectively encapsulating large aromatic guests. The necessary features to achieve this function are: 1) small pore sizes to isolate guests from the environment, [8] 2) large cavity sizes to ensure sufficient volume for the guests of interest, 3) enough flexibility and lability to allow guests to enter and exit the host, and 4) regions of the cage walls rich in p-electron density to provide favorable interactions with targeted guests.[9] The selective encapsulation of large aromatic molecules is an attractive goal since their physicochemical properties are similar, which can render their separation difficult. The higher fullerenes represent particularly attractive targets because their potential applications [10] remain difficult to explore because of the challenges associated with their separation, despite recent advances. [11] Employing principles of geometric analysis, [5] we determined that combination of the C 4 -symmetric tetrakis-bidentate ligand shown in Figure 1 with the C 3 -symmetric iron(II) tris(pyridylimine) center would result in the formation of an O-symmetric cubic structure of general formula M 8 L 6 , in which the corners of the cube are defined by the metal centers and the faces by the ligands (Figure 1). This cage represents the first example of a new class of closed-face metallosupramolecular cubic hosts to be synthesized. In order to provide favorable binding sites for our target guests we incorporated porphyrin moieties, which have previously been demonstrated to interact with large aromatic molecules, [11a-c, 12] into our design. This design also provides for small pore sizes and the potential to create new chemical functionality through the introduction of different metal ions into the centers of the N 4 macrocycle and by substituting these metals axial ligands. We chose to employ labile iron(II) centers with pyridylimine ligands as chelating agents to allow for the formation of the liga...

A series of terphenyl-edged Fe(4)L(6) cages were synthesized from substituted 4,4''-diamino-p-terphenyls, 2-formylpyridine, and iron(II). For the parent diaminoterphenyl, all three possible diastereomers, with T, S(4), and C(3) point symmetries, were formed in nearly equal amounts, as determined by (1)H and (13)C NMR. When 2,2″-dimethylterphenylenediamine was used, the T-symmetry diastereomer was observed to predominate. The use of 2',3',5',6'-tetramethylterphenylenediamine generated predominantly the S(4) cage diastereomer, whereas 2',5'-dimethylterphenylenediamine produced the C(3)-symmetric cage to a greater degree than the other two diastereomers. The factors contributing to the transfer of chiral information between metal vertices were analyzed, and the general principles underlying the delicately balanced thermodynamics were determined.

Molecular machines that assemble polymers in a programmed sequence are fundamental to life. They are also an achievable goal of nanotechnology. Here, we report synthetic molecular machinery made from DNA that controls and records the formation of covalent bonds. We show that an autonomous cascade of DNA hybridization reactions can create oligomers, from building blocks linked by olefin or peptide bonds, with a sequence defined by a reconfigurable molecular program. The system can also be programmed to achieve combinatorial assembly. The sequence of assembly reactions and thus the structure of each oligomer synthesized is recorded in a DNA molecule, which enables this information to be recovered by PCR amplification followed by DNA sequencing.

Current environmental monitoring studies are generally confined to several target organophosphate esters (OPEs), and there is a lack of strategies for comprehensively screening all potential OPEs in environmental samples.Here, an effective and accurate strategy was developed for the target, suspect, and functional group-dependent screening of OPEs by the use of ultrahighperformance liquid chromatography−Q Exactive hybrid quadrupole−Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS), and this strategy was applied for the analysis of n = 74 sediment samples (including 23 surface sediment samples and 51 sediment core samples) collected from Taihu Lake (eastern China) in 2019. In these analyzed samples, we successfully identified n = 35 OPEs, and 23 of them were reported in this region for the first time. In addition, this strategy also presented other interesting findings, i.e., (1) OPE concentrations decreased with increasing distance from the coast of the lake; (2) the newly identified 3-hydroxyphenyl diphenyl phosphate (meta-OH-TPHP) was not statistically significantly correlated with triphenyl phosphate (TPHP; r = 0.02494, p = 0.9101) but with resorcinol bis(diphenyl phosphate) (RDP) (r = 0.9271, p < 0.0001) and three other OPEs; and (3) the summed concentrations of aryl OPEs (∑ aryl OPEs) in sediment core samples exhibited significantly increasing trends as the depth decreased. Collectively, this study provided an effective strategy that was successfully applied for comprehensive screening of OPEs in the sediments of Taihu Lake, and this strategy could have promising potential to be extended to other environmental matrices or samples.

A series of aromatic-paneled FeL cages was synthesized through iron(II)-templated subcomponent self-assembly of 2-formylpyridine and C-symmetric diamine building blocks having differing geometries, including many with a large degree of lateral offset between metal-binding sites. The new cages were characterized using X-ray crystallography, NMR spectroscopy, and mass spectrometry. Investigations of the guest binding properties of the cages provided insights into the structural factors important for the observation of guest binding. Both the size and arrangement of the aromatic panels were shown to be crucial for achieving effective encapsulation of large hydrophobic guests, including fullerenes, polycyclic aromatic hydrocarbons, and steroids, with subtle differences in the structure of subcomponents resulting in incommensurate effects on the binding abilities of the resulting hosts. Cages with large, offset aromatic panels were observed to be the most effective hosts as a result of a preference for a ligand conformation where the aromatic panels lie tangent to the edges of the tetrahedron, thus maximizing cavity enclosure.

Auxin acts synergistically with cytokinin to control the shoot stem-cell niche, while both hormones act antagonistically to maintain the root meristem. In aluminum (Al) stress-induced root growth inhibition, auxin plays an important role. However, the role of cytokinin in this process is not well understood. In this study, we show that cytokinin enhances root growth inhibition under stress by mediating Al-induced auxin signaling. Al stress triggers a local cytokinin response in the root-apex transition zone (TZ) that depends on IPTs, which encode adenosine phosphate isopentenyltransferases and regulate cytokinin biosynthesis. IPTs are up-regulated specifically in the root-apex TZ in response to Al stress and promote local cytokinin biosynthesis and inhibition of root growth. The process of root growth inhibition is also controlled by ethylene signaling which acts upstream of auxin. In summary, different from the situation in the root meristem, auxin acts with cytokinin in a synergistic way to mediate aluminum-induced root growth inhibition in .

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Optimizing cytokinin distribution patterns is a promising strategy for simultaneously enhancing grain yield, grain quality, and stress resistance in plants, as observed in ARGONAUTE2-overexpressing rice.