Chirality- and Threefold-Symmetry-Directed Assembly of Homochiral Octupolar Metal−Organoboron Frameworks

Homochiral octupolar metal−organoboron frameworks with the general formula [M2L(OH)(MeOH)]·3H2O [M = Co (1), Mn (2), Ni (3), Cu (4), Zn (5), Cd (6)] have been constructed from racemic C3-symmetric tris(4-benzoic acid)tridurylborane and the divalent metal ions. Compounds 1−6 are isostructural and crystallize in the chiral cubic space group F432, and they adopt an eightfold-interpenetrating (10,3)-a network formed by linking bimetal building blocks with three bidentate carboxylate groups of bridging Λ-L ligands. Bulk crystals of each of the six compounds are not a racemic mixture, and their optical activity and enantiomeric nature were demonstrated by solid-state circular dichroism spectra. Consistent with their polar structures, the colorless compounds 5 and 6 exhibit powder second harmonic generation intensities 3−4 times higher than that of potassium dihydrogen phosphate, making them, to the best of our knowledge, the first two examples of NLO-active, homochiral octupolar metal−organic solids

Chirality- and Threefold-Symmetry-Directed Assembly of Homochiral Octupolar Metal−Organoboron Frameworks

Homochiral octupolar metal−organoboron frameworks with the general formula [M2L(OH)(MeOH)]·3H2O [M = Co (1), Mn (2), Ni (3), Cu (4), Zn (5), Cd (6)] have been constructed from racemic C3-symmetric tris(4-benzoic acid)tridurylborane and the divalent metal ions. Compounds 1−6 are isostructural and crystallize in the chiral cubic space group F432, and they adopt an eightfold-interpenetrating (10,3)-a network formed by linking bimetal building blocks with three bidentate carboxylate groups of bridging Λ-L ligands. Bulk crystals of each of the six compounds are not a racemic mixture, and their optical activity and enantiomeric nature were demonstrated by solid-state circular dichroism spectra. Consistent with their polar structures, the colorless compounds 5 and 6 exhibit powder second harmonic generation intensities 3−4 times higher than that of potassium dihydrogen phosphate, making them, to the best of our knowledge, the first two examples of NLO-active, homochiral octupolar metal−organic solids

Anion-Driven Conformational Polymorphism in Homochiral Helical Coordination Polymers

Three homochiral 3D frameworks are assembled based on periodically ordered arrays of helices built from axial chiral 3,3′-bipyridine-5,5′,6,6′-tetramethyl-2,2′-dimethoxy-1,1′-biphenyl ligands and linearly coordinated Ag(I) ions. The aggregation behavior of silver salts and the ditopic ligand in solutions was investigated by a variety of techniques, including 1H NMR, UV−vis, CD, GPC and MALDI-TOF. The cationic polymer skeleton exhibits an unprecedented conformational polymorphism in the solid-state, folding into two-, three- and four-fold helices with NO3−, PF6− and ClO4− as the counteranion, respectively. The two-fold helices cross-link via argentophilic Ag−Ag interactions to form sextuple helices, which lead to a three-dimensional (3D) chiral framework. The three-fold or four-fold helices, on the other hand, self-associates in pairs to form three-dimensional tubular architectures. This anion-dependent self-assembly behavior can be rationalized by considering the sizes, geometries and binding abilities of the counteranions and subsequent chain conformation to minimize steric repulsions and maximize secondary interactions

Constructing <i>de Novo</i> H₂O₂ Signaling via Induced Protein Proximity

A new chemical strategy has been developed to generate <i>de novo</i> signaling pathways that link a signaling molecule, H₂O₂, to different downstream cellular events in mammalian cells. This approach combines the reactivity-based H₂O₂ sensing with the chemically induced protein proximity technology. By chemically modifying abscisic acid with an H₂O₂-sensitive boronate ester probe, novel H₂O₂ signaling pathways can be engineered to induce transcription, protein translocation and membrane ruffle formation upon exogenous or endogenous H₂O₂ stimulation. This strategy has also been successfully applied to gibberellic acid, which provides the potential to build signaling networks based on orthogonal cell stimuli

A Chiral Quadruple-Stranded Helicate Cage for Enantioselective Recognition and Separation

The self-assembly of enantiopure pyridyl-functionalized metallosalan units affords a homochiral helicate cage, [Zn₈<b>L</b>₄Cl₈], in which the optical rotation of each ligand is increased by a factor of 10 upon coordination. The octanuclear cage featuring a chiral amphiphilic cavity exhibits enantioselective luminescence enhancement by amino acids in solution. The cage exists in two different crystalline polymorphic forms that possess porous structures built of helicate cages interconnected by 1D channels or pentahedral cages and have the ability to separate small racemic molecules by adsorption but with different enantioselectivities

Anion-Driven Conformational Polymorphism in Homochiral Helical Coordination Polymers

Three homochiral 3D frameworks are assembled based on periodically ordered arrays of helices built from axial chiral 3,3′-bipyridine-5,5′,6,6′-tetramethyl-2,2′-dimethoxy-1,1′-biphenyl ligands and linearly coordinated Ag(I) ions. The aggregation behavior of silver salts and the ditopic ligand in solutions was investigated by a variety of techniques, including 1H NMR, UV−vis, CD, GPC and MALDI-TOF. The cationic polymer skeleton exhibits an unprecedented conformational polymorphism in the solid-state, folding into two-, three- and four-fold helices with NO3−, PF6− and ClO4− as the counteranion, respectively. The two-fold helices cross-link via argentophilic Ag−Ag interactions to form sextuple helices, which lead to a three-dimensional (3D) chiral framework. The three-fold or four-fold helices, on the other hand, self-associates in pairs to form three-dimensional tubular architectures. This anion-dependent self-assembly behavior can be rationalized by considering the sizes, geometries and binding abilities of the counteranions and subsequent chain conformation to minimize steric repulsions and maximize secondary interactions

Genetic Incorporation of ε‑<i>N</i>‑2-Hydroxyisobutyryl-lysine into Recombinant Histones

Here, we report the evolution of an orthogonal amber suppressor pyrrolysyl–tRNA synthetase (PylRS)/tRNA_CUA^Pyl pair that genetically encodes the post-translationally modified amino acid, ε-<i>N</i>-2-hydroxyisobutyryl-lysine (HibK), in bacteria and mammalian cells. HibK is a new type of histone mark that is widely distributed in histone proteins. The ability to site-specifically incorporate HibK into proteins provides a useful tool to probe the biological function of this newly identified post-translational modification

A Chiral Quadruple-Stranded Helicate Cage for Enantioselective Recognition and Separation

The self-assembly of enantiopure pyridyl-functionalized metallosalan units affords a homochiral helicate cage, [Zn₈<b>L</b>₄Cl₈], in which the optical rotation of each ligand is increased by a factor of 10 upon coordination. The octanuclear cage featuring a chiral amphiphilic cavity exhibits enantioselective luminescence enhancement by amino acids in solution. The cage exists in two different crystalline polymorphic forms that possess porous structures built of helicate cages interconnected by 1D channels or pentahedral cages and have the ability to separate small racemic molecules by adsorption but with different enantioselectivities

A Sirtuin-Dependent T7 RNA Polymerase Variant

Transcriptional regulation is of great significance for cells to maintain homeostasis and, meanwhile, represents an innovative but less explored means to control biological processes in synthetic biology and bioengineering. Herein we devised a T7 RNA polymerase (T7RNAP) variant through replacing an essential lysine located in the catalytic core (K631) with Nε-acetyl-l-lysine (AcK) via genetic code expansion. This T7RNAP variant requires the deacetylase activity of NAD-dependent sirtuins to recover its enzymatic activities and thereby sustains sirtuin-dependent transcription of the gene of interest in live cells including bacteria and mammalian cells as well as in in vitro systems. This T7RNAP variant could link gene transcription to sirtuin expression and NAD availability, thus holding promise to support some relevant research

Controlling the Ring Curvature, Solution Assembly, and Reactivity of Gigantic Molybdenum Blue Wheels

We describe the synthesis, structure, self-assembly, solution chemistry, and mass spectrometry of two new gigantic decameric molybdenum blue wheels, {Mo200Ce12} (1) and {Mo100Ce6} (2), by building block rearrangement of the tetradecameric {Mo154} framework archetype and control of the architecture’s curvature in solution from the addition of Ce­(III). The assembly of 1 and 2 could be directed accordingly by adjusting the ionic strength and acidity of the reaction mixture. Alternatively, the dimeric cluster {Mo200Ce12} could be transformed directly to the monomeric species {Mo100Ce6} upon addition of a potassium salt. ESI-ion mobility mass spectra were successfully obtained for both {Mo200Ce12} and {Mo100Ce6}, which is the first report in molybdenum blue chemistry thereby confirming that the gigantic clusters are stable in solution and that ion mobility measurements can be used to characterize nanoscale inorganic molecules