Three-dimensional (3D) π-conjugated dendrimers are a new class of structurally defined macromolecules for use in organic electronics. Herein, a new family of dendritic oligothiophenes (DOT-c-BTs) up to the 2nd generation with benzothiadiazole (BT) groups at the core have been synthesized by a precise convergent approach. The well-defined chemical structures and the monodispersed nature of these DOT-c-BTs were fully confirmed by NMR spectroscopy, MALDI-TOF mass spectrometry (MALDI-TOF MS), high-resolution mass spectrometry (HR MS), and gel-permeation chromatography (GPC) measurements. The optical and electrochemical properties were investigated by UV-vis absorption, and cyclic voltammetry. The insertion of electron-deficient benzothiadiazole (BT) groups into the core of the conjugated dendritic oligothiophenes resulted in a large redshift compared to all-thiophene dendrimers. Cyclic voltammetry measurements showed one reversible reduction process and multiple oxidation waves for these functionalized dendritic oligothiophenes, due to the reduction of the BT core and the oxidation of different π-conjugated chains, respectively. Applications of DOT-c-BTs in organic solar cells as the electron donor were presented. However, unfavorable nanophase separation in the blended film led to poor device performance.

An environmentally friendly new protocol for the selective aerobic cleavage of styrene to carbonyl compounds using the Fe(III)-PyBisulidine catalyst has been reported recently. The catalyst features several unusual characteristics, such as its high efficiency lies on the ferric center instead of ferrous used by most iron-containing oxygenases and the catalyst specifically oxidizes phenyl-substituted olefins but exhibits no activity on nonconjugated olefins. Herein, we have investigated the mechanism of the oxidative cleavage reaction catalyzed by Fe(III)-PyBisulidine at the quantum chemistry level. Our computational study shows that the catalyst uses a dioxygen ligation mechanism to activate dioxygen to receive one electron from olefin, which triggers the oxidative cleavage reaction. Our study rationalizes that the Fe(II)-PyBisulidine catalyst is inactivated because ferrous is unable to raise the oxidizing ability of dioxygen. The exclusive oxidative cleavage of the phenyl-substituted olefin mainly results from the stability of the carbon cation, the orbital symmetry between the conjugated olefin and dioxygen, as well as a lower energy level of HOMO in conjugated olefin.

As a multi-function enzyme, AceK integrates kinase, phosphatase and ATPase activities in a single active site. In contrast to most kinases, AceK exhibits unusually high ATPase activity compared to its kinase and phosphatase activities. The reason that AceK possesses such a high ATPase activity and its multi-function regulation are still elusive. In this work, we have employed DFT methods to exploit the ATP hydrolysis mechanism of AceK and revealed a dissociative pathway with an activation energy of only 17.85 kcal mol−1, which is highly favorable for ATPase activity. The high ATPase activity of AceK may play a role in producing ADP as a proton acceptor to fulfill its phosphatase function. Based on our calculation and structural analysis, binding with substrate ICDH causes a catalytically important residue, Asp477, to flip over and further suppress ATPase activity with a markedly increased activation energy of 21.68 kcal mol−1, thus favoring kinase or phosphatase activity. Our work has shed new light on the function switch and ATP hydrolysis mechanism of AceK.

Diacylglycerol kinase is an integral membrane protein which catalyzes phosphoryl transfer from ATP to diacylglycerol. As the smallest kinase known, it shares no sequence homology with conventional kinases and possesses a distinct trimer structure. Thus far, its catalytic mechanism remains elusive. Using molecular dynamics and quantum mechanics calculations, we investigated the co-factor and the substrate binding and phosphoryl transfer mechanism. Based on the analysis of density functional theory calculations, we reveal that the phosphorylation reaction of diacylglycerol kinase features the same phosphoryl transfer mechanism as other kinases, despite its unique structural properties. Our results further show that the active site is relatively open and able to accommodate ligands in multiple orientations, suggesting that the optimization of binding orientations and conformational changes would occur prior to actual phosphoryl transfer.

We have revealed that bifunctional AceK kinase/phosphatase utilizes a stepwise addition–elimination mechanism in its dephosphorylation reaction. This work explains how AceK enables opposite kinase and phosphatase activities with Asp477 and a single Mg2+ ion.

By combining 60° bis(ferrocenyl) di-Pt(II) acceptors and the complementary 120° dipyridyl or dicarboxylate donors substituted with [G-1]–[G-3] Fréchet-type dendrons, self-assembly of a new series of charged or neutral dendritic tetrakis(ferrocenyl) rhomboids was realized under mild conditions in high yields, respectively. The structures of all difunctionalized rhomboids were characterized by multinuclear NMR (1H and 31P), ESI-TOF-MS, CSI-TOF-MS, and elemental analysis. Moreover, their electrochemical behavior was studied through cyclic voltammetry investigations. Further insight into the structural characterization of all rhomboidal metallacycles, such as the shape and size, was obtained via molecular simulation by PM6 semiempirical molecular orbital methods.

Escherichia coli tyrosine kinase (Etk) regulates the export of pathogenic capsular polysaccharide (CPS) by intermolecularly autophosphorylating its C-terminal tyrosine cluster. The kinase Etk, however, needs to be first activated by the intramolecular phosphorylation of a tyrosine residue, Y574, next to the active site. The recently determined structure of Etk shows that dephosphorylated Y574 blocks the active site and prevents substrate access. After phosphorylation, the negatively charged P-Y574 side chain was previously postulated to flip out to associate with a positively charged R614, unblocking the active site. This proposed activation is unique among protein kinases; however, there is no direct structural evidence in support of this hypothesis. In this paper, we carried out molecular dynamics simulation, mutagenesis, and biochemical analysis to study the activation mechanism of Etk. Our simulation results are in excellent agreement with the proposed molecular switch involving P-Y574 and R614 in the activation of Etk. Further, we show that a previously unidentified residue, R572, modulates the rotation of the P-Y574 side chain through electrostatic interaction, slowing down the opening of the active site. Our enzymatic assays demonstrate that the R572A mutant of Etk possesses significantly increased kinase activity, providing direct experimental support for the unique activation mechanism of Etk. In addition, the simulation of the Etk Y574F mutant predicted short periods of unblocked active site by Y574F, in good agreement with the low kinase activity of this mutant. The C-terminal substrate peptide and the nucleotide cofactor were also docked into the active site, and their implications are discussed.

We have revealed that bifunctional AceK kinase/phosphatase utilizes a stepwise addition–elimination mechanism in its dephosphorylation reaction. This work explains how AceK enables opposite kinase and phosphatase activities with Asp477 and a single Mg2+ ion.

Diacylglycerol kinase is an integral membrane protein which catalyzes phosphoryl transfer from ATP to diacylglycerol. As the smallest kinase known, it shares no sequence homology with conventional kinases and possesses a distinct trimer structure. Thus far, its catalytic mechanism remains elusive. Using molecular dynamics and quantum mechanics calculations, we investigated the co-factor and the substrate binding and phosphoryl transfer mechanism. Based on the analysis of density functional theory calculations, we reveal that the phosphorylation reaction of diacylglycerol kinase features the same phosphoryl transfer mechanism as other kinases, despite its unique structural properties. Our results further show that the active site is relatively open and able to accommodate ligands in multiple orientations, suggesting that the optimization of binding orientations and conformational changes would occur prior to actual phosphoryl transfer.

An environmentally friendly new protocol for the selective aerobic cleavage of styrene to carbonyl compounds using the Fe(III)-PyBisulidine catalyst has been reported recently. The catalyst features several unusual characteristics, such as its high efficiency lies on the ferric center instead of ferrous used by most iron-containing oxygenases and the catalyst specifically oxidizes phenyl-substituted olefins but exhibits no activity on nonconjugated olefins. Herein, we have investigated the mechanism of the oxidative cleavage reaction catalyzed by Fe(III)-PyBisulidine at the quantum chemistry level. Our computational study shows that the catalyst uses a dioxygen ligation mechanism to activate dioxygen to receive one electron from olefin, which triggers the oxidative cleavage reaction. Our study rationalizes that the Fe(II)-PyBisulidine catalyst is inactivated because ferrous is unable to raise the oxidizing ability of dioxygen. The exclusive oxidative cleavage of the phenyl-substituted olefin mainly results from the stability of the carbon cation, the orbital symmetry between the conjugated olefin and dioxygen, as well as a lower energy level of HOMO in conjugated olefin.