DNA Origami Scaffolds as Templates for Functional Tetrameric Kir3 K+ Channels

In native systems, scaffolding proteins play important roles in assembling proteins into complexes to transduce signals. This concept is yet to be applied to the assembly of functional transmembrane protein complexes in artificial systems. To address this issue, DNA origami has the potential to serve as scaffolds that arrange proteins at specific positions in complexes. Herein, we report that Kir3 K⁺ channel proteins are assembled through zinc‐finger protein (ZFP)‐adaptors at specific locations on DNA origami scaffolds. Specific binding of the ZFP‐fused Kir3 channels and ZFP‐based adaptors on DNA origami were confirmed by atomic force microscopy and gel electrophoresis. Furthermore, the DNA origami with ZFP binding sites nearly tripled the K⁺ channel current activity elicited by heterotetrameric Kir3 channels in HEK293T cells. Thus, our method provides a useful template to control the oligomerization states of membrane protein complexes in vitro and in living cells.     

Synthesis,conformational preferences in gas and solution,and molecular gear rotation in 1-(dimethylamino)-1-phenyl-1-silacyclohexane by gas phase electron diffraction (GED), LT NMR and theoretical calculations

1-(Dimethylamino)-1-phenyl-1-silacyclohexane 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED), low temperature ¹³C NMR spectroscopy and quantum-chemical calculations. The predominance of the 1-Ph_ax conformer (1-Ph_eq:1-Ph_ax ratio of 20:80%, ΔG°(317?K)?=??0.87?kcal/mol) in the gas phase is close to the theoretically estimated conformational equilibrium. In solution, low temperature NMR spectroscopy showed analyzable decoalescence of C_ipso and C(1,5) carbon signals in ¹³C NMR spectra at 103?K. Opposite to the gas state in the freon solution employed (CD₂Cl₂/CHFCl₂/CHFCl₂?=?1:1:3), which is still liquid at 100?K, the 1-Ph_eq conformer was found to be the preferred one [(1-Ph_eq: 1-Ph_ax?=?77%: 23%, K?=?77/23?=?2.8; ?ΔG°?=??RT ln K (at 103?K)?=?0.44?±?0.1?kcal/mol]. When comparing 1 with 1-phenyl-1-(X)silacylohexanes (X?=?H, Me, OMe, F, Cl), studied so far, the trend of predominance of the Ph_ax conformer in the gas phase and of the Ph_eq conformer in solution is confirmed.     

Solution 1H NMR characterization of axial interactions of the proximal and distal His in the cyanomet complexes of the isolated chains and the 65 kDa intact tetramer of human hemoglobin A.

Solution 1H NMR has been used to investigate the axial bonding of the proximal His and the hydrogen-bonding of the distal His to the bound ligand in the isolated chains as well as the subunits of intact, tetrameric, cyanomet human hemoglobin A. The complete proximal His, including all ring protons necessary to monitor bonding in each subunit, could be definitively assigned by 1D/2D methods despite the large size (approximately 65 kDa) and severe relaxation (to T(1) approximately 3 ms, line width approximately 1.5 kHz) of two of the protons. The complete distal His E7 ring was assigned in the alpha-chain and alpha-subunit of HbA, and the dipolar shifts and relaxation were analyzed to reveal a disposition intermediate between the positions adopted in HbCO and HbO2 that is optimal for forming a hydrogen bond with bound cyanide. The lability of the alpha-subunit His E7 NepsilonH is found to be similar to that in sperm whale cyanomet myoglobin. The orientation of the distal His E7 in the beta-subunit is found to be consistent with that seen in either HbCO or HbO2. While the His E7 labile NepsilonH proton signal could not be detected in either the beta-chain or subunit, it is concluded that this more likely reflects increased lability over that of the alpha-subunit, and not the absence of a hydrogen bond to the bound ligand. Analysis of the heme mean methyl hyperfine shift, which has been shown to be very sensitive to the presence of distal hydrogen bonds to bound cyanide (Nguyen, B. D.; Xia, Z.; Cutruzzolá, F.; Travaglini Allocatelli, C.; Brancaccio, A.; Brunori, M.; La Mar, G. N. J. Biol. Chem. 2000, 275, 742-751), directly supports the presence of a distal His E7 hydrogen bond to cyanide in the beta-chain and beta-subunit which is weaker than the same hydrogen bond in the alpha-subunit. The potential for the proximal His hyperfine shifts in serving as indicators of axial strain in the allosteric transition of HbA is discussed.     

Library of biphenyl privileged substructures using a safety-catch linker approach

A biphenyl privileged structure library containing three attachment points were synthesized using a catechol-based safety-catch linker strategy. The method requires the attachment of a bromo-acid to the linker, followed by a Pd-catalyzed Suzuki cross-coupling reaction. Further derivatization, activation of the linker with strong acid and aminolysis afforded the respective products in high purity and good overall yield. To show the versatility of the synthesis, a 199-member library was generated. The library samples both conformational and chemical diversity about a well-known privileged substructure.     

Enhanced electrochemical performance of submicron LiCoO<Subscript>2</Subscript> synthesized by polymer pyrolysis method

Submicron LiCoO₂ was synthesized by a polymer pyrolysis method using LiOH and Co(NO₃)₂ as the precursor compounds. Experimental results demonstrated that the powders calcined at 800 °C for 12 h appear as well-crystallized, uniform submicron particles with diameter of about 200 nm. As a result, the as-prepared LiCoO₂ electrode displayed excellent electrochemical properties, with an initial discharge capacity of 145.5 mAh/g and capacity retention of 86.1% after 50 cycles when cycled at 50 mA/g between 3.5 and 4.25 V. When cycled between 3.5 and 4.5 V, the discharge capacity increased to 177.9 mAh/g with capacity retention of 85.6% after 50 cycles.     

Rapid decolorization of azo dyes in aqueous solution by an ultrasound-assisted electrocatalytic oxidation process

In this study, we developed a novel ultrasound-assisted electrocatalytic oxidation (US–EO) process to decolorize azo dyes in aqueous solution. Rhodamine B was decolorized completely within several minutes in this developed US–EO system. Oxidation parameters such as applied potentials, power of the ultrasound, initial pH of the solution, and initial concentration of RhB were systematically studied and optimized. An obvious synergistic effect was found in decolorization of RhB by the US–EO process when comparing with either ultrasound (US) process or electrocatalytic oxidation (EO) one. Additionally, the decolorization of other azo dyes, such as methylene blue, reactive brilliant red X-3B, and methyl orange, were also effective in the US–EO system. The results indicated that US–EO system was effective for the decolorization of azo dyes, suggesting its great potential in dyeing wastewater treatment.     

水相法合成二氯二甲茂钛与水杨酸类配合物

Ｃｐ2 ＴｉＣｌ2 具有很好的抗癌活性 ,已成为第三代抗癌药物[1 - 3] 。为了寻求活性更高的抗癌药物 ,探索抗癌机理 ,我们用 (ＭｅＣｐ) 2 ＴｉＣｌ2 、水杨酸或其衍生物 ,按水相法合成了甲茂钛的水杨酸类配合物。合成路线如下图所示 :其中 :Ⅰ为ｐＨ <4 ,Ｘ =Ｈ ,Ｙ =Ｈ的产物 ;Ⅱ为ｐＨ <4 ,Ｘ =Ｈ ,Ｙ =ＮＯ2 的产物 ;Ⅲ为ｐＨ >6 ,Ｘ =ＮＯ2 ,Ｙ =ＮＯ2 ,Ｚ =Ｏ的产物 ;Ⅳ为ｐＨ >6 ,Ｘ =Ｈ ,Ｙ =Ｈ ,Ｚ =Ｓ的产物。 (Ⅰ～Ⅳ为新化合物 )1　实验部分1 .1　仪器与试剂水杨酸、ＴｉＣｌ4,ＡＲ ;5 -硝基水杨酸、3,5 -二硝基水杨酸、5 -磺基…     

Pb(3)F(5)NO(3), a cationic layered material for anion-exchange

Our research involves the development of new cationic materials for anion-based applications. We report the solvothermal synthesis and characterization of Pb(3)F(5)NO(3), a new layered lead fluoride material that, unlike the majority of layered and open-framework materials, is cationic in charge. The structure consists of polyhedral lead centers connected by doubly and triply bridging fluoride groups. We quantitatively exchanged the interlamellar nitrate groups of Pb(3)F(5)NO(3) for dichromate, under ambient aqueous conditions. Nuclear magnetic resonance and UV-vis spectroscopy show the reaction proceeds to 61.0% completion in several days. The material is also stable to 450 degrees C, which is vastly superior to organic resins that are still the standard for anion-exchange. The presence of extraframework anions also opens up other potentially unique anion-based properties, such as new catalytic reactions, anion intercalation, or growth of anionic clusters within the void spaces of the cationic material.     

Secondary Metabolites from the Fruiting Bodies of Coriolopsis aspera in Vietnam and their Bioactivities

Chemistry of Natural Compounds -     

Colorimetric detection of peroxynitrite-induced DNA damage using gold nanoparticles, and on the scavenging effects of antioxidants

We describe a rapid and convenient colorimetric method for the detection of oxidative DNA damage caused by peroxynitrite (ONOO^?) using unmodified gold nanoparticles (AuNPs). AuNPs are stable in the presence of single-stranded DNA (ssDNA) against the aggregation induced by a high ionic strength. If adsorbed ssDNA are cleaved by ONOO^? to form smaller fragments, the AuNPs rapidly aggregate due to electrostatic attraction. As a result, the color of the solution changes from red to blue, and this can be seen with bare eyes. We also have evaluated the activity of the antioxidants gallic acid, ascorbic acid and caffeic acid to scavenge ONOO^?. This method therefore also can be applied to screen for anti-oxidation drugs and agents.