Three-dimensional helical coordination networks of a hexanuclear manganese metallamacrocycle as a helical tecton

We report on helical coordination networks that were prepared using a hexanuclear manganese metallamacrocycle as a helical tecton. We were able to prepare the three-dimensional helical coordination networks using a hexanuclear manganese metallamacrocycle, [Mn(6)(lshz)(6)], as a helical tecton, where N-lauroyl salicylhydrazide (H(3)lshz) was used as the primary building unit to generate the helical tecton as a secondary building unit. While the 4(1)/4(3) screw symmetry-linked helical coordination network was obtained when the primary building units had an N-acetyl group, both the 3(1)/3(2) screw symmetry-linked and the 4(1)/4(3) screw symmetry-linked helical coordination networks were obtained simultaneously in the same batch when the primary building unit had a long alkyl N-lauroyl group at the N-acetyl site.     

Kinetics and mechanism of the pyridinolysis of aryl furan-2-carbodithioates in acetonitrile

Kinetic studies on the pyridinolysis of aryl furan-2-carbodithioates 1 are carried out at 60.0 degrees C in acetonitrile. The biphasic rate dependence on the pyridine basicity with a breakpoint at pK(a) degrees = 5.2 is interpreted to indicate a change of the rate-limiting step from breakdown (beta(X) = 0.7-0.8) to formation (beta(X) = 0.2) of the tetrahedral intermediate, T(+/-), at the breakpoint as the basicity of the pyridine nucleophile is increased. Observation of the breakpoint is possible with pyridines since the expulsion rate of the pyridine (k(-)(a)) from T(+/-) is sufficiently low, with the low k(-)(a)/k(b) ratio leading to a low breakpoint, pK(a) degrees. The clear-cut change in the cross-interaction constants, rho(XZ), from a positive (rho(XZ) = +0.86) to a small negative (rho(XZ) = -0.11) value at the breakpoint supports the mechanistic change proposed. The magnitudes of rho(Z) and activation parameters are also consistent with the proposed mechanism.     

Eumelanin as a support for efficient palladium nanoparticle catalyst for Suzuki coupling reaction of aryl chlorides in water

Eumelanin-supported palladium (Pd) nanoparticle (NP) catalysts was found to exhibit excellent catalytic activities with high turnover number (TON, 2000) and turnover frequency (TOF, 1000 h^?1) for Suzuki cross coupling reaction of aryl chlorides in water. We propose that the amphiphilic property of the eumelanin support helps Pd NPs to catalyse the C–C coupling reaction in water through hydrophobic effect.     

In Vitro Osteoblast Differentiation is Negatively Regulated by Hoxc8

Hoxc8 has multiple roles in normal skeletal development. In this paper, a MC3T3-E1 subclone 4 osteogenic cell differentiation model was used to examine expression of Hoxc8 at multiple stages of osteogenesis. We found that Hoxc8 expression levels do not change in the early stage but increase in the middle stage and decrease in the late stage of osteogenesis. A knockdown of Hoxc8 by small-interfering RNA transfection in C2C12 cells indicated that Hoxc8 is a negative regulator of osteogenesis. Similarly, expression of Hoxc8 in C2C12 cells decreases alkaline phosphatase levels induced by bone morphogenetic protein-2 (BMP-2). The results of this study showed that Hoxc8 is involved in BMP-2-induced osteogenesis, and osteoblast differentiation in vitro is negatively regulated by Hoxc8, suggesting that Hoxc8 regulation is essential for osteoblast differentiation.     

The Extended Hadamard Transform: Sensitivity-Enhanced NMR Experiments Among Labile and Non-Labile 1Hs of SARS-CoV-2-derived RNAs

Hadamard encoded saturation transfer can significantly improve the efficiency of NOE-based NMR correlations from labile protons in proteins, glycans and RNAs, increasing the sensitivity of cross-peaks by an order of magnitude and shortening experimental times by ≥100-fold. These schemes, however, fail when tackling correlations within a pool of labile protons – for instance imino-imino correlations in RNAs or amide-amide correlations in proteins. Here we analyze the origin of the artifacts appearing in these experiments and propose a way to obtain artifact-free correlations both within the labile pool as well as between labile and non-labile ¹Hs, while still enjoying the gains arising from Hadamard encoding and solvent repolarizations. The principles required for implementing what we define as the extended Hadamard scheme are derived, and its clean, artifact-free, sensitivity-enhancing performance is demonstrated on RNA fragments derived from the SARS-CoV-2 genome. Sensitivity gains per unit time approaching an order of magnitude are then achieved in both imino-imino and imino-amino/aromatic protons 2D correlations; similar artifact-free sensitivity gains can be observed when carrying out extended Hadamard encodings of 3D NOESY/HSQC-type experiments. The resulting spectra reveal significantly more correlations than their conventionally acquired counterparts, which can support the spectral assignment and secondary structure determination of structured RNA elements.     

Relationship between oversulfation and conformation of low and high molecular weight fucoidans and evaluation of their in vitro anticancer activity

Low and high molecular weight fucoidans (F(5-30K) and F(>30K)) were chemically modified through the addition of sulfate groups, and the effect of oversulfation on the in vitro anticancer activity was investigated. After the addition of sulfate groups, a considerable increase of 35.5 to 56.8% was observed in the sulfate content of the F(5-30K) fraction, while the sulfate content of the F(>30K) fraction increased to a lesser extent (from 31.7 to 41.2%). Significant differences in anticancer activity were observed between the oversulfated F(5-30K) and F(>30K) fractions, with activities of 37.3-68.0% and 20.6-35.8%, respectively. This variation in the anticancer activity of oversulfated fucoidan derivatives was likely due to differences in their sulfate content. The results suggest that the molecular conformation of these molecules is closely related to the extent of sulfation in the fucan backbones and that the sulfates are preferably substituted when the fucoidan polymers are in a loose molecular conformation.     

Polymer-based electrospray device with multiple nozzles to minimize end effect phenomenon

In this paper, “end effect”, which represents the deflection of meniscus of boundary nozzles in an array due to asymmetric electric field and repulsive forces between adjacent nozzles, is experimentally investigated and a polymer-based electrospray device is fabricated and tested to minimize the end effect. For the electrically conductive nozzles of electrospray, the end effect could be reduced by dummy nozzles, through which no liquid is supplied, mounted at the boundary of the array. However, the polymer-based electrospray device can eliminate the end effect without using the dummy dry nozzles due to dielectric characteristic. A novel multiple nozzles of Polymethyl Methacrylate (PMMA)-based electrospray device was successfully fabricated and evaluated for reducing the end effect, showing no deflection of menisci through the boundary nozzles. And ten nozzles device was fabricated and observed to eject liquid jet simultaneously. The electrical current of the spray issued from the nozzles of the polymer-based electrospray device is measured with respect to flow rate and shows a good agreement with the scaling law.