Synthesis of hollow CaCO3 nanospheres templated by micelles of poly(styrene-b-acrylic acid-b-ethylene glycol) in aqueous solutions

An asymmetric triblock copolymer, poly(styrene-b-acrylic acid-b-ethylene glycol) (PS-b-PAA-b-PEG), was synthesized via reversible addition-fragmentation chain transfer controlled radical polymerization. Micelles of PS-b-PAA-b-PEG with PS core, PAA shell, and PEG corona were then prepared in aqueous solutions, followed by extensive characterization based on dynamic light scattering, zeta-potential, and transmission electron microscopy (TEM) measurements. The well-characterized micelles were used to fabricate hollow nanospheres of CaCO(3) as a template. It was elucidated from TEM measurements that the hollow nanospheres have a uniform size with cavity diameters of ca. 20 nm. The X-ray diffraction analysis revealed a high purity and crystallinity of the hollow nanospheres. The hollow CaCO(3) nanospheres thus obtained have been used for the controlled release of an anti-inflammatory drug, naproxen. The significance of this study is that we have overcome a previous difficulty in the synthesis of hollow CaCO(3) nanospheres. After mixing of Ca(2+) and CO(3)(2-) ions, the growth of CaCO(3) is generally quite rapid to induce large crystal, which prevented us from obtaining hollow CaCO(3) nanospheres with controlled structure. However, we could solve this issue by using micelles of PS-b-PAA-b-PEG as a template. The PS core acts as a template that can be removed to form a cavity of hollow CaCO(3) nanospheres, the PAA shell is beneficial for arresting Ca(2+) ions to produce CaCO(3), and the PEG corona stabilizes the CaCO(3)/micelle nanocomposite to prevent secondary aggregate formation.     

The novel approach to indole alkaloids by using Pd(II)-catalyzed cyclization

The synthesis of indole skeleton by using Pd(II)-catalyzed cyclization of the urethane has been achieved. The urethanes with allylic alcohol were converted into vinyl indolines in good yield. The vinyl indoline was transformed into some intermediates of indole alkaloids.     

Stable and lipophilic technetium-99m dithiosemicarbazone complexes with 5-6-5 membered chelate ring structure

Modification of the chelate ring structure of technetium-99m (99mTc) dithiosemicarbazone (DTS) chelate was carried out in pursuit of a more stable and lipophilic compound. A new DTS chelating molecule, pentane-2,4-dione bis(N-methylthiosemicarbazone) (PETS), with a 5-6-5 membered chelate ring structure, was synthesized and labeled with 99mTc, PETS generated two 99mTc compounds as major products. Both had much higher stability and lipophilicity than a 5-5-5 membered 99mTc DTS compound, as well as great stability in plasma. Both 99mTc-PETS compounds were rapidly extracted by the brain and heart when injected into mice. Thus, the modified chelate ring structure afforded a preferable characteristics to DTS chelate as for the chelating site for technetium radiopharmaceuticals.     

Liquid chromatographic assay for constituent disaccharides of hyaluronic acid and chondroitin sulphate isomers

An improved high-performance liquid chromatographic (HPLC) method for unsaturated disaccharides prepared from hyaluronic acid and various chondroitin sulphate and dermatan sulphate isomers was developed, which involves an ion-exchange resin prepared from a sulphonated styrene-divinylbenzene copolymer. The retention times of the individual unsaturated disaccharides were unique and reproducible, the disaccharides appearing in the following order: unsaturated non-sulphated disaccharide derived from hyaluronic acid, then unsaturated 6-sulphated, non-sulphated and 4-sulphated disaccharides from chondroitin sulphate isomers. Unsaturated disulphated disaccharide G had a much shorter retention time than the unsaturated non-sulphated disaccharide derived from hyaluronic acid. The contents of these individual unsaturated disaccharides could be determined with similar sensitivities on the basis of their ultraviolet absorbance. Selective and unique retention times and good resolutions were found for various unsaturated disulphated and trisulphated disaccharides. The proposed method can be used to determine various chondroitin sulphate and dermatan sulphate isomers in addition to hyaluronic acid in amounts as small as 100 ng to 8 micrograms. The practicality of this method was verified by its application to the separation and determination of the different types of chondroitin sulphate and dermatan sulphate isomers derived from human arteries in the presence of appreciable amounts of hyaluronic acid.     

Characterization of flower-inducing compound in Lemna paucicostata exposed to drought stress

A flower-inducing compound, LDS1, was isolated from a free-floating aquatic plant, Lemna paucicostata. The chemical structure and the absolute stereochemistry of LDS1 were determined as (9R,13R,11E,15Z)-9,13-dihydroxy-10-oxooctadeca-11,15-dienoic acid for its most abundant diastereomer. LDS1 was enzymatically produced when the plant was exposed to drought stress, and induced flowering at a concentration of 10 nM.     

Controlled Dynamic Helicity of a Folded Macrocycle Based on a Bisterephthalamide with a Twofold Z‐Shaped Structure

Dynamic helicity in a folded macrocycle and control of the helical preference are described. We designed macrocycle 1 with a dual mode of folding through the integration of two flexible units that are arranged twice to form a cyclic structure. As a folding unit, we used a terephthalamide skeleton and a Z‐shaped hydrocarbon: the former acted as a control unit to induce a preference of a particular sense of dynamic helicity and the latter was just a spacer. A terephthalamide unit provided a binding site for capturing a ditopic hydrogen‐bonding guest when it adopted helically folded syn forms (M/P). Thus, only the terephthalamide unit controlled the helical sense of dynamic helicity in a folded macrocycle through the supramolecular transmission of chirality upon complexation with a chiral ditopic guest. In addition, chirality on a host could also contribute to the control of the helical preference in a folded macrocycle, which led to exceptionally enhanced chiroptical signals.     

Application of plug–plug technique to ACE experiments for discovery of peptides binding to a larger target protein: A model study of calmodulin‐binding fragments selected from a digested mixture of reduced BSA

To discover peptide ligands that bind to a target protein with a higher molecular mass, a concise screening methodology has been established, by applying a “plug–plug” technique to ACE experiments. Exploratory experiments using three mixed peptides, mastoparan‐X, β‐endorphin, and oxytocin, as candidates for calmodulin‐binding ligands, revealed that the technique not only reduces the consumption of the protein sample, but also increases the flexibility of the experimental conditions, by allowing the use of MS detection in the ACE experiments. With the plug–plug technique, the ACE–MS screening methodology successfully selected calmodulin‐binding peptides from a random library with diverse constituents, such as protease digests of BSA. Three peptides with K_d values between 8–147 μM for calmodulin were obtained from a Glu‐C endoprotease digest of reduced BSA, although the digest showed more than 70 peaks in its ACE–MS electropherogram. The method established here will be quite useful for the screening of peptide ligands, which have only low affinities due to their flexible chain structures but could potentially provide primary information for designing inhibitors against the target protein.