Effects of (+)-, (-)- and (+/-)-indenestrols A and B on microtubule polymerization.

Indenestrol A (IA) is a metabolite of diethylstilbestrol (DES), and indenestrol B (IB) is an analog of IA. IA was simply obtained from E,E-dienestrol in the presence of dilute sulfuric acid, and a mixture of IA and IB was formed by thermal cyclization of E,E-dienestrol. In order to elucidate the effects of optically active IA and IB on microtubule assembly, the IA and IB enantiomers were separated to greater than 99% purity by high-pressure liquid chromatography using a chiral column. The di(4-bromobenzoate) of (-)-IB was analyzed by X-ray crystallography and its absolute structure was determined as C(3)-S. The (+)-, (-)-, and (+/-)-indenestrols A and B were shown to be inhibitors of microtubule assembly in vitro using microtubule proteins from porcine brain. (+/-)-IB is more active than (+/-)-IA, and the order of inhibitory activity of the enantiomers on microtubule assembly was (+)-IB greater than (+)-IA greater than (-)-IA greater than (-)-IB.     

Preparation of microcapsules containing a curing agent for epoxy resin by polyaddition reaction with the self-assembly of phase-separated polymer method in an aqueous dispersed system

To prepare cured epoxy resin particles encapsulating a curing agent (diamine), the self-assembly of phase-separated polymer (SaPSeP) method was developed to be applicable to polyaddition reaction of a stoichiometrically imbalanced system. The SaPSeP method was developed by the authors for preparation of micrometer-sized, hollow cross-linked polymer particles by radical polymerization based on the self-assembly of phase-separated polymer at the inner interface of particles. Although a polyaddition reaction, in general, requires that the reactants are in stoichiometric balance for the cure reaction to proceed well, diamine was successfully encapsulated within a cured epoxy resin shell by utilizing the SaPSeP method regardless of stoichiometric imbalance. The results provide further support of the previously proposed SaPSeP mechanism for the formation of hollow particles. Moreover, such diamine capsules can be employed in one-component epoxy adhesives.     

Control of iron(III) spin-state in the model complexes of azide hemoprotein by porphycene, corrphycene, and hemiporphycene macrocycles

Spin states of the iron(III) complexes of porphyrin, porphycene, hemiporphycene, and corrphycene bearing both 1-methylimidazole and azide as axial ligands were analyzed with infrared (IR) spectroscopy at 20 degrees C. The IR stretching band of coordinating azide split into two peaks around 2047 and 2017 cm(-1) reflecting an equilibrium between the high- (S = 5/2) and low- (S = 1/2) spin states. The high-spin fraction changed over a 0-90% range among the macrocycles, demonstrating that the tetrapyrrole array is essential to control the equilibrium.     

Spectrophotometric determination of ammonia-nitrogen after preconcentration as indothymol on a glass-fiber filter in the presence of a cationic surfactant

Ammonia-nitrogen, in the range 0.06 to 2 g in 20 ml of water sample, is treated with hypochlorite and thymol to form an intensely blue anionic dye called indothymol. The indothymol is collected on a glass-fiber filter as the ion-pair with benzyldimethyltetradecylammonium ion. The indothymol collected on the filter is dissolved in a small volume of dimethylformamide (DMF) and the absorbance due to the indothymol is measured at 675 nm against the reagent blank. An unexpectedly high sensitivity was obtained because of the increased molar absorptivity of indothymol in DMF (3.2 × 10⁴ l mol^–1 cm^–1, _max = 675 nm), approximately 3 times larger than that in water (1.16 × 10⁴ l mol^–1 cm^–1, _max = 660 nm). The detection limit, defined as three times the standard deviation of the blank, is better than 1 g 1^–1 of ammonia-nitrogen with 5-fold preconcentration.     

A strictly "pair"-selective synthesis of conjugated diynes via Pd-catalyzed cross coupling of 1,3-diynylzincs: a superior alternative to the Cadiot-Chodkiewicz reaction

A strictly "pair"-selective synthesis of conjugated diynes via Pd-catalyzed cross coupling of 1,3-diynylzincs is described. This method, like the Cadiot-Chodkiewicz reaction, requires three steps for the synthesis of R(1)Ctbd1;CCtbd1;CR(2) from R(1)Ctbd1;CH, R(2)X, and HCtbd1;CH. However, the high "pair"-selectivity permitting high-yield production of the desired conjugated diynes without separation of symmetrical diynes promises to make the present protocol superior to the Cadiot-Chodkiewicz reaction in many cases.     

An effective method for the synthesis of the cap structure of eukaryotic messenger ribonucleic acids

A new promising “capping agent” (9) was synthesized by use of a lipophilic amino protecting group and an activatable pyrophosphate protecting group. This agent reacted homogeneously with 5′_5′-nucleotides in the presence of AgNO₃ to afford the cap structures (m7G pppNu).