Fullerenes separation with monomeric type C30 stationary phase in high-performance liquid chromatography

The temperature effect on the separation of fullerenes in LC was examined using monomeric type C30, C18 and C8 alkyl bonded stationary phases. It appears that the C30 phase exhibits superior separation ability for fullerenes. It is observed that the maximum retention temperature of fullerenes on the C30 phase is around 20 degrees C. A strong correlation between the changes in NMR spectra and the retention behavior of the solutes was found. The interpretation of the retention behavior of fullerenes on the alkyl bonded stationary phases, including the behavior in subambient temperature, is discussed using the information obtained by CP-MAS solid-state NMR spectroscopy and LC.     

One‐Shot Double Elimination Process: A Practical and Concise Protocol for Diaryl Acetylenes

A variety of diaryl acetylenes were obtained in good yields when lithium hexamethyldisilazide was added to a solution of arylmethyl sulfone, aryl aldehyde, and chlorodiethylphosphate in THF. In this one‐shot process, a number of transformations such as aldol reaction, phosphorylation of aldolate, and double elimination of the resulting β‐substituted sulfone proceeded successively to afford the desired acetylenes. The one‐shot process was accelerated by the substitution of halogen atoms on the phenyl groups, and unsymmetrically substituted diaryl acetylenes were obtained without contamination of the dehalogenated products. Diaryl acetylenes with other substituents such as CF₃, ethoxycarbonyl, dimethylamino, TMS‐acetylene groups, as well as pyridinyl and thienyl moieties were also accessible with this method. However, methoxy‐substituted compounds were obtained in moderate yields under the same conditions, but the yields were increased when lithium diisopropylamide was used instead.     

Proton-block strategy for the synthesis of oligodeoxynucleotides without base protection,capping reaction,and P-N bond cleavage reaction

A new N-unprotected phosphoramidite method called the "proton-block" approach was developed for the chemical synthesis of oligodeoxynucleotides based on the hitherto simplest and rational principle of acid-base reactions. This concept involves protection of the nucleobases of deoxycytidine and deoxyadenosine with "protons" to convert them to unreactive protonated bases during condensation by use of promoters having pK(a) values lower than 2.8. This strategy was applied to the synthesis of d[CpT] and d[ApT] to check the side reactions associated with the base residues. In this "proton-block" method, 5-nitrobenzimidazolium triflate (NBT) was found to be the best promoter, and THF was superior to CH(3)CN as the solvent so that the concomitant detritylation due to the inherent acidity of the promoter could be greatly suppressed. Application of this strategy to the solid-phase synthesis gave d[CpT], d[ApT], d[ApA], d[CpC], and d[GpT] as almost single peaks in HPLC analysis. Similarly, d[ApApApT] and d[CpCpCpT] were successfully synthesized without significant side reactions. Finally, d[CpCpCpCpCpCpT] and d[ApApApApApApT] were obtained as the main products. In the case of a longer oligomer, d[CpApGpTpCpApGpTpCpApGpT], a mixed solvent of CH(3)CN-N-methylpyrrolidone (1:1, v/v) was superior to THF so that the desired oligodeoxynucleotide could be isolated in a satisfactory yield. These results suggest that DNA synthesis can be carried out simply by using the protonated bases at the oligomer level not only without base protection but also without the capping reaction and the posttreatment of branched chains with MeOH-benzimidazolium triflate that previously was requisite. It is concluded that most of the reactions and solvent effects involved in this strategy can be explained in terms of simple acid-base reactions. Some problems associated with the previous posttreatment are also discussed with our own results.     

Water polarizability in condensed phase: ab initio evaluation by cluster approach

The polarizability of a water molecule in liquid is evaluated via ab initio and density functional calculations for water clusters. This work has considerably improved our previous effort [J Chem Phys 1999, 110, 11987] to attain quantitative accuracy for polarizability. The calculations revealed that the water polarizability in the liquid is reduced from that in the gaseous phase by 7-9%. These results suggest significant implications for polarizable water models.     

Cu-Chelex as a selective adsorbent for o-nitroso derivatives of phenolic substances

Summary Chelex resins in several metal forms were tested for selective uptake of o-nitrosonaphthols and o-nitrosophenols from aqueous solution. Cu-Chelex was the most efficient resin over a wide pH range, and the taken-up nitroso compounds were effectively eluted with concentrated ammonia: acetonitrile (4:1, v/v) after washing the resin with acetonitrile to eliminate non-specific binding. The upper and lower limits of uptake capacity of the resin for 1-nitroso-2-naphthol were 0.5 mol/100 mg and 1.25 mol/100 mg, respectively. A preliminary recovery experiment using urine and cucumber juice showed that Cu-Chelex would be useful for screening of o-nitroso derivatives of phenolic substances in complicated samples such as biological fluids and foods.     

A new method for the synthesis of some 9-β-D-arabinofuranosylpurines by a combination of chemical and enzymatic reactions

An enzymatic transarabinosylation between 2-chlorohypoxanthine and 1-β-$\text{D}$-arabinofuranosyluracil gave 9-β-$\text{D}$-arabinofuranosyl-2-chlorohypoxanthine which was chemically converted to 9-β-$\text{D}$-arabinofuranosylguanine and its derivatives.     

Two-dimensional network formation of cardiac myocytes in agar microculture chip with 1480 nm infrared laser photo-thermal etching

We have developed a new method that enables agar microstructures to be used to cultivate cells and that allows cell network patterns to be controlled. The method makes use of non-contact three-dimensional photo-thermal etching with a 1480 nm infrared focused laser beam, which is strongly absorbed by water and agar gel, to form the shapes of agar microstructures. It allows microstructures to be easily formed in an agar layer within a few minutes, with cell-culture holes formed by the spot heating of a 100 mW laser and tunnels by the tracing of a 100 microm s(-1), 40 mW laser. We cultivated rat cardiac myocytes in adjacent microstructures and observed synchronized beating in them 90 min after they had made physical contact. Our results indicate that the system can make and use microstructures for cell-network cultivation in a minimal amount of time without any expensive microfabrication facilities or complicated procedures.     

Slurry sampling techniques for the determination of lead in Bangladeshi fish samples by electrothermal atomic absorption spectrometry with a metal tube atomizer

Ultrasonic slurry sampling electrothermal atomic absorption spectrometry with a metal tube atomizer has been applied to the determination of lead in Bangladeshi fish samples. The slurry sampling conditions, such as slurry stabilizing agent, slurry concentration, pyrolysis temperature for the slurried fish samples, particle size and ultrasonic agitation time, were optimized for electrothermal atomic absorption spectrometry with the Mo tube atomizer. Thiourea was used as the chemical modifier for the interference of matrix elements. The detection limit was 53 fg (3S/N). The determined amount of lead in Bangladeshi fish samples was consistent with those measured in the dissolved acid-digested samples. The advantages of the proposed methods are easy calibration, simplicity, low cost and rapid analysis.     

Electrodeposition of manganese and molybdenum mixed oxide thin films and their charge storage properties

Manganese and molybdenum mixed oxides in a thin film form were deposited anodically on a platinum substrate by cycling the electrode potential between 0 and +1.0 V vs Ag/AgCl in aqueous manganese(II) solutions containing molybdate anion (MoO(4)2-). A possible mechanism for the film formation is as follows. First, electrooxidation of Mn2+ ions with H2O yields Mn oxide and protons. Then, the protons being accumulated near the electrode surface react with MoO(4)2- to form polyoxomolybdate through a dehydrated condensation reaction (by protonation and dehydration). The condensed product coprecipitates with the Mn oxide. Cyclic voltammetry of the Mn/Mo oxide film-coated electrode in aqueous 0.5 M Na2SO4 solution exhibited a pseudocapacitive behavior with higher capacitance and better rate capability than that of the pure Mn oxide prepared similarly, most likely as a result of an increase in electrical conductivity of the film. Electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy clearly demonstrated that the observed pseudocapacitive behavior results from reversible extraction/insertion of hydrated protons to balance the charge upon oxidation/reduction of Mn3+/Mn4+ in the film.     

High performance liquid chromatography with an electrochemical detector in the cathodic mode as a tool for the determination of p-nitrophenol and assay of acid phosphatase in urine samples

Utilizing a commercially available helium-purging device and PEEK tubes for all tubing, especially for connection between the mobile phase and pump, high performance liquid chromatography with an electrochemical detector (ECD/HPLC) at the cathodic mode is a simple and precise method for the determination of p-nitrophenol (NP). Studies with cyclic and hydrodynamic voltammetry indicated that 25% aqueous MeOH containing 0.1% (v/v) CF(3)CO(2)H and -0.8 V vs. Ag/AgCl are the best mobile phase and detection potential for cathodic ECD/HPLC. With the present system, the limits of detection and determination were 0.2 and 0.25 microM, respectively, and up to 50 microM, a linear calibration curve was afforded. Within-day precisions for the analysis of 5 and 50 microM NP were 0.8 and 0.7% (n=6), respectively, and between-day precisions (n=6) for these samples were 3.5 and 2.2%, respectively. Compared with the commonly used Bessey-Lowry-Brock method, cathodic ECD/HPLC was useful for the assay of acid phosphatase in urine samples with p-nitrophenyl phosphate disodium salt as a substrate.