Online tool for calculating null points in various inversion recovery sequences

Accurate equations for calculating the inversion time of the null point (TI_null) in inversion recovery (IR) sequences are required for adequate suppression of fat or cerebrospinal fluid (CSF) but are not widely known. The purpose of this study is to elucidate the process of deriving accurate TI_null equations using schematic diagrams that allow the equations to be easily understood, and to devise a convenient online tool for instant calculation of TI_null.     

General Method for the 11C‐Labeling of 2‐Arylpropionic Acids and Their Esters: Construction of a PET Tracer Library for a Study of Biological Events Involved in COXs Expression

Cyclooxygenase (COX) is a critical enzyme in prostaglandin biosynthesis that modulates a wide range of biological functions, such as pain, fever, and so on. To perform in vivo COX imaging by positron emission tomography (PET), we developed a method to incorporate ¹¹C radionuclide into various 2‐arylpropionic acids that have a common methylated structure, particularly among nonsteroidal anti‐inflammatory drugs (NSAIDs). Thus, we developed a novel ¹¹C‐radiolabeling methodology based on rapid C‐[¹¹C]methylation by the reaction of [¹¹C]CH₃I with enolate intermediates generated from the corresponding esters under basic conditions. One‐pot hydrolysis of the above [¹¹C]methylation products also allows the synthesis of desired ¹¹C‐incorporated acids. We demonstrated the utility of this method in the syntheses of six PET tracers, [¹¹C]Ibuprofen, [¹¹C]Naproxen, [¹¹C]Flurbiprofen, [¹¹C]Fenoprofen, [¹¹C]Ketoprofen, and [¹¹C]Loxoprofen. Notably, we found that their methyl esters were particularly useful as proradiotracers for a study of neuroinflammation. The microPET studies of rats with lipopolysaccharide (LPS)‐induced brain inflammation clearly showed that the radioactivity of PET tracers accumulated in the inflamed region. Among these PET tracers, the specificity of [¹¹C]Ketoprofen methyl ester was demonstrated by a blocking study. Metabolite analysis in the rat brain revealed that the methyl esters were initially taken up in the brain and then underwent hydrolysis to form pharmacologically active forms of the corresponding acids. Thus, we succeeded in general ¹¹C‐labeling of 2‐arylpropionic acids and their methyl esters as PET tracers of NSAIDs to construct a potentially useful PET tracer library for in vivo imaging of inflammation involved in COXs expression.     

Gel formation in cationic polymerization of divinyl ethers. II. 2,2-Bis{4-[(2-vinyloxy)ethoxy]phenyl}propane

Cationic polymerization of 2,2-bis{4-[(2-vinyloxy)ethoxy]phenyl}propane [CH₂CH O CH₂CH₂O C₆H₄ C(CH₃)₂ C₆H₄ OCH₂CH₂ O CHCH₂; 2], a divinyl ether with oxyethylene units adjacent to the polymerizable vinyl ether groups and a bulky central spacer, was investigated in CH₂Cl₂ at 0°C with the diphenyl phosphate [(C₆H₅O)₂P(O)OH]/zinc chloride (ZnCl₂) initiating system. The polymerization proceeded quantitatively and gave soluble polymers up to 85% monomer conversion. In the same fashion as the polymerization of 1,4-bis[2-vinyloxy(ethoxy)]benzene (CH₂CH O CH₂CH₂O C₆H₄ OCH₂CH₂ O CHCH₂; 1) that we already studied, the content of the unreacted pendant vinyl ether groups of the produced soluble polymers decreased with monomer conversion, and almost all the pendant vinyl ether groups were consumed in the soluble products prior to gelation. Alternatively, endo-type double bonds were gradually formed in the polymer main chains by chain transfer reactions and other side reactions as the polymerization proceeded. The polymerization behavior of isobutyl vinyl ether (3), a monofunctional vinyl ether, under the same conditions, showed that the endo-type olefins in the polymer backbones are of no polymerization ability with the growing active species involved in the present polymerization systems. These results indicate that the intermolecular crosslinking reactions occurred primarily by the pendant vinyl ether groups, and the final stage of crosslinking process leading to gelation also may occur by the small amount of the residual pendant vinyl ether groups (supposedly less than 2%). The formation of the soluble polymers that almost lack the unreacted pendant vinyl ether groups is most likely due to the frequent occurrence of intramolecular crosslinking reactions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1931–1941, 1999     

The Distribution of Arsenic Compounds in the Ocean: Biological Activity in the Surface Zone and Removal Processes in the Deep Zone

The vertical profies of inorganic arsenic [As(III)+As(V)], monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) were investigated at four sampling stations in the Pacific Ocean and a sampling station in the southern Tasman Sea. In addition, the concentrations of those compounds in surface waters of the Pacific Ocean and Tasman Sea have been determined. The vertical profiles of inorganic arsenic showed the low concentrations in both the surface and deep/bottom zones. The depleted concentrations in the surface zone varied from 1000 to 1700 ng dm⁻³ and that in the deep/bottom zone varied from 1300 to 2050 ng dm⁻³. The maximum concentrations that varied from 1500 to 2450 ng dm⁻³ were usually observed at a depth of about 2000 m. Both MMAA and DMAA were observed throughout the water column at sampling stations in the north-western and equatorial regions of the Pacific Ocean. At the sampling station in the central northern Pacific gyre, DMAA was the only methylated arsenic compound observed throughout the water column. On the contrary, at the sampling station in the southern Tasman Sea, the only detected methylated arsenic compound throughout the water column was MMAA. Their vertical profiles showed maximum concentrations in the surface water which abruptly dropped with depth from 0 to 200 m. The concentration in the surface water was close to 10 ng dm⁻³ for MMAA and varied from 27 to 185 ng dm⁻³ for DMAA. At depths greater than 100 m, MMAA and DMAA were at comparable concentrations which varied from 0.7 to 14 ng dm⁻³. The low inorganic arsenic concentration in the surface zone was due to biological activity. This activity resulted in the uptake of As(V) and subsequent reduction and methylation to MMAA and DMAA. DMAA was the main predominant arsenic compound resulting from biological activity in surface waters. The low inorganic arsenic concentrations in the deep and bottom zones were likely to be caused by the adsorption of dissolved inorganic arsenic onto sinking particulates rich in iron and manganese oxides.     

ESR linewidth broadening of a hydrophobic probe in some surfactant solutions

ESR linewidth of tetradecanoyloxy-2,2,6,6-tetramethyl-piperidinyl-l-oxyl was observed in aqueous solutions of hexadecyltrimethylammonium bromide and sodium alkyl (C₁₂ and C₁₄) sulfates at 30 °C. The linewidth increases quadratically with the spin probe concentration to various extents, depending upon micellar properties. The diversity of the linewidth broadening is, however, reduced by plotting the relative linewidth, W/W₀, vs. the average solubilization number, m, where W₀ is the linewidth at the extremely dilute spin probe concentration. All the experimental points fall on a curve regardless of the diverse micellar properties. The broadening is interpreted in terms of a bimolecular and multimolecular collisions between the spin probes exclusively concentrated in micelles in accordance with the Poisson distribution of the spin probe.     

Unusual reactivity of (6,9)purinophanes due to stereoelectronic effect

[n](6,9)Purinophanes 2a–c were synthesized and their unusual reactivity toward nucleophiles was explained by the stereoelectronic effect in the fairly rigid tetrahedral intermediate.     

Automatic superposition of drug molecules based on their common receptor site

Summary We have prevously developed a new rational method for superposing molecules in terms of submolecular physical and chemical properties, but not in terms of atom positions or chemical structures as has been done in the conventional methods. The program was originally developed for interactive use on a three-dimensional graphic display, providing goodness-of-fit indices on molecular shape, hydrogen bonds, electrostatic interactions and others.Here, we report a new unbiased searching method for the best superposition of molecules, covering all the superposing modes and conformational freedom, as an additional function of the program. The function is based on a novel least-squares method which superposes the expected positions and orientations of hydrogen bonding partners in the receptor that are deduced from both molecules. The method not only gives reliability and reproducibility to the result of the superposition, but also allows us to save labor and time. It is demonstrated that this method is very efficient for finding the correct superposing mode in such systems where hydrogen bonds play important roles.     

Ruthenium catalyzed synthesis of secondary or tertiary amines from amines and alcohols

Unsymmetrical secondary and tertiary amines are prepared by the ruthenium catalyzed reaction of alcohols with amines, which provides highly efficient method for synthesis of cyclic amines.     

Extraction-spectrophotometric determination of trace iron (II) in sea water with 2-[2-(3,5-dibromopyridyl)azo]-5-diethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of iron(II) with 2-[2-(3,5-dibromopyridyl)azo]-5-diethyl-aminobenzoic acid. The reagent forms a stable and blue 12 iron/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the iron(II) complex is 1.09 × 10⁵ 1 mol^–1 cm^–1 at 624 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper, nickel and vanadium can be removed by using dimethylglyoxime and EDTA. The method is applied to the determination of iron (II) in sea water and aluminium alloys with good precision and accuracy.