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Sokkalingam, Punidha,Lee, Chang-Hee American Chemical Society 2011 Journal of organic chemistry Vol.76 No.10
<P>A simple, convenient, and inexpensive method has been developed to quantitatively determine fluoride anion concentration in acetonitrile as well as in water. The method exhibited a high selectivity and a great sensitivity toward fluoride anions through “turn-on” chromogenic and fluorogenic dual modes. The fluoride driven silyl deprotection and the subsequent spectral changes of hydroxyl coumarin were the operating foundations for the observed selectivity and sensitivity. <SUP>1</SUP>H NMR spectral titration with F<SUP>–</SUP> revealed that complete deprotection of a triisopropylsilyl (TIPS) group needed exactly 1 equiv of TBAF. UV–vis and fluorescence titration studies exhibited the appearance of a new intense absorption band centered at 434 nm and green emission peak at 500 nm, accompanied by bright yellow color development to the naked eye. An easy-to-prepare test paper, obtained by dipping the paper into the solution of TIPS-protected coumarin derivative, was able to detect F<SUP>–</SUP> in aqueous media. The method has also shown highly promising results in detecting all kinds of fluoride salts, regardless of being organic or inorganic, and thus could be potentially useful in real applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/joceah/2011/joceah.2011.76.issue-10/jo200138t/production/images/medium/jo-2011-00138t_0016.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jo200138t'>ACS Electronic Supporting Info</A></P>
Receptor That Can Capture a Discrete Monohydrated Fluoride Anion
Sokkalingam, Punidha,Kee, Se-Young,Kim, Youngmee,Kim, Sung-Jin,Lee, Phil Ho,Lee, Chang-Hee American Chemical Society 2012 Organic letters Vol.14 No.24
<P>A ‘picket calix[4]pyrrole’ bearing a well-defined binding domain has allowed the stabilization of a monohydrated fluoride anion. The monohydrated F<SUP>–</SUP> was observed only when CsF (not the TBAF) was treated with a host in aqueous acetonitrile. The structure of the receptor-bound, monohydrated F<SUP>–</SUP> was fully characterized by single crystal X-ray diffraction analysis as well as by low temperature <SUP>1</SUP>H and <SUP>19</SUP>F NMR spectroscopy. Further analysis revealed that the complex formed a three-dimensional, salt mediated organic framework in the solid state.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orlef7/2012/orlef7.2012.14.issue-24/ol302996y/production/images/medium/ol-2012-02996y_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ol302996y'>ACS Electronic Supporting Info</A></P>
Joel Ben-Awuah,Eswaran Padmanabhan,Rajalingam Sokkalingam 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.2
Geochemistry, paleoweathering, provenance, tectonic setting, paleoclimate and paleoenvironment of deposition of offshore Miocene sedimentary rocks in the West Baram Delta have been examined through multi-element geochemistry and mineralogy. Materials and methods used in the study include ninety four core samples from four subsurface wells, XRF, thin sections and FESEM. Four main groups of samples are identified in the wells: porous sandstones, cemented sandstones, siltstones and mudstones. The sandstones are classified as sublitharenites, litharenites and Fe-rich sandstones based on chemical composition and mineralogy. Variations in compositional trends suggest strong lithological and diagenetic controls on the geochemical composition of the samples. Petrography of the samples indicates that they are composed mainly of quartz, K-feldspar, siderite and clay minerals. The samples are characterized by moderate to high degree of chemical weathering with CIA values between 52–76 and PIA values from 65–100. Provenance analysis of the samples shows predominantly felsic and intermediate igneous provenance with minor mafic contribution. The samples are inferred to have originated from a passive margin tectonic setting that followed the continental collision and rifting stages of the foreland basin development phase of the Sarawak Basin. The paleoclimate of deposition of the samples is interpreted to be warm and humid enhancing the chemical weathering. The paleoenvironment of deposition is predominantly suboxic to anoxic.
Effect of edaravone in diabetes mellitus-induced nephropathy in rats
Varatharajan, Rajavel,Lim, Li Xin,Tan, Kelly,Tay, Chai Sze,Teoh, Yi Leng,Akhtar, Shaikh Sohrab,Rupeshkumar, Mani,Chung, Ivy,Abdullah, Nor Azizan,Banik, Urmila,Dhanaraj, Sokkalingam A.,Balakumar, Pitch The Korean Society of Pharmacology 2016 The Korean Journal of Physiology & Pharmacology Vol.20 No.4
Edaravone, a synthetic-free radical scavenger, has been reported to reduce ischemia-reperfusion-induced renal injury by improving tubular cell function, and lowering serum creatinine and renal vascular resistance. The present study investigated the effect of edaravone in diabetes mellitus-induced nephropathy in rats. A single administration of streptozotocin (STZ, 55 mg/kg, i .p.) was employed to induce diabetes mellitus in rats. The STZ-administered diabetic rats were allowed for 10 weeks to develop nephropathy. Mean body weight, lipid alteration, renal functional and histopathology were analysed. Diabetic rats developed nephropathy as evidenced by a significant increase in serum creatinine and urea, and marked renal histopathological abnormalities like glomerulosclerosis and tubular cell degeneration. The kidney weight to body weight ratio was increased. Moreover, diabetic rats showed lipid alteration as evidenced by a significant increase in serum triglycerides and decrease in serum high-density lipoproteins. Edaravone (10 mg/kg, i .p., last 4-weeks) treatment markedly prevented the development of nephropathy in diabetic rats by reducing serum creatinine and urea and preventing renal structural abnormalities. In addition, its treatment, without significantly altering the elevated glucose level in diabetic rats, prevented diabetes mellitus-induced lipid alteration by reducing serum triglycerides and increasing serum high-density lipoproteins. Interestingly, the renoprotective effect of edaravone was comparable to that of lisinopril (5 mg/kg, p.o, 4 weeks, standard drug). Edaravone prevented renal structural and functional abnormalities and lipid alteration associated with experimental diabetes mellitus. Edaravone has a potential to prevent nephropathy without showing an anti-diabetic action, implicating its direct renoprotection in diabetic rats.