Identification of 3-enol sulfate of Cypridina luciferin,Cypridina luciferyl sulfate,in the sea-firefly Cypridina (Vargula) hilgendorfii

Cypridina luciferin from the luminous ostracod Cypridina (Vargula) hilgendorfii has an imidazopyrazinone core structure (3,7-dihydroimidazopyrazin-3-one), which is identical to that of coelenterazine. Cypridina luciferyl sulfate (3-enol sulfate of Cypridina luciferin) was isolated for the first time and the chemical structure was identified by LC/ESI–TOF–MS analysis. Furthermore, Cypridina luciferyl sulfate was chemically synthesized, and its absorption and MS/MS spectra were in agreement with that of Cypridina luciferyl sulfate isolated. Using the crude extracts of Cypridina specimens, Cypridina luciferyl sulfate could be converted to Cypridina luciferin in the presence of adenosine 3′,5′-diphosphate (PAP), and Cypridina luciferin was converted to Cypridina luciferyl sulfate in the presence of 3′-phosphoadenosine 5′-phosphosulfate (PAPS). These results suggested that a sulfotransferase catalyzes the reversible sulfation of Cypridina luciferin in Cypridina hilgendorfii. In aqueous solution, Cypridina luciferyl sulfate was more stable than Cypridina luciferin and might be a storage form of Cypridina luciferin.     

一种降低井下核磁共振振铃的新方法

核磁共振（NMR）测井仪在测量过程中,振铃噪声幅度一般很高,会影响回波信号的检测. 常用的交叉相位对脉冲序列（PAPS）虽然能有效地降低振铃影响,但由于振铃与频率有关,使PAPS叠加只能在同频率之间展开,大大降低了NMR测井的纵向分辨率. 利用回波信号和振铃噪声的相位特征,设计了一种脉冲序列,采用PAPS和回波间叠加相结合的方式降低振铃噪声. 研究表明,相对于PAPS技术,提高了测量效率,同时提高了回波串的信噪比和NMR测井的纵向分辨率.     

High-performance liquid chromatography with sequential injection for online precolumn derivatization of some heavy metals

HPLC was coupled with sequential injection (SI) for simultaneous analyses of some heavy metals, including Co(II), Ni(II), Cu(II), and Fe(II). 2-(5-Nitro-2-pyridylazo)-5-[N-propyl-N-(3-sulfopropyl)amino]phenol (nitro-PAPS) was employed as a derivatizing reagent for sensitive spectrophotometric detection by online precolumn derivatization. The SI system offers an automated handling of sample and reagent, online precolumn derivatization, and propulsion of derivatives to the HPLC injection loop. The metal-nitro-PAPS complexes were separated on a C(18)-muBondapak column (3.9x300 mm(2)). Using the proposed SI-HPLC system, determination of four metal ions by means of nitro-PAPS complexes was achieved within 13 min in which the parallel of derivatization and separation were processed at the same time. Linear calibration graphs were obtained in the ranges of 0.005-0.250 mg/L for Cu(II), 0.007-1.000 mg/L for Co(II), 0.005-0.075 mg/L for Ni(II), and 0.005-0.100 mg/L for Fe(II). The system provides means for automation with good precision and minimizing error in solution handling with the RSD of less than 6%. The detection limits obtained were 2 microg/L for Cu(II) and Co(II), and 1 microg/L for Ni(II) and Fe(II). The method was successfully applied for the determination of metal ions in various samples, including milk powder for infant, mineral supplements, local wines, and drinking water.