A comparison of the Raman LAM and electron microscopy in determining crystallite thickness distributions: Polyethylenes with narrow size distributions

A detailed quantitative comparison between thin section electron microscopy, utilizing the chlorosulfonation technique, and the Raman low-frequency acoustical mode (LAM) in determining the crystallite size distribution in polyethylenes having narrow distributions is made. Three different polyethylene systems have been analyzed, one of which was specifically prepared for this work. Very good quantitative agreement is obtained between these two analytical methods when account is taken of the chain tilt and the distribution is restrained to be narrow. Systems having broad crystallite size distributions introduce complexities into this comparison.     

Synthesis of pyrazolo[1,5-alpha]pyrimidinone regioisomers

This work describes two distinct routes to prepare pyrazolo[1,5-alpha]pyrimidin-7-ones and two distinct routes to prepare pyrazolo[1,5-alpha]pyrimidin-5-ones. Use of 1,3-dimethyluracil as the electrophile in the preparation of the pyrimidin-5-one regioisomer represents a correction of previously reported results. Also, a novel reaction to prepare this isomer was identified and the reaction mechanism elucidated. This work provides the experimentalist with complimentary synthetic pathways that afford either the pyrimidin-7-one or the pyrimidin-5-one regioisomer.     

Development and optimization of an LC-MS/MS-based method for simultaneous quantification of vitamin D2 , vitamin D3 , 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3

Simultaneous and accurate measurement of vitamin D and 25-hydroxyvitamin D in biological samples is a barrier limiting our ability to define "optimal" vitamin D status. Thus, our goal was to optimize conditions and evaluate an LC-MS method for simultaneous detection and quantification of vitamin D(2) , vitamin D(3) , 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3) in serum. Extraction and separation of vitamin D forms were achieved using acetone liquid-liquid extraction and by a reversed phase C8 column, respectively. Detection was performed on a triple quadrupole tandem mass spectrometer (QQQ-MS/MS) equipped with atmospheric pressure photo ionization source. The LOQs for all analytes tested were 1 ng/mL for hydroxylated molecules and 2 ng/mL for the parent vitamin Ds. RSD at lower LOQ (2 ng/mL) and in medium (80 ng/mL) and high (200 ng/mL) quality control samples did not exceed 20 and 15% CV, respectively. Accuracy of the method for determination of hydroxylated molecules was also validated using National Institutes of Standards and Technology standard samples and found to be in the range of 90.9-111.2%. In summary, a sensitive and reproducible method is reported for simultaneous quantification of vitamin D(2) , vitamin D(3) , 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3) molecules in biological samples.     

Quantum dots as contrast agents for in vivo tumor imaging: progress and issues

Quantum dots (QDs) have shown promise as imaging agents in cancer, heart disease, and gene therapy research. This review focuses on the design of QDs, and modification using peptides and proteins for mediated targeting of tissues for fluorescence imaging of tumors in vivo. Recent examples from the literature are used to illustrate the potential of QDs as effective imaging agents. The distribution and ultimate fate of QDs in vivo is considered, and considerations of designs that minimize potential toxicity are presented.     

Impact of quality parameters on the recovery of putrescine and cadaverine in fish using methanol-hydrochloric acid solvent extraction

Methanol (MeOH) extraction by AOAC Official Method 996.07 has resulted in low amine recoveries in fresh fish tissue. Addition of 25% 0.4 M HCl to the 75% methanol-water extraction solvent resulted in higher recoveries of putrescine and cadaverine. Average putrescine recovery increased from 55 to 92% in flounder, scup, bluefish, and salmon; from 92 to 98% in mackerel; and from 83 to 107% in processed mackerel. Average cadaverine recovery increased from 57 to 95% in flounder, scup, bluefish, and salmon; from 91 to 97% in mackerel; and from 92 to 108% in processed mackerel. Fish stored on ice for 12 days also showed differences between background concentrations determined with the two solvents. However, the values decreased with storage time, indicating that degradation of the protein matrix may cause more comparable measurements between the two solvents. However, consistently higher putrescine and cadaverine measurements were determined using MeOH-HCl. Although significant differences in the extraction of amines from the high-fat fish tissue were not seen between MeOH and MeOH-HCl, it would be ideal to have one solvent for biogenic amine extraction. This study confirms that MeOH-HCl is a better solvent for complete extraction and recovery of putrescine and cadaverine in fresh and processed fish tissues.     

Visible,near‐infrared,and ultraviolet laser‐excited Raman spectroscopy of the monocytes/macrophages (U937) cells

Raman spectra of the monocytes were recorded with laser excitation at 532, 785, 830, and 244 nm. The measurements of the Raman spectra of monocytes excited with visible, near‐infrared (NIR), and ultraviolet (UV) lasers lad to the following conclusions. (1) The Raman peak pattern of the monocytes can be easily distinguished from those of HeLa and yeast cells; (2) Positions of the Raman peaks of the dried cell are in coincidence with those of the monocytes in a culture cell media. However, the relative intensities of the peaks are changed: the peak centered around 1045 cm⁻¹ is strongly intensified. (3) Raman spectra of the dead monocytes are similar to those of living cells with only one exception: the Raman peak centered around 1004 cm⁻¹ associated with breathing mode of phenylalanine is strongly intensified. The Raman spectra of monocytes excited with 244‐nm UV laser were measured on cells in a cell culture medium. A peak centered at 1485 cm⁻¹ dominates the UV Raman spectra of monocytes. The ratio I₁₅₇₄/I₁₆₁₃ for monocytes is found to be around 0.71. This number reflects the ratio between proteins and DNA content inside a cell and it is found to be twice as high as that of E. coli and 5 times as high as that of gram‐positive bacteria. Copyright © 2009 John Wiley & Sons, Ltd.     

Short-chain polyphosphates: Extraction effects on migration and size estimation of Saccharomyces cerevisiae extracts with polyacrylamide gel electrophoresis

Polyacrylamide gel electrophoresis is commonly used to characterize the chain length of polyphosphates (polyP), more generally called condensed phosphates. After separation, nonradioactive, optical polyP staining is limited to chain lengths greater than 15 ${\mathrm{PO}}_3^{-}$monomers with toluidine blue or 4′,6-diamidino-2-phenylindole. PolyP chain lengths longer than 62${\mathrm{PO}}_3^{-}$monomers were correlated to the shortest DNA ladders. In this study, synthetic linear polyPs (Sigma-Aldrich “Type 45”, estimated mean length of 45 ${\mathrm{PO}}_3^{-}$ monomers), trimetaphosphate (trimetaP: 3 ${\mathrm{PO}}_3^{-}$ ring), tripolyphosphate (tripolyP), pyrophosphate (PP_i), and inorganic orthophosphate (o-P_i) were visualized after separation by an in situ hydrolytic degradation process to o-P_i that was subsequently stained with methyl green. Statistically insignificant migration reduction of synthetic short-chain polyP after perchloric acid or phenol–chloroform extraction was confirmed with the Friedman test. ³¹P diffusion–ordered NMR spectroscopy confirmed that extraction also reduced PP_i diffusivity by <10%. Linear regression between the R_f peak migration value and the logarithm of synthetic polyP molecular weights enabled estimation of extracted polyP chain lengths from 2 to 45 ${\mathrm{PO}}_3^{-}$monomers. Linear polyP extracts from Saccharomyces cerevisiae grown in aerobic conditions were generally shorter than extracts cultured in anaerobic conditions. Extractions from both aerobic and anaerobic S. cerevisiae included tripolyP and o-P_i, but no PP_i.