Interferons (IFNs) have been shown to negatively regulate osteoclastogenesis. In a proteomic study to assess protein expression during osteoclastogenesis, we discovered that the expression level of Jak1 was significantly decreased during the early stage of osteoclast differentiation from mouse bone marrow macrophages (

Photodissociation (PD) tandem mass spectra have been obtained at 266 nm for the protonated molecules of a tryptic peptide, ASHLGLAR, and of its phenyl isothiocyanate and 4-sulfophenyl isothiocyanate derivatives, generated by matrix-assisted laser desorption/ionization. Derivatization with the aromatic chromophores greatly reduced the intensity of the laser required for efficient PD. Major fragment ions observed in the three spectra are quite similar. General features of the PD tandem mass spectra and their potential utility for analytical purposes are discussed.

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Analytical method for an accurate determination of folic acid in human serum has been established using isotope dilution ultra-high-pressure liquid chromatography/mass spectrometry (ID-UPLC/MS). Sample extract was prepared from 0.5 mL of human serum spiked with 13 C 5 -folic acid solution and then LC-MS/ MS experiment was performed on multiple reaction monitoring mode for 20 min. The method was tested for repeatability using homogeneous human serum and it showed good repeatability with relative standard deviation of 1.8%. Further evaluation was carried out through NIST SRM 1955 samples (level I, II, and III) and the measurement results were in good agreement with the certified values with good reproducibility over two periods. It was also revealed that the obtained relative expanded uncertainty was 12% which is much smaller than that of previously reported methods, indicating that this method is very reliable and accurate for determining the content of folic acid in human serum.

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