25876-54-4Relevant articles and documents
Analysis of derivatised steroids by matrix-assisted laser desorption/ionisation and post-source decay mass spectrometry
Khan, Muhammad Atif,Wang, Yuqin,Heidelberger, Sibylle,Alvelius, Gunvor,Liu, Suya,Sjoevall, Jan,Griffiths, William J.
, p. 42 - 53 (2006)
Neutral steroids are difficult to analyse using desorption ionisation methods coupled with mass spectrometry (MS). However, steroids with an unhindered ketone group can readily be derivatised with the Girard P (GP) reagent to give GP hydrazones. Steroid GP hydrazones contain a quaternary nitrogen atom and are readily desorbed in the matrix-assisted laser desorption/ionisation (MALDI) process, giving an improvement in sensitivity of two orders of magnitude. Steroids without a ketone group, but with a 3β-hydroxy-Δ5 function, can be readily converted to 3-oxo-Δ4 steroids and subsequently derivatised to GP hydrazones for MALDI analysis. In addition to giving strong [M]+ ions upon MALDI, steroid GP hydrazones give informative post-source decay (PSD) spectra. By using the accurate mass of the precursor-ion measured by MALDI-MS, in combination with the structural information encoded in its PSD spectrum, steroid structures can readily be determined.
Identification of unusual oxysterols and bile acids with 7-oxo or 3,5,6-trihydroxy functions in human plasma by charge-tagging mass spectrometry with multistage fragmentation
Griffiths, William J.,Gilmore, Ian,Yutuc, Eylan,Abdel-Khalik, Jonas,Crick, Peter J.,Hearn, Thomas,Dickson, Alison,Bigger, Brian W.,Wu, Teresa Hoi-Yee,Goenka, Anu,Ghosh, Arunabha,Jones, Simon A.,Wang, Yuqin
, p. 1058 - 1070 (2018)
7-Oxocholesterol (7-OC), 5,6-epoxycholesterol (5,6-EC), and its hydrolysis product cholestane-3,5,6-triol (3,5,6-triol) are normally minor oxysterols in human samples; however, in disease, their levels may be greatly elevated. This is the case in plasma from patients suffering from some lysosomal storage disorders, e.g., Niemann-Pick disease type C, or the inborn errors of sterol metabolism, e.g., Smith-Lemli-Opitz syndrome and cerebrotendinous xanthomatosis. A complication in the analysis of 7-OC and 5,6-EC is that they can also be formed ex vivo from cholesterol during sample handling in air, causing confusion with molecules formed in vivo. When formed endogenously, 7-OC, 5,6-EC, and 3,5,6-triol can be converted to bile acids. Here, we describe methodology based on chemical derivatization and LC/MS with multistage fragmentation (MSn) to identify the necessary intermediates in the conversion of 7-OC to 3-hydroxy-7-oxochol-5-enoic acid and 5,6-EC and 3,5,6-triol to 3,5,6-trihydroxycholanoic acid. Identification of intermediate metabolites is facilitated by their unusual MSn fragmentation patterns. Semiquantitative measurements are possible, but absolute values await the synthesis of isotope-labeled standards.—Griffiths, W. J., I. Gilmore, E. Yutuc, J. Abdel-Khalik, P. J. Crick, T. Hearn, A. Dickson, B. W. Bigger, T. H-Y. Wu, A. Goenka, A. Ghosh, S. A. Jones, and Y. Wang. Identification of unusual oxysterols and bile acids with 7-oxo or 3,5,6-trihydroxy functions in human plasma by charge-tagging mass spectrometry with multistage fragmentation.
CHOLESTEROL CONVERSION TO Δ4-CHOLESTENONE BY CHOLESTEROL OXIDASE IN POLYPHASIC SYSTEMS : EXTENSION TO THE SELECTIVE OXIDATION OF 7Β-HYDROXYCHOLESTEROL
Lee, Kang Min,Biellmann, Jean-Francois
, p. 1135 - 1140 (2007/10/02)
The preparative use of cholesterol oxidase has been extended to polyphasic systems.The enzyme is active in microemulsions with the organic phase composed of mixtures of cyclohexane and chloroform.The kinetic data for oxidation of 7α- and 7β-hydroxycholesterol in microemulsion with the enzyme from Streptomyces are similar to those of cholesterol.The cholesterol oxidase is active in the two phase system aqueous buffer - butyl acetate and preparative enzymic conversion of 7β-hydroxycholesterol to Δ4-7β-hydroxycholestenone was performed in this medium.The enzymic conversion of cholesterol to Δ4-cholestenone was also performed in two liquis-solid systems, in buffer with cholesterol adsorbed on silica gel and in organic medium with cholesterol oxidase and catalase entrapped in Chromosorb.
