title: The biochemical metabolite screen in the Munich ENU Mouse Mutagenesis Project: determination of amino acids and acylcarnitines by tandem mass spectrometry.
abstract: BACKGROUND
  Gene mutations often result in altered protein expression and, in turn, lead to changes in metabolite levels in one or more distinct biochemical pathways. Traditional analytical methods for metabolite determination are usually time consuming, expensive, and, thus, not suitable for high throughput analysis. However, recent developments in electrospray-tandem-mass-spectrometry allow comprehensive metabolite scanning from very small amounts of blood with high speed, cost effectiveness, and accuracy.
  
  
  METHODS
  A blood spot from a filter paper equivalent to 3 microl of blood was punched out and transferred to a 96-well microtiter plate. After addition of a set of 14 stable isotope-labeled internal standards, amino acids and acylcarnitines were extracted with methanol. The dried residue was derivatized with butanolic hydrochloric acid and subjected to MSMS analysis.
  
  
  RESULTS
  Acyl-carnitines were all determined by a precursor ion scan of 85 Da. Neutral loss scanning of 102 Da was suitable for the quantitation of threonine, serine, proline, histidine, alanine, aspartic acid, glutamic acid, methionine, tyrosine, phenylalanine, isoleucine/leucine and valine. Glycine was detected by a loss of a 56-Da fragment, whereas a 119-Da loss was suitable for the measurement of citrulline, ornithine, arginine, and lysine. Specific problems encountered: owing to their identical molecular weight, isoleucine and leucine could not be quantitated separately, and, owing to their instability, glutamine and asparagine were found to be decarboxylated to their respective acids. Determination was linear over the concentration range tested (20 to 1000 micromol/L), and intraassay and interassay coefficients of variation were in the range of 10-15%.
  
  
  CONCLUSIONS
  ESI-MSMS proved to be a highly sensitive, linear, and sufficiently precise method for the quantitative determination of amino acids and acylcarnitines in mouse blood, allowing large-scale screening applications when speed and cost effectiveness are mandatory.
authors.affiliation: Kinderklinik und Kinderpoliklinik im Dr. von Haunerschen Kinderspital, Ludwig-Maximilians-University, Lindwurmstrasse 4, D-80337 Munich, Germany. Rolinsky@kk-i.med.uni-muenchen.de
authors.forename: B
authors.initials: B
authors.lastname: Rolinski
authors.forename: R
authors.initials: R
authors.lastname: Arnecke
authors.forename: T
authors.initials: T
authors.lastname: Dame
authors.forename: J
authors.initials: J
authors.lastname: Kreischer
authors.forename: B
authors.initials: B
authors.lastname: Olgemöller
authors.forename: E
authors.initials: E
authors.lastname: Wolf
authors.forename: R
authors.initials: R
authors.lastname: Balling
authors.forename: M
authors.initials: M
authors.lastname: Hrabé de Angelis
authors.forename: A A
authors.initials: AA
authors.lastname: Roscher
mesh_terms: D000596:Amino Acids / Q000097:blood*; D000818:Animals; D015415:Biomarkers / Q000097:blood; D002331:Carnitine / Q000031:analogs & derivatives* / Q000097:blood; D005038:Ethylnitrosourea; D013058:Mass Spectrometry; D051379:Mice / Q000235:genetics*; D016296:Mutagenesis; D009153:Mutagens
chemical_list: D000596:Amino Acids; D015415:Biomarkers; D009153:Mutagens; C116917:acylcarnitine; D005038:Ethylnitrosourea; D002331:Carnitine