title: Polyalanine - a practical polypeptide mass calibration standard for matrix-assisted laser desorption/ionization mass spectrometry and tandem mass spectrometry in positive and negative mode.
abstract: BACKGROUND
  Mass calibration in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is currently obtained using mixtures of individual peptides. This procedure has several drawbacks, including laborious preparation, limited shelf life and unequal calibration mass spacing. Polyalanine, a simple to prepare polydisperse molar mass standard, alleviates these problems.
  
  
  METHODS
  Polyalanine is prepared by the typical protocols for biological sample analytics.
  
  
  RESULTS
  Polyalanine is the first polymeric standard providing abundant signals in both, positive and negative polarity mode with the typical matrices DHB and HCCA.
  
  
  CONCLUSIONS
  Facile MS as well as MS/MS calibration is thus enabled for the first time in both polarity modes by employing this polydisperse standard.
authors: Competence Center Analytics, BASF SE, Ludwigshafen, Germany.
authors: Till
authors: T
authors: Gruendling
authors: Bruker Daltonik GmbH, Bremen, Germany. volker.sauerland@bruker.com.
authors: Volker
authors: V
authors: Sauerland
authors: Bruker Daltonik GmbH, Bremen, Germany.
authors: César
authors: C
authors: Barahona
authors: Competence Center Analytics, BASF SE, Ludwigshafen, Germany.
authors: Corinna
authors: C
authors: Herz
authors: Competence Center Analytics, BASF SE, Ludwigshafen, Germany.
authors: Ute
authors: U
authors: Nitsch