Fiber washout

Although raw material costs are higher (some estimates are 18 to 20%), and some physical properties are reduced, woven fabric shortens layup times, avoids tape spread-out problems at abrupt contour changes, remains in place during cure (no distortion or fiber washout), and is frequently easier to drill or machine. 

In preparation for sequencing, the peptide (normally 100 pmol, but the optimal quantity depends on the sequencer being utilized) dissolved in acetonitrile or methanol is spotted onto a membrane [for example, a coated glass-fiber membrane (Biobrene ABI) or a polyvinylidene difluoride (PVDF) membrane such as Immobilon (Millipore) or Problott (ABI)] the sample is air dried and then the membrane is loaded directly into the sequence cartridge. If severe problems with washout are experienced, techniques for covalent coupling of a peptide to the membrane can be employed, provided that specific residues (e.g., an amino acid with a free amine on its side chain) are present in the sequence. However, a drawback of this approach is that amino acids that are covalently coupled will not produce a signal in the subsequent HPLC analysis. 

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