Reducing chemical background noise in automated protein sequencers.

Baseline noise resulting from the by-products of the automated Edman degradation of proteins is reduced using nonstandard coupling chemicals and dual-wavelength diode array detection of phenylthiohydantoin (PTH) amino acids. Changes to the chemistry include lowering the phenylisothiocyanate (PITC) concentration and using a novel coupling base diisopropylethylamine (DIPEA). The diode array is configured to cancel the UV absorbance of reaction by-products without adversely affecting the PTH signal intensities. Combining these techniques gives a significant reduction in chemical noise on analytical chromatograms. Less sample is required for sequence analysis since low-level amino acid peaks are more easily identified.