subject on an array with unspecific bovine igg did not evoke any significant signal as presented in fig4 a 4 b and 4 c however incubation of csf of this same subject on an array with monoclonal antibody specific for a u03b2 peptide 6e10 resulted in clear mass spectrometry signals as presented in fig4 d 4 e and 4 f similarly incubation of csf from a patient with ad with the array pre coated with 6e10 evoked mass spectrometry signals as presented in fig4 g 4 h and 4 i four novel previously not reported mass spectrometry peaks were observed in this study corresponding to peptides with molecular masses of 4525 1 da 4846 8da 7755 8 da and 3882 2 da however it cannot be excluded that the signal at 3882 2 da represents a doubly charged peptide with molecular mass of 7755 8 da and therefore currently both these signals must be treated as resulting from one a u03b2 peptide fig5 presents seldi tof ms signal to noise ratios of a u03b2 peptide with molecular mass 4525 1 da a u03b2 4525 1 which was significantly decreased fig5 a and signal to noise ratio of a u03b2 peptide with molecular mass 4846 8 da a u03b2 4846 8 which was significantly increased fig5 b in ad compared to controls signal to noise ratios of two peptides commonly used as ad biomarkers namely a u03b21 42 fig5 c and a u03b21 40 fig5 d were decreased and unaltered respectively in patients with ad the signal to noise ratio of a u03b2 peptide with molecular mass 7755 8 a u03b2 7755.