Bio-Rad Matrix-Prepared Surfaces - Manual (Page 4)

3 © 2007 Bio-Rad Laboratories, Inc.
Technical Considerations
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If your sample has salt or urea contamination, proceed directly
to Protocol 2. Otherwise, perform Protocol 1 first. If there is
insufficient signal after reading the arrays, a cleanup step is
recommended: Add 5 µl of 0.1% trifluoroacetic acid (TFA) to
the spot; do not agitate; remove the 0.1% TFA droplet after
30 sec; and add 5 µl 25% acetonitrile (ACN) and 0.1% TFA to
the spot. Allow to dry, and read the arrays again
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With ProteinChip SEND ID arrays, it is essential that you mix
your sample with a solution of 50% ACN and 0.2% TFA at a
1:1 (v/v) ratio before adding to the spot
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Ideally, the final concentration of ACN after dilution is 25%;
a final concentration of greater than 40% ACN is not compatible
with the ProteinChip SEND ID array
Factors That Can Result in Weak Signal
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We do not recommend washing on-spot (by pipetting the
sample up and down) because this can reduce signal
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Weak signal can be improved by adding ACN to your sample
as described in Protocol 1
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A predominant peak at mass-to-charge ratio (m/z) 211
indicates sodium contamination, and you should perform
sample cleanup as described in Protocol 2, step 5. This
contamination can suppress sample peaks and result in
weak signal