Bio-Rad Matrix-Prepared Surfaces - Manual (Page 5)

4 © 2007 Bio-Rad Laboratories, Inc.
Chemical Noise
Because ProteinChip alpha-cyano-4-hydroxycinnamic acid
(CHCA) matrix is integral to the array surface, chemical noise
from matrix peaks are significantly reduced with the ProteinChip
SEND ID array when compared to standard MALDI or SELDI
analysis. Some chemical noise will be seen; the amount seen is
affected by two main factors (Figure 3):
n
Increased laser intensity will increase chemical noise
n
The higher the concentration of sample, the lower the intensity
of chemical noise peaks
Produced by Ciphergen ProteinChipÆ Software
A
B
0 250 500 750
20
15
10
5
0
75
50
25
0
171.0+H
189.0+H
378.0+H
Intensity
m/z
Intensity
Fig. 3. Comparison of chemical noise peaks due to variation in sample
concentration and laser intensity. A, minimal chemical noise is seen when
concentration of sample is high and laser intensity is low (1 pmol of sample applied
directly to the array); B, increased chemical noise is seen below 600 Da when sample
concentration is decreased to 50 fmol and increased laser intensity is necessary.
m/z, mass-to-charge ratio.