STP-2: SILVER STAINING.
Our excellent silver stain is based on
silver/formaldehyde method of Oakley et. al. (Anal.
Biochem.105: 361, 1980.) This method involves preliminary
glutaraldehyde treatment of the slab gel to fix proteins by
cross linking. The pre-treatment also adds glutaraldehyde
side chains to the proteins, increasing sensitivity since
these groups are sites for silver deposition (Dion A, and
Pomenti A, Anal. Biochem. 129: 390, 1983). We find
this method to be >10 times more sensitive than
Coomassie blue staining, depending on the protein, even
though less protein is loaded. Generally, 50 ng of purified
protein gives a highly visible spot.(see our
internal standard). However, some proteins that are
detectable with Coomassie don't stain at all with silver.
Although very sensitive, this method gives semi-quantitative
rather than quantitative results. The linear range for plots
of stain density versus ng protein varies from
protein to protein with different saturation levels. Day to
day variability in stain and background intensity occurs.
Even so, silver staining is useful for computerized
comparisons because spot values are normalized - expressed
as a percentage of all spots combined. Values from duplicate
gels are always averaged. Silver staining is not compatible
with mass spectroscopy fingerprinting but the patterns match
well to a heavily loaded, Coomassie stained duplicate gel.
Any spot present on the latter, no matter how faint, is
within range for identification mass spectrometry.
Price: STP-2 Standard
Format Add $35 per
2D gel; STP-2LF
add $45 each. Duplicate
silvers for computer comparisons are free.
SPECIAL SILVER STAINING FOR MASS SPECTROMETRY.
This special silver stain (O’Connell and Stults,
Electrophoresis 18: 349-359, 1997) omits the
glutaraldehyde step and is compatible with mass spectroscopy
fingerprinting. It often negatively stains proteins and so
is not appropriate for computerized analysis. However, the
pattern can be matched to our regular stain without
difficulty. Note however, that silver deposition interferes
with the enzymatic digestion required for mass spectrometry
for most mammalian proteins. If possible use the less
sensitive but more reliable Coomassie stain.
Price: Standard Format
gels Add $35 per 2D gel;
Large Format gels add $45/gel.
Format 2D Gel
Prices: 2D-ES-1: 1 sample, $185;
2-3 samples, $175 each;
samples, $155 each;
21-200 samples, $147 each;
More than 200 samples -
Large Format 2D Gel Prices: 2D-ES-5:
1 sample $260;
2D-ES-5A: 2-3 samples
4-12 samples $235
2D-ES-5C: 13-200 samples
$225 each, LF-Dup:
Large Format 2D duplicate gels: $105
More than 200 samples - Inquire.