Resolving gel (%)
5
7.5
10
12
15
Total vol
8 ml
8 ml
8 ml
8 ml
8 ml
ddH2O
4.5 ml
3.8 ml
3.2 ml
2.6 ml
1.8 ml
30 % Acry/Bis
1.33 ml
2 ml
2.67 ml
3.2 ml
4 ml
1.5 M Tris–HCl (pH 8.8)
2 ml
2 ml
2 ml
2 ml
2 ml
20 % SDS
40 μL
40 μL
40 μL
40 μL
40 μL
10 % APS
80 μL
80 μL
80 μL
80 μL
80 μL
TEMED
8 μL
8 μL
8 μL
8 μL
8 μL
Mr (kDa)
25–200
15–70
12–45
Stacking gel (%)
4
Total vol
5 ml
ddH2O
3
30 % Acry/bis
0.67 ml
0.5 M Tris pH 6.8
1.25 ml
20 % SDS
25 μL
10 % APS
50 μL
TEMED
5 μL
3.
Carefully cover the top of the gel with water-saturated isobutanol (or any other tertiary amyl alcohol), and allow complete gel polymerization (30–60 min) (see Note 16 ).
5.
Remove the isobutanol top layer and rinse the gel extensively with distilled water.
6.
Dry the inner sides of the glass plates thoroughly with Whatman 3MM paper.
7.
Add 10 μL of TEMED to the stacking gel solution; mix and pour immediately.
8.
Insert the desired clean comb (1 mm thickness), and allow the gel to polymerize completely (approximately 20 min). Check for leaks.
10.
Place the gel sandwich in the appropriate electrophoresis apparatus.
11.
Fill the tank and cassette holder reservoir with 1× SDS Running Buffer. Ensure that there are no leaks and remove bubbles.
12.
Boil samples at 95 °C in 1× final SDS Sample Buffer for 4–5 min and briefly spin down.
13.
Load samples (~20 μg/lane), including one well with prestained molecular weight markers.
14.
Run gels at 90 V (8–15 milliamps current) until the dye front has moved through the stacking gel. The current can then be increased (25–35 milliamps), and the gel run until the dye front reaches the bottom of the gel.
3.3 Western Blotting
1.
2.
Immerse membrane in blocking buffer and incubate with gentle agitation for 2 h at room temperature or overnight at 4 °C (see Note 23 ).
3.
4.
5.
Wash three times in TBS-T for 5 min each time.
6.
Dilute secondary antibody in blocking buffer (as recommended by the manufacturer), and incubate with the membrane for 1 h at room temperature with gentle agitation.
7.
Wash three times for 5 min each with an excess of TBS-T.
8.
Detect proteins with a chemiluminescence kit according to the manufacturer’s recommendations.
3.4 Membrane Stripping
If samples are limited, bound antibody can be stripped from membranes, which can then be reprobed with a different first antibody.
3.5 RNA Isolation
1.
3.
Transfer homogenate to a new tube and leave for 5 min at room temperature.
4.
Add 140 μL (1/5 v:v) chloroform and shake vigorously for 15 s or until a uniform pink suspension is obtained.
6.
Centrifuge at 12,000 × g for 15 min at 4 °C.
7.
Transfer the RNA-containing upper aqueous phase to a new tube.