Using an overnight transfer protocol could also yield better results. To estimate whether there is an overtransfer, you can use two membranes: if there is some protein in the second membrane, decrease the time of transfer. For TGX gels transfer at 100V for 30 minutes. In general, we recommend 100V, 60 minute transfers unless you are using TGX™ gels. Irrespective of what is stated in the protocol, some optimization of transfer time may be needed for your protein. For CAPS/Tris discontinuous buffer system in semi-dry transfer refer to Bio-Rad bulletin 2134. Note: CAPS 20% methanol buffer is recommended for wet transfer. This buffer can be useful for proteins with >50 kD MW. Mix 2.21 g CAPS in 600 ml of ddH 2O, adjust the pH to 11.0 with NaOH. This is especially good for semi-dry applications.ġ0 mM CAPS (3-(cyclohexylamino)-1-propane sulfonic acid), 20% v/v methanol, pH 11. Dissolve 0.84 g NaHCO 3 and 0.318 g Na 2 CO 3 (anhydrous) in ddH 2O (add 200 ml of methanol) adjust volume to 1 L with ddH 2O. Dunn carbonate transfer buffer for SDS-proteins using nitrocellulose (with methanol) or Zeta-Probe membrane (without methanol):ġ0 mM NaCHO 3, 3 mM Na 2 CO 3 (20% methanol), pH 9.9.Do not use it with Trans-Blot ® Turbo™ cassettes. Note: This buffer is only for wet transfer and the Trans-Blot ® SD semi-dry transfer cell. Add 200 ml of methanol adjust volume to 1 L with ddH 2O. Dissolve 5.82 g Tris and 2.93 g glycine in distilled, deionized water (ddH 2O). Bjerrum and Schafer-Nielsen transfer buffer for SDS proteins using nitrocellulose (with methanol) or Zeta-Probe ® membrane (without methanol) (Bjerrum and Schafer-Nielsen 1986):Ĥ8 mM Tris, 39 mM glycine (20% methanol), pH 9.2.If your protein has a high molecular weight (MW) or high pI, you can try the following buffer options: Using a smaller pore size nitrocellulose membrane (0.2 µm), can be effective in eliminating this loss. Large proteins (>100,000 Da) denatured by SDS may transfer poorly if alcohol is added to the transfer buffer. SDS also increases the conductivity of the buffer and the heat generated during transfer. This might result in denaturation of some proteins. Therefore, if SDS is added to the transfer buffer, it is important to also include methanol (10–20%). Adding SDS (up to 0.1%) to the transfer buffer increases the transfer efficiency of proteins, but reduces the amount of binding to the membrane. Eliminating alcohol from SDS-protein transfers results in considerably diminished binding. Alcohol increases binding of SDS-bound proteins to nitrocellulose, but decreases pore sizes in the gel. Varying the amounts of SDS and AlcoholĬoncentrations of methanol and SDS can be adjusted to improve transfer efficiency. You can start with Towbin transfer buffer (25 mM Tris, 192 mM glycine, pH 8.3) and alcohol (20% methanol or 10% ethanol or 15% isopropyl alcohol) as the basic buffer for any of the proteins and recalibrate based on how it performs. Whether you are using an existing lab protocol or one from a publication, you may need to recalibrate buffer formulations based on your protein of interest.
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