A reproducible pH gradient is crucial for successful IEF. Commercially available IPG strips are easy to use and provide reproducible and stable gradients during extended IEF runs. The strip length required is dictated largely by the size of the second-dimension gels to be used, with longer strips and larger gels providing larger sample capacity and higher resolution.
Bio-Rad's ReadyStrip IPG strips are produced using high-purity IPG monomers and are thoroughly tested for quality, performance, and reproducibility.
- Available in 7, 11, 17, 18, and 24 cm lengths to fit Bio-Rad's vertical SDS-PAGE systems
- Standard, broad-range pH gradients (pH 3–10 linear and nonlinear strips) display the most proteins in a single gel
- Narrow-range gradients (pH 3–6, 4–7, 5–8, and 7–10) improve resolution with more centimeters of gel per pH unit compared to a pH 3–10 range
- Micro-range gradients (pH 3.0–5.1, 4.7–5.9, 5.5–6.7, and 6.3–8.3) enable finer resolution
Relative focusing power expresses the enhanced resolution expected in the first dimension when using IPG strips of different lengths or pH ranges. The 7 cm pH 3–10 IPG strip is assigned a baseline focusing power of 1.0 to calculate the relative focusing powers of the other strips, as shown in the table above. The calculations are performed as follows:
- When two strips have the same pH range but differ in length — the ratio of the strip lengths gives the relative focusing power of the longer strip. Thus, compared to a 7 cm pH 3–10 strip, the 11 cm pH 3–10 strip has a relative focusing power of 11 cm/7 cm = 1.6
- When two strips have the same length but differ in pH range — the ratio of the pH ranges (in number of pH units) gives the relative focusing power of the strip with the smaller range. Thus, compared to a 7 cm pH 3–10 strip, the 7 cm pH 5–8 strip has a relative focusing power of (7 pH units)/(3 pH units) = 2.3
