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Bis-tris methane, also known as BIS-TRIS or BTM, is a buffering agent used in biochemistry. Bis-tris methane is an organic tertiary amine with labile protons having a pKa of 6.46 at 25 °C. It is an effective buffer between the pH 5.8 and 7.2. Bis-tris methane binds strongly to Cu and Pb ions as well as, weakly, to Mg, Ca, Mn, Co, Ni, Zn and Cd ...
Bis-tris propane, or 1,3-bis(tris(hydroxymethyl)methylamino)propane, also known as BTP, is a chemical substance that is used in buffer solutions. It is a white to off-white crystalline powder that is soluble in water. It has a wide buffering range, from 6 to 9.5 due to its two pK a values which are close in value.
The useful buffer range for tris (pH 7–9) coincides with the physiological pH typical of most living organisms. This, and its low cost, make tris one of the most common buffers in the biology/biochemistry laboratory. Tris is also used as a primary standard to standardize acid solutions for chemical analysis.
The following table presents pK a values at 20 °C. Values change by about 0.01 per degree of temperature. [1] [3] Good's original 1966 paper had two older buffers (marked with italics) for comparison.
The buffer should also be unreactive and not modify or react with most proteins. Different buffers may be used as cathode and anode buffers, respectively, depending on the application. Multiple pH values may be used within a single gel, for example in DISC electrophoresis. Common buffers in PAGE include Tris, Bis-Tris, or imidazole.
Buffer capacity falls to 33% of the maximum value at pH = pK a ± 1, to 10% at pH = pK a ± 1.5 and to 1% at pH = pK a ± 2. For this reason the most useful range is approximately pK a ± 1. When choosing a buffer for use at a specific pH, it should have a pK a value as close as possible to that pH. [2]
Tris-buffered saline (TBS) is a buffer used in some biochemical techniques to maintain the pH within a relatively narrow range. Tris (with HCl) has a slightly alkaline buffering capacity in the 7–9.2 range. The conjugate acid of Tris has a pK a of 8.07 at 25 °C.
A very widespread discontinuous buffer system is the tris-glycine or "Laemmli" system that stacks at a pH of 6.8 and resolves at a pH of ~8.3-9.0. A drawback of this system is that these pH values may promote disulfide bond formation between cysteine residues in the proteins because the pKa of cysteine ranges from 8-9 and because reducing agent ...