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Tris buffered saline
Tris-buffered saline (abbreviated 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. Tris has a pKa of 8.06 at 25 °C. The pKa declines approximately 0.03 units per degree Celsius rise in temperature. This can lead to relatively dramatic pH shifts when there are shifts in solution temperature.
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Applications
TBS has many uses because it is isotonic and non-toxic. It can be used to dilute substances. Additives can be used to add function. TBS is often used in immuno-blotting for both membrane washing and antibody dilution.
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The following is a sample recipe for TBS:
Adjust pH with HCl to pH 7.6.
Note that concentration of tris and NaCl as well as the pH can vary, and the resulting solution would still be referred to as "TBS". Tris concentration (giving buffering capacity) can vary from 10 to 100 mM. As TBS is used to emulate physiological conditions (as in animal or human body), the pH value is slightly alkaline, ranging from 7.4 to 8.0. NaCl gives the isotonic (mostly used 150 mM NaCl corresponds to physiological conditions: 0.9% NaCl) or hypertonic (500mM NaCl) salt concentration. Additionally Tween 20 can also be added in order to use it as wash solution in immunoassays or to block. (TTBS or TBST)