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BamHI > FAQ |  | BamHI FAQ
See the Restriction Endonucleases FAQ also.
Q1: Has the buffer supplied with this enzyme changed from a unique buffer to a standard NEBuffer?
Q2: What is the most convenient method of using BamHI with another enzyme that requires a low salt buffer?
Q3: What is Star Activity and how can it be avoided?
Q4: How can this enzyme be inactivated?
Q1: Has the buffer supplied with this enzyme changed from a unique buffer to a standard NEBuffer?
A1: In an effort to simplify our buffer system, BamHI, Sau3AI and BceAI are now being supplied with one of our NEBuffers. All of these enzymes have been carefully purified and characterized so there is no loss of activity in its newly supplied buffer. If you are still using a unique buffer that was previously supplied with some of our enzymes, please refer to our website for double digest information with unique buffers.
Q2: What is the most convenient method of using BamHI with another enzyme that requires a low salt buffer?
A2: Perform the first digest in the low salt buffer. Then supplement with 100–150mM NaCl using a concentrated NaCl stock solution (i.e. 5 M NaCI). Alternatively, perform the low salt digest in a 20 µl reaction volume and then increase the reaction volume to 50 µl, by adding 5 µl 10X NEBuffer 3, BamHI, BSA and water.
Q3: What is Star Activity and how can it be avoided?
A3: It has been demonstrated that under extreme non-standard conditions, restriction endonucleases are capable of cleaving sequences which are similar but not identical to their defined recognition sequence. This altered or relaxed specificity has been termed "star" activity. It has been suggested that star activity may be a general property of restriction endonucleases and that any restriction endonuclease can be made to cleave noncanonical sites under certain extreme conditions.
The manner in which an enzyme's specificity is altered depends on the enzyme and on the conditions employed to induce the star activity. The most common types of altered activity are single base substitutions, truncation of the outer bases in the recognition sequence, and single-strand nicking.
Star activity is completely controllable in the vast majority of cases and is generally not a concern when performing restriction endonuclease digests. New England Biolabs' enzymes will not exhibit star activity when used under recommended conditions in their supplied NEBuffers. Listed below are reaction conditions known to induce or inhibit star activity.
Conditions that Contribute to Star Activity
1. High glycerol concentration [> 5% v/v]
2. High units to µg of DNA ratio [Varies with each enzyme, usually >100 units/µg]
3. Low ionic strength [< 25 mM]
4. High pH [> pH 8.0]
5. Presence of organic solvents [DMSO, ethanol, ethylene glycol, dimethylacetamide, dimethylformamide, sulphalane]
6. Substitution of Mg++ with other divalent cations [Mn++, Cu++, Co++, Zn++]
Inhibiting Star Activity
If you are concerned about star activity, we recommend the following guidelines.
1. Use as few units as possible to get a complete digestion. This avoids overdigestion and reduces the final glycerol concentration in the reaction.
2. Make sure the reaction is free of any organic solvents such as alcohols which might be present in the DNA preparation.
3. Raise the ionic strength of the reaction buffer to 100?150 mM (provided the enzyme is not inhibited by high salt).
4. Lower the pH of the reaction buffer to pH 7.0.
5. Use Mg++ as the divalent cation.
Q4: How can this enzyme be inactivated?
A4: To inactivate enzymes that cannot be heat killed, we recommend a phenol extraction followed by ethanol precipitation or a commercial spin column designed to purify DNA.
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