Star Activity Generating Extra Bands (Restriction Enzyme Digest)

Question

Accepted Answer

Extra bands appear on gel beyond expected digestion products. Enzyme cleaves at non-canonical sites with relaxed sequence specificity under suboptimal conditions. Common causes: 1) Incorrect buffer used instead of recommended NEBuffer 2) Excessive enzyme units in reaction causing promiscuous cleavage 3) Glycerol concentration >5% v/v from adding >10% enzyme volume 4) Prolonged incubation time beyond minimum required for complete digestion 5) Use of wild-type enzyme instead of High-Fidelity (HF) engineered variant Solutions: 1) Use recommended NEBuffer supplied with the restriction enzyme 2) Decrease enzyme units to minimum effective amount (3–5 U/μg DNA) 3) Ensure enzyme volume ≤10% of total reaction volume to keep glycerol <5% v/v 4) Use minimum incubation time required for complete digestion; avoid overnight incubations 5) Switch to High-Fidelity (HF) restriction enzyme engineered for reduced star activity