Using Solarbio Agarose Gel DNA Recovery Kit (D1200). This protocol describes the recovery and purification of DNA fragments separated by agarose gel electrophoresis. The kit uses a silica membrane-based spin column format with a chaotropic salt buffer system for efficient DNA binding and recovery.
Principle
The Agarose Gel DNA Recovery Kit (D1200) operates on the principle of chaotropic salt-mediated DNA binding to silica membranes. Gel slices are dissolved at 50–55°C in a high-concentration guanidine hydrochloride buffer, which denatures agarose and exposes DNA for adsorption onto the silica membrane. After washing with an ethanol-based buffer to remove residual agarose, salts, and proteins, DNA is eluted in low-ionic-strength Elution Buffer or nuclease-free water. The entire procedure is completed in 15–20 minutes without phenol-chloroform extraction or ethanol precipitation.
Equipment and Reagents Checklist
| Item |
Specification |
Purpose |
| Microcentrifuge |
Capable of 12,000–16,000×g |
Column centrifugation steps |
| Heat block or water bath |
50–55°C |
Gel slice dissolution |
| Analytical balance |
±0.01 g |
Gel slice weighing |
| Sterile scalpel or razor blade |
New, single-use per sample |
Band excision |
| Nuclease-free 1.5 mL microcentrifuge tubes |
Certified RNase/DNase-free |
Collection and elution |
| Pipettes and filtered tips |
10 μL, 200 μL, 1000 μL |
Accurate volume delivery |
| Vortex mixer |
Standard |
Mixing during dissolution |
Materials
| Item |
Volume Per Prep |
Notes |
| Excised gel slice |
≤400 mg |
Trim excess agarose to minimize slice weight |
| Gel Dissolving Buffer |
3× gel volume (approx. 400–600 μL per 0.1 g) |
Pre-warm to 55°C if crystals visible; contains guanidine HCl |
| Wash Buffer (ethanol added) |
700 μL per wash (2 washes) |
Ethanol must be added before first use; do not skip |
| Elution Buffer |
30–50 μL |
Pre-warm to 65°C for improved recovery of fragments >5 kb |
Detailed Protocol (Step by Step)
Step 1: Excise Target Band
Separate DNA fragments on a TAE or TBE agarose gel using appropriate voltage (5–8 V/cm for standard gels). Use a UV transilluminator with a wavelength of 302–365 nm to visualize the target band.
- Using a clean, sterile scalpel, excise the target band with minimal excess agarose. A narrow cut reduces the gel slice volume and improves recovery efficiency.
- Transfer the gel slice to a pre-weighed 1.5 mL microcentrifuge tube and record the weight.
- For maximum DNA integrity, minimize UV exposure time — use a longer-wavelength UV (365 nm) when possible and limit exposure to under 30 seconds.
Step 2: Dissolve Gel Slice
- Add 3 volumes of Gel Dissolving Buffer to 1 volume of gel slice (e.g., 300 μL buffer for 100 mg gel slice).
- Incubate at 50–55°C for 5–10 minutes. Vortex briefly every 2–3 minutes to facilitate dissolution.
- The gel slice is fully dissolved when no visible agarose fragments remain and the solution appears clear and homogenous. Prolonged incubation beyond complete dissolution does not harm DNA yield.
Step 3: Bind DNA to Column
- Transfer the dissolved gel solution to a Solarbio spin column placed in a 2 mL collection tube.
- Centrifuge at 12,000–16,000×g for 1 minute at room temperature.
- Discard the flow-through and reinsert the column into the same collection tube.
- Note: If the dissolved solution volume exceeds the column capacity (>800 μL), load in sequential aliquots, centrifuging between each load.
Step 4: Wash
- Add 700 μL Wash Buffer (ethanol added) to the spin column.
- Centrifuge at 12,000×g for 1 minute. Discard flow-through.
- Repeat the wash step for a total of 2 washes.
- After the second wash, centrifuge at 12,000×g for an additional 2 minutes to remove residual ethanol. Residual ethanol can interfere with downstream applications such as ligation and sequencing.
Step 5: Elute
- Transfer the spin column to a clean 1.5 mL microcentrifuge tube.
- Add 30–50 μL Elution Buffer or nuclease-free water directly onto the center of the silica membrane. Avoid touching the membrane with the pipette tip.
- Incubate at room temperature for 2 minutes. For fragments >5 kb, pre-warm the elution buffer to 65°C to improve recovery.
- Centrifuge at 12,000×g for 2 minutes.
- The eluted DNA is ready for downstream applications (ligation, restriction digestion, sequencing, labeling). Store at −20°C for long-term storage.
Quality Checks During Protocol
| Stage |
Check |
Expected Result |
| After excision |
Gel slice weight |
≤400 mg per column |
| After dissolution |
Solution clarity |
Clear, no visible agarose fragments |
| After elution |
DNA quantification (A₂₆₀) |
Typical yield: 50–500 ng (varies by band intensity and size) |
| After elution |
A₂₆₀/A₂₈₀ ratio |
1.7–1.9 (pure DNA) |
| After elution |
A₂₆₀/A₂₃₀ ratio |
≥1.8 (no chaotropic salt carryover) |
Expected Recovery
| Fragment Size |
Typical Recovery Rate |
Notes |
| 100–500 bp |
>75% |
Recovery decreases for fragments <100 bp; use DNA Purification Kit (D1300) for <100 bp |
| 500–2000 bp |
>85% |
Optimal size range; highest recovery efficiency |
| 2–8 kb |
>80% |
Pre-warm Elution Buffer to 65°C for improved yield |
| 8–10 kb |
30–50% |
For fragments >10 kb, consider electroelution or low-melting-point agarose methods |
Recovery rates are based on 100–500 ng starting DNA in a 50 mg gel slice using a 30 μL elution volume. Actual recovery depends on starting DNA amount, gel percentage, UV exposure, and elution conditions.
Troubleshooting Table
| Issue |
Cause |
Solution |
Prevention |
| Low DNA recovery |
Gel slice too large |
Use ≤400 mg per column; split large slices across multiple columns |
Excise bands tightly — minimize excess agarose |
|
Incomplete dissolution |
Incubate longer at 55°C; vortex periodically |
Use fresh Gel Dissolving Buffer; pre-warm if crystals present |
|
Elution buffer volume too small |
Elute in 30–50 μL; do not reduce below 25 μL |
Always apply buffer directly to membrane center |
|
UV damage to DNA |
Reduce UV transilluminator exposure time |
Use 365 nm UV; shield unused gel areas |
| DNA fails in downstream application |
Ethanol carryover |
Dry column with 2 min centrifugation after final wash |
Verify Wash Buffer had ethanol added |
|
Chaotropic salt carryover |
Measure A₂₆₀/A₂₃₀ ratio; re-purify if <1.5 |
Use correct Gel Dissolving Buffer volume |
| A₂₆₀/A₂₃₀ ratio <1.5 |
Contamination from Gel Dissolving Buffer |
Add an additional wash step (total 3 washes) |
Ensure dissolved solution is fully clear before loading |
| Column clogged |
Gel slice too large or gel percentage too high |
Centrifuge longer (2–3 min); reduce gel slice weight |
For >2% agarose gels, use ≤200 mg gel slice |
Optimization Notes
- For fragments <100 bp: Use the DNA Purification Kit (D1300) instead of gel extraction. The binding efficiency of very small fragments on the D1200 column is reduced.
- For high-percentage agarose gels (>2%): The high agarose concentration increases the dissolved solution volume. Reduce gel slice weight to ≤200 mg per column and extend incubation to 15 minutes at 55°C with frequent vortexing.
- For downstream ligation: If performing T4 DNA ligation after extraction, use Elution Buffer (provided) rather than nuclease-free water; the buffer contains EDTA-free TE which is compatible with T4 ligase.
- Scaling up: For preparative extractions requiring >500 ng recovered DNA, process multiple gel slices on separate columns and pool the eluates. Do not exceed 400 mg gel per column.
solarbio.store | solarbio.store