Preparation of glucose and RNase A containing resuspension buffer for the isolation of plasmid by alkaline lysis method


  • Glucose-containing resuspension buffer is used to resuspend bacterial cells during plasmid isolation by alkaline lysis method.
  • Glucose is added to make the resuspension buffer isotonic. However, isotonicity is not required for cell wall containing bacteria including E. coli DH5α. Cell wall containing bacteria can withstand a wide range of solution concentration.
  • Glucose-containing resuspension buffers are prone to microbial growth, therefore cannot be stored for a long time, and need to be kept at 4°C.
  • Resuspension buffer can be supplemented with RNase A. RNase A is a very stable enzyme and is active under the very stringent condition including high alkaline condition, the presence of detergents and chelating agents (EDTA, CDTA).
  • RNase A digest RNAs which are released from bacteria during lysis step, thus allow plasmid preparation free from RNA contamination. However, such plasmid preparation cannot be used for in-vitro transcription due to contamination of RNases.

To know more, please the read article: Preparation of resuspension buffer (solution I) for isolation of plasmid by alkaline lysis method.


  • Reagents
    • 1M Glucose solution, filter sterilized
    • 1M Tris.Cl (pH 8.0) solution, autoclaved
    • 0.5 EDTA (pH 8.0) solution, autoclaved
    • 10 mg/ml RNase A
    • Deionized / Milli-Q water
  • Equipment and disposables
    • Measuring cylinder
    • Conical flask / Beaker
    • Magnetic stirrer (optional)


  • 50 mM Glucose
  • 25 mM Tris.Cl (pH 8.0)
  • 10 mM EDTA (pH 8.0)
  • 100 μg/ml RNase A


Preparation of 100 ml of resuspension buffer (solution I)


Step 1: To prepare 100 ml of resuspension buffer, take 89.5 ml of deionized / Milli-Q water in a 100 ml measuring cylinder/beaker.
  • Do not mix concentrated stock solutions together. This can cause precipitation.
Step 2: Add 5 ml of 1 M glucose solution, 2.5 ml of Tris.Cl (pH 8.0), 2.0 ml of EDTA (pH 8.0), and 1 ml RNase A. Mix and transfer to a transparent bottle.
  • A transparent bottle can easily be examined for any microbial growth in resuspension buffer.


The solution can be stored at 4°C for 3 – 6 months.

  • Frequently check the presence of any microbial growth in resuspension buffer. Discard if you detect any microbial growth.


Preparation of plasmid DNA by alkaline lysis method

Follow the table to prepare resuspension buffer of various volume.
Reagents / Volume 10 ml 25 ml 50 ml 100 ml
1M Glucose solution 0.5 ml 1.25 ml 2.5 ml 5 ml
1M Tris.Cl (pH 8.0) 0.25 ml 0.625 ml 1.25 ml 2.5 ml
0.5 M EDTA (pH 8.0) 0.2 ml 0.5 ml 1.0 ml 2.0 ml
10 mg/ml RNase A 0.1 ml 0.25 ml 0.5 ml 1.0 ml
Water 8.95 ml 22.375 ml 44.75 ml 89.5 ml