Reason for degradation or low concentration of DNA in TE buffer under -20 degree for long period?
It should not be happening. Couple of potential reasons come to mind. You can test most of them experimentally:
- Auto-defrost freezer setting causes mechanical damage by freeze-thaw cycling
- Freezer light stays on causing photodamage
- Contamination of the DNA with enzyme (A260 / 280 ratio?)
- Contamination of the water with metals or other compounds (reagents not pure)
- Acidification of the buffer by CO2 from air exposure over time
the storage buffer contents are important in fidelity of the storage time as mentioned by Qiagen. Also, it is better it keep such stuff in -80 C if possible, that would be better.
Check your TE components. I had a similar problem and tracked it to contaminated EDTA.
From my experience, it will not. For years we can keep the DNA in TE without any damage.
In general, there are four broad strategies for long-term DNA preservation:
Room temperature on a ‘dry’ solid matrix
–20°C
–80°C
–196°C (storage in liquid nitrogen)
Two of these methods, dried and stored at room temperature and storage at –196°C, share a common mechanism where the DNA is maintained in a glassy (or vitreous) state. In the glassy state, molecules lose the ability to diffuse such that the movement of a proton is estimated to be approximately one atomic diameter in 200 years, thereby preventing chemical and nuclease degradation. If moisture is added to the ‘dry state’ or the temperature is raised above the glass transition temperature of water, movement and reactivity of protons is re-established and damage to the DNA can occur.
Please refer to the attached ref.
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