Luckau Protocols:Low TE

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Purpose

Low TE buffer is used to store DNA.

• EDTA chelates Mg²⁺ and other divalent metals ions
  • (inhibits DNAse and RNAse to suppress DNA and RNA degradation)
• Tris is a buffering agent to keep the solution at a defined pH
  • The 'Cl' or 'HCl' indicates the pH was attained using aqueous hydrochloric acid (HCl), since Tris is naturally basic

Protocol

1x Low TE = 10 mM Tris-HCl + 0.1 mM EDTA

to make 1 liter of 1x Low TE:

Volume	Reagent	[Final]
20 ml	0.5M Tris-HCl, pH 8.0	10 mM
0.2 ml	0.5M EDTA, pH 8.0	0.1 mM
979.8 ml	ddH2O

to make 500 mL of 1x Low TE:

Volume	Reagent	[Final]
10 ml	0.5M Tris-HCl, pH 8.0	10 mM
0.1 ml	0.5M EDTA, pH 8.0	0.1 mM
489.9 ml	ddH2O

• Sterilize by autoclaving for 20 min at 15 psi (1.05 kg/cm2) on liquid cycle
• Store at 4°C or room temperature

FYI

• Note, downstream reactions (PCR) typically require Mg²⁺, potentially making the presence of EDTA in the reaction problematic. So, when using DNA or RNA that was suspended in TE, keep track of the amount of EDTA in the mix to make sure there is still enough Mg²⁺ for subsequent reactions to proceed successfully. Each EDTA molecule chelates one Mg²⁺ ion.
• TE versus Low TE:

-	Tris-Cl	EDTA
TE	10 mM	1 mM
Low TE	10 mM	0.1 mM

• Some people use TE buffers with different pH's for different applications
  • DNA is stored at pH 8 to reduce depurination, which is acid catalyzed
  • RNA is stored at pH 7.5 to reduce degradation of RNA, which is base-catalyzed
  • Most downstream reactions will not be influenced by the slightly different pH storage conditions.

Sources

• OpenWetWare's Materials TE page
• Cold Spring Harb Protoc; 2006; doi:10.1101/pdb.rec8018
• Cytographica