Removal of Melanin from DNA/RNA

Glen Gaughan gaughan at bms.com
Mon Oct 30 08:08:15 EST 1995


In article <46rtqi$b8i at pulp.ucs.ualberta.ca>, msingh at gpu4.srv.ualberta.ca
(Madhu Singh) wrote:

> Hi experts:
> I was wondering if anyone has got rid of the problem of melanin 
> coprecipitation in DNA/RNA samples.  When isolated from dark skin, or 
> melanocytes, the DNA and RNA samples are black due to melanin sticking to 
> them.  Melanin has very wide range of absorption property for UV which 
> makes it almost impossible to estimate the quantity of nucleic acids.  
> Melanin is generally negatively charged pigment with highly recalcitrant 
> features.  Although, polymer of phenolics, it does not separate in the 
> phenol:chloroform extraction and remains in the aqueous phase.  Some high 
> molecular weight material can be removed by centrifugation, but a lot 
> remains.


Depends somewhat on the tissue source but for malanophores see JBC 268,
19126 (93). In short you need to spin out the melanosomes after lysis in
GITC before extraction (ca. 14k X g / 2 min). This worked well for me.
Note that it may take a couple spins and careful separation of phases for
best results.

Glen Gaughan
Bristol-Myers Squibb



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