Modified primers

A limiting aspect of microarray experiments is the efficient production of labelled cDNA probes from small amounts of starting material (typically over 20 μg of total RNA is required) . In the July issue of Nature Biotechnology, Charlie Xiang and colleagues describe a technique for efficient and inexpensive probe production using random hexamer oligonucleotide primers that have been modified with free amino groups at their 5' ends (Nat Biotechnol 2002, 20:738-742).

This method allows for the generation of fluorescent probes for microarray hybridization using as little as 1 μg of total RNA. They used random primers with 5' amino C6dT (thymidine modified at the 5' position with an 8-9 carbon chain ending in a primary amine) and incorporated aminoallyl-dUTP during cDNA synthesis. The fluorescent dyes (Cy3 and Cy5) were then chemically added to the free amino groups.

Xiang et al. used microarray experiments to demonstrate that...