Sep 1 2010
Certain chemical pollutants can imitate hormones produced naturally in the body; bisphenol-A, for example, can mimic estrogen. Because estrogen can pass directly through cell walls to influence the transfer of genetic information, measuring changes in hormone activity with DNA-level accuracy is critically important. Xiaodi Su from the Institute of Material Research and Engineering, Edison Liu from the Genome Institute of Singapore and co-workers from these A*STAR institutes in Singapore have now developed an assay that instantly measures binding interactions between estrogen receptor proteins and specific DNA sequences1. This approach can detect single mutations in DNA strands as distinct color changes thanks to the optical capabilities of gold nanoparticles.
When hormone receptor proteins capture estrogen molecules that have entered the cell, the receptors move to the nucleus and regulate gene expression by binding to DNA sequences called estrogen response elements. Small changes in the nucleotide composition of these DNA strands can greatly affect transcription rates, but detecting sequence-dependent interactions currently requires time-consuming labeling and separation techniques, or complex instrumentation.
The method developed by Su and her co-workers uses the well-known aggregation behavior of gold nanoparticles to allow rapid identification of estrogen protein–DNA interactions by the naked eye. Gold nanoparticles have a rich supply of electrons oscillating at their surfaces, and when clustered together they appear differently colored than when dispersed in solution. Mixing biomolecules into gold nanoparticle solutions can strongly influence aggregation, factors the researchers exploited to create their assay.
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