Gold Nanoparticle Conjugates (IMAGE) Optica Caption Gold nanoparticle conjugates change from bright red to dull purple with the addition of target viral DNA. Credit Credit: Matthew Mancuso. Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.