Gold particles make the invisible visible

To understand how enzymes work, scientists need to make molecules involved in enzymatic activities visible through techniques such as fluorescence microscopy.

However, many times molecules cannot be detected because they don’t emit light. Gold can be the solution to such problem.

A researcher with the Leiden Institute of Physics decided to tackle the issue by attaching single molecules to gold nanorods. The nanorods act as very small antennas by emitting light, enhancing the fluorescence of the attached molecule. This allowed Biswajit Pradhan to study single proteins and other complexes that are otherwise undetectable by fluorescence.

In detail, the scientist permanently attached a short single-stranded DNA to the tip of a gold nanorod. Then he allowed complementary DNA strands to diffuse around it. Each complementary strand contained a single molecule that he wanted to investigate. "Because of the weak binding of the short DNA strands, the binding time is short. Each complementary strand binds temporarily and is then replaced by a new complementary strand. This allowed us to study single molecules on the same nano-antenna," Pradhan said in a media statement.

This technique -he added- can be applied to many research fields, such as improving solar-cell efficiency and phototherapy of cancer.