Chemists clarify a chiral conundrum

It's always good when your intuition turns out to be right, but scientists at Rice University studying proteins and particles were more "right" than they expected.
Rice chemists Christy Landes and Stephan Link and lead author and Smalley-Curl Postdoctoral Fellow Qingfeng Zhang reported this week in Science that bovine serum albumin (BSA), a standard-issue protein in nano-bio lab experimentation, is prone to pushing gold nanorods into right-handed chiral assemblies -- while producing chiral plasmonic signals to match.
The result was a surprise to the researchers who set out to untangle the mysterious interactions between three phenomena: the aggregation of metallic nanoparticles, their plasmonic properties and protein chirality. Light triggers ensembles of particles and proteins to emit data-enriched light in response, but until now researchers haven't known what parts of the ensemble were responsible for the signals and whether they could be refined.
The work hints it may become possible to sense the handedness, or chirality, of single proteins, a potential boon for pharmaceutical companies that require drug purity. A protein with the correct chirality can save a life, while the same molecule of the opposite chirality can be highly toxic.
The Rice experiments revealed multilevel chirality in the way BSA proteins prompted the 100-nanometer-long particles to align and in how the particles' plasmons responded to light in the much smaller proteins' presence. (Plasmons are resonating electron waves that ripple along the surface of a metal particle when triggered by light.)
The response was measured as circular dichroism (CD), the rotation of a polarized light wave's electric field, which interacts with material in either a clockwise (right) or counterclockwise (left) direction.