Very hot! But too quick to melt…

No my blog has not been hacked.

Shabir Hassan et al report the “Response of Villin Headpiece-Capped Gold Nanoparticles to Ultrafast Laser Heating” in J Phys Chem B. Nice collaborative work with the group of Peter Hamm at the University of Zurich.


The integrity of a small model protein, the 36-residue villin headpiece HP36, attached to gold nanoparticles (AuNP) is examined, and its response to laser excitation of the AuNPs is investigated. To that end, it is first verified by stationary IR and CD spectroscopy, together with denaturation experiments, that the folded structure of the protein is fully preserved when attached to the AuNP surface. It is then shown by time-resolved IR spectroscopy that the protein does not unfold, even upon the highest pump fluences that lead to local temperature jumps on the order of 1000 K of the phonon system of the AuNPs, since that temperature jump persists for too short a time of a few nanoseconds only to be destructive. Judged from a blue shift of the amide I band, indicating destabilized or a few broken hydrogen bonds, the protein either swells, becomes more unstructured from the termini, or changes its degree of solvation. In any case, it recovers immediately after the excess energy dissipates into the bulk solvent. The process is entirely reversible for millions of laser shots without any indication of aggregation of the protein or the AuNPs and with only a minor fraction of broken protein–AuNP thiol bonds. The work provides important cornerstones in designing laser pulse parameters for maximal heating with protein-capped AuNPs without destroying the capping layer.


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