October 2011, Issue 3 - Publication Spotlight

Publication Spotlight
TERS Research Capabilities

Ever since the pioneering work of Zenobi et al. [R.M. Stöckle, Y.D. Suh, V. Deckert, R. Zenobi, Chem. Phys. Lett. 318 (2000) 131], tip-enhanced Raman spectroscopy (TERS) has been receiving increasing interest as it enables the non-destructive, label-free detection of specific chemistries (i.e., chemical bond identity) with nanoscale spatial resolution. As TERS is a developing cutting edge technique with the attendant experimental and data interpretation challenges, a significant part of the initial focus has been on suitably idealized model systems, i.e., samples of appropriate robustness, limited complexity and with relatively large Raman scattering cross sections. As a consequence, limited penetration has been seen in the target rich environment presented by the complex hierarchical spatio-chemical structure of biological systems. The recent publication of Gullekson et al. [Biophysical Journal Volume 100 April 2011 1837–1845] represents an important step in bringing to bear the power of TERS as a nanochemical ID technique on biological assemblies. The work was done using a Bruker BioScope™ AFM that enables this work as it optimizes optical access for best TERS sensitivity, provides integration software for handshaking communication with the Raman system, and provides leading AFM force control, preserving the delicate sample and TERS tip.

Gullekson et al. interrogate fibrils of collagen, the most abundant protein in the human body. Nanoscale surface chemistry is key for collagen. It is a key aspect of the necessary post translational modifications (failures of which are associated with diseases, e.g., Osteogenesis Imperfecta and Scurvy) that then enable the correct formation of collagen fibrils in the extra cellular space. And it is key to the mechanical properties enabling the function of collagen as structural protein that are affected by the assembly of fibrils and the underlying secondary protein structures. The publication of Gullekson et al. demonstrates that as a nanoscale chemical ID technique, TERS is uniquely positioned to reveal the specific chemistries exposed at the surface of collagen fibrils. In particular, it identifies individual secondary structures at the surface of collagen fibrils and proposes a specific orientation of exposed phenylalanine residues. Read the complete article here.