AVS 47th International Symposium
    Biomaterial Interfaces Monday Sessions
       Session BI+MC-MoA

Paper BI+MC-MoA5
Enhanced TOF-SIMS Imaging of a Micropatterned Protein by Stable Isotope Protein Labeling

Monday, October 2, 2000, 3:20 pm, Room 202

Session: Characterization of Biomaterial Interfaces
Presenter: A. Chilkoti, Duke University
Authors: A. Chilkoti, Duke University
A. Belu, Physical Electronics
Z.P. Yang, Imation Inc.
R. Aslami, Duke University
Correspondent: Click to Email
Patterning of biomolecules on surfaces is an increasingly important technological goal. Because the fabrication of biomolecule arrays often involves step-wise, spatially resolved derivatization of surfaces, spectroscopic imaging of these arrays is important in their fabrication and optimization. Although imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a powerful method for spatially resolved surface analysis of organic molecules on surfaces, TOF-SIMS images of micropatterned proteins on organic substrates can be difficult to acquire because of the lack of high intensity, protein specific molecular ions that are essential for imaging under static conditions. In contrast, low mass ions are of suitable intensity for imaging, but can originate from different chemical species on the surface. A potential solution to this problem is utilize stable-isotope labeled proteins, an approach that has heretofore not been explored in TOF-SIMS imaging of micropatterned proteins and peptides. In order to investigate the feasibility of stable isotope enhanced TOF-SIMS imaging of proteins, we synthesized @super 15@N-labeled streptavidin by metabolic labeling of the protein during expression from a recombinant gene. The spatial distribution of streptavidin bound to biotin micropatterns, fabricated on a polymer and on a self-assembled monolayer on gold, was imaged by TOF-SIMS. Imaging of high intensity, low m/z secondary ions (e.g., C@super 15@N@super -@ and C@super 15@NO@super -@) unique to streptavidin, enabled unambiguous spatial mapping of the micropatterned protein with a lateral resolution of a few microns. TOF-SIMS imaging of micropatterned @super 15@N-labeled streptavidin also illustrated the exquisite sensitivity of TOF-SIMS to low fractional coverage of protein (0.5 nm effective thickness) in the background regions of the protein micropattern.