2:30 PM–5:30 PM, Thursday, March 16, 2006
Baltimore Convention Center - 323
Sponsoring Unit:
DBP
Chair: J. Timothy Sage, Northeastern University
Abstract ID: BAPS.2006.MAR.W26.6
4:18 PM–4:30 PM
M. Shane Hutson
Yaowu Xiao
(Dept of Physics and Astronomy, Vanderbilt University and VIIBRE - Vanderbilt Institute for Integrative Biosystem Research and Education)
Mingsheng Guo
(Dept of Physics, Fisk University)
Single pulses of the Mark-III free electron laser have been used to ablate porcine corneas at a fluence of 240 J/cm$^{2}$ and wavelengths of 2.77 and 6.45 $\mu $m. As previously characterized, the non-volatile ablation debris shows evidence of wavelength-dependent collagen fragmentation. We have measured micro-Raman spectra of the debris and the ablation crater to determine if any wavelength-dependent conformational changes have taken place. Comparison of the spectra from two different wavelengths shows that a 938 cm$^{-1}$ Raman band -- assignable to the peptide C$_{C=O}$-C$_{\alpha }$ stretch of collagen -- loses substantial intensity during 6.45-$\mu $m ablation, but not in 2.77-$\mu $m ablation. This intensity decrease may be associated with a reduction of collagen triple-helix structure. Other spectral techniques yield mixed results; signatures for the loss of triple-helix structure are evident in UV-CD and some aspects of $^{13}$C-NMR spectra, but not in FTIR spectra. Raman measurements on thermally-treated corneal slices display similar changes at high temperatures, suggesting that higher protein temperatures are reached during ablation at 6.45 $\mu $m when compared to 2.77 $\mu $m. These observations suggest that any pre-vaporization loss of protein structural integrity includes not only collagen fragmentation, but also a loss of collagen triple-helix structure.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.MAR.W26.6