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Proceedings Paper

Protein structural failure in mid-IR laser ablation of cornea
Author(s): M. Shane Hutson; Yaowu Xiao; Mingsheng Guo
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Paper Abstract

Researchers have previously observed that tissue ablation with a free electron laser tuned to wavelengths between 6-7 μm is accompanied by remarkably little collateral damage. Attempts to explain these observations have invoked a wavelength-dependent loss of protein structural integrity; however, the molecular nature of this structural failure has been heretofore ill-defined. In this report, we evaluate several candidates for the relevant transition by analyzing the non-volatile debris ejected during ablation. Porcine corneas were ablated with a free electron laser tuned to either 2.77 or 6.45 μm - wavelengths that are equally well absorbed by hydrated corneas, but that respectively target water or protein as the primary chromophore. The ejected debris was characterized via gel electrophoresis, as well as FTIR, micro-Raman and 13C-NMR spectroscopy. We find that high-fluence (240 J/cm2) ablation at 6.45 μm, but not at 2.77 μm, leads to protein fragmentation. This fragmentation is accompanied by the accumulation of nitrile and alkyne species. Although these initial experiments did not detect significant protein unfolding, the loss of collagen triple-helix structure was evident using UV and vibrational circular dichroism. The candidate transition most consistent with all these observations is scission of the collagen protein backbone at N-alkylamide bonds. Identifying this transition is a key step towards understanding the observed wavelength-dependence of collateral damage.

Paper Details

Date Published: 7 June 2006
PDF: 10 pages
Proc. SPIE 6261, High-Power Laser Ablation VI, 62612N (7 June 2006); doi: 10.1117/12.669004
Show Author Affiliations
M. Shane Hutson, Vanderbilt Univ. (United States)
Yaowu Xiao, Vanderbilt Univ. (United States)
Mingsheng Guo, Fisk Univ. (United States)


Published in SPIE Proceedings Vol. 6261:
High-Power Laser Ablation VI
Claude R. Phipps, Editor(s)

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