Wavelength-dependent conformational changes in collagen after mid-infrared laser ablation of cornea.
We ablated porcine corneas with a free electron laser tuned to either 2.77 or 6.45 microm, two matched wavelengths that predominantly target water and protein, respectively. The ejected nonvolatile debris and the crater left behind were examined by circular dichroism, Raman spectroscopy, and scanning electron microscopy to characterize the postablation conformation of collagen proteins. We found near-complete unfolding of collagen secondary and tertiary structure at either ablating wavelength. On the other hand, we found excess fibril swelling and evidence for excess cis-hydroxyproline in the 6.45-microm debris. These results support the hypothesis that the favorable ablative properties of protein-targeting wavelengths rest on selective heating of tissue proteins.
Xiao
Yaowu
Y
Department of Physics and Astronomy, Vanderbilt Institute for Integrative Biosystem Research and Education, Vanderbilt University, Nashville, Tennessee 37235, USA.
Guo
Mingsheng
M
Zhang
Peng
P
Shanmugam
Ganesh
G
Polavarapu
Prasad L
PL
Hutson
M Shane
MS
D000818:Animals; D003094:Collagen / Q000737:chemistry* / Q000528:radiation effects* / Q000648:ultrastructure; D003315:Cornea / Q000737:chemistry* / Q000528:radiation effects*; D006358:Hot Temperature; D066298:In Vitro Techniques; D007259:Infrared Rays; D007834:Lasers; D011487:Protein Conformation / Q000528:radiation effects; D013552:Swine
D003094:Collagen