SPECTROSCOPY, IMAGING, OTHER TECHNIQUES |
Kinetics of a Collagen-like Polypeptide Fragmentation after Mid-IR Free-Electron Laser Ablation
Andrey Zavalin 1*, David L Hachey 1, Munirathinam Sundaramoorthy 1, Surajit Banerjee 1, Steven H Morgan 2, Leonard Feldman 1, Norman Tolk 1 and David Piston 1
1 Vanderbilt University
2 Fisk University
* To whom correspondence should be addressed. E-mail: andrey.zavalin{at}vanderbilt.edu.
Submitted on September 13, 2007
Revised on October 25, 2007
Accepted on 3 April 2008
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Abstract |
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Tissue ablation with mid-Infrared irradiation tuned to collagen vibrational modes results in minimal collateral damage. Hypothesis for this effect includes selective scission of protein molecules and excitation of surrounding water molecules, with the scission process currently favored. Here we describe the post-ablation IR spectral decay kinetics in a model collagen-like peptide (Pro-Pro-Gly)10. We find that the decay is exponential with different decay times for other, simpler dipeptides. Furthermore, we find that collagen-like polypeptides, such as (Pro-Pro-Gly)10, show multiple decay times indicating multiple scission locations and cross-linking to form longer chain molecules. In combination with data from high resolution mass-spectrometry, we interpret these products to result from generation of reactive intermediates, such as free radicals, cyanate ions and isocyanic acid, having the ability to form cross-links and protein adducts. Our results lead to a more complete explanation of the reduced collateral damage resulting from IR laser irradiation through a mechanism involving cross-linking in which collagen-like molecules form a network of crosslinked fibers.
Key Words:
Free Electron Laser, collagen-like polypeptides, ketene, laser tissue welding, mid-IR ablation
