Ultrashort Laser Pulse Induced Electromagnetic Stress on Biological Macromolecular Systems.
Abstract
The threshold damage mechanisms resulting from picosecond laser irradiation of biological macromolecular systems similar to constituents of living cells are examined theoretically and experimentally. Three classes of potential damage mechanisms are possible: laser-induced infrared photochemistry, thermal and catalytic mechanisms, and stress-induced mechanical strains. A preliminary theoretical treatment is presented of the problem of stress distribution in a rodlike array of optically anisotropic elements in a viscous fluid that is exposed to an intense polarized light field. The results of experimental studies with poly(L-lysine) and calf-thymus DNA are presented. Solutions of these biological macromolecules are exposed to ultrashort pulses produced by a mode-locked Nd:Glass laser at a wavelength of 1060 nm. The effects of single pulses and one or more entire pulse trains are investigated. Molecular damage is monitored by measuring changes in the molecular translational diffusion coefficients between irradiated and control samples through the technique of dynamic light scattering. Although, thus far, damage thresholds for single picosecond pulses have not been established, it has been found that energy densities of the order of 100-150 mJ/cm.sq. for an entire mode-locked pulse train appear to be required to produce detectable damage in samples of DNA. Under similar conditions no damage is observed in poly(L-lysine). This suggests that in living tissue the hereditary material may be more susceptible to damage than the proteins.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1979
- Accession Number
- ADA081230
Entities
People
- Adam P. Bruckner
- Eddie Chang
- J. Michael Schurr
Organizations
- University of Washington