title: Quantitative second-harmonic generation microscopy in collagen.
abstract: The second-harmonic signal in collagen, even in highly organized samples such as rat tail tendon fascicles, varies significantly with position. Previous studies suggest that this variability may be due to the parallel and antiparallel orientation of neighboring collagen fibrils. We applied high-resolution second-harmonic generation microscopy to confirm this hypothesis. Studies in which the focal spot diameter was varied from approximately 1 to approximately 6 microm strongly suggest that regions in which collagen fibrils have the same orientation in rat tail tendon are likely to be less than approximately 1 microm in diameter. These measurements required accurate determination of the focal spot size achieved by use of different microscope objectives; we developed a technique that uses second-harmonic generation in a quartz reference to measure the focal spot diameter directly. We also used the quartz reference to determine a lower limit (dXXX > 0.4 pm/V) for the magnitude of the second-order nonlinear susceptibility in collagen.
authors.affiliation: M Division, Lawrence Livermore National Laboratory, L-174, P.O. Box 808, Livermore, California 94551, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Stoller
authors.forename: Peter M
authors.initials: PM
authors.lastname: Celliers
authors.forename: Karen M
authors.initials: KM
authors.lastname: Reiser
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Rubenchik
mesh_terms: D000818:Animals; D003094:Collagen / Q000648:ultrastructure*; D008027:Light; D008853:Microscopy; D008962:Models, Theoretical; D051381:Rats; D017207:Rats, Sprague-Dawley; D013623:Tail; D013710:Tendons / Q000378:metabolism* / Q000648:ultrastructure*
chemical_list: D003094:Collagen