Exact action spectra for cellular responses relevant to phototherapy

Photomed Laser Surg. 2005 Aug;23(4):355-61. doi: 10.1089/pho.2005.23.355.


Objective: The aim of the present work is to analyze available action spectra for various biological responses of HeLa cells irradiated with monochromatic light of 580-860 nm.

Background data: Phototherapy (low-level laser therapy or photobiomodulation) is characterized by its ability to induce photobiological processes in cells. Exact action spectra are needed for determination of photoacceptors as well as for further investigations into cellular mechanisms of phototherapy.

Methods: Seven action spectra for the stimulation of DNA and RNA synthesis rate and cell adhesion to glass matrix are analyzed by curve fitting, followed by deconvolusion with Lorentzian fitting. Exact parameters of peak positions and bandwidths are presented.

Results: The peak positions are between 613.5 and 623.5 nm (in one spectrum, at 606 nm), in the red maximum. The far-red maximum has exact peak positions between 667.5 and 683.7 nm in different spectra. Two near infrared maxima have peak positions in the range 750.7-772.3 nm and 812.5-846.0 nm, respectively.

Conclusions: In the wavelength range important for phototherapy (600-860 nm), there are four "active" regions, but peak positions are not exactly the same for all spectra.

MeSH terms

  • Cell Adhesion / radiation effects
  • DNA / biosynthesis*
  • DNA / radiation effects
  • HeLa Cells
  • Humans
  • Low-Level Light Therapy / methods*
  • RNA / biosynthesis*
  • RNA / radiation effects


  • RNA
  • DNA