Journal of Photochemistry and Photobiology A: Chemistry 168 (2004) 59–65 Effect of red and near-infrared laser light on adenosine triphosphate (ATP) in the luciferine–luciferase reaction Albert Amat a,∗ , Josepa Rigau a , Renata Nicolau a,c , Maurice Aalders b , Maria Rosa Fenoll a , Martin van Gemert b , Josep Tomàs a a Histology and Neurobiology Unit, Faculty of Medicine and Health Sciences, Rovira i Virgili University, C. Sant Llorenç 21, 43201 Reus, Spain b Laser Centre, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands c Health School, Vale do Paraiba University, Sao Jose Dos Campos, SP, Brazil Received 29 April 2004; accepted 25 May 2004 Available online 3 July 2004 Abstract Adenosine triphosphate (ATP) is an important molecule in biology because it stores chemical energy and releases it to the biochemical processes occurring in the cell. In this study we analysed the biochemical behaviour of ATP after irradiating it with 635 and 830nm diode lasers. We analysed the luminescence peak, the reaction rate and the area under the luminescence curve at 2 × 10 -9 mol/l of ATP in the luciferine–luciferase luminescence reaction before and after irradiating the molecule at several irradiances and radiant exposures. The absorption spectrum of ATP at 3 × 10 -3 mol/l concentration was measured between 650 and 900 nm after laser irradiation at 635 nm (Argon-Dye) and 830nm (diode laser). We found significant differences in the measured parameters when ATP was irradiated with both wavelengths. The absorption spectra of non-irradiated and irradiated ATP show a physical–chemical difference in the ATP molecule after irradiation with both lasers. We can conclude that visible and near-IR laser light with the parameters that were used in this study changed the biochemical behaviour of ATP molecules. © 2004 Elsevier B.V. All rights reserved. Keywords: Adenosine 5-triphosphate (ATP); 630 and 830 nm diode laser; Firefly luciferine–luciferase photoluminescent reaction; Reaction kinetics; Spectroscopy 1. Introduction All cells obtain their energy from nutritional compounds (principally glucose) through biochemical reactions that have negative free energy changes (at the end of the pro- cess, the free energy of the system decreases because the energy is stored in energetic molecules such as ATP, which are used in most biochemical reactions). Vegetal cells ob- tain their energy from solar light through photosynthesis. In both of these cases, almost all the free energy is stored in chemical bonds that are to be used in the cell processes. In all organisms, the most important molecule in stor- ing and transferring that energy is adenosine triphosphate (ATP). Abbreviations: ATP, adenosine 5-triphosphate; V 0 , peak voltage of the luminescent signal; V(t), exponential function of the luminescent signal; k, constant of the light decay after 1 min; J/cm 2 , Joules/cm 2 radiant exposure units ∗ Corresponding author. Tel.: +34-977-759343; fax: +34-977-759322. E-mail address: alag@fmcs.urv.es (A. Amat). Ribonucleoside 5 ′ -trisphosphate acts as a donor of phos- phate groups in the cell’s energy cycle, transporting chem- ical energy from one metabolic cycle to another and acting as a shared intermediary that couples endergonic reac- tions to exergonic reactions. The hydrolysis of each of the high-energy phosphate anhydric bonds of ATP produces a notable change in free energy (-7.3 kcal/mol). The resulting diphosphate of adenosine (ADP) is recycled (phosphoriled) to ATP by two different mechanisms: chem- ical energy (during oxidation of nutritional compounds) or light energy (in photosynthetic cells) [1]. One-way laser light is used in medicine by inducing the photochemical effect at low irradiance. A photochemical ef- fect is produced when a chromophore is excited by absorb- ing a photon and this supplementary energy is transferred for the onset of a biochemical reaction [2]. Karu [3] described the absorption of various wavelengths at the mitochondrial respiratory chain level and defined several unspecific chro- mophores that change their redox potential to increase the electronic energy levels. This leads to an increase in ATP synthesis. Lubart et al. [4] described a possible intracellular 1010-6030/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jphotochem.2004.05.024