title: The kinetics of radiation damage to the protein luciferase and recovery of enzyme activity after irradiation.
abstract: Experimental observations are reported which follow the bioluminescence intensity of luciferase during irradiation by a 5 MeV proton beam. Bioluminescence is a measure of the protein enzyme activity and provides an assay of the enzyme rate of reaction in real time. Transient responses after a pulse of protons show recovery of the reaction rate with two time constants of 0.3 s(-1) and 0.01 s(-1). Changes in the reaction rate are due to radiation damage to the active form of the protein luciferase. Quantitative analysis of the radiation damage and recovery of the protein shows that products of the radiolysis of water play major part in the process of enzyme damage at room temperature. A few minutes after the pulse of protons, most of the enzyme activity has recovered. We attribute the fast recovery to the removal of charged ions, while the slow recovery involves refolding of denatured protein.
authors.affiliation: School of Physics and Astronomy, The University of Birmingham, Birmingham B15 2TT, United Kingdom. n.berovic@bham.ac.uk
authors.forename: Nikolas
authors.initials: N
authors.lastname: Berovic
authors.forename: Sirapat
authors.initials: S
authors.lastname: Pratontep
authors.forename: Andrew
authors.initials: A
authors.lastname: Bryant
authors.forename: Alex
authors.initials: A
authors.lastname: Montouris
authors.forename: Robert G
authors.initials: RG
authors.lastname: Green
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D049454:Firefly Luciferin / Q000378:metabolism* / Q000528:radiation effects; D019476:Insect Proteins / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects*; D007700:Kinetics; D008156:Luciferases / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects*; D008163:Luminescent Measurements; D011489:Protein Denaturation / Q000528:radiation effects; D017510:Protein Folding; D011522:Protons; D011675:Pulse Radiolysis; D014867:Water
chemical_list: D019476:Insect Proteins; D011522:Protons; D014867:Water; D049454:Firefly Luciferin; D000255:Adenosine Triphosphate; D008156:Luciferases