Radical dosimetry methods for in vivo hydroxyl radical protein foot-printing

A method of normalizing HRPF product abundance comprising:

• introducing a reference sample mixture into the photolysis cell of a flash photolysis system, the reference sample mixture including a dosimeter internal standard;
• determining the photometric absorbance of the reference sample mixture;
• irradiating the reference sample mixture using at least a single pulse of photolysis light;
• determining a change in photometric absorbance of said irradiated reference sample mixture, the change resulting from at least the single pulse;
• introducing an analyte sample mixture into the photolysis cell of the flash photolysis system, the analyte sample mixture including the dosimeter internal standard;
• determining the photometric absorbance of the analyte sample mixture;
• irradiating the analyte sample mixture using at least a single pulse of photolysis light;
• determining a photometric change in absorbance of the irradiated analyte sample mixture;
• analyzing a labeled reaction product produced from the irradiated analyte sample mixture;
• and
• multiplying a signal abundance of the labeled reaction product of the analyte sample mixture by a ratio of the change in photometric absorbance of the analyte sample mixture divided by the change in photometric absorbance of the reference sample mixture.