DESCRIPTION (Investigator's Abstract): In this phase I proposal the investigators seek to develop a method to inactivate pathogenic human viruses in platelet concentrates expanding on their preliminary work using photochemical decontamination (PCD) with psoralen and UV-A light. Preliminary data have been published showing that the combination of 8-MOP and UV-A inactivates HIV-1 virus in platelet concentrates. However, in order to preserve platelet function, the platelet concentrates required the reduction of ambient levels of O2 achieved by invasive gassing of blood bags with N2. This was necessary to reduce the production of free oxygen radials. Whereas this is not an acceptable means of oxygen control for blood bank practice, the current proposal will explore methods of more simply reducing levels of soluble O2 in the platelet concentrate and will also investigate psoralen derivatives other than 8-MOP which require lower concentration and are more efficient intercalators of DNA with a consequent reduction of free radical information.