Projecc Title: 16, N. Molecular and Cellular Radiobiology Mechanisms of Action of Free Radicals and Hormones Technical Progress in FY 1973: Sutin (BNL Chemistry Department), (Cont'd.)} RX-03-02-(c) using stopped-flow and temperature- jump methods. Work reported last year on the reduction of ferric iron complexes (other than porphyrins) catalyzed by various bridging ligands suggested electron transfer to the central metal ion by way of the ligand's m electrons, a conclusion consistent with numerous indications from our porphyrin research program that redox changes of certain heme enzymes (such as cytochrome c) may proceed by way of free radical forms of their equatorial porphyrin ligands, However, additional progress this past year on acidsoluble tetrapyridyl derivatives of iron porphyrins gave evidence of direct reduction cf the central metal ion, so if heme enzymes shuttle redox equi- valents through their porphyrins, major effects on the electron pathway must be exerted by solvent and/or by the axial ligands. (Borg) “* : In studies on mechanisms of hormone action BOC-cysteine was successfully attached to solid supports and recovered by thiolysis, using essentially the methods developed for histidine peptides, Presently model peptides are being synthesized by this method, using special conditions required by the S-dinitrophenyl group situated in the beta position from the carboxyl of cysteine, In addition work began on development of enzymatically removable blocking groups for the amino group. Fundamental and broadly applicable new methods were worked out in the process of preparing the requisite intermediates for this project, and a practical scheme of enzymatic depro. tection seems to be evolving. 17. (Schwartz, Walter) Expected Results in FY 1974: With the acquisition of a second spectrometer and ELDOR, a specially modified signal-averager was ordered to provide accessory signal digitizing capability. It will require some modification of the present computer set-up to allow data transfer from this equipment with format compacibility so that it may be used as a means of data access to the main system. The Fortran computer programs for resolution enhancement of gaussian spectral lines by Fourier transform methods should be completed early next year. Subsequently machine-language versions will be developed for inclusion of the procedure in the on-line computer system, The ELDOR apparatus, although partially operative on strong test m, requires further check-out and minor correction by the manufacturer. promi on, some modifications of the computer system will be required for compatability. Application to EPR signals from tissues remains ¥, although difficult, but it is unlikely to proceed during this next Considering the progress of other laborayear Without additional personnel. tories, it will not be practical to await procurement or ENDOR apparatus. (See Continuation Sheet) [119303 RX- 243