PROLONGED EXPOSURE TO DIOXANE & ACETONITRILE OF SPIN-LABEL SUBTILISIN CARSBERG

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The sample of subtilisin Carsberg spin labeled at an active site was prepared in the laboratory of Professor Gabriel Barletta and was sent to ACERT to be investigated by high-field EPR. The idea was to determine accurately the parameters of the g-tensor to use it later at Professor Barletta group for simulations of molecular dynamic at X-band. The sample was transferred into the resonator and it was cooled with either nitrogen or helium. The experiments were done at 190 K for dioxane, and, since there is not a real rigid limit at this temperature, also at 80 K to guarantee the rigid limit. Modulation used was 5 G. After the experiments some of the spectra were phased to get rid of a small admixture of dispersion. For some of the spectra a small passage effect was observed, but this effect does not change the position of the lines. The g-factor was determined by comparison with the known g-factor of PDTempone. The sweep width was determined from the knowledge of the separation between the lines for water solution of Mn.