Electron nuclear double resonance from high- and low-spin ferric hemoglobins and myoglobins

On the Origin of the Low-Spin Character of Cytochrome P450cam in the Resting State—Investigations of Enzyme Models with Pulse EPR and ENDOR Spectroscopy

“…[15] In the high-spin case the expected proton hyperfine coupling along g k (a iso A(g k )) lies around 6 MHz and is predominantly dipolar in character. [16] The three-pulse ESEEM spectrum of 7-H 2 O shows no evidence of such a strong proton interaction (Figure 2 a). Stirring 7-H 2 O in a mixture of 2-methyltetrahydrofuran (MTHF) and D 2 O for 12 h provided the corresponding deuterated complex 7-D 2 O; its three-pulse ESEEM spectrum reveals an intensive deuterium signal pair centered at the nuclear Zeeman frequency of deuterium with a splitting of 1.04 MHz (Figure 2 b).…”

EPR analysis of cyanide complexes of wild-type human neuroglobin and mutants in comparison to horse heart myoglobin

“…Although the origin of the observed 13 C NMR shift is the same as that of the 13 C hyperfine interaction addressable by ENDOR techniques, only few studies have attempted to obtain this information for ferric cyanide complexes of haem proteins [26,36]. To our knowledge, the only determination of a full 13 C hyperfine tensor for such a system, is the one performed for cyanide-ligated cytochrome P450cam [36].…”

“…To our knowledge, the only determination of a full 13 C hyperfine tensor for such a system, is the one performed for cyanide-ligated cytochrome P450cam [36]. For cyanide-ligated globins, only the study of Mulks et al [26] reports a partial determination of the hyperfine tensor for the swMb-CN and hHb-CN cases. The reason is clear: due to the high ganisotropy and large g strain and corresponding weak (or not detectable) high-field EPR feature (g = g x ), ENDOR spectroscopy becomes challenging.…”

“…Although electron paramagnetic resonance (EPR) has often been used to characterize ferric cyanideligated globins [25][26][27][28][29][30][31], no EPR data of cyanide-ligated Ngbs have been reported so far. In the present work, continuous-wave (CW) and pulsed EPR techniques are used to investigate the cyanide-ligated…”

“…All findings are compared in detail with reported EPR data on other cyanideligated ferric globin forms. Furthermore, although 13 C NMR of the iron-bound cyanide in ferric cyanide complexes of haem proteins has been shown to reveal important information about the haem reactivity [32][33][34][35], only a few studies have attempted to determine the full 13 C hyperfine tensor of the cyanide carbon of such haem complexes [26,36]. Here, Davies 13 C-ENDOR is applied to extract information on this tensor for cyanide-ligated NGB variants in comparison to those of the cyanide complex of horse heart myoglobin (hhMb-CN).…”