Details of the way in which haemplane orientations were deduced from
g
-value measurements on five different crystal types of acid-met myoglobin were given in parts I and I I (Bennett, Gibson & Ingram 1957, and Bennett
et al
. 1961). This paper now summarizes more detailed measurements of line-width and
g
-value variations observed in both the acid-met and azide derivatives of type
A
myoglobin crystals. Since these crystals are those for which a detailed X-ray analysis is now available, a direct comparison of this with the electron resonance measurements can now be made. The
g
-values obtained for the azide derivative are first analysed, and their anisotropy and asymmetry are related to the possible orientation of the azide group itself. The line widths of the electron resonance absorptions, and their angular variations are then summarized and discussed. It is shown that their large magnitudes and rapid variation with angle can be explained in terms of a slight random misorientation of the molecular axes within the crystal, and that, due to the large
g
-value anisotropy in the acid-met derivative, a standard deviation of only 1.6° in angular distribution is sufficient to explain the results obtained. A similar analysis is also applied to the results on the azide derivative.
The fast-electron irradiation of piperidine in a matrix of adamantane, thiourea or molecular sieve results in the formation of only one identifiable radical species, piperidin-2-yl. The most stable conformer of this radical is the boat form but, except at low temperatures, it undergoes rapid inversion which exchanges the axial and equatorial hydrogens of the methylene groups adjacent to the N atom and the radical C atom. The inversion gives rise to a distinct alternating line width effect for each methylene group, from which activation energies of 35.5 k 5 kJ mol-I and 22k 5 kJ mol-1 can be derived for the processes.CND0/2 calculations predict hyperfke splittings for the boat form in very good agreement with those observed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.