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Polarized proton spin density images the tyrosyl radical locations in bovine liver catalase

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ABSTRACT

A tyrosyl radical, as part of the amino acid chain of bovine liver catalase, supports dynamic proton spin polarization (DNP). Finding the position of the tyrosyl radical within the macromolecule relies on the accumulation of proton polarization close to it, which is readily observed by polarized neutron scattering. The nuclear scattering amplitude due to the polarization of protons less than 10 Å distant from the tyrosyl radical is ten times larger than the amplitude of magnetic neutron scattering from an unpaired polarized electron of the same radical. The direction of DNP was inverted every 5 s, and the initial evolution of the intensity of polarized neutron scattering after each inversion was used to identify those tyrosines which have assumed a radical state. Three radical sites, all of them close to the molecular centre and the haem, appear to be equally possible. Among these is tyr-369, the radical state of which had previously been proven by electron paramagnetic resonance.

No MeSH data available.


The neutron scattering intensity from catalase as recorded by the area detector of D22. The large peaks on the left and right side of the beamstop are part of the primary beam. It is the neutron beam polarizer about half a metre upstream of the diaphragm at the sample which slightly enlarges the beam in the horizontal direction. The red lines denote the limits of the spherical averaging of the scattering intensity (see Fig. 7).
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fig4: The neutron scattering intensity from catalase as recorded by the area detector of D22. The large peaks on the left and right side of the beamstop are part of the primary beam. It is the neutron beam polarizer about half a metre upstream of the diaphragm at the sample which slightly enlarges the beam in the horizontal direction. The red lines denote the limits of the spherical averaging of the scattering intensity (see Fig. 7).

Mentions: SANS data from the frozen solutions of catalase in glycerol–water mixtures, as recorded by the area detector of D22, are shown in Fig. 4 ▸. The unexpected large sharp peaks to the left and right of the beam stop are spurs of the primary beam, which has accidentally been enlarged in the horizontal plane by the neutron spin polarizer, less than half a metre upstream of the sample. Initially, it was argued that the intensity of the peaks could serve as an accurate measure of the transmission of the sample. This point will be discussed in more detail below.


Polarized proton spin density images the tyrosyl radical locations in bovine liver catalase
The neutron scattering intensity from catalase as recorded by the area detector of D22. The large peaks on the left and right side of the beamstop are part of the primary beam. It is the neutron beam polarizer about half a metre upstream of the diaphragm at the sample which slightly enlarges the beam in the horizontal direction. The red lines denote the limits of the spherical averaging of the scattering intensity (see Fig. 7).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5391855&req=5

fig4: The neutron scattering intensity from catalase as recorded by the area detector of D22. The large peaks on the left and right side of the beamstop are part of the primary beam. It is the neutron beam polarizer about half a metre upstream of the diaphragm at the sample which slightly enlarges the beam in the horizontal direction. The red lines denote the limits of the spherical averaging of the scattering intensity (see Fig. 7).
Mentions: SANS data from the frozen solutions of catalase in glycerol–water mixtures, as recorded by the area detector of D22, are shown in Fig. 4 ▸. The unexpected large sharp peaks to the left and right of the beam stop are spurs of the primary beam, which has accidentally been enlarged in the horizontal plane by the neutron spin polarizer, less than half a metre upstream of the sample. Initially, it was argued that the intensity of the peaks could serve as an accurate measure of the transmission of the sample. This point will be discussed in more detail below.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

A tyrosyl radical, as part of the amino acid chain of bovine liver catalase, supports dynamic proton spin polarization (DNP). Finding the position of the tyrosyl radical within the macromolecule relies on the accumulation of proton polarization close to it, which is readily observed by polarized neutron scattering. The nuclear scattering amplitude due to the polarization of protons less than 10 Å distant from the tyrosyl radical is ten times larger than the amplitude of magnetic neutron scattering from an unpaired polarized electron of the same radical. The direction of DNP was inverted every 5 s, and the initial evolution of the intensity of polarized neutron scattering after each inversion was used to identify those tyrosines which have assumed a radical state. Three radical sites, all of them close to the molecular centre and the haem, appear to be equally possible. Among these is tyr-369, the radical state of which had previously been proven by electron paramagnetic resonance.

No MeSH data available.