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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.


Measured time-dependent neutron scattering intensities. (a) Black squares indicate the intensity of the peaks near the beamstop (see Fig. 4 ▸), and the solid line shows the result after a one-dimensional Fourier analysis truncated at /N/ = 1. (b) Black and open squares indicate SANS at Q = 0.044 and 0.055 Å−1, respectively, and the lines present the time-dependent intensities after a one-dimensional Fourier analysis terminated at /N/ = 1; the dashed line refers to the open symbols. The relative changes in the intensities in parts (a) and (b) are 7.0 × 10−4 and 4.0 × 10−4, respectively. The units of intensity in part (b) are as in Fig. 5 ▸.
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fig6: Measured time-dependent neutron scattering intensities. (a) Black squares indicate the intensity of the peaks near the beamstop (see Fig. 4 ▸), and the solid line shows the result after a one-dimensional Fourier analysis truncated at /N/ = 1. (b) Black and open squares indicate SANS at Q = 0.044 and 0.055 Å−1, respectively, and the lines present the time-dependent intensities after a one-dimensional Fourier analysis terminated at /N/ = 1; the dashed line refers to the open symbols. The relative changes in the intensities in parts (a) and (b) are 7.0 × 10−4 and 4.0 × 10−4, respectively. The units of intensity in part (b) are as in Fig. 5 ▸.

Mentions: Let us start with the first case. The intensity of both the prominent peaks near the beam stop (Fig. 6 ▸a) and of the SANS data from catalase (Fig. 6 ▸b) varies during one cycle of DNP in a way which can be described by a sinusoidal function. We try to extract some of the features of these data by a Fourier analysis of their time-dependent part. Zexp(Q, t) is then defined as a two-dimensional array of intensity at [Q, mΔt], with 1 ≤ m ≤ M, where M = 200 is the number of time frames during one cycle of DNP. Omitting Δt = 0.05 s, we have FC and FS are the Fourier coefficients. A reasonably good fit of the data is achieved by terminating the Fourier series at /N/ = 1 (Fig. 6 ▸).


Polarized proton spin density images the tyrosyl radical locations in bovine liver catalase
Measured time-dependent neutron scattering intensities. (a) Black squares indicate the intensity of the peaks near the beamstop (see Fig. 4 ▸), and the solid line shows the result after a one-dimensional Fourier analysis truncated at /N/ = 1. (b) Black and open squares indicate SANS at Q = 0.044 and 0.055 Å−1, respectively, and the lines present the time-dependent intensities after a one-dimensional Fourier analysis terminated at /N/ = 1; the dashed line refers to the open symbols. The relative changes in the intensities in parts (a) and (b) are 7.0 × 10−4 and 4.0 × 10−4, respectively. The units of intensity in part (b) are as in Fig. 5 ▸.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig6: Measured time-dependent neutron scattering intensities. (a) Black squares indicate the intensity of the peaks near the beamstop (see Fig. 4 ▸), and the solid line shows the result after a one-dimensional Fourier analysis truncated at /N/ = 1. (b) Black and open squares indicate SANS at Q = 0.044 and 0.055 Å−1, respectively, and the lines present the time-dependent intensities after a one-dimensional Fourier analysis terminated at /N/ = 1; the dashed line refers to the open symbols. The relative changes in the intensities in parts (a) and (b) are 7.0 × 10−4 and 4.0 × 10−4, respectively. The units of intensity in part (b) are as in Fig. 5 ▸.
Mentions: Let us start with the first case. The intensity of both the prominent peaks near the beam stop (Fig. 6 ▸a) and of the SANS data from catalase (Fig. 6 ▸b) varies during one cycle of DNP in a way which can be described by a sinusoidal function. We try to extract some of the features of these data by a Fourier analysis of their time-dependent part. Zexp(Q, t) is then defined as a two-dimensional array of intensity at [Q, mΔt], with 1 ≤ m ≤ M, where M = 200 is the number of time frames during one cycle of DNP. Omitting Δt = 0.05 s, we have FC and FS are the Fourier coefficients. A reasonably good fit of the data is achieved by terminating the Fourier series at /N/ = 1 (Fig. 6 ▸).

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.