Abstract
The light-induced, charge-separated state P .+ 700A .- 1 in single crystals of Photosystem I (PSI) from the cyanobacterium Synechococcus elongatus is investigated with transient, direct-detection EPR spectroscopy. The orientation of the phylloquinone head group of A 1 within the PSI reaction center is determined from the orientation dependence of the spin-polarized X-band EPR spectrum of the radical pair P .+ 700A .- 1 made up of the primary donor, P 700, and the acceptor, A 1. From the angular dependence of the overall spin-polarization pattern an upper limit 〈(c, z d) ≤ 30° is evaluated for the angle between the crystallographic c-axis, collinear with the membrane normal, and the dipolar axis, z d, connecting the electron spin density centers of P .+ 700 and A .- 1. A partially resolved hyperfine coupling (hfc) is assigned to the hfc tensor of the 2-methyl group of A 1. Its A a principal axis encloses an angle of β = 35°-55° with c. Simulations of the rotation patterns support a lower limit for the angle 〈(c, z d) ≥ 25° with a larger error than for the upper limit. z d is confirmed to be parallel to both the g xx principal axis of g(A .- 1) and to the C=O carbonyl bonds within ±5°. With respect to rotation around the g xx axis, the angle between the (c, z d) plane and the quinone plane of the A .- 1 head group can only be specified within an upper limit of 60°. Together with independent knowledge about the location of A 1 within the PSI reaction center, a nearly complete structural model for the head group of the functional A 1 cofactor is achieved.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 8266-8277 |
| Number of pages | 12 |
| Journal | Journal of Physical Chemistry B |
| Volume | 102 |
| Issue number | 42 |
| State | Published - Oct 15 1998 |
| Externally published | Yes |
Fingerprint
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
Cite this
The radical pair state P .+ 700A .- 1 in photosystem I single crystals : Orientation dependence of the transient spin-polarized EPR spectra. / Kamlowski, Andreas; Zech, Stephan G.; Fromme, Petra; Bittl, Robert; Lubitz, Wolfgang; Witt, Horst T.; Stehlik, Dietmar.
In: Journal of Physical Chemistry B, Vol. 102, No. 42, 15.10.1998, p. 8266-8277.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - The radical pair state P .+ 700A .- 1 in photosystem I single crystals
T2 - Orientation dependence of the transient spin-polarized EPR spectra
AU - Kamlowski, Andreas
AU - Zech, Stephan G.
AU - Fromme, Petra
AU - Bittl, Robert
AU - Lubitz, Wolfgang
AU - Witt, Horst T.
AU - Stehlik, Dietmar
PY - 1998/10/15
Y1 - 1998/10/15
N2 - The light-induced, charge-separated state P .+ 700A .- 1 in single crystals of Photosystem I (PSI) from the cyanobacterium Synechococcus elongatus is investigated with transient, direct-detection EPR spectroscopy. The orientation of the phylloquinone head group of A 1 within the PSI reaction center is determined from the orientation dependence of the spin-polarized X-band EPR spectrum of the radical pair P .+ 700A .- 1 made up of the primary donor, P 700, and the acceptor, A 1. From the angular dependence of the overall spin-polarization pattern an upper limit 〈(c, z d) ≤ 30° is evaluated for the angle between the crystallographic c-axis, collinear with the membrane normal, and the dipolar axis, z d, connecting the electron spin density centers of P .+ 700 and A .- 1. A partially resolved hyperfine coupling (hfc) is assigned to the hfc tensor of the 2-methyl group of A 1. Its A a principal axis encloses an angle of β = 35°-55° with c. Simulations of the rotation patterns support a lower limit for the angle 〈(c, z d) ≥ 25° with a larger error than for the upper limit. z d is confirmed to be parallel to both the g xx principal axis of g(A .- 1) and to the C=O carbonyl bonds within ±5°. With respect to rotation around the g xx axis, the angle between the (c, z d) plane and the quinone plane of the A .- 1 head group can only be specified within an upper limit of 60°. Together with independent knowledge about the location of A 1 within the PSI reaction center, a nearly complete structural model for the head group of the functional A 1 cofactor is achieved.
AB - The light-induced, charge-separated state P .+ 700A .- 1 in single crystals of Photosystem I (PSI) from the cyanobacterium Synechococcus elongatus is investigated with transient, direct-detection EPR spectroscopy. The orientation of the phylloquinone head group of A 1 within the PSI reaction center is determined from the orientation dependence of the spin-polarized X-band EPR spectrum of the radical pair P .+ 700A .- 1 made up of the primary donor, P 700, and the acceptor, A 1. From the angular dependence of the overall spin-polarization pattern an upper limit 〈(c, z d) ≤ 30° is evaluated for the angle between the crystallographic c-axis, collinear with the membrane normal, and the dipolar axis, z d, connecting the electron spin density centers of P .+ 700 and A .- 1. A partially resolved hyperfine coupling (hfc) is assigned to the hfc tensor of the 2-methyl group of A 1. Its A a principal axis encloses an angle of β = 35°-55° with c. Simulations of the rotation patterns support a lower limit for the angle 〈(c, z d) ≥ 25° with a larger error than for the upper limit. z d is confirmed to be parallel to both the g xx principal axis of g(A .- 1) and to the C=O carbonyl bonds within ±5°. With respect to rotation around the g xx axis, the angle between the (c, z d) plane and the quinone plane of the A .- 1 head group can only be specified within an upper limit of 60°. Together with independent knowledge about the location of A 1 within the PSI reaction center, a nearly complete structural model for the head group of the functional A 1 cofactor is achieved.
UR - http://www.scopus.com/inward/record.url?scp=0001122297&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0001122297&partnerID=8YFLogxK
M3 - Article
VL - 102
SP - 8266
EP - 8277
JO - Journal of Physical Chemistry B Materials
JF - Journal of Physical Chemistry B Materials
SN - 1520-6106
IS - 42
ER -