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10:52
Direct Imaging of Laser-driven Ultrafast Molecular Rotation
Published on: February 4, 2017
Anchored LH2 complexes in 2D polarization imaging.
Sumera Tubasum1, Shunsuke Sakai, Takehisa Dewa
1Department of Chemical Physics, Lund University , SE-22 100, Lund, Sweden.
The Journal of Physical Chemistry. B
|May 9, 2013
Summary
Single-molecule spectroscopy reveals that anchoring light-harvesting complexes (LH2) increases disorder in the B850 pigment ring. This disorder arises from film-induced tilting, affecting B850 more than B800.
Area of Science:
- Biophysics
- Spectroscopy
- Photosynthesis
Background:
- Proteins are disordered, making bulk spectroscopy average out details.
- Single-molecule spectroscopy offers higher resolution for studying protein complexes.
Purpose of the Study:
- To investigate the structural disorder of single light-harvesting complexes (LH2) using polarization-resolved spectroscopy.
- To compare the spectroscopic properties of LH2 complexes embedded in a film versus those anchored to a surface.
Main Methods:
- Single-molecule fluorescence spectroscopy with independent rotation of excitation and detection polarizations.
- Studying peripheral antenna (LH2) complexes from Rhodopseudomonas acidophila in polyvinyl alcohol (PVA) films and anchored to glass.
Main Results:
- B800 excitation polarization properties were similar for both embedded and anchored LH2 samples.
- B850 emission polarization statistics differed significantly between the two sample preparations.
- The B850 band of the anchored sample exhibited substantially greater disorder.
Conclusions:
- The tilt of anchored LH2 complexes, induced by PVA film spin-casting and shear forces, explains the observed polarization properties.
- This tilt leads to similar orientation statistics for both samples, but greater disorder in the B850 band of anchored complexes.
- The B850 pigment ring is more susceptible to disorder due to its proximity to the substrate and tilt-induced strain.
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