23 Ultrafast Energy Transfer of Biohybrid Photosynthetic Antenna …
395
Fig. 23.7 Graphical description of LH2-A647 conjugate consisting of B800, B850, LH2α-, and
β-polypeptides. Evaluated donor–acceptor distances R calcd from B800 (a) and B850 (b) to A647
are depicted by green (a) and red circles (b). Possible range of A647 attached to K5 and K51 with
linkage was estimated to be 31 Å as fully extended conformation, which is depicted by blue circles.
The figure modified with permission from American Chemical Society Ref. [9] Copyright 2015
R calcd was 27 Å. The A647 attached to either K5 or K51 is possible to be the direct
donor to B850 as shown in Fig. 23.7b.
This work using the photosynthetic component LH2 indicates that by conjugation
with appropriate donor chromophores close to B800, the ultrafast energy transfer
cascade can be accomplished, where the natural ultrafast channel B800 → B850 is
involved.
23.4 Energy Transfer Dynamics of Cys-Bearing LH2
Conjugate (LH2-NC-A647) in Micellar and Lipid
Bilayer Systems [10]
As described above, fluorescent dyes attached to a protein scaffold exhibit multiexponential energy transfer dynamics in many cases [11]. This is probably due to
inhomogeneity of the attached chromophores, in terms of their surrounding environments, diverse orientation and donor–acceptor distance, multiple binding sites,
and so on. Here, we designed a cysteine-bearing LH2 for the site-selective modification of A647. In this section, we described use of engineered LH2 bearing cysteine
(LH2-NC) from Rba. sphaeroides IL106 strain. The amino acid sequences were
shown in Fig. 23.2. The reactive cysteine was introduced into the N-terminal region
on the LH2β-polypeptide, which enables the attachment of A647 maleimide in a
site-selective manner proximate to the B800-BChl. Using A647-attached LH2-NC
conjugate (LH2-NC-A647), we revealed the dynamics of sequential energy transfer
A647 → B800 → B850 in micellar and reconstituted lipid bilayer systems. We
have briefly discussed the potential of LH2 complex as a remarkable platform for
construction of biohybrid antennae.
Absorption spectrum of LH2-NC-A647 was similar to that of LH2-A647. The
intrinsic ultrafast energy transfer was confirmed to be maintained by femtosecond
395
Fig. 23.7 Graphical description of LH2-A647 conjugate consisting of B800, B850, LH2α-, and
β-polypeptides. Evaluated donor–acceptor distances R calcd from B800 (a) and B850 (b) to A647
are depicted by green (a) and red circles (b). Possible range of A647 attached to K5 and K51 with
linkage was estimated to be 31 Å as fully extended conformation, which is depicted by blue circles.
The figure modified with permission from American Chemical Society Ref. [9] Copyright 2015
R calcd was 27 Å. The A647 attached to either K5 or K51 is possible to be the direct
donor to B850 as shown in Fig. 23.7b.
This work using the photosynthetic component LH2 indicates that by conjugation
with appropriate donor chromophores close to B800, the ultrafast energy transfer
cascade can be accomplished, where the natural ultrafast channel B800 → B850 is
involved.
23.4 Energy Transfer Dynamics of Cys-Bearing LH2
Conjugate (LH2-NC-A647) in Micellar and Lipid
Bilayer Systems [10]
As described above, fluorescent dyes attached to a protein scaffold exhibit multiexponential energy transfer dynamics in many cases [11]. This is probably due to
inhomogeneity of the attached chromophores, in terms of their surrounding environments, diverse orientation and donor–acceptor distance, multiple binding sites,
and so on. Here, we designed a cysteine-bearing LH2 for the site-selective modification of A647. In this section, we described use of engineered LH2 bearing cysteine
(LH2-NC) from Rba. sphaeroides IL106 strain. The amino acid sequences were
shown in Fig. 23.2. The reactive cysteine was introduced into the N-terminal region
on the LH2β-polypeptide, which enables the attachment of A647 maleimide in a
site-selective manner proximate to the B800-BChl. Using A647-attached LH2-NC
conjugate (LH2-NC-A647), we revealed the dynamics of sequential energy transfer
A647 → B800 → B850 in micellar and reconstituted lipid bilayer systems. We
have briefly discussed the potential of LH2 complex as a remarkable platform for
construction of biohybrid antennae.
Absorption spectrum of LH2-NC-A647 was similar to that of LH2-A647. The
intrinsic ultrafast energy transfer was confirmed to be maintained by femtosecond