2 research outputs found
Photophysical Properties of the Excited States of Bacteriochlorophyll <i>f</i> in Solvents and in Chlorosomes
Bacteriochlorophyll <i>f</i> (BChl <i>f</i>) is a photosynthetic pigment predicted
nearly 40 years ago as a
fourth potential member of the <i>Chlorobium</i> chlorophyll
family (BChl <i>c</i>, <i>d</i>, and <i>e</i>). However, this pigment still has not been found in a naturally
occurring organism. BChl <i>c</i>, <i>d</i>, and <i>e</i> are utilized by anoxygenic green photosynthetic bacteria
for assembly of chlorosomesî—¸large light-harvesting complexes
that allow those organisms to survive in habitats with extremely low
light intensities. Recently, using genetic methods on two different
strains of Chlorobaculum limnaeum that
naturally produce BChl <i>e</i>, two research groups produced
mutants that synthesize BChl <i>f</i> and assemble it into
chlorosomes. In this study, we present detailed investigations on
spectral and dynamic characteristics of singlet excited and triplet
states of BChl <i>f</i> with the application of ultrafast
time-resolved absorption and fluorescence spectroscopies. The studies
were performed on isolated BChl <i>f</i> in various solvents,
at different temperatures, and on BChl <i>f</i>-containing
chlorosomes in order to uncover any unusual or unfavorable properties
that stand behind the lack of appearance of this pigment in natural
environments
Polymer–Chlorosome Nanocomposites Consisting of Non-Native Combinations of Self-Assembling Bacteriochlorophylls
Chlorosomes
are one of the characteristic light-harvesting antennas
from green sulfur bacteria. These complexes represent a unique paradigm:
self-assembly of bacteriochlorophyll pigments within a lipid monolayer
without the influence of protein. Because of their large size and
reduced complexity, they have been targeted as models for the development
of bioinspired light-harvesting arrays. We report the production of
biohybrid light-harvesting nanocomposites mimicking chlorosomes, composed
of amphiphilic diblock copolymer membrane bodies that incorporate
thousands of natural self-assembling bacteriochlorophyll molecules
derived from green sulfur bacteria. The driving force behind the assembly
of these polymer–chlorosome nanocomposites is the transfer
of the mixed raw materials from the organic to the aqueous phase.
We incorporated up to five different self-assembling pigment types
into single nanocomposites that mimic chlorosome morphology. We establish
that the copolymer-BChl self-assembly process works smoothly even
when non-native combinations of BChl homologues are included. Spectroscopic
characterization revealed that the different types of self-assembling
pigments participate in ultrafast energy transfer, expanding beyond
single chromophore constraints of the natural chlorosome system. This
study further demonstrates the utility of flexible short-chain, diblock
copolymers for building scalable, tunable light-harvesting arrays
for technological use and allows for an in vitro analysis of the flexibility
of natural self-assembling chromophores in unique and controlled combinations