Nanoscale Confinement
and Fluorescence Effects of
Bacterial Light Harvesting Complex LH2 in Mesoporous Silicas
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Abstract
Many key chemical and biochemical reactions, particularly
in living
cells, take place in confined space at the mesoscopic scale. Toward
understanding of physicochemical nature of biomacromolecules confined
in nanoscale space, in this work we have elucidated fluorescence
effects of a light harvesting complex LH2 in nanoscale chemical environments.
Mesoporous silicas (SBA-15 family) with different shapes and pore
sizes were synthesized and used to create nanoscale biomimetic environments
for molecular confinement of LH2. A combination of UV–vis absorption,
wide-field fluorescence microscopy, and in situ ellipsometry supports
that the LH2 complexes are located inside the silica nanopores. Systematic
fluorescence effects were observed and depend on degree of space confinement.
In particular, the temperature dependence of the steady-state fluorescence
spectra was analyzed in detail using condensed matter band shape theories.
Systematic electronic-vibrational coupling differences in the LH2
transitions between the free and confined states are found, most likely
responsible for the fluorescence effects experimentally observed