IMMOBILIZATION OF PHOTOSYNTHETICALLY ACTIVE …
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IMMOBILIZATION OF PHOTOSYNTHETICALLY ACTIVE COMPONENTS WITHIN A NOVEL SILICA GEL Photosynthetically active components (PAC) can absorb light and transfer energy. All eucaryotic cells using photosynthesis contain light-harvesting complexes (Lhc) to optimize light utilization. The Lhc is a protein-pigment complex containing different pigments like chlorophyll a/b and carotenoids, Figure 1. However, PACs are extremely unstable and need to be stabilized outside of the cell in order to use these highly effective components in third generation photovoltaics and artificial photosynthesis, respectively [1]. In this work we present two novel silica gels to stabilize chlorophyllin as a model substance as well as a Lhc isolated from Chlamydomonas reinhardtii . INTRODUCTION RESULTS Silica gels for immobilization For immobilization (entrapment) of PACs two novel silica gels were synthesized using the sol-gel method. A mixture of 5-25 % novel precursor (obtained from Edwin Kroke, TU Bergakademie Freiberg) and demineralized water first formed a liquid sol and subsequently a transparent gel. Both gels can be produced under biocompatible conditions (e.g. room temperature) and without toxic by-products (like methanol or ethanol). Depending on the requirements of the PACs the properties of the silica gels were adjusted. The two resulting gels differ in viscosity and gelling time. Gel 1 has higher viscosity ( ) than gel 2 ( ), gelling times were 2 h and 10 min for gel 1 and gel 2, respectively. The model substance chlorophyllin was entrapped in gel 1 and the Lhc (obtained from Olaf Kruse, University Bielefeld) was entrapped in gel 2, Figure 2. 5 2070 x 10 Pa s at shear -1 rate 0,1 s 4740 Pa s at shear rate -1 0,1 s Influence of light exposure on the photostability of PACs Figure 2: Two novel silica gels containing photosynthetically active components (A) gel 1 and (B) gel 2 The influence of light exposure on the stability of PACs was studied using UV-Vis spectroscopy at specific wavelengths (chlorophyllin: 640 nm, Lhc: 671 nm). Light absorption of free chlorophyllin and free Lhc was reduced by 29 % and 62 % after 2 h, respectively. After entrapment of chlorophyllin, the light absorption was reduced by 10 % after 2 h. Entrapment of Lhc resulted in absorption reduced by 51 % after 2 h, Figure 3. These results indicate a stabilizing effect of the novel silica gels. Figure 3: The absorption of free and immobilized chlorophyllin (640 nm) and light-harvesting complex (671 nm) as a function of time Free Lhc has typically absorbance maxima at 430 nm-470 nm (carotenoids) and 650 nm- 671 nm (chlorophyll a/b), corresponding to the different pigments bound to the complex, Figure 4. Immobilized Lhc showed no change of absorbance maxima after the gel formation. This indicates that the protein-pigment structure remains unchanged in the gel directly after immobilization. Furthermore, the influence of immobilization on the absorption spectra of Lhc was studied using UV-Vis spectroscopy. Figure 4: UV-Vis spectra of free and immobilized light- harvesting complex REFERENCES Two novel silica gels were synthesized with the sol-gel method under biocompatible conditions. Furthermore, PCAs like chlorophyllin and a Lhc were successfully entrapped into these silica gels resulting in improved photostability of both PCAs. Finally the Lhc showed no difference in absorption spectra after gelling indicating that the protein-pigment structure remains unchanged in the gel. [1] J. Rooke, C. Meunier, A. Leonard, and B. Su (2008) Energy from photobioreactors: Bioencapsulation of photosynthetically active molecules, organelles, and whole cells within biologically inert matrices, Pure and applied Chemistry, vol. 80, Nr. 11, pp. 2345-2376 [2] Liu Z. et al (2004) Crystal structure of spinach major light-harvesting complex at 2.72 Å resolution, Nature 428, pp. 287-292 C. Mueller, M. Hanitzsch, A. Patel University of Applied Sciences-Engineering and Alternative Fuels - Bielefeld, Germany Wilhelm-Bertelsmann-Str. 10 - D-33602 Bielefeld (+49 521 106-7318, 4+49 521 106-7152, : [email protected] - www.fh-bielefeld.de A B Figure 1: Model structure of light- harvesting complex, PDB ID: 1RWT [2] CONCLUSION
Transcript of IMMOBILIZATION OF PHOTOSYNTHETICALLY ACTIVE …
IMMOBILIZATION OF
PHOTOSYNTHETICALLY ACTIVE COMPONENTS
WITHIN A NOVEL SILICA GEL
Photosynthetically active components (PAC) can absorb light and transfer energy. All eucaryotic cells using photosynthesis contain
light-harvesting complexes (Lhc) to optimize light utilization. The Lhc is a protein-pigment complex containing different pigments like
chlorophyll a/b and carotenoids, Figure 1. However, PACs are extremely unstable and need to be stabilized outside of the cell in order
to use these highly effective components in third generation photovoltaics and artificial photosynthesis, respectively [1]. In this work we
present two novel silica gels to stabilize chlorophyllin as a model substance as well as a Lhc isolated from Chlamydomonas reinhardtii .
INTRODUCTION
RESULTS
Silica gels for immobilization
For immobilization (entrapment) of PACs two
novel silica gels were synthesized using the
sol-gel method. A mixture of 5-25 % novel
precursor (obtained from Edwin Kroke, TU
Bergakademie Freiberg) and demineralized
water first formed a liquid sol and subsequently
a transparent gel. Both gels can be produced
under biocompatible conditions (e.g. room
temperature) and without toxic by-products
(like methanol or ethanol). Depending on the
requirements of the PACs the properties of the
silica gels were adjusted. The two resulting
gels differ in viscosity and gelling time. Gel 1
has higher viscosity (
) than gel 2 (
), gelling times were 2 h and 10 min for
gel 1 and gel 2, respectively. The model
substance chlorophyllin was entrapped in gel 1
and the Lhc (obtained from Olaf Kruse,
University Bielefeld) was entrapped in gel 2,
Figure 2.
52070 x 10 Pa s at shear
-1rate 0,1 s 4740 Pa s at shear rate
-10,1 s
Influence of light exposure on the photostability of PACs
Figure 2: Two novel silica gels containing photosynthetically active components
(A) gel 1 and (B) gel 2
The influence of light exposure on the stability
of PACs was studied using UV-Vis
spectroscopy at specific wavelengths
(chlorophyllin: 640 nm, Lhc: 671 nm).
Light absorption of free chlorophyllin and free
Lhc was reduced by 29 % and 62 % after 2 h,
respectively. After entrapment of chlorophyllin,
the light absorption was reduced by 10 % after
2 h. Entrapment of Lhc resulted in absorption
reduced by 51 % after 2 h, Figure 3.
These results indicate a stabilizing effect of the
novel silica gels.
Figure 3: The absorption of free and immobilized chlorophyllin (640 nm) and light-harvesting complex
(671 nm) as a function of time
Free Lhc has typically absorbance maxima at
430 nm-470 nm (carotenoids) and 650 nm-
671 nm (chlorophyll a/b), corresponding to the
different pigments bound to the complex,
Figure 4.
Immobilized Lhc showed no change of
absorbance maxima after the gel formation.
This indicates that the protein-pigment
structure remains unchanged in the gel
directly after immobilization.
Furthermore, the influence of immobilization
on the absorption spectra of Lhc was studied
using UV-Vis spectroscopy.
Figure 4: UV-Vis spectra of free and immobilized light-harvesting complex
REFERENCES
Two novel silica gels were synthesized with the sol-gel method under biocompatible conditions. Furthermore, PCAs like chlorophyllin and a Lhc were
successfully entrapped into these silica gels resulting in improved photostability of both PCAs. Finally the Lhc showed no difference in absorption spectra
after gelling indicating that the protein-pigment structure remains unchanged in the gel.
[1] J. Rooke, C. Meunier, A. Leonard, and B. Su (2008) Energy from photobioreactors: Bioencapsulation of photosynthetically active molecules, organelles, and
whole cells within biologically inert matrices, Pure and applied Chemistry, vol. 80, Nr. 11, pp. 2345-2376
[2] Liu Z. et al (2004) Crystal structure of spinach major light-harvesting complex at 2.72 Å resolution, Nature 428, pp. 287-292
C. Mueller, M. Hanitzsch, A. Patel
University of Applied Sciences-Engineering and Alternative Fuels - Bielefeld, Germany Wilhelm-Bertelsmann-Str. 10 - D-33602 Bielefeld (+49 521 106-7318, 4+49 521 106-7152, : [email protected] - www.fh-bielefeld.de
A B
Figure 1: Model structure of light-
harvesting complex, PDB ID: 1RWT [2]
CONCLUSION
