Studying nonlinear optical properties of the plant light harvesting protein LHCII [Elektronische Ressource] / von Axel Schubert

Axel Schubert

Sujets

• Biologie

Informations

• Publié par: humboldt-universitat_zu_berlin
• Publié le: 01 janvier 2004
• Nombre de lectures: 23
• Langue: English
• Poids de l'ouvrage: 10 Mo

Extrait

Studying nonlinear optical properties of
the plant light-harvesting protein LHCII
DISSERTATION
Zur Erlangung des akademischen Grades
doctor rerum naturalium
(Dr. rer. nat.)

im Fach Biophysik

eingereicht an der
Mathematisch-Naturwissenschaftlichen Fakultät I
der Humboldt-Universität zu Berlin

von
Diplom-Physiker Axel Schubert
geboren am 15.03.1970 in Jena
Präsident der Humboldt-Universität zu Berlin
Prof. Dr. Jürgen Mlynek
Dekan der Mathematisch-Naturwissenschaftlichen Fakultät
Prof. Dr. Michael Linscheid

Gutachter: 1. Prof. Dr. Bernhard Grimm, HU Berlin
2. Dr. sc. nat. Dieter Leupold, MBI Berlin
3. Prof. Dr. Gernot Renger, TU Berlin

Tag der mündlichen Prüfung: 08.03.2004






































In memoriam to my grandfather,

Prof. Dr. Alfred Schubert (1915-2000).










‘Der vollkommene Weltmann wäre der,
welcher nie in Unschlüssigkeit stockte
und nie in Übereilung geriete.’

Arthur Schopenhauer


Preface V
Preface
The thesis on hand was realized in the framework of two successive research projects
(Ho 1757/2-1 and Ho 1757/2-2) financed by the DFG. Both projects extended a long-
standing collaboration between Prof. Paul Hoffmann, Chair for Plant Physiology at
Humboldt-University Berlin, and Dr. Dieter Leupold, Max-Born Institute for Nonlinear
Optics and Short-Pulse Spectroscopy Berlin. This co-operation is currently continued
under the roof of SFB 429, including the participation of Dr. Heiko Lokstein and Prof.
Bernhard Grimm (successor at the Chair for Plant Physiology). The unique combination
of nonlinear optics and plant biology apparently embeds my studies into the present
merging process between life sciences and applied physics. In spite of its high
synergistic potential, these two research fields are still confronted by distinct background
education, working methods and specialist terms. Accordingly, the presented work was
especially shaped to reflect proper gearing between both sciences. Physical as well as
biological issues with relevance for following discussions are thus explained in the
introduction section. In particular, the biological system of key interest is described by
an adequate physical model in Chapter 1.2.
The central objective of my thesis can be outlined as investigation of an intricate
pigment-containing protein by using newly introduced laser-spectroscopic techniques.
More precisely, the main light-harvesting complex of the higher plants (LHCII) is
primarily studied by nonlinear polarization spectroscopy in the frequency domain
(NLPF, see Chapter 2.2). These measurements were aimed to improve the interpretation
of biological function in terms of physical mechanisms. The combined complexity of
both investigated object and experimental method required comprehensible illustrations
of their mutual interaction. This problem is addressed by simulating the nonlinear
response of several heterogeneous, LHCII-like systems in NLPF experiments (see
Chapter 3.1). In this way, direct ‘by-eye’ verification of the parameter influence on
measured NLPF spectra is enabled. Accordingly, this approach facilitates intuitive
understanding of the experimental results obtained for LHCII without knowing
underlying physical principles in detail.
Strong sensitivity of the NLPF method to numerous physical parameters of LHCII
complicated model improvements by ‘just’ fitting measured NLPF spectra. In other
words, significant modeling was hard to achieve without knowledge about at least one
part of the relevant parameter space. For that reason, all available supplementary
information about molecular parameters of LHCII has been carefully summarized and
further extended by own experiments. Basic absorption parameters were thus determined
from reconstituted mutant samples of LHCII in co-operation with biochemists from the
group of Prof. Werner Kühlbrandt, MPI Frankfurt (see Chapter 3.2). Moreover, the
application of two other nonlinear laser spectroscopic techniques yielded valuable
information about electronic interactions within the light-harvesting complex (see
Chapter 3.3 and 3.4). These additionally determined parameters enabled finally
improvements for the parameter model of LHCII by evaluating measured NLPF spectra
in Chapter 3.5. The relevance of obtained information for understanding biological
VI Preface
functionality within the photosynthetic apparatus is conclusively drawn in Chapter 4.
This section summarizes also achieved experimental and model developments from the
physical point of view.
As outlined above, the presented thesis combines different experimental methods
from the fields of physics and biology. Accordingly, an intense integration of my studies
into the work of other collaborators became necessary. These co-operations represented
in the end an inevitable basis for successful completion of the whole research project.
Nevertheless, an exact distinction between contributions from the author and other co-
workers to the results published in this thesis is strongly required. For that reason, each
chapter in the results and discussion section explicitly lists any additional aid from other
scientists.

Preface VII

The work presented in this thesis is partially published in the following papers:
A. Schubert, B. Voigt, D. Leupold, W. Beenken, J. Ehlert, P. Hoffmann, and H.
Lokstein (1997) ‘Direct observation of spectral substructure in the Q -absorption band of y
light-harvesting complex II by nonlinear polarization spectroscopy in the frequency
domain at low temperature’ Biochim. Biophys. Acta, 1321, 195-199.
A. Schubert, A., M.A. Krikunova, H. Stiel, J. Ehlert, D. Leupold, and H. Lokstein
(1998) ‘Determination of the aggregate size in chlorophyll a oligomers by nonlinear
absorption spectroscopy on the ps and fs timescale’ in: Photosynthesis: Mechanisms and
Effects, Vol. I., G. Garab (Editor), Kluwer, Dordrecht, 469-472.
A. Schubert, W. Beenken, H. Stiel, D. Leupold and H. Lokstein, (2002) ‘Excitonic
coupling of chlorophylls in the plant light-harvesting complex LHC-II’ Biophys. J., 82,
1030-1039.
H. Rogl, R. Schödel, H. Lokstein, W. Kühlbrandt and A. Schubert (2002)
‘Assignment of spectral substructures to pigment-binding sites in higher plant light-
harvesting complex LHCII’ Biochemistry, 41, 2281-2287.
A. Schubert, B. Voigt, W.J.D. Beenken, J. Ehlert, D. Leupold, and H. Lokstein
‘Energy equilibration in the plant light-harvesting complex LHCII studied by nonlinear
polarization spectroscopy’ manuscript in preparation.


Further relevant publications including contributions from the author:
C. Tietz, F. Jelezko, U. Gerken, S. Schuler, A. Schubert, H. Rogl, and J. Wachtrup
(2001) ‘Single molecule spectroscopy on the light harvesting complex II of higher
plants’ Biophys. J., 81, 556-562.
H. Lokstein, B. Voigt, A. Schubert, M. Krikunova, W. Beenken, K. Teuchner, J.
Ehlert, K.-D. Irrgang, G. Renger, D. Leupold. (2001) ‘Spectral substructure and
excitonic interactions in the plant antenna complexes LHC II and CP29 as revealed by
nonlinear laser spectroscopy’ Proceedings of the 12th International Congress on
Photosynthesis, Brisbane, Australia, CSIRO Publishing.
H. Lokstein, A. Schubert, B. Voigt, and D. Leupold (1998) ‘Direct resolution of
spectral fine-structure and ultrafast exciton dynamics in light-harvesting complex II by
nonlinear polarization spectroscopy in the frequency domain’ in: Photosynthesis:
Mechanisms and Effects, Vol. I., G. Garab, editor, Kluwer, Dordrecht. 293-296.

VIII Abstract and keywords
Zusammenfassung
Ultraschnelle Energietransferprozesse zwischen den Anregungszuständen organischer
Pigmentmoleküle in photosynthetischen Lichtsammelkomplexen gehören zu den
schnellsten bisher untersuchten biologischen Ereignissen. Diese Vorgänge wurden
insbesondere auch für den Haupt-Antennenkomplex der höheren Pflanzen (LHCII)
beobachtet, der mehr als die Hälfte des pflanzlichen Chlorophylls (Chl) bindet (5 Chl b
und 7 Chl a pro Monomer). Offenbar ist dieser Pigment-Protein-Komplex entscheidend
für Regulationsmechanismen verantwortlich, die eine schnelle Adaptation des Photo-
syntheseapparats an wechselnde Belichtungsbedingungen ermöglichen. Die Struktur von
LHCII ist mit einer Auflösung von 3.4 Å bekannt und erlaubt (im Prinzip) die
Berechnung des Anregungsenergietransfers auf der Basis eines Förster-Mechanismus. In
diesem Zusammenhang gibt es jedoch noch zahlreiche ungeklärte Fragen, die vor allem
die Orientierung der Pigmente zueinander sowie deren mögliche starke (exzitonische)
Wechselwirkung betreffen. Allerdings sind konventionelle spektroskopische Methoden
nicht geeignet, diese Merkmale ausreichend aufzuklären. Aus diesem Grund wird in
dieser Arbeit unt