TY - JOUR A1 - Lokstein, Heiko A1 - Krikunova, Maria A1 - Teuchner, Klaus A1 - Voigt, Bernd T1 - Elucidation of structure-function relationships in photosynthetic light-harvesting antenna complexes by non-linear polarization spectroscopy in the frequency domain (NLPF) JF - Journal of plant physiology : biochemistry, physiology, molecular biology and biotechnology of plants N2 - Photosynthetically active pigments are usually organized into pigment-protein complexes. These include light-harvesting antenna complexes (LHCs) and reaction centers. Site energies of the bound pigments are determined by interactions with their environment, i.e., by pigment-protein as well as pigment-pigment interactions. Thus, resolution of spectral substructures of the pigment-protein complexes may provide valuable insight into structure-function relationships. By means of conventional (linear) and time-resolved spectroscopic techniques, however, it is often difficult to resolve the spectral substructures of complex pigment-protein assemblies. Nonlinear polarization spectroscopy in the frequency domain (NLPF) is shown to be a valuable technique in this regard. Based on initial experimental work with purple bacterial antenna complexes as well as model systems NLPF has been extended to analyse the substructure(s) of very complex spectra, including analyses of interactions between chlorophylls and "optically dark" states of carotenoids in LHCs. The paper reviews previous work and outlines perspectives regarding the application of NLPF spectroscopy to disentangle structure-function relationships in pigment-protein complexes. KW - Excitonic interactions KW - Laser spectroscopy KW - Light-harvesting complex KW - Nonlinear polarization spectroscopy in the frequency domain KW - Pigment-pigment interactions Y1 - 2011 U6 - https://doi.org/10.1016/j.jplph.2010.12.012 SN - 0176-1617 VL - 168 IS - 12 SP - 1488 EP - 1496 PB - Elsevier CY - Jena ER - TY - JOUR A1 - Vladkova, Radka A1 - Koynova, Rumiana A1 - Teuchner, Klaus A1 - Tenchov, Boris T1 - Bilayer structural destabilization by low amounts of chlorophyll a N2 - The present study shows that small admixtures of one chlorophyll a (Chla) molecule per several hundred lipid molecules have strong destabilizing effect on lipid bilayers. This effect is clearly displayed in the properties of the L-alpha-H-II transformations and results from a Chla preference for the H-II relative to the L-alpha phase. Chla disfavors the lamellar liquid crystalline phase L-alpha and induces its replacement with inverted hexagonal phase H-II, as is consistently demonstrated by DSC and X-ray diffraction measurements on phosphatidylethanolamine (PE) dispersions. Chla lowers the L-alpha-H-II transition temperature (42 degrees C) of the fully hydrated dipalmitoleoyl PE (DPoPE) by similar to 8 degrees C and similar to 17 degrees C at Chla/DPoPE molar ratios of 1:500 and 1:100, respectively. Similar Chla effect was recorded also for dielaidoyl PE dispersions. The lowering of the transition temperature and the accompanying significant loss of transition cooperativity reflect the Chla repartitioning and preference for the H-II phase. The reduction of the H-II phase lattice constant in the presence of Chla is an indication that Chla favors v phase formation by decreasing the radius of spontaneous monolayer curvature, and not by filling up the interstitial spaces between the H-II phase cylinders. The observed Chla preference for H-II phase and the substantial bilayer destabilization in the vicinity of a bilayer-to-nonbilayer phase transformation caused by low Chla concentrations can be of interest as a potential regulatory or membrane-damaging factor. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00052736 U6 - https://doi.org/10.1016/j.bbamem.2010.05.008 SN - 0005-2736 ER - TY - JOUR A1 - Schneider, M. A1 - Teuchner, Klaus A1 - Leupold, Dieter T1 - Two-photon fluorescence of ocular melanomas. Studies on a new diagnostic method N2 - Choroidal melanoma is the most frequent form of primary neoplasia among malignant ocular tumors. Since it is presumed that metastasis often occurs before the primary tumor is first diagnosed, early detection is exigent. The aim of the studies described in this report was to develop an objective, noninvasive method for the diagnosis of choroidal melanoma. The underlying new principle of fluorescence excitation is presented. This is based on the observation that melanin, due to its unique absorption characteristics, is selectively excited into fluorescence via stepwise absorption of two photons of a femtosecond laser emitting at 800 nm. In the experiment described, the fluorescence of excised tissue from healthy choroidal pigment epithelium was compared to that of excised choroidal melanoma. The fluorescence of choroidal melanomas exhibited a more reddish appearance and less intensity than that of healthy tissue. This implies that the configuration of melanin apparently changes during the process of malignant degeneration. The method described here could thus serve as an evidentiary objective diagnostic technique before initiating treatment for choroidal melanomas Y1 - 2005 SN - 0941-293X ER -