TY - JOUR
T1 - Spectral Properties of Bacteriochlorophyll c in Organisms and in Model Systems
AU - Goc, Jacek
AU - Dudkowiak, Alina
AU - Gryczyński, Zygmunt
AU - Gryczyński, Ignacy
AU - Zelent, Bogumil
AU - Fra̧ckowiak, Danuta
N1 - Funding Information:
Z. Gryczyński, I. Gryczyński, and B. Zelent were supported by NIH, National Center for Research resources (RR-08119). D. Fra¸ckowiak, J. Goc, and A. Dudkowiak were supported by Polish KBN Grant 6 PO4A 010 17.
PY - 2001
Y1 - 2001
N2 - Polarized absorption and fluorescence spectra of bacteriochlorophyll c and green photosynthetic bacterium Prostheecochloris aestuarii cells and cell fragments embedded in stretched polymer film were measured. In pigment samples the artificial oligomers of bacteriochlorophyll c (with absorption about 750 nm) and other forms of this pigment and bacteriopheophytin (with absorption at 670 nm) were present. In bacteria samples, embedded in polymer, oligomers were in high degree disaggregated and as a result the absorption about 670 nm was observed. Previously for similar sets of samples the decay of fluorescence excited only at one wavelength was analyzed on three exponential components, but exact lifetime values of these components for various samples were different. The aim of present paper was to check if these differences occur because of various contributions to decay from three well defined forms or if they were related to the existence of several pigment forms with slightly different lifetimes. The global analysis of data obtained for various excitation and observation wavelengths of fluorescence were done. From this analysis it follows that the second situation occurs. For a model system containing artificial oligomers the largest component of decay has a τ4 of about 0.183 ns or 0.136 ns depending on observation wavelength. For the bacteria sample, in which the emission at 680 nm is the superposition from various pigments, global analysis done for various excitation wavelengths shows also that the τ values differ depending on the regions of fluorescence observation. From polarized spectra, it follows that in the model system the pigments absorbing at 670 nm are randomly distributed whereas oligomers are highly oriented. In bacteria fragments absorbing at 670 nm pigment molecules can be divided into two groups: one oriented along the axis of film stretching and the second practically randomly distributed. In living organisms, under some conditions, small amount of 670 nm pigments can be present and can work as excitation energy traps or as antenna transferring the excitation. Present results show that the role of various pools of 670 nm absorbing pigments can be different because of their differing orientation.
AB - Polarized absorption and fluorescence spectra of bacteriochlorophyll c and green photosynthetic bacterium Prostheecochloris aestuarii cells and cell fragments embedded in stretched polymer film were measured. In pigment samples the artificial oligomers of bacteriochlorophyll c (with absorption about 750 nm) and other forms of this pigment and bacteriopheophytin (with absorption at 670 nm) were present. In bacteria samples, embedded in polymer, oligomers were in high degree disaggregated and as a result the absorption about 670 nm was observed. Previously for similar sets of samples the decay of fluorescence excited only at one wavelength was analyzed on three exponential components, but exact lifetime values of these components for various samples were different. The aim of present paper was to check if these differences occur because of various contributions to decay from three well defined forms or if they were related to the existence of several pigment forms with slightly different lifetimes. The global analysis of data obtained for various excitation and observation wavelengths of fluorescence were done. From this analysis it follows that the second situation occurs. For a model system containing artificial oligomers the largest component of decay has a τ4 of about 0.183 ns or 0.136 ns depending on observation wavelength. For the bacteria sample, in which the emission at 680 nm is the superposition from various pigments, global analysis done for various excitation wavelengths shows also that the τ values differ depending on the regions of fluorescence observation. From polarized spectra, it follows that in the model system the pigments absorbing at 670 nm are randomly distributed whereas oligomers are highly oriented. In bacteria fragments absorbing at 670 nm pigment molecules can be divided into two groups: one oriented along the axis of film stretching and the second practically randomly distributed. In living organisms, under some conditions, small amount of 670 nm pigments can be present and can work as excitation energy traps or as antenna transferring the excitation. Present results show that the role of various pools of 670 nm absorbing pigments can be different because of their differing orientation.
KW - Bacteriochlorophyll c
KW - Green bacteria
KW - Lifetime of fluorescence
KW - Oligomers of bacteriochlorophyll c
KW - Polarized spectroscopy
KW - Polymer films
UR - http://www.scopus.com/inward/record.url?scp=0043283844&partnerID=8YFLogxK
U2 - 10.1023/A:1016699616249
DO - 10.1023/A:1016699616249
M3 - Article
AN - SCOPUS:0043283844
SN - 1053-0509
VL - 11
SP - 53
EP - 63
JO - Journal of Fluorescence
JF - Journal of Fluorescence
IS - 1
ER -