by Î. Robert, A. Vermeglio, R. Steiner, Î. Scheer and Î. Lutz. 355 ... by R. van Grondelle, H. Bergström, V. Sundström, R.J. van Dorssen,. M. Vos and C.N. ...
Photosynthetic Light-Harvesting Systems Organization and Function
Proceedings of an International Workshop October 12-16,1987 Freising, Fed Rep. of Germany Editors Hugo Scheer · Siegfried Schneider
W G Walter de Gruyter · Berlin · New York 1988 DE
CONTENTS
List of Participants SECTION I .
XIII
ORGANIZATION: BIOCHEMICAL METHODS
I n t r o d u c t i o n : The B i o c h e m i s t r y o f L i g h t - H a r v e s t i n g Complexes by R.J. Cogdell
1
P h y c o b i l i s o m e - T h y l a k o i d I n t e r a c t i o n : The Nature o f High M o l e c u l a r Weight P o l y p e p t i d e s by E. Gantt C.A. L i p s c h u l t z and F.X. Cunningham J r
11
On t h e S t r u c t u r e o f Photosystem I I - P h y c o b i l i s o m e Complexes o f Cyanobacteria by E. Mörschel and G.-H. Schatz
21
S t r u c t u r e o f C r y p t o p h y t e P h o t o s y n t h e t i c Membranes by W. Wehrmeyer
35
S t r u c t u r a l and P h y l o g e n e t i c R e l a t i o n s h i p s o f P h y c o e r y t h r i n s from C y a n o b a c t e r i a , Red Algae and Cryptophyceae by W. S i d l e r and H. Zuber
49
I s o l a t i o n and C h a r a c t e r i z a t i o n o f t h e Components o f t h e Phycobilisome f r o m M a s t i g o c l a d u s laminosus and Crossl i n k i n g Experiments by R. Rümbeli and H. Zuber
61
C-Phycocyanin f r o m M a s t i g o c l a d u s laminosus: Chromophore Assignment i n Higher Aggregates by C y s t e i n M o d i f i c a t i o n by R. F i s c h e r , S. S i e b z e h n r l i b l and H. Scheer
71
Photochromic P r o p e r t i e s o f C-Phycocyanin by G. Schmidt, S. Siebzehnrübl, R. F i s c h e r and H. Scheer
77
Concerning t h e R e l a t i o n s h i p o f L i g h t H a r v e s t i n g B i l i p r o t e i n s t o Phycochromes i n Cyanobacteria by W. K u f e r
89
Subunit S t r u c t u r e and Reassembly o f t h e L i g h t - H a r v e s t i n g Complex f r o m R h o d o s p i r i Hum rubrum G9+ by R. Ghosh, ThT~Rosatzin ancTR. B a c l o f e n
93
Primary S t r u c t u r e Analyses o f B a c t e r i a l Antenna P o l y p e p t i d e s - C o r r e l a t i o n o f Aromatic Amino Acids w i t h S p e c t r a l P r o p e r t i e s - S t r u c t u r a l S i m i l a r i t i e s w i t h Reaction Center Polypeptides by R.A. B r u n i s h o l z and H. Zuber
103
VIII The
S t r u c t u r e o f t h e "Core * o f t h e P u r p l e B a c t e r i a l synthetic Unit by D.J. Dawkins, L.A. Ferguson and R.J. Cogdell 1
Photo115
A Comparison o f t h e B a c t e r i o c h l o r o p h y l 1 C--Binding P r o t e i n s o f Chlorobium and C h l o r o f l e x u s by P.D. G e r o l a , P. H p j r u p and J.M. Olson
129
I n t e r a c t i o n s between B a c t e r i o c h l o r o p h y l 1 c Molecules i n Oligomers and i n Chlorosomes o f Green P h o t o s y n t h e t i c Bacteria by D.C. Brune, G.H. King and R.E. B l a n k e n s h i p
141
L i g h t - H a r v e s t i n g Complexes o f C h l o r o p h y l l c - C o n t a i n i n g by A.W.D. Larkum and R.G. H i l l e r
Algae
I s o l a t i o n and C h a r a c t e r i z a t i o n o f a C h l o r o p h y l l a/c-Heterox a n t h i n / D i a d i n o x a n t h i n L i g h t - H a r v e s t i n g Complex f r o m P l e u r o c h l o r i s m e i r i n g e n s i s (Xanthophyceae) by C. W i l h e l m , C. Bliche I and B. Rousseau The
Antenna Components o f Photosystem I I w i t h Emphasis on t h e Major P i g m e n t - P r o t e i n , LHC l i b by G.F. Peter and P. Thornber
SECTION I I :
153
167
175
ORGANIZATION: MOLECULAR GENETICS AND CRYSTALLOGRAPHY
M o l e c u l a r B i o l o g y o f Antennas by G. Drews
187
H i g h - R e s o l u t i o n C r y s t a l S t r u c t u r e o f C-Phycocyanin and Polarized O p t i c a l Spectra o f Single C r y s t a l s by T. Schirmer, W. Bode and R. Huber
195
C r y s t a l l i z a t i o n and S p e c t r o s c o p i c I n v e s t i g a t i o n o f P u r p l e B a c t e r i a l B800-850 and RC-B875 Complexes by W. Welte, Τ. Wacker and A. Becker Structure of the Light-Harvesting Chlorophyll Complex from C h l o r o p l a s t Membranes by W. Kühlbrandt
201
a/b-Protein 211
P h y c o b i I i somes o f Synchechococcus Sp. PCC 7002, Pseudanabaena Sp. PCC 7409, and Cyanopnora paracioxa: An "Analysis by" HoTecular Genetics by D.A. Bryant
217
O r g a n i z a t i o n and Assembly o f B a c t e r i a l Antenna Complexes by G. Drews
233
IX The Use o f Mutants t o I n v e s t i g a t e t h e O r g a n i z a t i o n o f t h e P h o t o s y n t h e t i c Apparatus o f Rhodobacter sphaeroides by C.N. Hunter and R. van Grondel l e 77.77
247
Mechanisms o f P l a s t i d and Nuclear Gene Expression During T h y l a k o i d Membrane Biogenesis i n Higher P l a n t s by P. W e s t h o f f ,Η. Grüne, Η. Schrubar,Α. Oswald,Μ. S t r e u b e l , U. L j u n g b e r g and R.G. Herrmann
261
SECTION I I I :
ORGANIZATION: SPECIAL SPECTROSCOPY TECHNIQUES AND MODELS
Assigment o f S p e c t r a l Forms i n t h e P h o t o s y n t h e t i c Antennas t o C h e m i c a l l y D e f i n e d Chromophores by A. Scherz
277
L i n e a r D i c h r o i s m and O r i e n t a t i o n o f Pigments i n Phycobilisomes and t h e i r S u b u n i t s by L. Juszcak, N.E. Geacintov, B.A. Z i l i n s k a s and J. B r e t o n
281
Low Temperature Spectroscopy o f C y a n o b a c t e r i a ! Antenna Pigments by W. Köhler, J. F r i e d r i c h , R. F i s c h e r and H. Scheer
293
Chromophore Conformations i n Phycocyanin and A l l o p h y c o c y a n i n as S t u d i e d by Resonance Raman Spectroscopy by B. S z a l o n t a i , V. Csizmadia, Z. Gombos, K. Csatorday and M. L u t z
307
Coherent A n t i - S t o k e s Raman Spectroscopy o f Phycobi1isomes, Phycocyanin and A l l o p h y c o c y a n i n f r o m Mastigocladus laminosus by S. S c h n e i d e r , F. Baumann, W. S t e i n e r , R. F i s c h e r , S. S i e b z e h n r l i b l and H. Scheer
317
O p t i c a l A b s o r p t i o n and C i r c u l a r D i c h r o i s m o f B a c t e r i o c h l o r o p h y l 1 Oligomers i n T r i t o n X-100 and i n t h e Light-Harvesting-Complex B850; A Comparative Study by V. Rozenbach-Belkin, P. Braun, P. Kovatch and A.Scherz
323
A b s o r p t i o n Detected Magnetic Resonance i n Zero Magnetic F i e l d on Antenna Complexes f r o m Rps. a c i d o p h i l a 7050 - The Temperature Dependence o f tfie CarotenoTiTTrTpTet S t a t e Properties by J . U l l r i c h , J.U. v. Schütz and H.C. Wolf
339
E f f e c t o f L i t h i u m Dodecyl S u l f a t e onΒ 800-850 Antenna Complexes f r o m Rhodopseudomonas a c i d o p h i l a : A Resonance Raman Study by B. Robert and H. Frank
349
χ B a c t e r i o c h l o r o p h y l 1 a/b i n Antenna Complexes o f P u r p l e B a c t e r i a by Β. R o b e r t , A. V e r m e g l i o , R. S t e i n e r , Η. Scheer andΜ. Lutz
355
B a c t e r i o c h l o r o p h y l l c Aggregates i n Carbon T e t r a c h l o r i d e as Models f o r C h l o r o p h y l l O r g a n i z a t i o n i n Green Photosynthetic Bacteria by J.M. Olson and J.P. Pedersen
365
O r i e n t a t i o n o f t h e Pigments i n t h e Reaction Center and t h e Core Antenna o f Photosystem I I by J. B r e t o n , J. Duranton and K. Satoh
375
Non-Linear A b s o r p t i o n Spectroscopy o f Antenna C h l o r o p h y l l a i n Higher P l a n t s by D. L e u p o l d , H. S t i e l and P. Hoffmann
387
SECTION I V :
FUNCTION: ELECTRONIC EXCITATION AND ENERGY TRANSFER
E x c i t a t i o n Energy T r a n s f e r i n P h o t o s y n t h e s i s by R. van G r o n d e l l e and V. Sundström
403
Fluorescence Spectroscopy o f A l l o p h y c o c y a n i n Complexes f r o m Synechococcus 6301 S t r a i n AN112 by P.Maxson, K T T a u e r and A.N. Glazer
439
Picosecond Energy T r a n s f e r K i n e t i c s i n A l l o p h y c o c y a n i n Aggregates f r o m M a s t i g o c l a d u s laminosus by E. B i t t e r s m a n n , W. Reuter, W. Wehrmeyer and A.R. Holzwarth
451
Picosecond Time-Resolved Energy T r a n s f e r K i n e t i c s w i t h i n C-Phycocyanin and A l l o p h y c o c y a n i n Aggregates by T. G i l l b r o , A. Sandström, V. Sundström, R. F i s c h e r and H. Scheer
457
Energy T r a n s f e r i n " N a t i v e " and C h e m i c a l l y M o d i f i e d C-Phycoc y a n i n T r i m e r s and t h e C o n s t i t u e n t Subunits by S. S c h n e i d e r , P. G e i s e l h a r t , F. Baumann, S. Siebzehnrübl, R. F i s c h e r andΗ. Scheer
469
E f f e c t o f P r o t e i n Environment and E x c i t o n i c Coupling on t h e Excited-State P r o p e r t i e s o f t h e Bilinchromophores i n C-Phycocyanin by S. S c h n e i d e r , Ch. S c h a r n a g l , M. Dürring, T. Schirmer and W. Bode
483
E x c i t a t i o n Energy M i g r a t i o n i n C-Phycocyanin Aggregates I s o l a t e d f r o m Phormidium l u r i d u m : P r e d i c t i o n s f r o m t h e Förster's I n d u c t i v e Resonance Theory by J. Grabowski and G.S. Björn
491
XI
Energy T r a n s f e r C a l c u l a t i o n s f o r two C-Phycocyanins Based on R e f i n e d X-Ray C r y s t a l S t r u c t u r e C o o r d i n a t e s of Chromophores by K. Sauer and H. Scheer
507
Energy T r a n s f e r i n L i g h t - H a r v e s t i n g Antenna o f Purple B a c t e r i a S t u d i e d by Picosecond Spectroscopy by V. Sundström, H. Bergström, Τ. G i l l b r o , R. van G r o n d e l l e , W. W e s t e r h u i s , R.A. Niederman and R.J. Cogdell
513
E x c i t a t i o n Energy T r a n s f e r i n t h e L i g h t - H a r v e s t i n g Antenna o f P h o t o s y n t h e t i c P u r p l e B a c t e r i a : The Role o f t h e Long-WaveLength A b s o r b i n g Pigment B896 by R. van G r o n d e l l e , H. Bergström, V. Sundström, R.J. van Dorssen, M. Vos and C.N. Hunter
519
The F u n c t i o n o f Chlorosomes i n Energy T r a n s f e r i n Green P h o t o synthetic Bacteria by R.J. van Dorssen, M. Vos and J. Amesz
531
Energy T r a n s f e r i n C h l o r o f l e x u s a u r a n t i a c u s : E f f e c t s o f Temperature and T S a e r o b i c ^ o n ö n H o n s by B.P. W i t t m e r s h a u s , D.C. Brune and R.E. Blankenship
543
I n t e r p r e t a t i o n o f Optical Spectra o f Bacteriochlorophyl 1 Antenna Complexes by R.M. P e a r l s t e i n
555
Time R e s o l u t i o n and K i n e t i c s o f "F680" a t Low Temperatures i n Spinach C h l o r o p l a s t s by R. Knox and S. L i n
567
Picosecond S t u d i e s o f Fluorescence and Absorbance Changes i n Photosystem I I P a r t i c l e s f r o m Synechococcus Sp. by A.R. H o l z w a r t h , G.H. Schatz and H. Brock
579
A n a l y s i s o f E x c i t a t i o n Energy T r a n s f e r i n T h y l a k o i d Membranes by t h e Time-Resolved F l u o r e s c e n c e Spectra by M. Mimuro
589
V. CONCLUDING REMARKS F u t u r e Problems on Antenna Systems and Summary Remarks by E. Gantt
601
Author Index
605
S u b j e c t Index
609
EFFECT OF PROTEIN ENVIRONMENT AND EXCITONIC COUPLING ON THE EXCITED-STATE PROPERTIES OF THE ΒILINCHROMOPHORES I N C-PHYCOCYANIN
S. S c h n e i d e r , Ch.Scharnag 1 I n s t i t u t für P h y s i k a l i s c h e und T h e o r e t i s c h e Chemie d e r T e c h n i s c h e n Universität München, D-8046 G a r c h i n g M. D u e r r i n g ,
T. S c h i r m e r , W.
Max-Planck-Institut
Bode
für B i o c h e m i e , D-8033 M a r t i n s r i e d
Introduction C - P h y c o c y a n i n (C-PC), one o f t h e l i g h t - h a r v e s t i n g p i g m e n t s o f cyanobacteria, former
chromophores apoprotein The
i s composed o f
contains
one,
(phycocyanobi1 i n ) ,
geometries
and
have r e c e n t l y
that
individual
a
absorption
and
0. The
tetrayrrole
bound
to
the
(1)). of
the three
Mastigocladus
laminosus
sequencing
(2) and
( 3 a , b , c ) . The
crystal
similiarity
spectroscopic,
Lately
bands
of
by p e p t i d e
strong
p r o p e r t i e s must be m a i n l y surroundings.
α
environments
X-ray c r y s t a l l o g r a p h y
displays
different
(see e.g.
phycocyanin
been d e t e r m i n e d
high resolution
subunits, covalently
v i a t h i o e t h e r linkages
chromophores i n t h e
structure
two
t h e l a t t e r two o p e n - c h a i n
o f g e o m e t r i e s , so
biochemical
and
functional
a t t r i b u t e d t o the d i f f e r e n t protein
i t has (maxima)
been to
possible
the
to
different
assign the phycocyanin
chromophores u n a m b i g u o u s l y i n t h e f o l l o w i n g manner
(4,5):
A84:
A max i a b s ) = 616 - 618 nm (4)
618 nm (5)
B84:
622 - 624 nm (4)
624 - 632 nm (5)
B155:
598 - 600 nm (4)
m
594 - 598 nm (5) 582 - 598 nm
Photosynthetic Light-Harvesting Systems © 1988 Walter de Gruyter & Co., Berlin · New York
(5,CD)
484 CD-spectroscopy elucidate
the
t i v e probe the
is
an
source
e f f e c t of p r o t e i n - c h r o m o p h o r e and
mechanical
the
model
to
information a
and get
studied
in
by means of
order
to
quantum
improve
our
c o n t r i b u t i o n of these i n t e r a c t i o n s t o
functional properties an
to
sensi
chromophore-chromophore
chiroptic properties
calculations,
knowledge about the spectral
of
chromophores and
t o n o n c o v a l e n t i n t e r a c t i o n s . T h e r e f o r e we
i n t e r a c t i o n s on
and
important
c o n f o r m a t i o n of b i l i n
e s t i m a t e of
the
of t h e
the
phycobi1inproteins
significance
of t h e s e
inter
actions .
Methods Our
calculations
are based on
f o r chromophore and result
from
standard
a
protein
of s i n g l y e x c i t e d redshift
and
lated without The
and
and
6
in
tion potential
(PPP)
with
occupied,
6
(CI)
virtual
l e a d s t o a 10 t o 15 the
other
and
calcu
(6a,6b,7). t r e a t e d as
one
a l l i n t e r a c t i o n s b e t w e e n perma included.
Polar
l y i n g i n a sphere w i t h
10
A
were t a k e n i n t o a c c o u n t . s i m u l a t e d by v a r y i n g
the
effective ioniza
( I P ' ) of t h e h e t e r o a t o m s i n c e a w i t h d r a w a l
the hydrogen from a center to
pyrrole nitrogen f r o m 19.6
IP' midway
and
pyridine
n i t r o g e n ) . The
are
given elsewhere
(6,7).
eV
of
causes t h e i r - e l e c t r o n s
de l o c a l i z e more e a s i l y . The
changed a c c o r d i n g l y
(strong bonding,
nm
calculated
f - v a l u e s are
s u r r o u n d i n g s are
amino a c i d r e s i d u e s
Hydrogen bonds are
was
their
Therefore,
a r o u n d CIO
X-ray d a t a
interaction
t r a n s i t i o n charge d i s t r i b u t i o n s are
aromatic
of t h i s
variations
f u r t h e r approximations
chromophores
radius
(Cl-basis:
rotatory strengths
"supermolecule". n e n t and
calculation
configuration
a larger Cl-basis
small
p r o p e r t i e s ) . The
model and
states
molecular o r b i t a l s ;
high-resolution
(3c). Approximative wavefunctions
ττ-electron
parametrisation
the
parameter
(no b o n d i n g )
between t h e v a l u e s of
t o 16.5
values f o r a l l other
IP' eV
pyrrole
parameters
485 Results Single
and D i s c u s s i o n Chromophores
Figures
1
and
2
show
the variations
of
the absorption
w a v e l e n g t h and r o t a t o r y s t r e n g t h R o f t h e r e d band o f B84 and B155,
respectively,
We r e s t r i c t separated
due t o c h r o m o p h o r e - p r o t e i n
our discussion from
other
to this
interactions.
band because
transitions
and
i t i swell
therefore easier t o
a n a l y s e - t h e o r e t i c a l l y as w e l l as e x p e r i m e n t a l l y . Case Case
I : i s o l a t e d chromophore, n e g l e c t i n g a l l s i d e II:
I + p r o p i o n i c a c i d side chains
Case I I I :
I I + a s p a r t a t e r e s i d u e n e a r p y r r o l e r i n g s Β and C (B87
Case
IV: I I I
and B39, r e s p e c t i v e l y )
+ residues
o f p o l a r amino a c i d s n e a r t h e
propionic side Case
chains
a t t a c h e d t o C8 + C12
chains
V: IV + a l l p o l a r and a r o m a t i c
residues
i n a sphere of
10 A a r o u n d CIO Case
V I : V + amide g r o u p s o f t h e p r o t e i n backbone w i t h i n t h e same s p h e r e ( i n b r a c k e t s )
The c a l c u l a t e d t r a n s i t i o n e n e r g i e s phores ( I )
a r e around
hypsochromic (6a,6b,7),
shift, is
o r below when
compared
the significant
g e o m e t r y . Coulombic i n t e r a c t i o n first
order
energies
f o rthe
perturbation
(bathochromic
to
CI-wavefunctions
and
a
planar
effects
the
transition
o r b i t a l s . The r o t a t o r y
t h e concomitant
coefficients modified
i n the
mixing
of
and m a g n e t i c t r a n s i t i o n moments.
Inclusion of the carboxylate
groups only
chains
tautomerism
( I I ) exhibits i s f i x e d by
of
the propionic acid
small e f f e c t s
the interaction
(the proton
w i t h adjacent
amino
(3c) ) .
B o t h chromophores A84)
calculations
from
because o f t h e d i f f e r e n t
o f changed
side acids
chromo
( s t a t i c c o u p l i n g i n terms of
theory)
s t a b i l i z a t i o n of t h e v a r i o u s molecular
electric
prior
deviation
s h i f t ) mainly
s t r e n g t h i s a l t e r e d because
isolated
550 nm. The o r i g i n f o r t h i s
(as w e l l
as t h e t h i r d ,
not displayed, at
show a common p r i n c i p l e o f i n t e r a c t i o n w i t h t h e p r o t e i n .
486
Figure
1: C a l c u l a t e d r o t a t o r y s t r e n g t h R o f t h e longwavel e n g t h a b s o r p t i o n band o f t h e B84 chromophore (1 DBM=0.93 10 c g s ; case I t o V I : see t e x t ) . The shaded r e g i o n s show t h e s p e c t r a l v a r i a t i o n s w i t h t h e tautomerism of t h e a r g i n i n e groups: a) B80 as shown b) t a u t o m e r i c f o r m 1) B79 and B86 as shown 2) t a u t o m e r i c f o r m
487
F i g u r e 2: C a l c u l a t e d r o t a t o r y s t r e n g t h R o f t h e longwavel e n g t h a b s o r p t i o n band o f t h e B155 chromophore. The shaded a r e a r e f l e c t s t h e b a t h o c h r o m i c s h i f t c a l c u l a t e d f o r an i n c r e a s i n g o f t h e h y d r o g e n bond s t r e n g t h t o t h e B39 a s p a r t a t e r e s i d u e , a) N23-H-tautomer b) N22-H-tautomer
488 They a r c h
a r o u n d an
aspartate residue
t h e n i t r o g e n s of p y r r o l e r i n g s Β w i t h i n hydrogen oxygens. T h i s
and
bonding d i s t a n c e
(B87
C
and B39,
(N22
o f one
and
resp.),
N23)
of t h e
being
carboxylate
i n t e r a c t i o n dominates the wavelength
adjustment
(III) . For ΒΘ4
(and A84)
chromophore, necessary
the assumption of a p r o t o n t r a n s f e r t o
leaving
a
shift
the
to
negative
aspartate
calculated
the
counterion, i s
electronic
excitation
energy i n t o the e x p e r i m e n t a l l y e s t a b l i s h e d r e g i o n . B155
deviates
result
in
t h a t B155 Only a
from t h i s
a transition and
a s p a r t a t e B39
positive partial
as -0-H)
behaviour; n e a r 700
yields a
m e r i s m (N22-H
a
nm.
proton t r a n s f e r would Therefore
are coupled
via
c h a r g e n e a r N22 and
postulate
a h y d r o g e n bond.
and N23
r e d s h i f t . Depending
o r N23-H)
we
(0D2
on t h e
treated
methen t a u t o -
t h e h y d r o g e n bond s t r e n g t h , t h e
v i s u a l a b s o r p t i o n band v a r i e s i n a w a v e l e n g t h r e g i o n o f 50 nm w i d t h Inclusion
(shaded a r e a s i n f i g u r e 2 ) . of
the
(case
IV: A r g B80;
B119,
T h r B124, in
geometry
charged
and
case V:
A r g B79,
T h r B118)
strong indication, role
about
tuning
an exchange
charges) r e s u l t
in
a
A r g B86,
around
Ser
B84
B72,
Tyr
arginine residues
play a v i t a l
t r a n s i t i o n energy. Small v a r i a t i o n s i n
(e.g. a r o t a t i o n of the
equivalent to
residues
leads t o f u r t h e r s h i f t s . There i s a
t h a t the the
aromatic
2
of p o s i t i v e
drastic
wavelength. Therefore,
- C ( N H ) ( N H ) - g r o u p s by
these
and
variation r e s i d u e s may
the h e t e r o g e n e i t y observed i n
the
negative
of
the
180°,
partial
transition
be r e s p o n s i b l e f o r
fluorescence
kinetics
of
smaller aggregates ( 8 ) . I n c l u s i o n of the charges i n t h e s u r r o u n d i n g Thr B151,
Asn
B35;
case V:
Lys B36,
a d d i t i o n a l r e d s h i f t s of t h e f i r s t for
o f B155
G l u B33)
(case
IV:
induces
also
electronic transition.
Only
t h e N23-H-tautomer i s t h e t h e o r e t i c a l r e s u l t , however, i n
agreement w i t h o b s e r v a t i o n . The
i n t e r a c t i o n w i t h t h e amide g r o u p s of t h e p r o t e i n backbone
(case V I ) p r o d u c e s state
properties
approximation
only and
studies.
small can
corrections
therefore
be
to
the e x c i t e d
ignored
in first
489 ß-subunit The r e s u l t s two,
d e s c r i b e d so f a r p r e d i c t t h a t t h e CD-spectrum o f
non-interacting
exhibit
a
large
chromophores
i n t h e Ö-subunit
s t r e n g t h a r o u n d 6 2 0 nm. T h i s i s ,
rotatory
however, i n c o n t r a d i c t i o n
to
the experimental
finding
e x t e n d e d o u r model c a l c u l a t i o n s
account
chromophores
and t h e i r e n v i r o n m e n t s
status
chromophore-protein
both
selected
according t o
of
approximation VI
i s marked
wavelength
region
and
also
t o take
into
together. interaction
i n f i g u r e s 1 and 2
f o r b o t h chromophores. I t y i e l d s t r a n s i t i o n correct
(4)
longwave l e n g t h a b s o r p t i o n band, a t t r i b u t e d t o B 8 4 ) .
(inactive
T h e r e f o r e , we The
should
energies
the required
s p a c i n g f o r B 8 4 and B 1 5 5 . F i g u r e 3 shows t h e t h e r e b y
i n the energy
obtained
t h e o r e t i c a l CD-spectrum o f t h e ß-subunit.
R= 1 DBM
580
600
590
610 X/nm
F i g u r e 3: C a l c u l a t e d v i s i b l e CD-spectrum o f i n d i v i d u a l chromophores (B84 • · , B155 · -) and t h e ß-subunit w i t h e x c i t o n i c c o u p l i n g included ( ) .
Due t o (γ+=0.9 which
e x c i t o n i c coupling, t h e s h o r t e r wavelength γ*(Β155) +
i s lost
This f i n a l very
w i t h charged
ψ*(Β84)) g a i n s
i n the corresponding
result f i t s
well
0.1
and
longwave l e n g t h t r a n s i t i o n .
the experimentally
i s a clear indication,
residues c o n t r o l s
transition
rotatory strength, f o u n d CD-bandshape that the interaction
a l s o t h e chromophore-chromo-
490 phore c o u p l i n g
within the phycobi1iproteins.
more a w a r n i n g t h a t may
the properties
I t i s further
of isolated
n o t be e x t r a c t e d f r o m measurements
chromophores
on b i o l o g i c a l
systems
Scheer f o r many f r u i t f u l
discus
w i t h i n t e r a c t i n g chromophores.
Acknowledgement We want t o t h a n k s i o n s . Free
P r o f . H.
computer t i m e
and t h e a c c e s s t o NOS/VE by t h e
L e i b n i z Rechenzentrum d e r B a y e r i s c h e n schaften i s greatly
Akademie
d e r Wissen
appreciated.
References 1. Scheer, Η. 1983. I n : L i g h t R e a c t i o n P a t h o f P h o t o s y n t h e s i s (F. K. Fong, e d . ) . S p r i n g e r V e r l a g , B e r l i n , P P . 7-45. 2. F r a n k , G., W. S i d l e r , H. Widmer and H. Z u b e r . 1978. H o p p e - S e y l e r ' s Z. P h y s i o l . Chem. 359, 1491-1507. 3a. S c h i r m e r , T., W. Bode, R. Huber, W. S i d l e r and H. Zuber. 1985. J . M o l . B i o l . 184, 257-277 b. S c h i r m e r , T., R. Huber, M. S c h n e i d e r , W. Bode, M. M i l l e r and M. L. H a c k e r t . 1986. J . M o l . B i o l . 188, 651-676 c. S c h i r m e r , T., W. Bode and R. Huber. 1987. J . M o l . B i o l . 196, 677-695 4. Siebzehnrübl, S., R. F i s c h e r and H. Scheer. 1987. Z. N a t u r f o r s c h . 4 2 c , 258-262. 5. Mimuro, M., R. Rümbe1i, P. Füg l i s t a l l e r and Η. Zuber. 1987. B i o c h i m i c a e t B i o p h y s i c a A c t a 8 5 1 , 447-456. 6a. B l a u e r , G. and G. Wagniöre. 1975. J . Am. Chem. Soc. 97, 1949-1954. b. B l a u e r , G. and G. Wagni£re. 1976. J . Am. Chem. Soc. 98, 7806-7810. 7. S c h a r n a g l , Ch., Ε. Köst-Reyes, S. S c h n e i d e r , H.-P. K o s t and Η. Scheer. 1983. Z. N a t u r f o r s c h . 3 8 c , 951-959. 8. S c h n e i d e r , S., P. G e i s e l h a r t , F. Baumann, S. Siebzehnrübl, R. F i s c h e r and H. Scheer. C o n t r i b u t i o n i n t h i s v o l u m e .
