Vol. 186, No. 1, 1992
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
July 15, 1992
Pages 327-333
P H O T O T H E R M A L S P E C T R O S C O P Y OF B A C T E R I O C H L O R O P H Y L L COMPLEXES
LIPOPROTEIN
-
D. F r ~ c k o w i a k i, R. Cegielski i, I. A b d o u r a k h m a n o v z and R. M. Leblanc 3
llnstitute of Physics, PoznaA Technical University~ 60-965 Pozna~, Poland
Piotrowo
2Institute of Soil Science and Photosynthesis, USSR Sciences, Pushchino, Moscow region, USSR 3Centre de Recherche en Photobiophysique, Trois-Rivieres, 3351 Boulevard des Trois-RiviSres,
QuSbec,
Academy
3,
of
Universit$ du Quebec Forges, C.P. 500,
Canada G9A 5H7
Received May 16, 1992
SUMMARY: P h o t o a c o u s t i c spectra at room and 85 K t e m p e r a t u r e s as well as photothermal beam deflection spectra of bacteriochlorophyll - lipoprotein complexes from purple bacterium CAyot~c~u~ ~ u ~ i s s i ~ < z ~ were measured. Spectra were compared and obtained differences were tentatively explained by various inertion of these two methods. Photothermal beam d e f l e c t i o n method measure the heat which is generated in close surroundings of absorbing pigment molecule, whereas usage of more inert photoacoustic signal is averaged over contributions from various pigments located in a larger sample volume and therefore is similar to a b s o r p t i o n spectra. ©1992AcademicPress,Inc.
Photoacoustic spectrum
of
transformed
that
part
spectroscopy of
(PAS) is used
absorbed
light
organisms can be t r a n s f e r r e d to other emitted as fluorescence
photochemical possibilities, is
the
energy
into heat through n o n r a d i a t i v e d e e x c i t a t i o n
(i). The light energy absorbed by the pigments
heat~
to
reactions.
of
molecules,
or delayed
of
excitation
energy
which
is
processes
photosynthetic
or
among
but in the case of antenna pigments,
process
the
exchanged
emission,
There is a c o m p e t i t i o n
study
transfer
into
used
for
these
all
very efficient to
the
next
0006-291X/92 $4.00 327
Copyright © 1992 by Academic Press, Inc. All rights of reproduction in any form reserved.
Vol. 186, No. 1, 1992
participant
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
in the d o n o r - a c c e p t o r chain t u n n e l i n g
to r e a c t i o n centers the
division
of
(2).
In various types of antenna
excitation different,
energy
deexcitation
is
physiological
role in photosynthesis.
converted
the
what
excitation chromophores
between
various,
paths
closly
related
to
is
now
is
spectroscopy
predominantly (2-4).
From technical
averaged over contributions sample volume,
therefore
contributions
from
photothermal
properties.
photothermal
measured
from pigments
investigations model
closly
located Recently
sample,
is
(mono
and
deflection
s p e c t r o s c o p y therefore
about heat generated In this
methods. complexes
been
in
of
method
we
deflections
The suspensions
and
shown
detected
gradient
tool
less
of
antenna
the
is
that
for
the
and
in The
inert
give
of near
chlorophylls).
could
the
various
organisms
is
it
compare
for the same p h o t o s y n t h e t i c beam
large
(gas or liquid)
sensitive
in close surroundings paper
having
in which signal
multilayers
photoacoustic
photothermal
has
pigments
beam
obtained
(5)
very
photothermal
molecules.
chromophores
in the fluid
of p h o t o s y n t h e t i c
systems
photoacoustic
located in rather
laser beam d e f l e c t i o n caused by
illuminated
systems up
it is not possible to d i s t i n g u i s h between
the index of r e f r a c t i o n produced the
applying
(3,4).
reason this method deliver data
d e f l e c t i o n spectroscopy,
by the periodic
energy
methods
The steady state thermal d e a c t i v a t i o n of p h o t o s y n t h e t i c to
their
A part of e x c i t a t i o n
into heat can be m e a s u r e d by photothermal
of
than
information
absorbing
pigment
photothermal
spectra
complexes
phoioacoustic
of the b a c t e r i o c h l o r o p h y l l
by
means
spectroscopy -
lipoprotein
from purple bacterium CA~or~,~fu~ mi~u~isg~r~.'u~ were taken
as the samples. The differences
between the spectra were t e n t a t i v e l y explained
the different delay of measured
thermal
deactivation
signal
by in
respect to a b s o r p t i o n of light.
MATERIALS AND METHODS under
B a c t e r i u m CA~o~7~zzLi'um m i n u ~ i / i t ~ u ~ was cultured at 303 K i000 lux in Parsen medium (7). P i g m e n t - l i p o p r o t e i n complexes
328
Vol. 186, No. 1, 1992
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
w e r e s e p a r a t e d a c c o r d i n g to M o s k a l e n k o (8) from 4-5 days culture. C o m p l e x e s in 0 . 0 4 M Tris b u f f e r w i t h 0.022 M g l y c i n (pH 9.2) were introduced to PVA film as previously (9). The polarized f l u o r e s c e n c e and a b s o r p t i o n s p e c t r a of i n v e s t i g a t e d sample where reported previously (I0). In C A ~ o ~ ~inu~i~rl~ purple b a c t e r i a t h r e e types of a n t e n n a c o m p l e x e s (6), denoted according their near IR absorption maxima as B870~ B800-820 and B800-850, o c c u r r but u n d e r special c u l t u r i n g conditions a large a m o u n t of B 8 0 0 - 8 2 0 is s y n t h e s i z e d . The p h o t o a c o u s t i c s p e c t r a at r o o m (298 K) a n d low t e m p e r a t u r e s (85 K) w e r e m e a s u r e d w i t h a single-beam photoacoustic spectrometer c o n s t r u c t e d in T r o i s R i v i e r e s (Ii,12). The f r e q u e n c y of light b e a m m o d u l a t i o n was 35 Hz (at r o o m t e m p e r a t u r e ) and II Hz (at 85K). The light b e a m i n t e n s i t y at 680 nm was 2.68 W / m 2. The p h o t o t h e r m a l b e a m d e f l e c t i o n (PD) spectrometer allow rapid m e a s u r e m e n t s of t h e r m a l d i s s i p a t i o n of a b s o r b e d light on the basis of "mirage effect" was d e s c r i b e d in details previously (5). In this m e t h o d the m o d u l a t e d heat emission from illuminated with intensity-modulated light was m e a s u r e d ~ic~ the detection of the periodic deflection of a laser beam parallel to the sample surface.
RESULTS
AND D I S C U S S I O N Fig.l
shows
PD a n d PAS methods. PAS
spectra
there
As
are
between
the r e s u l t s
between
positions
film w i t h
room
but the m a x i m a are
these
effects:
for PAS
the
4 ms
same
time,
also
0.25
the
measuring measured
a n d the
shifted changed.
two
methods
energy
closer ms are
in
a
luminescence thermal
case
of
influencing
serious
the
PD
hermetically
closed
329
PVA
in PAS.
emission
etc
only
difference
these
of
At
measured
two
cell,
in
37 Hz u s e d
occurring
at the in
time
of
There
is
conditions
of
methods: which
in
storage
a shorter
the
time
occurring
spectrum.
between
found
intensities
energy with
in P V A
be
less d e l a y e d
than
and
Analogy
can
constant
measured
with
PD
differences
between
is
of the
of a s a m p l e
deactivation
difference samples
big
fundamental
time
signal
of
methods.
in fluid
of a b s o r p t i o n
with
PD
to the p h o t o e x c i t a t i o n ,
photosynthetic the
and
is
the
the measured
stored~
whereas
in
but a l s o
relations
There
by m e a n s
comparison
PAS m a x i m a
are
second
in
PAS
PD s p e c t r u m
is c o m p e t i n g
intermediate
using
obtained
the
similarities,
temperature
to the p r o c e s s
about
around
some
from
low t e m p e r a t u r e
in PD m e t h o d
in r e s p e c t
spectra
it f o l l o w s
obtained
of
dramatically
between
photothermal
PAS
causes
is very
Vol. 186, No. 1, 1 9 9 2
BIOCHEMICAL A N D BIOPHYSICAL RESEARCH C O M M U N I C A T I O N S
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