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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Photothermal spectroscopy of bacteriochlorophyll-lipoprotein complexes.

Photoacoustic spectra at room and 85 K temperatures as well as photothermal beam deflection spectra of bacteriochlorophyll-lipoprotein complexes from ...
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