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T. Noguchi et al. / A new system for detection of thermoluminescence and delayed luminescence
keeping it constant during the measurement is particularly important for obtaining data suitable for accu-
rate theoretical analysis. Also, fixing the sample temperature precisely is crucial for DL measurements.
In this study, we have developed a new system for TL and DL measurements capable of accurate temper-
ature control. We have applied this system to measure TL glow curves of PSII membranes with various
heating rates and also DL decays at various temperatures.
2. Materials and methods
The oxygen-evolving PSII membranes [13] were prepared from spinach following the method by
Ono and Inoue [14]. The membranes were suspended in a buffer including 40 mM Mes, 400 mM su-
crose, 20 mM CaCl2, 20 mM NaCl2, and 30% (v/v) glycerol (pH 6.5) at a concentration of 0.3 mg
chlorophyll/ml. The membrane suspension also included 1 µM 3-(3,4-dichlorophenyl)-1,1-dimethylurea
(DCMU) to block the electron transfer from QA to QB.
3. Instrumentation
Figure 1 shows the block diagram of the system for TL and DL measurements (A) and the expanded
view of the sample unit (B). The sample unit is formed by modifying the freezing/heating stage for
microscope (LINKAM, TH-600RH). In this freezing/heating stage, the heat block is heated by a sheath
heater and is cooled by cold N2 gas that is passed through liquid N2 (Fig. 1B). The temperature of the
stage is detected by a platinum resistance thermometer buried in the heat block and monitored by a
temperature controller, which in turn determines the voltage to the heater to control the temperature and
the heating rate. An aluminum sample holder (20 mm ∅; 1 mm in thickness) with a hollow (15 mm ∅;
0.5 mm in depth) was placed on the stage. A sample solution (85 µl) is placed in the hollow and covered
by an acrylic plate. When the sample is a leaf or a piece of filter paper that absorbs sample solution, it
is directly placed on the stage and covered by an acryl plate. The sample temperature is monitored with
a digital multi-thermometer (Advantest, TR-2114H) using a sheath thermocouple (type T; 0.5 mm ∅),
which is inserted into the sample solution or pressed against the leaf or filter paper. The flow rate of
cold N2 gas is controlled by a valve with a low-flow bypass (CKD, AMD31-15-12-3). When the sample
temperature is fixed or raised at a certain heating rate, the valve is closed and the low-flow bypass is used.
Rapid cooling of the sample after illumination is done by opening the valve using an electric switch to
obtain a high flow rate. The sample unit is purged by N2 gas to avoid frosting.
Light illumination on the sample is performed by flash light with duration of ∼ 4 µs from a Xe-flash
source (Sugawara, SL-230S) controlled by a stroboscope (Sugawara, MS-230). The flash light was led
to the sample using a ring-type light guide (HOYA-SCHOTT, FGR6F1000D18R). Emission from the
sample is collected by a light guide (16 mm ∅) (HOYA-SCHOTT, LGS16F1000D18-72E), which is
fitted into the inner hole of the ring-type light guide and placed above the sample at a close distance
of ∼7 mm (Fig. 1B). At the other end of the light guide, the emitted light is focused onto a cooled
photomultiplier (Hamamatsu, R943-02). Electromagnetic shutters (Copal, EC-601) are placed in front of
the Xe lamp and the photomultiplier, and the former shutter is opened whereas the latter is closed during
flash illumination by a trigger from a homemade shutter driver. The signal from the photomultiplier
is processed by a photon counting unit (Hamamatsu, C3866) and is transmitted to a personal computer
through a photon counting board (Hamamatsu, M3949). This emission data together with the temperature
Ogata
