J. Gallant et al., SURFACE AND SPECTROSCOPIC PROPERTIES OF PHOTOSYSTEM-II CORE COMPLEX AT THE NITROGEN WATER INTERFACE/, Langmuir, 14(14), 1998, pp. 3954-3963
We have studied surface and spectroscopic properties of Photosystem II
core complex (PS LI CC) for the first time in monolayers at the nitro
gen/water interface. A new instrument was thus specially built to perf
orm absorption and fluorescence spectroscopic measurements directly at
the nitrogen/water interface. The effect of initial surface density,
incubation time, and compression speed have been studied. When PS II C
C was spread at an initial surface pressure of 5.7 mN/m and immediatel
y compressed at a speed of 40 nm(2)/moleeule.min, it retained its nati
ve spectroscopic characteristics. Even though a slower speed of compre
ssion (10 nm(2)/molecule.min) produced more homogeneous films, the abs
orption maxima suffered a blue shift, indicating denaturation of PS II
CC. Compression at a speed of 80 nm(2)/molecule.min produced aggregat
es of intact PS II CC as indicated by Delta V-A isotherms, absorption
spectra, and fluorescence micrographs. We also conclude that spreading
of PS II CC at an initial surface pressure of 0.6 mN/m followed by a
30 min incubation time is inadequate to maintain PS II CC surface and
spectral properties. Indeed, pi-A and Delta V-A isotherms measured in
that condition showed transitions which suggested that PS II CC underw
ent physical changes during compression. Moreover, absorption and fluo
rescence maxima were blue shifted, indicating that PS II CC is denatur
ed under that condition.