Energization and ultrastructural pattern of thylakoids formed under periodic illumination followed by continuous light.

Bean leaves grown under periodic illumination (56 cycles of 2 min light and 98 min darkness) were subsequently exposed to continuous illumination, and in connection with granum formation and accumulation of the light-harvesting pigment-protein complex thermoluminescence and light-induced shrinkage of thylakoid membranes were studied. Juvenile chloroplasts with large double sheets of thylakoids obtained under periodic light exhibited low temperature spectra of polarized fluorescence yielding fluorescence polarization (FP) values < 1 at 695 nm, characteristic for pheophytin emission. In the course of maturation under continuous light when normal grana appeared and the chlorophyll a/b light-harvesting photosystem II complex was incorporated into the membrane, at 695 nm the relative intensity of fluorescence dropped and FP changed to a value of > 1, suggesting an overlap between the emission of pheophytin and that of the chlorophyll a/b light-harvesting photosystem II complex.

The light-harvesting chlorophyll a/b protein acts as a torque aligning chloroplasts in a magnetic field.

Displacement of particles from the purified light-harvesting chlorophyll a/b protein aggregate (LHC) was studied in magnetic fields of various strengths (0 to 1.6 T) by polarized fluorescence measurements. Macromolecular aggregates of LHC have a considerable magnetic susceptibility which enables the particles to rotate and align with their nematic axes parallel with H.

[Polarization fluorescence of chloroplasts oriented in polyacrylamide gel. Experiment and theoretical analysis].

Maize mesophyll chloroplasts were oriented in polyacrylamide gel upon squeezing of gel samples. Fluorescence polarization was measured as a function of the gel deformation parameter. Linearly polarized fluorescence spectra were recorded at -140 degrees.

Organization of Chlorophyll a in the Light-Harvesting Chlorophyll a/b Protein Complex as Shown by Circular Dichroism : Liquid Crystal-Like Domains.

The development of thylakoid stacking, accumulation of the light-harvesting chlorophyll a/b protein complex (LHCP), and the changes of circular dichroism (CD) which reflect the organization of chlorophyll molecules in greening thylakoids of bean Phaseolus vulgaris cv Red Kidney leaves were investigated.Chloroplasts formed under intermittent light contained large double sheets of membrane with extensive appression in addition to separate lamellae. Thylakoids of such chloroplasts were devoid of LHCP and exhibited a relatively small CD in the chlorophyll absorption region.

Distribution of characteristic membrane proteins in granum and stroma thylakoids.

Membrane fractions obtained by ultrasonication of Vicia faba thylakoids were analyzed by sodium dodecyl sulphate gel electrophoresis. The polypeptide patterns revealed a six-times-higher ratio of the apoprotein (1) of P700 chlorophyll a protein to the apoprotein (2) of one of the chlorophyll a proteins in photosystem II in the light (stroma) fraction as compared with the heavy (grana) fraction indicating different distribution of the two photosystems. Additionally, the light fraction was clearly depleted in chlorophyll a/b apoproteins 2a and 2b of the light-harvesting complex and enriched in CF1 alpha and beta subunits.

Chiroptical properties of chlorophyll-protein complexes separated on Deriphat/polyacrylamide gel.

Circular dichroism (c.d.) was measured for four chlorophyll-protein complexes, resolved from sodium dodecyl sulphate extracts of chloroplasts by electrophoresis in polyacrylamide gel containing Deriphat 160 (disodium N-dodecyl beta-imidopropionate), a zwitterionic detergent.

Structural and functional stability of isolated intact chloroplasts.

The effect of in vitro ageing on the ultrastructure, electron transport, thermoluminescence and flash-induced 515 nm absorbance change of isolated intact (type A) chloroplasts compared with non-intact (types B and C) chloroplasts was studied.When stored in the dark for 18 h at 5°C, the structural characteristics of intact and non-intact chloroplasts were only slightly altered. The most conspicuous difference between the two was in the coupling of the electron transport which was tighter and more stable in intact chloroplasts.

Macromolecular organization of chlorophyll a in aggregated chlorophyll a/b protein complex as shown by circular dichroism at room and cryogenic temperatures.

This report concerns the circular dichroic (CD) signal of intact chloroplasts of higher plants. The CD spectra of chloroplasts are compared with the aggregated form of the light-harvesting chlorophyll a/b complex at 25 degrees C and -250 degrees C. The light-harvesting chlorophyll aggregate has a CD of magnitude equal to or greater than chloroplasts, but of opposite sign, and it is not related to the CD of the unaggregated form, and hence its arrangement is an artefact compared to the arrangement in the chloroplast.

Characteristics of the Flash-induced 515 Nanometer Absorbance Change of Intact Isolated Chloroplasts.

In intact (type A) chloroplasts isolated from mesophyll protoplasts of maize (Zea mays L. convar. KSC 360) the flash-induced 515 nanometer absorbance change was much higher than in conventionally prepared (types B and C) chloroplasts.

Differential light-scattering of granal and agranal chloroplasts and their fragments.

Intact (class-A) granal and agranal maize chloroplasts and chloroplast fragments were examined for differential scattering of circularly polarized light (measured at 90 degrees) and c.d. (circular dichroism) (measured at 0 degrees) by using a modified spectropolarimeter with a large acceptance angle.

Functional characteristics of intact chloroplasts isolated from mesophyll protoplasts and bundle sheath cells of maize.

A procedure was developed to isolate mesophyll and bundle sheath chloroplasts of a high degree of intactness and low cross-contamination. Light-induced (14)CO2 fixation of isolated chloroplasts was similar to that of protoplasts and cells in that it was low and was stimulated by the addition of exogenous substrates. O2 evolution was absent in both bundle sheath chloroplasts and cells.

Flash-induced 515 nm absorbance change in chloroplasts with various granum contents.

The 515 nm absorbance change was studied in mesophyll and bundle sheath chloroplasts of maize, which contain different amounts of grana. The amplitude of the 515 nm signal (induced by 3 micro seconds flashes repeated at 4 s intervals) has shown a correlation with the granum content of the samples. However, upon addition of N-methylphenazonium methosulphate the 515 nm signal became independent of the amount of grana: in agranal thylakoids a large pool of silent Photosystem I was activated and, as a result, the amplitude of the 515 nm signal of agranal chloroplasts increased to the level exhibited by granal chloroplasts.

Selective scattering spectra as an approach to internal structure of granal and agranal chloroplasts.

Selective scattering spectra of granal and agranal chloroplasts were measured in the red spectral region and compared with calculations based on the Mie theory. The spectra were influenced considerably by the intactness and ultrastructural pattern of the chloroplasts. It was demonstrated that the spectra consist of two components: one attributable to grana and the other, to single lamellae.

X-ray microanalytical study of Mn and Fe compartmentation in maize chloroplasts.

X-ray microanalysis of mesophyll and bundle sheath maize chloroplasts showed that bound manganese is located within thylakoids, whereas bound iron is equally present in thylakoids and stroma. A simple correlation between manganese content and oxygen evolution capacity (Photosystem II activity) is unlikely since Mn is also present in bundle sheath thylakoids of low Photosystem II activity. A major part of manganese has probably a distinct function and only a minor part plays a role in the process of oxygen evolution.

Circular dichroism spectra of granal and agranal chloroplasts of maize.

Granum-containing chloroplasts from mesophyll cells of maize (Zea mays L. var. MV 861) leaves exhibited circular dichroism spectra with a large double signal; peaks at 696 nm (+) and 680 nm (-).

Pigment composition and plastid structure in leaves of carotenoid mutants of maize.

In monogenic, recessive chloroplast mutants of maize which contain chlorophylls, and lycopene or χ-carotene but no normal carotenoids, great variability in the size of plastids was associated with a number of ultrastructural abnormalities. In the mutant accumulating lycopene some plastids contain dense bundles of lamellae, whereas the chloroplasts of the χ-carotene mutant show poor thylakoid development. Neither of the mutants was able to form normal grana.