scholarly journals The rotational model: a new hypothesis for thylakoid stacking

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Antonios Castorinis
Keyword(s):  
Photosystem Ii ◽  
Vertical Axis ◽  
Electrostatic Forces ◽  
Rotational Model ◽  
Light Harvesting Complexes ◽  
Cylindrical Structures ◽  
New Model ◽  
Physicochemical Factors ◽  
Thylakoid Stacking ◽  
New Hypothesis

The most enigmatic feature of mature thylakoids of Angiosperms is the presence of piles of membranous discs forming the cylindrical structures known as grana. Although some models aim to elucidate their formation, until now the mechanism governing the architecture of thylakoid stacks remains obscure. In this work a new model is presented aiming to explain the way thylakoids stack. In comparison with previous models, this model proposes a dynamic mechanism for the rapid selfassembly of thylakoid stacks and their subsequent disassembly under the influence of a variety of physicochemical factors and is consistent with the evolutionary origin of these membranes and their ontogenetic continuity. The model proposes that, under the influence of attractive electrostatic forces, the membranes come closer in a parallel alignment and the photosystem II/light harvesting complexes migrate laterally forming circular aggregates. Finally the thylakoids rotate around the vertical axis of the superimposed aggregates, under the action of a torque.

scholarly journals Determination of the Stoichiometry and Strength of Binding of Xanthophylls to the Photosystem II Light Harvesting Complexes

1999 ◽  
Vol 274 (15) ◽  
pp. 10458-10465 ◽  
Author(s):  
Alexander V. Ruban ◽  
Pamela J. Lee ◽  
Mark Wentworth ◽  
Andrew J. Young ◽  
Peter Horton
Keyword(s):  
Photosystem Ii ◽  
Light Harvesting ◽  
Light Harvesting Complexes

A new model refractometer for determining the refractive indices of gem-stones, crystals, and liquids

1927 ◽  
Vol 21 (118) ◽  
pp. 324-328 ◽  
Author(s):  
Bristow J. Tully
Keyword(s):  
Optical System ◽  
Vertical Axis ◽  
The Body ◽  
Refractive Indices ◽  
Main Body ◽  
General Outline ◽  
New Model ◽  
Vital Part

The general outline and weight of the body of the instrument are devised to ensure perfect rigidity and steadiness during use, all necessary adjustments, such as the focusing of the rotating eyepiece, movement of the revolving stage, reflector, or screen, being quite independent of the optical system; which, being contained in the main body in a dust-proof receptacle, entirely prevents any vital part of the refractometer getting out of adjustment, unless deliberately tampered with.The eyepiece, which by rotation is capable of giving a wide variation of focus, is set at the most convenient angle to ensure easy and comfortable observation.The forward projecting portion attached to the main body is rectangular in shape, and hollow, the upper surface forming a platform in which revolves a circular plated stage with a milled edge capable of being turned about a vertical axis through 360°, with an engraved scale marked at every 45° to enable the observer to read with accuracy the least and greatest refractive indices of all doubly refracting stones.

scholarly journals Investigations of the role of the main light-harvesting chlorophyll-protein complex in thylakoid membranes. Reconstitution of depleted membranes from intermittent-light-grown plants with the isolated complex.

1984 ◽  
Vol 98 (1) ◽  
pp. 163-172 ◽  
Author(s):  
D A Day ◽  
I J Ryrie ◽  
N Fuad
Keyword(s):  
Photosystem Ii ◽  
Light Harvesting ◽  
Gradient Centrifugation ◽  
Freeze Fracture ◽  
Direct Role ◽  
Lhc Ii ◽  
Intermittent Light ◽  
Light Harvesting Complex ◽  
Thylakoid Stacking

The functions of the light-harvesting complex of photosystem II (LHC-II) have been studied using thylakoids from intermittent-light-grown (IML) plants, which are deficient in this complex. These chloroplasts have no grana stacks and only limited lamellar appression in situ. In vitro the thylakoids showed limited but significant Mg2+-induced membrane appression and a clear segregation of membrane particles into such regions. This observation, together with the immunological detection of small quantities of LHC-II apoproteins, suggests that the molecular mechanism of appression may be similar to the more extensive thylakoid stacking seen in normal chloroplasts and involve LHC-II polypeptides directly. To study LHC-II function directly, a sonication-freeze-thaw procedure was developed for controlled insertion of purified LHC-II into IML membranes. Incorporation was demonstrated by density gradient centrifugation, antibody agglutination tests, and freeze-fracture electron microscopy. The reconstituted membranes, unlike the parent IML membranes, exhibited both extensive membrane appression and increased room temperature fluorescence in the presence of cations, and a decreased photosystem I activity at low light intensity. These membranes thus mimic normal chloroplasts in this regard, suggesting that the incorporated LHC-II interacts with photosystem II centers in IML membranes and exerts a direct role in the regulation of excitation energy distribution between the two photosystems.

scholarly journals Organization of the photosystem II centers and their associated antennae in the thylakoid membranes: a comparative ultrastructural, biochemical, and biophysical study of Chlamydomonas wild type and mutants lacking in photosystem II reaction centers.

1980 ◽  
Vol 87 (3) ◽  
pp. 728-735 ◽  
Author(s):  
F A Wollman ◽  
J Olive ◽  
P Bennoun ◽  
M Recouvreur
Keyword(s):  
Photosystem Ii ◽  
Fluorescence Analysis ◽  
Thylakoid Membranes ◽  
Reaction Centers ◽  
Type Number ◽  
Wild Type ◽  
Light Harvesting Complexes ◽  
Biophysical Study ◽  
In The Wild ◽  
Type C

We investigated the ultrastructure of thylakoid membranes that lacked either some or all of their Photosystem II centers in the F34SU3 and F34 mutants of Chlamydomonas reinhardtii. We obtained the following results: (a) There are no particles of the 160-A size class on the EF faces of the thylakoids in the absence of Photosystem II centers (as in F34); the F34SU3 contains 50% of the wild-type number of PSII centers and EF particles. (b) The density of the particles on the PF faces of the thylakoids is higher in the mutants than in the wild type. (c) The fluorescence analysis shows that the organization of the pigments is the same regardless of whether 50% of the PSII centers are temporarily inactivated (by preilluminating the wild type) or are actually missing from the thylakoid membrane (F34SU3). Our results, therefore, support a model in which: (a) each 160-A EF particle has only one PSII center surrounded by light-harvesting complexes and (b) part of the PSH antenna is associated with 80-A PF particles in both of the mutants and the wild type.

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