Small-Angle X-Ray and Neutron Scattering on Photosynthetic Membranes

Jakubauskas, Dainius; Mortensen, K.; Jensen, Poul Erik; Kirkensgaard, Jacob J. K.

doi:10.3389/fchem.2021.631370

Cited by 5 publications

(3 citation statements)

References 101 publications

(194 reference statements)

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“…Small-angle X-ray scattering (SAXS) was measured to characterize the membranes and the multilamellar organization of grana, and to attempt detecting the H II phases. SAXS is a powerful technique, which carries information on membrane systems on the mesoscopic scale of 1-100 nm [14,15]. The ultrastructure of granum and stroma TMs were inspected with the aid of freeze-fracture and scanning EM techniques, FF-EM and SEM, respectively, and by cryo-electron tomography (CET).…”

Section: Introductionmentioning

confidence: 99%

Lipid Polymorphism of the Subchloroplast—Granum and Stroma Thylakoid Membrane–Particles. II. Structure and Functions

Dlouhý

Karlický

Arshad

et al. 2021

Cells

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In Part I, by using 31P-NMR spectroscopy, we have shown that isolated granum and stroma thylakoid membranes (TMs), in addition to the bilayer, display two isotropic phases and an inverted hexagonal (HII) phase; saturation transfer experiments and selective effects of lipase and thermal treatments have shown that these phases arise from distinct, yet interconnectable structural entities. To obtain information on the functional roles and origin of the different lipid phases, here we performed spectroscopic measurements and inspected the ultrastructure of these TM fragments. Circular dichroism, 77 K fluorescence emission spectroscopy, and variable chlorophyll-a fluorescence measurements revealed only minor lipase- or thermally induced changes in the photosynthetic machinery. Electrochromic absorbance transients showed that the TM fragments were re-sealed, and the vesicles largely retained their impermeabilities after lipase treatments—in line with the low susceptibility of the bilayer against the same treatment, as reflected by our 31P-NMR spectroscopy. Signatures of HII-phase could not be discerned with small-angle X-ray scattering—but traces of HII structures, without long-range order, were found by freeze-fracture electron microscopy (FF-EM) and cryo-electron tomography (CET). EM and CET images also revealed the presence of small vesicles and fusion of membrane particles, which might account for one of the isotropic phases. Interaction of VDE (violaxanthin de-epoxidase, detected by Western blot technique in both membrane fragments) with TM lipids might account for the other isotropic phase. In general, non-bilayer lipids are proposed to play role in the self-assembly of the highly organized yet dynamic TM network in chloroplasts.

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Section: Introductionmentioning

confidence: 99%

Lipid Polymorphism of the Subchloroplast—Granum and Stroma Thylakoid Membrane–Particles. II. Structure and Functions

Dlouhý

Karlický

Arshad

et al. 2021

Cells

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“…High-resolution TEM, although requiring sample fixation, remains the most favored method to study the grana morphology due to the nanometer length scale of the grana structural details. The thylakoid ultrastructure might also be assessed using small-angle scattering methods that enable a noninvasive analysis of high volume samples (Ünnep et al, 2017;Jakubauskas et al, 2019;Ünnep et al, 2020;Zsiros et al, 2020;Jakubauskas et al, 2021). Only periodic membrane attributes can be registered, while no information on grana diameter or details of membrane connections could be revealed.…”

Section: Methods Used In the Visualization Of Granum Morphology And Their Limitationsmentioning

confidence: 99%

How to Measure Grana – Ultrastructural Features of Thylakoid Membranes of Plant Chloroplasts

2021

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Granum is a basic structural unit of the thylakoid membrane network of plant chloroplasts. It is composed of multiple flattened membranes forming a stacked arrangement of a cylindrical shape. Grana membranes are composed of lipids and tightly packed pigment-protein complexes whose primary role is the catalysis of photosynthetic light reactions. These membranes are highly dynamic structures capable of adapting to changing environmental conditions by fine-tuning photochemical efficiency, manifested by the structural reorganization of grana stacks. Due to a nanometer length scale of the structural granum features, the application of high-resolution electron microscopic techniques is essential for a detailed analysis of the granum architecture. This mini-review overviews recent approaches to quantitative grana structure analyses from electron microscopy data, highlighting the basic manual measurements and semi-automated workflows. We outline and define structural parameters used by different authors, for instance, granum height and diameter, thylakoid thickness, end-membrane length, Stacking Repeat Distance, and Granum Lateral Irregularity. This article also presents insights into efficient and effective measurements of grana stacks visualized on 2D micrographs. The information on how to correctly interpret obtained data, taking into account the 3D nature of grana stacks projected onto 2D space of electron micrograph, is also given. Grana ultrastructural observations reveal key features of this intriguing membrane arrangement, broadening our knowledge of the thylakoid network’s remarkable plasticity.

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“…In these cases, the electron density probability distribution in the sample could change significantly. For another example, see Jakubauskas et al (2021). However, if the probability distribution of electron density at a particular spatial frequency together with a corresponding distribution of scattered intensity both remain stable, then a reference sample can provide useful information linking a desired contrast to noise level to a target CCC for the intensities.…”

Section: General Imaging Regimementioning

confidence: 99%

Which resolution?

Nave

2023

IUCrJ

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The relationship between the contrast to noise ratio and intensity based cross-correlation coefficients for both protein crystallography and X-ray imaging are compared. It is concluded that, for protein crystallography at near atomic resolution, the intensity based cross-correlation coefficients give a reasonable indication of the quality of the corresponding electron density. For X-ray imaging of biological materials such as cells and soft tissue, the wide range of contrast of the features means that intensity based correlation coefficients can give a poor indication of the interpretability of an image. Rather than the term resolution, it is the contrast to noise ratio for a feature of interest at the relevant spatial frequency that is more relevant. Additional metrics are required to describe the quality of an image, and these are discussed.

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Small-Angle X-Ray and Neutron Scattering on Photosynthetic Membranes

Cited by 5 publications

References 101 publications

Lipid Polymorphism of the Subchloroplast—Granum and Stroma Thylakoid Membrane–Particles. II. Structure and Functions

Lipid Polymorphism of the Subchloroplast—Granum and Stroma Thylakoid Membrane–Particles. II. Structure and Functions

How to Measure Grana – Ultrastructural Features of Thylakoid Membranes of Plant Chloroplasts

Which resolution?

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