scholarly journals Structural analysis of a new carotenoid-binding protein: the C-terminal domain homolog of the OCP

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Maria Agustina Dominguez-Martin ◽  
Michal Hammel ◽  
Sayan Gupta ◽  
Sigal Lechno-Yossef ◽  
Markus Sutter ◽  
...  
Keyword(s):  
Bioinformatic Analysis ◽  
Water Soluble ◽  
Structural Description ◽  
X Ray ◽  
Terminal Domain ◽  
New Family ◽  
X Ray Scattering ◽  
Water Soluble Protein ◽  
Orange Carotenoid Protein ◽  
Critical Residues

Abstract The Orange Carotenoid Protein (OCP) is a water-soluble protein that governs photoprotection in many cyanobacteria. The 35 kDa OCP is structurally and functionally modular, consisting of an N-terminal effector domain (NTD) and a C-terminal regulatory domain (CTD); a carotenoid spans the two domains. The CTD is a member of the ubiquitous Nuclear Transport Factor-2 (NTF2) superfamily (pfam02136). With the increasing availability of cyanobacterial genomes, bioinformatic analysis has revealed the existence of a new family of proteins, homologs to the CTD, the C-terminal domain-like carotenoid proteins (CCPs). Here we purify holo-CCP2 directly from cyanobacteria and establish that it natively binds canthaxanthin (CAN). We use small-angle X-ray scattering (SAXS) to characterize the structure of this carotenoprotein in two distinct oligomeric states. A single carotenoid molecule spans the two CCPs in the dimer. Our analysis with X-ray footprinting-mass spectrometry (XFMS) identifies critical residues for carotenoid binding that likely contribute to the extreme red shift (ca. 80 nm) of the absorption maximum of the carotenoid bound by the CCP2 dimer and a further 10 nm shift in the tetramer form. These data provide the first structural description of carotenoid binding by a protein consisting of only an NTF2 domain.

Phosphate tungsten bronze series: crystallographic and structural properties of low-dimensional conductors

2001 ◽  
Vol 57 (5) ◽  
pp. 603-632 ◽  
Author(s):  
P. Roussel ◽  
O. Pérez ◽  
Ph. Labbé
Keyword(s):  
Crystal Structures ◽  
Structural Properties ◽  
Tungsten Bronze ◽  
Structural Description ◽  
X Ray ◽  
X Ray Scattering ◽  
Modulated Structures ◽  
Low Dimensionality ◽  
Low Dimensional ◽  
Thickness Function

Phosphate tungsten bronzes have been shown to be conductors of low dimensionality. A review of the crystallographic and structural properties of this huge series of compounds is given here, corresponding to the present knowledge of the different X-ray studies and electron microscopy investigations. Three main families are described, monophosphate tungsten bronzes, Ax (PO2)4(WO3)2m , either with pentagonal tunnels (MPTBp) or with hexagonal tunnels (MPTBh), and diphosphate tungsten bronzes, Ax (P2O4)2(WO3)2m , mainly with hexagonal tunnels (DPTBh). The general aspect of these crystal structures may be described as a building of polyhedra sharing oxygen corners made of regular stacking of WO3-type slabs with a thickness function of m, joined by slices of tetrahedral PO4 phosphate or P2O7 diphosphate groups. The relations of the different slabs with respect to the basic perovskite structure are mentioned. The structural description is focused on the tilt phenomenon of the WO6 octahedra inside a slab of WO3-type. In this respect, a comparison with the different phases of the WO3 crystal structures is established. The various modes of tilting and the different possible connections between two adjacent WO3-type slabs involve a great variety of structures with different symmetries, as well as the existence of numerous twins in MPTBp's. Several phase transitions, with the appearance of diffuse scattering and modulation phenomena, were analysed by X-ray scattering measurements and through the temperature dependence of various physical properties for the MPTBp's. The role of the W displacements within the WO3-type slabs, in two modulated structures (m = 4 and m = 10), already solved, is discussed. Finally, the complexity of the structural aspects of DPTBh's is explained on the basis of the average structures which are the only ones solved.

scholarly journals The Unique Protein-To-Protein Carotenoid Transfer Mechanism

2017 ◽  
Author(s):  
Eugene G. Maksimov ◽  
Nikolai N. Sluchanko ◽  
Yury B. Slonimskiy ◽  
Kirill S. Mironov ◽  
Konstantin E. Klementiev ◽  
...  
Keyword(s):  
Transfer Process ◽  
Targeted Delivery ◽  
Green Light ◽  
Water Soluble ◽  
Uncharacterized Protein ◽  
Water Soluble Protein ◽  
Orange Carotenoid Protein ◽  
Highly Hydrophobic

Orange Carotenoid Protein (OCP) is known to be an effector and regulator of cyanobacterial photoprotection. This 35 kDa water-soluble protein provides specific environment for keto-carotenoids, the excitation of which induced by the absorption of blue-green light causes dramatic but fully reversible rearrangements of the OCP structure, including carotenoid translocation and separation of C- and N-terminal domains upon transition from the basic orange to photoactivated red OCP form. While recent studies significantly improved our understanding of the OCP photocycle and interaction with phycobilisomes and the fluorescence recovery protein, the mechanism of OCP assembly remains unclear. Apparently, this process requires targeted delivery and incorporation of a highly hydrophobic carotenoid molecule into the water-soluble apoprotein of OCP. Recently, we introduced a novel carotenoid carrier protein, COCP, which consists of dimerized C-domain(s) of OCP and can combine with the isolated N-domain to form transient OCP-like species. Here, we demonstrate that in vitro COCP efficiently transfers otherwise tightly bound carotenoid to the full-length OCP apoprotein, resulting in formation of the photoactive OCP from completely photoinactive species. We accurately analyze peculiarities of this carotenoid transfer process which, to the best of our knowledge, seems unique, previously uncharacterized protein-to-protein carotenoid transfer process. We hypothesize that a similar OCP assembly can occur in vivo, substantiating specific roles of the COCP carotenoid carrier in cyanobacterial photoprotection.

scholarly journals Encapsulation Through The Use Of Emulsified Microemulsions

2021 ◽  
Author(s):  
Ruby R. Rafanan
Keyword(s):  
Controlled Release ◽  
Continuous Phase ◽  
Pharmaceutical Products ◽  
Water Soluble ◽  
Scanning Calorimetry ◽  
Food Grade ◽  
X Ray ◽  
X Ray Scattering ◽  
Food Applications ◽  
Glycerol Monooleate

Emulsified microemulsions (EMEs), first described in detail in 2005 by the group of Garti, consist of a thermodynamically stable water-in-oil microemulsion phase (w1/o) further dispersed within an aqueous continuous phase (w2). These internally-structured w1/o/w2 dispersions are promising controlled release vehicles for water-soluble flavouring compounds, drugs and nutraceuticals. With a stable internal droplet structure, storage stability is improved over non-thermodynamically stable structured emulsions and may exhibit unique controlled release behaviour. Use of food-grade components allows for wider and safer applications in food and pharmaceutical products. In this thesis, a food-grade w1/o microemulsion consisting of glycerol monooleate, tricaprylin and water was dispersed in an aqueous (w2) phase by membrane emulsification and stabilized by a caseinate-pectin complex to produce w1/o/w2 EMEs. The resulting EME showed no signs of phase separation for weeks at room temperature. The microemulsion and EME were characterized by differential scanning calorimetry (DSC), cryo-TEM and small angle x-ray scattering (SAXS) to determine whether the microemulsion’s internal structure was maintained after emulsification. It was shown that EME droplets displayed ordering around the periphery consistent with some loss of microemulsion structure, but maintained the characteristic disordered microemulsion structure at the droplet core. Overall, this research demonstrated the feasibility of developing EME for possible applications in food and non-food applications.

scholarly journals Encapsulation Through The Use Of Emulsified Microemulsions

2021 ◽  
Author(s):  
Ruby R. Rafanan
Keyword(s):  
Controlled Release ◽  
Continuous Phase ◽  
Pharmaceutical Products ◽  
Water Soluble ◽  
Scanning Calorimetry ◽  
Food Grade ◽  
X Ray ◽  
X Ray Scattering ◽  
Food Applications ◽  
Glycerol Monooleate

Emulsified microemulsions (EMEs), first described in detail in 2005 by the group of Garti, consist of a thermodynamically stable water-in-oil microemulsion phase (w1/o) further dispersed within an aqueous continuous phase (w2). These internally-structured w1/o/w2 dispersions are promising controlled release vehicles for water-soluble flavouring compounds, drugs and nutraceuticals. With a stable internal droplet structure, storage stability is improved over non-thermodynamically stable structured emulsions and may exhibit unique controlled release behaviour. Use of food-grade components allows for wider and safer applications in food and pharmaceutical products. In this thesis, a food-grade w1/o microemulsion consisting of glycerol monooleate, tricaprylin and water was dispersed in an aqueous (w2) phase by membrane emulsification and stabilized by a caseinate-pectin complex to produce w1/o/w2 EMEs. The resulting EME showed no signs of phase separation for weeks at room temperature. The microemulsion and EME were characterized by differential scanning calorimetry (DSC), cryo-TEM and small angle x-ray scattering (SAXS) to determine whether the microemulsion’s internal structure was maintained after emulsification. It was shown that EME droplets displayed ordering around the periphery consistent with some loss of microemulsion structure, but maintained the characteristic disordered microemulsion structure at the droplet core. Overall, this research demonstrated the feasibility of developing EME for possible applications in food and non-food applications.

Distribution of water-soluble phthalocyanine in latex polymer according to small-angle X-ray scattering

2013 ◽  
Vol 49 (3) ◽  
pp. 280-285 ◽  
Author(s):  
T. R. Aslamazova ◽  
V. A. Kotenev ◽  
A. A. Shiryaev ◽  
A. Yu. Tsivadze
Keyword(s):  
Small Angle ◽  
Water Soluble ◽  
X Ray ◽  
X Ray Scattering ◽  
Latex Polymer ◽  
Ray Scattering

Orange Carotenoid Protein (OCP): A Key Player in Non-photochemical Quenching of Cyanobacteria under Fluctuating Light Condition

2018 ◽  
Vol 4 (02) ◽  
pp. 35-40
Author(s):  
Yogesh Mishra ◽  
Akanksha Srivastava ◽  
Atul Tiwari ◽  
Raju Mondal ◽  
Sandhya Yadav ◽  
...  
Keyword(s):  
Active Form ◽  
Light Condition ◽  
High Irradiance ◽  
Water Soluble ◽  
Photochemical Quenching ◽  
Protective Mechanism ◽  
Terminal Domain ◽  
Fluctuating Light ◽  
Orange Carotenoid Protein ◽  
Non Photochemical Quenching

Fluctuating light condition poses major threat to photosynthetic organisms by evoking the production of reactive oxygen species (ROS). To endure the high irradiance level, plants and algae have evolved a photo-protective mechanism, referred as non-photochemical quenching (NPQ). This mechanism concerns with minimizing arrival of the excess excitation energy on reaction centers by dissipating surplus energy in form of harmless heat. Earlier cyanobacteria were not considered to capable of performing NPQ. Alternatively, state transition was supposed to be the major means that cyanobacteria preferably carried out to be protected under high light. Recently it was substantiated with evidence that these organisms can execute NPQ as a prominent photo-protective strategy. NPQ in cyanobacteria is mediated by a water soluble orange carotenoid protein (OCP) which is structurally and functionally modular. OCP consists of two domains (i) N-terminal domain (NTD) and (ii) C-terminal domain (CTD) with a single carotenoid as a chromophore spanning symmetrically in both domains. Blue-green or strong white light induces conversion of OCP from an inactive orange state (OCPO) to active red state (OCPR). Active form of OCP (OCPR) binds to core of light harvesting antenna complex, phycobilisome (PBS), where it quenches fluorescence and assists in dissipation of excess energy by non-radiative pathway. Prior to prevent wasteful quenching of fluorescence under light starvation, another protein named fluorescence recovery protein (FRP) partakes in decoupling OCPR from PBS and accelerates conversion of OCPR state back to OCPO state.

A new family of bent-core C2-symmetric liquid crystals

2010 ◽  
Vol 88 (7) ◽  
pp. 639-645 ◽  
Author(s):  
Kyle A. Hope-Ross ◽  
Paul A. Heiney ◽  
John F. Kadla
Keyword(s):  
Differential Scanning Calorimetry ◽  
Small Angle ◽  
Liquid Crystalline ◽  
Side Chains ◽  
Scanning Calorimetry ◽  
X Ray ◽  
New Family ◽  
X Ray Scattering ◽  
Factors Influencing ◽  
Liquid Crystalline Phases

A series of C2-symmetric compounds with different core sizes and varying lengths and numbers of alkoxy side chains were prepared, and the factors influencing their liquid crystalline mesophase behaviour were investigated. The compounds studied were based on benzophenone, dibenzylidene-acetone, and 1,9-diphenyl-nona-1,3,6,8-tetraen-5-one cores with either 1 or 2 linear alkoxy side chains. The side chains were varied in length from C6H13 to C12H25. The liquid crystalline mesophase behaviour of the compounds was investigated using differential scanning calorimetry, polarizing optical microscopy, and small-angle X-ray scattering (SAXS). It was found that a number of the molecules were able to self-assemble into smectic and nematic liquid crystalline phases.

Inorganic-Organic Hybrid Hierarchically Structured Methyl-modified Silica Monoliths

2004 ◽  
Vol 847 ◽  
Author(s):  
Doris Brandhuber ◽  
Nicola Hüsing ◽  
Herwig Peterlik
Keyword(s):  
Liquid Crystalline ◽  
Sol Gel ◽  
Analytical Techniques ◽  
Structural Features ◽  
Water Soluble ◽  
X Ray ◽  
Silica Monoliths ◽  
Organic Hybrid ◽  
X Ray Scattering ◽  
Highly Porous

ABSTRACTHighly porous inorganic-organic hybrid monoliths with mesopores in a macroporous network have been prepared from methyltris(2-hydroxyethoxy)silane (MeGMS) and tetrakis(2-hydroxyethoxy)silane (EGMS) in the presence of an amphiphilic block copolymer. The amount of methyltris(2-hydroxyethoxy)silane (MeGMS) in the gel has been varied from 0 to 100 %. These glycol-modified silanes have the advantage of being water-soluble and thus allowing for a direct templating of liquid-crystalline surfactant mesophases without the presence of a homogenizing organic solvent such as ethanol. The wet gels have been dried by supercritical extraction with carbon dioxide.In the present work, the sol-gel behaviour of these glycol-modified silanes is discussed especially with a focus on the formation of the meso- and macrostructure. In addition, the influences of the varying ratios of methyltris(2-hydroxyethoxy)silane on the structural features of the gels are investigated by various analytical techniques such as small angle X-ray scattering, nitrogen sorption, and scanning electron microscopy.

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