Search results for "Secondary"
showing 10 items of 1765 documents
Random mutations directed to transmembrane and loop domains of the light-harvesting chlorophyll a/b protein: impact on pigment binding.
1999
The major light-harvesting complex of photosystem II (LHCII) can be reconstituted in vitro by folding its bacterially expressed apoprotein, Lhcb, in detergent solution in the presence of chlorophylls and carotenoids. To compare the impact of alpha-helical transmembrane domains and hydrophilic loop domains of the apoprotein on complex formation and stability, we introduced random mutations into a segment of the protein comprising the stromal loop, the third (C-proximal) transmembrane helix, and part of the amphipathic helix in the C-terminal domain. The mutant versions of Lhcb were screened for the loss of their ability to form stable LHCII upon reconstitution in vitro. Most steps during the…
Water-Soluble Chlorophyll Protein (WSCP) Stably Binds Two or Four Chlorophylls
2017
Water-soluble chlorophyll proteins (WSCPs) of class IIa from Brassicaceae form tetrameric complexes containing one chlorophyll (Chl) per apoprotein but no carotenoids. The complexes are remarkably stable toward dissociation and protein denaturation even at 100 °C and extreme pH values, and the Chls are partially protected against photooxidation. There are several hypotheses that explain the biological role of WSCPs, one of them proposing that they function as a scavenger of Chls set free upon plant senescence or pathogen attack. The biochemical properties of WSCP described in this paper are consistent with the protein acting as an efficient and flexible Chl scavenger. At limiting Chl concen…
Amino acids in the second transmembrane helix of the Lhca4 subunit are important for formation of stable heterodimeric light-harvesting complex LHCI-…
2007
Photosynthetic light-harvesting complexes (LHCs) are assembled from apoproteins (Lhc proteins) and non-covalently attached pigments. Despite a considerable amino acid sequence identity, these proteins differ in their oligomerization behavior. To identify the amino acid residues determining the heterodimerization of Lhca1 and Lhca4 to form LHCI-730, we mutated the poorly conserved second transmembrane helix of the two subunits. Mutated genes were expressed in Escherichia coli and the resultant proteins were refolded in vitro and subsequently analyzed by gel electrophoresis. Replacement of the entire second helix in Lhca4 by the one of Lhca3 abolished heterodimerization, whereas it had no eff…
Localization of the N-terminal Domain in Light-harvesting Chlorophyll a/b Protein by EPR Measurements
2005
The conformational distribution of the N-terminal domain of the major light-harvesting chlorophyll a/b protein (LHCIIb) has been characterized by electron-electron double resonance yielding distances between spin labels placed in various domains of the protein. Distance distributions involving residue 3 near the N terminus turned out to be bimodal, revealing that this domain, which is involved in regulatory functions such as balancing the energy flow through photosystems (PS) I and II, exists in at least two conformational states. Models of the conformational sub-ensembles were generated on the basis of experimental distance restraints from measurements on LHCIIb monomers and then checked f…
Pathways to and within Higher Education for youths of immigrant backgrounds
2019
International audience; This presentation looks first at the access to higher education of immigrant youths and particularly through which tracks in secondary education. It then shows the choice of type of institution and field of study (vertical and horizontal differentiation) made by these youths once in higher education, as well as to what extent they succeed in obtaining a higher education diploma. The presentation focuses on comparative research across European countries as well as outside Europe (e.g. Canada), taking into account country contexts and the organization of the educational systems both in secondary and higher education. Moreover, differences between country of origin, gen…
The Short-Access Mother–Baby-(SAMBA) Cholangioscopy System
2014
Conventional mother–baby cholangioscopy systems have significant limitations including poor image resolution, limited maneuverability and fragile cholangioscopes. We propose the novel short-access mother–baby-(SAMBA) cholangioscopy system that involves a very short and flexible cholangioscope that is introduced in a dedicated mother duodenoscope with an extra distal side port. Clinical feasibility of this device is demonstrated in three complex cases with cholangiopathies. The strengths of SAMBA cholangioscopy are improved imaging quality and excellent maneuverability of the baby that allows access of small intrahepatic ducts. Evaluation of suspected intrahepatic biliary disease is an excel…
Synchronized gradient elution in capillary liquid chromatography
2013
Abstract The synchronization of injection valve operation and gradient elution in capillary liquid chromatography (cHPLC) is studied. Focus is placed on the cHPLC systems which rely on the splitting of a primary flow to provide the much smaller secondary flow required at the injection device and analytical column. Owing to the tiny secondary flow rates, synchronization is necessary to achieve proper optimization of gradient elution methods. Otherwise, there is a risk of having the analytes totally or partially eluted in the initial isocratic conditions, and there is no control on the actual gradient profile reaching the column. Synchronization is first achieved by switching back the valve t…
Diagnostic algorithm for familial chylomicronemia syndrome
2016
International audience; Background: Familial chylomicronemia syndrome (FCS) is a rare genetic disease that leads to severe hypertriglyceridemia often associated with recurrent episodes of pancreatitis. The recognition and correct diagnosis of the disease is challenging due to its rarity, and to the lack of specificity of signs and symptoms. Lipid experts, endocrinologists, gastroenterologists, pancreatologists, and general practitioners may encounter patients who potentially have FCS. Therefore, cooperation between experts and improved knowledge of FCS is essential in improving the diagnosis. Currently, a consensus on best practice for the diagnosis of FCS is lacking. Methods: Aiming to def…
Fluorescence and circular dichroism spectroscopy to understand the interactions between cyclodextrins and α-galactosidase from green coffee beans
2017
Abstract The potential of fluorescence measurement and circular dichroism spectroscopy (CDSP) to evaluate the interaction between cyclodextrins (CDs) (CD cavity size, concentration, pH, reaction time, and temperature as well as different side chain groups) and α-galactosidase was evaluated. A strong relationship was observed between α-galactosidase fluorescence intensity and CD cavity size, concentration, pH, reaction time, and temperature as well as different side chain groups. Therefore, it can be concluded that fluorescence intensity measurement can be a promising tool to ascertain β-CD-α-galactosidase interactions. CDSP is also an interesting tool to understand β-CD-α-galactosidase inte…
Entrapment of A Beta 1-40 peptide in unstructured aggregates
2012
Recognizing the complexity of the fibrillogenesis process provides a solid ground for the development of therapeutic strategies aimed at preventing or inhibiting protein-protein aggregation. Under this perspective, it is meaningful to identify the possible aggregation pathways and their relative products. We found that Aβ-peptide dissolved in a pH 7.4 solution at small peptide concentration and low ionic strength forms globular aggregates without typical amyloid β-conformation. ThT binding kinetics was used to monitor aggregate formation. Circular dichroism spectroscopy, AFM imaging, static and dynamic light scattering were used for structural and morphological characterization of the aggre…