Search results for "Secondary"
showing 10 items of 1765 documents
Topology-Dependent Swichability of Peptide Secondary Structures in Bioconjugates with Complex Architectures
2013
Peptide sequences, which exhibit a reversible pH-responsive coil to α-helix secondary structure transition, are conjugated to polymer precursors to yield linear AB and graft ABA peptide-poly(ethylene oxide) conjugates. While the PEO B-block is comparable, the conjugates differ in topologies of the peptide bearing A-blocks. The influences of topology on the structure transitions in the peptide segments are investigated, comparing linear AB-bioconjugates with graft ABA-bioconjugates having multiple peptide segments combined in star or pom-pom topologies.
Formation of covalent di-tyrosine dimers in recombinant α-synuclein
2015
Parkinson's disease is associated with fibril deposition in the diseased brain. Misfolding events of the intrinsically disordered synaptic protein α-synuclein are suggested to lead to the formation of transient oligomeric and cytotoxic species. The etiology of Parkinson's disease is further associated with mitochondrial dysfunction and formation of reactive oxygen species. Oxidative stress causes chemical modification of native α-synuclein, plausibly further influencing misfolding events. Here, we present evidence for the spontaneous formation of covalent di-tyrosine α-synuclein dimers in standard recombinant protein preparations, induced without extrinsic oxidative or nitrative agents. The…
Identification of the membrane penetrating domain of Vibrio cholerae cytolysin as a β-barrel structure
2005
Summary Vibrio cholerae cytolysin (VCC) is an oligomerizing pore-forming toxin that is related to cytolysins of many other Gram-negative organisms. VCC contains six cysteine residues, of which two were found to be present in free sulphydryl form. The positions of two intramolecular disulphide bonds were mapped, and one was shown to be essential for correct folding of protoxin. Mutations were created in which the two free cysteines were deleted, so that single cysteine substitution mutants could be generated for site-specific labelling. Employment of polarity-sensitive fluorophores identified amino acid side-chains that formed part of the pore-forming domain of VCC. The sequence commenced at…
Studies on the biosynthesis of paraherquamide. Construction of the amino acid framework
2001
Abstract It has been previously established in this laboratory that the β-methyl-β-hydroxyproline moiety of the potent anthelmintic agent paraherquamide A, is biosynthetically derived from l -isoleucine. The downstream events from l -Ile to paraherquamide A have now been investigated. The synthesis of [1- 13 C]-labeled l -β-methylproline is described by means of a Hoffman–Loeffler–Freytag reaction sequence from [1- 13 C]- l -Ile. This amino acid is shown to be a direct biosynthetic precursor to paraherquamide A by feeding and incorporation experiments in growing cultures of Penicillium fellutanum . Three tryptophan-containing dipeptides of l -β-methylproline have been constructed: [ 13 C 2 …
Omphalocarpoidone, a new lanostane-type furano-spiro-γ-lactone from the wood of Tridesmostemon omphalocarpoides Engl. (Sapotaceae)
2013
Abstract Phytochemical studies of the wood and the stem bark of Tridesmostemon omphalocarpoides Engl. (Sapotaceae) led to the isolation of omphalocarpoidone (1), a new lanostane-type furano-spiro-γ-lactone together with β-amyrin acetate (2), taraxerol (3), spinasterol (4), lichexanthone (5), epi-catechin (6), spinasterol 3-O-β- d -glucopyranoside (7), tormentic acid (8), and 1,2,3,4-tetrahydronorharman-1-one (9). Their structures were established on the basis of extensive NMR studies, mass spectrometry, and by comparison of the data with those previously reported in the literature. The structure of the new secondary metabolite was later confirmed by X-ray crystallography. Except for spinast…
Predicted secondary structure of hydroperoxide lyase from green bell pepper cloned in the yeast Yarrowia lipolytica
2010
International audience; Fatty acid hydroperoxide lyase (HPL) is a member of the cytochrome P450 family acting on fatty acid hydroperoxides in many organisms. The active green bell pepper HPL, cloned and expressed in the yeast Yarrowia lipolytica, was purified by immobilized metal-ion affinity chromatography (IMAC) in the presence of 2% of Triton X-100R. The secondary structure prediction by bioinformatics servers of HPL was realized by ANTHEPROT software, using the GOR, DPM and Predator methods. The theoretical results which are average values obtained from three different calculation methods showed 33% α-helix, 18% β-sheet, 7% turn and 42% coil. On the other hand, the secondary structure a…
Advanced descriptors for long-range noncovalent interactions between SARS-CoV-2 spikes and polymer surfaces.
2021
The recent pandemic triggered numerous societal efforts aimed to control and limit the spread of SARS-CoV-2. One of these aspects is related on how the virion interacts with inanimate surfaces, which might be the source of secondary infection. Although recent works address the adsorption of the spike protein on surfaces, there is no information concerning the long-range interactions between spike and surfaces, experimented by the virion when is dispersed in the droplet before its possible adsorption. Some descriptors, namely the interaction potentials per single protein and global potentials, were calculated in this work. These descriptors, evaluated for the closed and open states of the sp…
Conformation of dehydropentapeptides containing four achiral amino acid residues - controlling the role of L-valine.
2014
Structural studies of pentapeptides containing an achiral block, built from two dehydroamino acid residues (ΔZPhe and ΔAla) and two glycines, as well as one chiral L-Val residue were performed using NMR spectroscopy. The key role of the L-Val residue in the generation of the secondary structure of peptides is discussed. The obtained results suggest that the strongest influence on the conformation of peptides arises from a valine residue inserted at the C-terminal position. The most ordered conformation was found for peptide Boc-Gly-ΔAla-Gly-ΔZPhe-Val-OMe (3), which adopts a right-handed helical conformation.
Über die kinetik und den mechanismus der biosynthese der cellulose in den höheren pflanzen (nach versuchen an den samenhaaren der baumwolle)
1966
Abstract The quantity of cellulose synthesized on growing cotton bolls and the corresponding degree of polymerisation have been measured as a function of time. It was found that the biosynthesis proceeds in two distinct stages, beginning with a slow process yielding the “primary” cellulose with a non-uniform degree of polymerisation of about 2000–6000 followed by a more rapid process yielding a large amount of “secondary cellulose” with a high and uniform degree of polymerisation of about 14000 (mol. wt. 2.3·106). During the second stage the degree of polymerisation is independent of time. It is shown that the two kinds of cellulose correspond to the primary and secondary cell wall. In orde…
Neuere untersuchungen über größe und größenverteilung der β-glukosidischen ketten nativer cellulosen
1963
Der Polymerisationsgrad Pw der β-glukosidischen Ketten der Cellulose in unbehandelten Baumwollen verschiedener Herkunft liegt etwa zwischen 8500 und 9500. Die Molekulargewichtsverteilung zeigt 3 ausgepragte Maxima beim Polymerisationsgrad 11 500, 5500 und ca. 1500. Das letztere Maximum gehort wahrscheinlich zum Cellulosematerial der Primarwand, wahrend die beiden anderen Maxima dem Material der Sekundarwand angehoren. Die hohe Einheitlichkeit und der grose Mengenanteil des zum hochsten Maximum (bei P = 11 500) gehorenden Celluloseanteils legt es nahe, fur die biochemische Synthese der Cellulose einen POISSONmechanismus oder einen Matritzenmechanismus anzunehmen. Fasercellulosen aus anderen …