Search results for "Fibril"
showing 10 items of 836 documents
Cellulose nanofibrils prepared by gentle drying methods reveal the limits of helium ion microscopy imaging
2019
TEMPO-oxidized cellulose nanofibrils (TCNFs) have unique properties, which can be utilised in many application fields from printed electronics to packaging. Visual characterisation of TCNFs has been commonly performed using Scanning Electron Microscopy (SEM). However, a novel imaging technique, Helium Ion Microscopy (HIM), offers benefits over SEM, including higher resolution and the possibility of imaging non-conductive samples uncoated. HIM has not been widely utilized so far, and in this study the capability of HIM for imaging of TCNFs was evaluated. Freeze drying and critical point drying (CPD) techniques were applied to preserve the open fibril structure of the gel-like TCNFs. Both dr…
Thioflavin T Promotes Aβ(1−40) Amyloid Fibrils Formation
2015
Fibrillogenesis of the small peptide Aβ(1-40) is considered to be the hallmark of Alzheimer's disease. Some evidence indicates small oligomers, rather than mature fibrils, as the key cytotoxic agents. The fluorescent dye Thioflavin T (ThT) is often used to detect amyloid deposits in both in vivo and in vitro experiments, and it is used to study kinetic measurements, under the fundamental hypothesis that this probe does not influence the aggregation processes. We report experimental data showing that ThT may promote the Aβ(1-40) peptide amyloid aggregation changing solvent-peptide interactions and stabilizing more ordered β-like conformation. This finding has a two-fold importance: It is a f…
Photo-inhibition of Ab fibrillation mediated by a newly designed fluorinated oxadiazole
2015
Uncontrolled aggregation of amyloid beta peptide (A?) is the main cause of Alzheimer's Disease. Therapeutic approaches of intervention in amyloid diseases include the use of small molecules able to stabilize the soluble A? conformation, or to redirect the amyloidogenic pathway towards non-toxic and non-fibrillar states. Fluorometric measurements revealed that the 3-(4'-trifluoromethylphenyl)-5-(4'-methoxyphenyl)-1,2,4-oxadiazole, when irradiated, is able to interact with monomeric A? peptide readdressing the aggregation pathway toward the formation of amorphous aggregates as evidenced by means of CD, AFM, and SAXS measurements. We hypothesize that this compound, under radiation, forms a rea…
Supramolecular Polymers in Aqueous Media
2016
This review discusses one-dimensional supramolecular polymers that form in aqueous media. First, naturally occurring supramolecular polymers are described, in particular, amyloid fibrils, actin filaments, and microtubules. Their structural, thermodynamic, kinetic, and nanomechanical properties are highlighted, as well as their importance for the advancement of biologically inspired supramolecular polymer materials. Second, five classes of synthetic supramolecular polymers are described: systems based on (1) hydrogen-bond motifs, (2) large π-conjugated surfaces, (3) host-guest interactions, (4) peptides, and (5) DNA. We focus on recent studies that address key challenges in the field, provid…
Studies on the Fibrous Components of the Test ofCiona intestinalisLinnaeus. I. Cellulose-like Polysaccharide
1977
Chemical, histochemical and electron microscopic studies on the fibrous polysaccharide component of the test of Ciona intestinalis L. were made. The results showed cellulose-like fibres to be present in the cuticle layer and in the ground substance. Bundles of fibres varying in diameter from 80 to 600 nm interweave to form a conspicuous network. The bundle appears to be formed of flat fibres, 10–13 nm in width, while the fibre is composed of fibrils 3.5–5 nm; the rectangular cross section of fibres can be supposed. The probable role of this polysaccharide is discussed.
Chitin: A Structural Biopolysaccharide
2009
Chitin is a naturally occurring fibre-forming polymer that plays a protective role in many lower eukaryotes similar to that of cellulose in plants. Chemically it is a long-chain unbranched polysaccharide made of N-acetylglucosamine residues; it is the second most abundant organic compound in nature, after cellulose. Taking into account the structural role played by chitin, its metabolism (synthesis and degradation) is essential for different morphogenetic events. Absent in vertebrates and plants, chitin represents a parasite-specific target for chemotherapeutic attack and also plays a role in host immune responses. Because of its abundance in nature and its properties, biotechnological appl…
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…
Chitin: A Structural Biopolysaccharide with Multiple Applications
2014
Chitin is a naturally occurring fibre-forming polymer that plays a protective role in many lower eukaryotes similar to that of cellulose in plants. Chemically it is a long-chain unbranched polysaccharide made of N-acetylglucosamine residues linked through β-1,4 covalent bonds; it is the second most abundant organic compound in nature, after cellulose. Taking into account the role played by chitin in different biological structures (i.e. fungal cell walls, insect peritrophic matrix, insect and crustacean cuticles, eggshells from nematodes, cyst wall of protozoa), its metabolism (biosynthesis and degradation) is essential for different morphogenetic events. Absent in vertebrates and plants, c…
C1q
2000
Publisher Summary This chapter provides information to the physical properties, structure, and function of C1q protein. This protein is made up of three individual polypeptide chains, A, B and C, which are synthesized as pre-molecules with 22, 25, and 28 amino acid leader sequences, respectively. C1q has a characteristic appearance under the electron microscope, with six globular heads connected by six collagen-like stalks forming a central fibril stem. Glucosylgalactosyl disaccharide units are linked to certain hydroxylysine residues in the collagen regions of all three chains. C1q has a critical function in host defense and clearance of immune complexes. Antibody-independent activation of…
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…