Search results for "Spherulite"

The Use of Wild Plants in the Palaeolithic and Neolithic of Northwestern Africa: Preliminary Results from the PALEOPLANT Project

2018

Carrión Marco Y., Morales J., Portillo M., Pérez-Jordà G., Peña-Chocarro L., Zapata L. (2018) The Use of Wild Plants in the Palaeolithic and Neolithic of Northwestern Africa: Preliminary Results from the PALEOPLANT Project. En: Mercuri A., D'Andrea A., Fornaciari R., Höhn A. (eds.) Plants and People in the African Past. Springer, Cham

Ethanol Controls the Self-Assembly and Mesoscopic Properties of Human Insulin Amyloid Spherulites.

2018

Protein self-assembly into amyloid fibrils or highly hierarchical superstructures is closely linked to neurodegenerative pathologies as Alzheimer's and Parkinson's diseases. Moreover, protein assemblies also emerged as building blocks for bioinspired nanostructured materials. In both the above mentioned fields, the main challenge is to control the growth and properties of the final protein structure. This relies on a more fundamental understanding of how interactions between proteins can determine structures and functions of biomolecular aggregates. Here, we identify a striking effect of the hydration of the single human insulin molecule and solvent properties in controlling hydrophobicity/…

Polysorbate 80 controls Morphology, structure and stability of human insulin Amyloid-Like spherulites

2022

AbstractAmyloid protein aggregates are not only associated with neurodegenerative diseases and may also occur as unwanted by-products in protein-based therapeutics. Surfactants are often employed to stabilize protein formulations and reduce the risk of aggregation. However, surfactants alter protein-protein interactions and may thus modulate the physicochemical characteristics of any aggregates formed. Human insulin aggregation was induced at low pH in the presence of varying concentrations of the surfactant polysorbate 80. Various spectroscopic and imaging methods were used to study the aggregation kinetics, as well as structure and morphology of the formed aggregates. Molecular dynamics s…

Corrigendum to “Polysorbate 80 controls Morphology, structure and stability of human insulin Amyloid-Like spherulites” [J. Colloid Interface Sci. 606…

2023

Spherulites in Calcrete Laminar Crusts: Biogenic CACO3 Precipitation as a Major Contributor to Crust Formation

1995

ABSTRACT Spherulites (calcitic fibro-radial spherulitic polycrystals) are a major component of calcite layers in Quaternary calcrete laminar crusts. To explain the formation of spherulites, petrographic and chemical studies were performed on Pleistocene calcrete laminar crusts, Holocene biological crusts, and laboratory (in vitro) cultures of cyanobacterial strains. Spherulites were found to be formed of acicular and radiating crystals, either smooth and regular-edged, or twisted and irregular-edged. Spherulites were composed of low-Mg calcite, the concentration of Mg in the spherulites increasing from nucleus to periphery. The shape and chemistry of the in vitro spherulites and laminar cru…

Wide-range cooling characteristics of a selected isotactic polypropylene

1997

Abstract An increased knowledge of polymer crystallization kinetics and its effect on the crystalline structure is of particular importance at high cooling rates. The aims of this study were to explore the range of utility and complementarity of various methods (densitometry, microscopy, wide-angle x-ray diffraction [WAXD], and small-angle light scattering [SALS]) on the characterization of the crystalline structure of a high purity isotactic polypropylene (PP) in a wider cooling range than previously obtainable and to identify characteristic ranges of the structure as a function of cooling rate. High cooling rates, ranging to nearly 1000°C/sec, were obtained using a special quench device. …

Probing ensemble polymorphism and single aggregate structural heterogeneity in insulin amyloid self-assembly.

2020

Ensembles of protein aggregates are characterized by a nano- and micro-scale heterogeneity of the species. This diversity translates into a variety of effects that protein aggregates may have in biological systems, both in connection to neurodegenerative diseases and immunogenic risk of protein drug products. Moreover, this naturally occurring variety offers unique opportunities in the field of protein-based biomaterials. In the above-mentioned fields, the isolation and structural analysis of the different amyloid types within the same ensemble remain a priority, still representing a significant experimental challenge. Here we address such complexity in the case of insulin for its relevance…

Insights into localized manipulation of organogel-related microcrystalline spherulite formation

2015

Abstract The formation processes of microcrystalline spherulitic fiber systems related to bile acid amides were determined to include dominant interface-related aspects, the role of which were studied in terms of potential manipulation and increased control over the overall structure of the networks. The nucleation and growth properties and aggregation of two lithocholyl amide derivatives were studied in several organic solvents using thermomicroscopy, as well as thermal control at macroscopic level. Nucleation/crystallization at interfaces was observed to act as the main route for the formation of microcrystalline fibers/solids in six gelator–solvent systems, in which spherulite formation …

The route to protein aggregate superstructures: Particulates and amyloid-like spherulites.

2015

AbstractDepending on external conditions, native proteins may change their structure and undergo different association routes leading to a large scale polymorphism of the aggregates. This feature has been widely observed but is not fully understood yet. This review focuses on morphologies, physico-chemical properties and mechanisms of formation of amyloid structures and protein superstructures. In particular, the main focus will be on protein particulates and amyloid-like spherulites, briefly summarizing possible experimental methods of analysis. Moreover, we will highlight the role of protein conformational changes and dominant forces in driving association together with their connection w…

Spherulite formation in a ?noncrystalline? two-dimensional hydrogen-bond assembly

1996

4-Urazoyl benzoic acid groups 1 are attached as terminal end group to an oligoisobutene. According to wide-angle X-ray scattering the material is amorphous. Differential scanning calorimetry, small-angle X-ray scattering, transmission electron microscopy, and polarizing microscopy show that the polar head groups form ordered two-dimensional assemblies which organize into spherulites. Temperature-dependent SAXS measurements and the d.s.c. analysis give a close insight into the order-disorder (“melting”) process of the two-dimensional clusters which form macroscopic spherulites. The order-disorder transition of the clusters is closely related to the dynamics and order of the polyisobutene cha…