Interfacial Electrostatic Self-Assembly of Amyloid Fibrils into Multifunctional Protein Films.

Amyloid fibrils have generated steadily increasing traction in the development of natural and artificial materials. However, it remains a challenge to construct bulk amyloid films directly from amyloid fibrils due to their intrinsic brittleness. Here, a facile and general methodology to fabricate macroscopic and tunable amyloid films via fast electrostatic self-assembly of amyloid fibrils at the air-water interface is introduced.

Multi-length scale structural investigation of lysozyme self-assembly.

Reactive amyloid oligomers are responsible for cytotoxicity in amyloid pathologies and because of their unstable nature characterizing their behavior is a challenge. The physics governing the self-assembly of proteins in crowded conditions is extremely complex and its comprehension, despite its paramount relevance to understanding molecular mechanisms inside cells and optimizing pharmaceutical processes, remains inconclusive. Here, we focus on the amyloid oligomerization process in self-crowded lysozyme aqueous solutions in acidic conditions.

Different Folding States from the Same Protein Sequence Determine Reversible vs Irreversible Amyloid Fate.

The propensity to self-assemble into amyloid fibrils with a shared cross-β architecture is a generic feature of proteins. Amyloid-related diseases affect millions of people worldwide, yet they are incurable and cannot be effectively prevented, largely due to the irreversible assembly and extraordinary stability of amyloid fibrils. Recent studies suggest that labile amyloids may be possible in certain proteins containing low-complexity domains often involved in the formation of subcellular membraneless organelles.

Effect of Polysaccharide Conformation on Ultrafiltration Separation Performance.

The manifold array of saccharide linkages leads to a great variety of polysaccharide architectures, comprising three conformations in aqueous solution: compact sphere, random coil, and rigid rod. This conformational variation limits the suitability of the commonly applied molecular weight cut-off (MWCO) as selection criteria for polysaccharide ultrafiltration membranes, as it is based on globular marker proteins with narrow M and hydrodynamic volume relation. Here we show the effect of conformation on ultrafiltration performance using randomly coiled pullulan and rigid rod-like scleroglucan as model polysaccharides for membrane rejection and molecular weight distribution.

Globular protein assembly and network formation at fluid interfaces: effect of oil.

The formation of viscoelastic networks at fluid interfaces by globular proteins is essential in many industries, scientific disciplines, and biological processes. However, the effect of the oil phase on the structural transitions of proteins, network formation, and layer strength at fluid interfaces has received little attention. Herein, we present a comprehensive study on the effect of oil polarity on globular protein networks.

Formation of Higher Structural Levels in λ-Carrageenan Induced by the Antimalarial Drug Chloroquine.

The linear polysaccharide λ-carrageenan is the only one among the carrageenans not forming secondary, tertiary, and quaternary structures in the presence of inorganic ions. Chloroquine (CQ) is a well-established antimalaria drug also recently discussed in therapeutics against the COVID-19 pandemic. The interaction of this polysaccharide-ionic drug pair was investigated by combining UV-vis spectrophotometry and atomic force microscopy (AFM) imaging.

Time-temperature-resolved functional and structural changes of phycocyanin extracted from Arthrospira platensis/Spirulina.

Arthrospira platensis, commonly known as Spirulina, gains increasing importance as alternative protein source for food production and biotechnological systems. A promising area is functional high-value algae extracts, rich in phycocyanin, a protein-pigment complex derived from A. platensis.

Rigid, Fibrillar Quaternary Structures Induced by Divalent Ions in a Carboxylated Linear Polysaccharide.

Polysaccharides are ubiquitous in nature; they serve fundamental roles in vivo and are used for a multitude of food, pharmaceutical, cosmetic biomaterials, and biomedical applications. Here, the structure-property function for low acetylated Gellan gum hydrogels induced by divalent ions was established by means of optical, rheological, and microscopic techniques. The hydrogels interacted with visible light as revealed by birefringence and multiple scattering, as a consequence of quaternary, supramolecular fibrillar structures.

Primary, Secondary, Tertiary and Quaternary Structure Levels in Linear Polysaccharides: From Random Coil, to Single Helix to Supramolecular Assembly.

Polysaccharides are ubiquitous in nature and represent an essential class of biopolymers with multiple levels of conformation and structural hierarchy. However, a standardized structural nomenclature, as in the case of proteins, is still lacking due to uncertainty on their hierarchical organization. In this work we use carrageenans as model polysaccharides to demonstrate that several structural levels exist and can be unambiguously resolved by statistical analysis on high resolution Atomic Force Microscopy images, supported by spectroscopic, X-ray scattering and rheological techniques.

Adsorption and Interfacial Layer Structure of Unmodified Nanocrystalline Cellulose at Air/Water Interfaces.

Nanocrystalline cellulose (NCC) is a promising biological nanoparticle for the stabilization of fluid interfaces.  However, the adsorption and interfacial layer structure of NCC are poorly understood as it is currently unknown how to form  NCC interfacial layers. Herein, we present parameters for the adsorption of unmodified NCC at the air-water (A/W) interface.

Supramolecular chiral self-assembly and supercoiling behavior of carrageenans at varying salt conditions.

The self-assembly of anionic kappa and iota carrageenan polysaccharides in the presence of NaCl, KCl and CaCl2 is studied by high-resolution atomic force microscopy (AFM). A hierarchical supramolecular chirality amplification over various length scales is observed upon the addition of KCl, whereas in the presence of NaCl and CaCl2 the chains undergo solely a coil-helix transition with stiff kappa carrageenan and more flexible iota carrageenan helical conformations.

(212)Pb@C(60) and its water-soluble derivatives: synthesis, stability, and suitability for radioimmunotherapy.

Fullerenes could potentially play a valuable role in radioimmunotherapy by more stably encapsulating radionuclides, especially where conventional chelation chemistry is inadequate due to the physical and/or chemical properties of the radionuclide. One of the therapeutically useful radionuclides that requires improved containment in vivo is 212Pb (tau1/2 = 10.6 h), the beta-emitting parent to alpha-emitting 212Bi (tau1/2 = 60.