Multi Stimuli Responsive Materials Supported by Orthogonal Hydrogen and Halogen Bonding or I···Alkene Interaction

Smart materials represent an elegant class of (macro)-molecules endowed with the ability to react to chemical/physical changes in the environment. Herein, we prepared new photo responsive azobenzenes possessing halogen bond donor groups. The X-ray structures of two molecules highlight supramolecular organizations governed by unusual noncovalent bonds. In azo dye I-azo-NO2, the nitro group is engaged in orthogonal H···O···I halogen and hydrogen bonding, linking the units in parallel undulating chains. As concern parent I-azo-NH-MMA, a non-centrosymmetric pattern is formed due to a very rare I···π interaction involving the alkene group supplemented by hydrogen bonds. The Cambridge Structural Database contains only four structures with the same I···CH2=C contact. For all compounds, a 19F NMR spectroscopic analysis confirms the formation of halogen bonds in solution through a recognition process with chloride anion, and the reversible photo-responsiveness is demonstrated upon exposing a solution to UV light irradiation. Finally, intermediate I-azo-NO2 also shows a pronounced color change due to pH variation. These azobenzenes are thereby attractive building blocks to design multi-stimuli responsive materials for highly functional devices.

In-depth characterization of self-healing polymers based on π–π nteractions

The self-healing behavior of two supramolecular polymers based on π–π-interactions featuring different polymer backbones is presented. For this purpose, these polymers were synthesized utilizing a polycondensation of a perylene tetracarboxylic dianhydride with polyether-based diamines and the resulting materials were investigated using various analytical techniques. Thus, the molecular structure of the polymers could be correlated with the ability for self-healing. Moreover, the mechanical behavior was studied using rheology. The activation of the supramolecular interactions results in a breaking of these noncovalent bonds, which was investigated using IR spectroscopy, leading to a sufficient increase in mobility and, finally, a healing of the mechanical damage. This scratch-healing behavior was also quantified in detail using an indenter.

Heat-Induced Interaction of Milk Proteins: Impact on Yoghurt Structure

Heating milk for yoghurt preparation has a significant effect on the structural properties of yoghurt. Milk heated at elevated temperature causes denaturation of whey protein, aggregation, and some case gelation. It is important to understand the mechanism involved in each state of stabilization for tailoring the final product. We review the formation of these complexes and their consequence on the physical, rheological, and microstructural properties of acid milk gels. To investigate the interactions between denatured whey protein and casein, the formation of covalent and noncovalent bonds, localization of the complexes, and their impact on ultimate gelation and final yoghurt texture are reviewed. The information regarding this fundamental mechanism will be beneficial to develop uniform quality yoghurt texture and potential interest of future research.

Noncovalent Bonds through Sigma and Pi-Hole Located on the Same Molecule. Guiding Principles and Comparisons

Over the last years, scientific interest in noncovalent interactions based on the presence of electron-depleted regions called σ-holes or π-holes has markedly accelerated. Their high directionality and strength, comparable to hydrogen bonds, has been documented in many fields of modern chemistry. The current review gathers and digests recent results concerning these bonds, with a focus on those systems where both σ and π-holes are present on the same molecule. The underlying principles guiding the bonding in both sorts of interactions are discussed, and the trends that emerge from recent work offer a guide as to how one might design systems that allow multiple noncovalent bonds to occur simultaneously, or that prefer one bond type over another.

Effects of Pulsed Electric Fields on Yeast with Prions and the Structure of Amyloid Fibrils

Prions are misfolded, self-replicating, and transmissible proteins capable of causing different conditions that affect the brain and nervous system in humans and animals. Yeasts are the perfect model to study prion formation, dissemination, and the structure of protein aggregates. Yeast prions are related to stress resistance, cell fitness, and viability. Applying a pulsed electric field (PEF) as a factor capable of disintegrating the amyloid aggregates arises from the fact that the amyloid aggregates form via noncovalent bonds and stabilize via electrostatic interactions. In this research, we applied 2–26 kV/cm PEF delivered in sequences of 5 pulses of 1 ms duration to the Saccharomyces cerevisiae cell without prions and containing strong and weak variants of the [PSI+] prion (prion form of Sup35 translation termination factor). We determined that prions significantly increase cell survivability and resistance to PEF treatment. The application of PEF to the purified Sup35NM fibrils showed that the electric field causes significant reductions in the length of fibrils and the full disintegration of fibrils to Sup35 oligomers can be achieved in higher fields.

Ultrarobust, tough and highly stretchable self-healing materials based on cartilage-inspired noncovalent assembly nanostructure

Self-healing materials integrated with excellent mechanical strength and simultaneously high healing efficiency would be of great use in many fields, however their fabrication has been proven extremely challenging. Here, inspired by biological cartilage, we present an ultrarobust self-healing material by incorporating high density noncovalent bonds at the interfaces between the dentritic tannic acid-modified tungsten disulfide nanosheets and polyurethane matrix to collectively produce a strong interfacial interaction. The resultant nanocomposite material with interwoven network shows excellent tensile strength (52.3 MPa), high toughness (282.7 MJ m‒3, which is 1.6 times higher than spider silk and 9.4 times higher than metallic aluminum), high stretchability (1020.8%) and excellent healing efficiency (80–100%), which overturns the previous understanding of traditional noncovalent bonding self-healing materials where high mechanical robustness and healing ability are mutually exclusive. Moreover, the interfacical supramolecular crosslinking structure enables the functional-healing ability of the resultant flexible smart actuation devices. This work opens an avenue toward the development of ultrarobust self-healing materials for various flexible functional devices.

Detailed Structure and Pathophysiological Roles of the IgA-Albumin Complex in Multiple Myeloma

Immunoglobulin A (IgA)-albumin complexes may be associated with pathophysiology of multiple myeloma, although the etiology is not clear. Detailed structural analyses of these protein–protein complexes may contribute to our understanding of the pathophysiology of this disease. We analyzed the structure of the IgA-albumin complex using various electrophoresis, mass spectrometry, and in silico techniques. The data based on the electrophoresis and mass spectrometry showed that IgA in the sera of patients was dimeric, linked via the J chain. Only dimeric IgA can bind to albumin molecules leading to IgA-albumin complexes, although both monomeric and dimeric forms of IgA were present in the sera. Molecular interaction analyses in silico implied that dimeric IgA and albumin interacted not only via disulfide bond formation, but also via noncovalent bonds. Disulfide bonds were predicted between Cys34 of albumin and Cys311 of IgA, resulting in an oxidized form of albumin. Furthermore, complex formation prolongs the half-life of IgA molecules in the IgA-albumin complex, leading to excessive glycation of IgA molecules and affects the accumulation of IgA in serum. These findings may demonstrate why complications such as hyperviscosity syndrome occur more often in patients with IgA dimer producing multiple myeloma.

A New Proposed Mechanism of some Known Drugs Targeting the SARS-CoV-2 Spike Glycoprotein Using Molecular Docking

COVID-19 is caused by the novel enveloped beta-coronavirus with a genomic RNA closely related to severe acute respiratory syndrome-corona virus (SARS-CoV) and is named coronavirus 2 (SARS-CoV-2). In this study, six synthetic drugs were specifically docked against the RBD. Most of the six compounds were observed to fit nicely with specific noncovalent interactions. Oseltamivir was found to be the most strongly interacting with the RBD, exhibiting high values of full fitness and low free energy of binding. It formed multiple noncovalent bonds in the region of the active site. Hydroxychloroquine also demonstrated high binding affinity in the solvent accessibility state and fit nicely into the S-protein's active pocket. The results revealed that these compounds could be potent inhibitors of S-protein that could, to some extent, block its interaction with ACE-2. It is obvious from the 3D structure of SARS-CoV-2 spike protein was changed with the interaction of different drugs, which led to the unsuitability to bind ACE2 receptor. Hence, laboratory studies elucidating the action of these compounds on SARS-CoV-2 are warranted for clinical assessments. Chloroquine, hydroxychloroquine, and oseltamivir interacted well with the receptor-binding domain of S-protein via noncovalent interactions and were recommended as excellent candidates for COVID-19.