Peptide-Based Biosensor for Express Diagnostics of Coronavirus Respiratory Infections

At the end of year 2019 the first reports appeared of a new coronavirus and on 31st December 2019 WHO declared a public health emergency of international concern. To date (as of 6:08 pm CET, 24th November 2020) according to WHO the new coronavirus, now called severe acute respiratory syndrome (SARS)-CoV-2, has infected 58,900,547 people and killed 1,393,305 people worldwide. It is extremely important to develop means for express diagnostics to ensure prompt action to limit the spread of infection. One of the diagnostic approaches, is the detection of viral particles in swabs. This approach can be realized using a biosensor with specific ligands, based on peptide molecules complementary to surface viral proteins. The concept of the so-called Systems of Conjugated Ionic-Hydrogen Bonds (abbreviated—SSIVS, CIHBS) implemented in the Protein-3D computer program, was applied to analyze the spatial structures of the bonds between the SARS-CoV-2 spike protein and the ACE-2 (Angiotensin converting enzyme 2) receptor, in order to reveal the perspective peptide sequences. There are two clearly marked areas of contact of the spike with the cell receptor—upper and lower, which are visualized in the SSIVS form, and the complex formed at this site is strong enough to ensure its attachment to the coronavirus spike and can compete for binding with the ACE-2 receptor. Two peptides were developed that form a spatial structure complementary to the coronavirus spike: of eight (No. one) and of 15 (No. two) amino acid residues. The peptides were covalently bound to biochip platforms via neutral linkers to form sites with peptides No. one and No. two. The third site has a neutral hydrophilic surface to serve as a reference. The platform was integrated with a microfluidic channel and was used as a flow through device. The detection of bound viral particles was carried out using UV excitation and direct registration of viral proteins fluorescence. The preliminary laboratory tests demonstrated the efficiency of the biosensor.

The effect of adenine protonation on RNA phosphodiester backbone bond cleavage elucidated by deaza-nucleobase modifications and mass spectrometry

The catalytic strategies of small self-cleaving ribozymes often involve interactions between nucleobases and the ribonucleic acid (RNA) backbone. Here we show that multiply protonated, gaseous RNA has an intrinsic preference for the formation of ionic hydrogen bonds between adenine protonated at N3 and the phosphodiester backbone moiety on its 5′-side that facilitates preferential phosphodiester backbone bond cleavage upon vibrational excitation by low-energy collisionally activated dissociation. Removal of the basic N3 site by deaza-modification of adenine was found to abrogate preferential phosphodiester backbone bond cleavage. No such effects were observed for N1 or N7 of adenine. Importantly, we found that the pH of the solution used for generation of the multiply protonated, gaseous RNA ions by electrospray ionization affects phosphodiester backbone bond cleavage next to adenine, which implies that the protonation patterns in solution are at least in part preserved during and after transfer into the gas phase. Our study suggests that interactions between protonated adenine and phosphodiester moieties of RNA may play a more important mechanistic role in biological processes than considered until now.

Cocrystals and Salts of 3,5-Bis(pyridinylmethylene)piperidin-4-one with Aromatic Poly-Carboxylates and Resorcinols: Influence of Stacking Interactions on Solid-State Luminescence Properties

Two bis-pyridyl-substituted α,β-unsaturated ketones were shown to form complexes with carboxylic acids and resorcinol derivatives. The neutral acid–acid homosynthon was observed in only one complex out of the five acid-bis-pyridyl containing complexes studied here, while the –COO−⋯HOOC– synthon was found to be dominant as it was observed in four complexes. The carboxylates self-assembled to form discrete dimeric, anionic, 1D chains and also exhibited mixed ionic hydrogen bonds. On the other hand, resorcinol derivatives displayed O–H⋯N hydrogen bonding to form tetrameric aggregates of bis-pyridyl ketone molecules and respective co-formers, while 3,5-dihydroxy benzoic acid (DHBA) molecules formed 1D chains by clipping two molecules of ketones with three DHBA molecules. Such clipping by the resorcinol derivatives promoted continuous π–π stacking interactions. Consequently, these materials emitted at higher wavelengths compared with the parent bis-pyridyl-substituted α,β-unsaturated ketones.

Intelligent rubber with tailored properties for self-healing and shape memory

Thermoreversible rubbers are prepared by the thiol-ene functionalized polybutadiene oligomers via dynamic ionic hydrogen bonds and covalent cross-links, exhibiting tailored properties for self-healing and shape memory functions.

THERMOREVERSIBLE CROSS-LINKING MALEIC ANHYDRIDE GRAFTED CHLOROBUTYL RUBBER WITH HYDROGEN BONDS (COMBINED WITH IONIC INTERACTIONS)

ABSTRACT Thermoreversible cross-linking polymers are designed based on reversible cross-linking bonds. These bonds are able to reversibly dissociate and associate upon the input of external energy, such as heat or light. Reprocessibility is possible for this kind of material. The objective was to thermoreversibly cross-link maleic anhydride grafted chlorobutyl rubber (MAH-g-CIIR) via a reaction with octadecylamine, with an excess to obtain amide-salts, which form both hydrogen bonds and ionic interactions. X-ray diffraction experiments showed the presence of microphase-separated aggregates that acted as physical cross-links for both the MAH-g-CIIR precursor and amide-salts. The tensile properties were improved by converting MAH-g-CIIR to amide-salts, because of the combination of hydrogen bonding and ionic interactions. The cross-linked materials could be repeatedly compression molded at 155 °C into homogeneous films. The differential scanning calorimetry curves and Fourier transform infrared spectra indicate that hydrogen bonds are of a thermoreversible nature, but the recovery of ionic bonds is impossible. After treatment with heating-cooling for up to three cycles, the tensile strength of the thermoreversible cross-linking CIIR was greatly reduced. The gradual reduction in the effectiveness of the ionic-hydrogen bonds is the major contribution to the reprocessibility of these materials.