Antimicrobial and antioxidant activity of proteins from Feijoa sellowiana Berg. fruit before and after in vitro gastrointestinal digestion

Abstract

In this paper we report for the first time a method for the extraction of the protein fraction from Feijoa sellowiana Berg. fruit and its electrophoretic analysis. In addition we analyzed the protein fraction for its antioxidant activity and its effectiveness against different Gram-positive and Gram-negative bacteria both as American type culture collection (ATCC) standard and clinically isolated strains. Both antimicrobial and antioxidant activity resulted stronger respect to that previously obtained for the acetonic extract from the same fruit. Further, we study both activities also on the product of in vitro gastrointestinal digestion of F. sellowiana fruit proteins. The results showed that in vitro gastrointestinal digestion increased 10 fold the antioxidant activity, while the antimicrobial activity, tested only on ATCC strains, resulted from 2 to 4 fold increased. MTT assays showed the non-toxicity of these proteins both before and after digestion.     

Lipid profile of fish species by liquid chromatography coupled to mass spectrometry and a novel linear retention index database

In a previous article, Rigano et al. established a new linear retention index system for the identification of triacylglycerols by liquid chromatography methods only on the basis of the retention behavior and independently from many experimental parameters. In that work, a database of 209 compounds was built, but only 54 of them, typical of vegetable oils, were confirmed by mass spectrometry. The aim of the present research is to extend the applicability of the novel approach to more complex samples, such as fish lipid extracts, and assess the complementarity between mass spectromtery and retention information to achieve univocal identification. With this purpose, a new software was implemented to make the identification process easy and automatic as in gas chromatography‐mass spectrometry where the retention index filter is added in the spectral search to discriminate between compounds with similar mass spectrometry spectra. A total of 69 species were identified and, thanks to their baseline separation obtained by an ultra high performance liquid chromatography method, a semiquantification was also performed. The species under investigation were Dicentrarchus labrax, coming from aquaculture and the wild. Some differences in their native lipid composition were observed, probably related to a different diet. A major number of samples would be necessary to confirm such a preliminary finding.     

Mechanically-Driven Vase–Kite Conformational Switch in Cavitand Cross-Linked Polyurethanes

The eligibility of tetraquinoxaline cavitands (QxCav) as molecular grippers relies on their unique conformational mobility between a closed (vase) and an open (kite) form, triggered in solution by conventional stimuli like pH, temperature and ion concentration. In the present paper, the mechanochemical conformational switching of ad hoc functionalized QxCav covalently embedded in an elastomeric polydimethylsiloxane and in a more rigid polyurethane matrix is investigated. The rigid polymer matrix is more effective in converting mechanical force into a conformational switch at the molecular level, provided that all four quinoxaline wings are covalently connected to the polymer.     

Semisynthetic and Enzyme‐Mediated Conjugate Preparations Illuminate the Ubiquitination‐Dependent Aggregation of Tau Protein

In the brain of individuals with Alzheimer's disease, the regulatory protein ubiquitin is found conjugated to different lysine residues of tau protein assembled into pathological paired helical filaments. To shed light on the hitherto unexplored ubiquitination‐linked conformational transitions of tau, the availability of in vitro ubiquitin conjugation methods is of primary importance. In our work, we focused on the four‐repeat domain of tau and assembled an enzymatic machinery formed by UBE1, Ubc13, and CHIP enzymes. The enzymatic reaction resulted in monoubiquitination at multiple sites, reminiscent of the ubiquitination pattern observed in vivo. We further exploited chemoselective disulfide coupling reactions to construct three tau regioisomers with site‐specific monoubiquitination. Protein aggregation experiments revealed that the multiple enzyme‐derived products were unable to convert into amyloid fibrils, while the semisynthetic conjugates exhibited diverse capability to form filaments. This study contributes novel insight into the effects of a key post‐translational modification on aberrant protein self‐assembly.     

Structural Characterization of N-Linked Glycans in the Receptor Binding Domain of the SARS-CoV-2 Spike Protein and their Interactions with Human Lectins

The glycan structures of the receptor binding domain of the SARS-CoV2 spike glycoprotein expressed in human HEK293F cells have been studied by using NMR. The different possible interacting epitopes have been deeply analysed and characterized, providing evidence of the presence of glycan structures not found in previous MS-based analyses. The interaction of the RBD ¹³C-labelled glycans with different human lectins, which are expressed in different organs and tissues that may be affected during the infection process, has also been evaluated by NMR. In particular, ¹⁵N-labelled galectins (galectins-3, -7 and -8 N-terminal), Siglecs (Siglec-8, Siglec-10), and C-type lectins (DC-SIGN, MGL) have been employed. Complementary experiments from the glycoprotein perspective or from the lectin's point of view have permitted to disentangle the specific interacting epitopes in each case. Based on these findings, 3D models of the interacting complexes have been proposed.     

Novel carbon nanotube composites by grafting reaction with water-compatible redox initiator system

Multi-walled carbon nanotubes were chemically functionalized with methacrylic acid and methacrylated bovine serum albumin by free radical grafting reaction to obtain novel nanocomposites. The nanotubes were synthesized by aerosol-assisted chemical vapor deposition, and then the monomers were directly grafted by the action of hydrogen peroxide/ascorbic acid redox pair which allows operating in water-compatible and eco-friendly environment without the generation of any toxic reaction by-product. A multi-technique approach was used to evaluate the effectiveness of the grafting process employing Fourier transform infrared, Raman, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analyses. Considering the high importance of methacrylate polymers and bovine serum albumin, the proposed nanocomposites could be of great applicability in biomedical and pharmaceutical fields.     

Totally positive functions through nonstationary subdivision schemes

In this paper a new class of nonstationary subdivision schemes is proposed to construct functions having all the main properties of B-splines, namely compact support, central symmetry and total positivity. We show that the constructed nonstationary subdivision schemes are asympotically equivalent to the stationary subdivision scheme associated with a B-spline of suitable degree, but the resulting limit function has smaller support than the B-spline although keeping its regularity.     

On the spatial behaviour in dynamics of elastic mixtures

This paper studies the spatial behaviour of the dynamic processes in elastic mixtures. With this aim we use the time-weighted surface power function method associated with the linear processes. Consequently, we obtain a precise determination of the domain of influence and the spatial decay estimates with time-independent decay rate inside of the domain of influence. A uniqueness theorem is proved for finite and infinite bodies and we note that it is free of any kind of a priori assumptions on the solutions at infinity.     

A Comparative Study of the Phospholipid Profiles of Guinea Pig Cardiac Muscle and Bullfrog Cardiac and Thigh Skeletal Muscle,and their In-Vitro Differential Deacylation by Endogenous Phospholipases. Thin Layer Chromatographic and Densitometric Analysis

JPC – Journal of Planar Chromatography – Modern TLC - The phospholipid profiles of guinea pig and bullfrog cardiac muscle and of bullfrog thigh skeletal muscle before and after in-vitro...