Structural insights in interactions between RNase from Bacillus Intermedius and rhamnogalacturonan I from potato

Extraction of pectin from watermelon and pomegranate peels with different methods and its application in ice cream as an emulsifier

Pectin extraction from watermelon peel (WP) and pomegranate peel (PP) was carried out using three different extraction methods: classical solvent extraction (CSE), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE). Extraction parameters (pH, temperature, time, and speed/amplitude/power) were optimized to target maximum crude pectin yield (CPY), while the sample-to-solvent ratio (SS) was determined to be fixed at 1:10 w/v at all experiments. CPY was increased by low pH, high temperature, and long time. The pectins obtained at optimum conditions were characterized regarding the physicochemical and rheological properties, and the pectin solutions were found to be typical pseudoplastic fluids. WP pectin extracted with MAE and PP pectin extracted with UAE were determined to have the best emulsifying properties and added to the ice cream formulations. MAE had the maximum CPY of 9.40% for WP (pH = 1.3, 6 min, 596 W) and the best emulsifying properties. UAE had the best emulsifying properties for PP and the CPY was 11.56% in conditions of pH = 1.5, a temperature of 69°C, an extraction time of 29 min, and a 32% amplitude. The use of PP pectin resulted in a significant increase in the apparent viscosity of ice cream mix and also the first dripping time and the hardness of ice cream over commercial emulsifier. Melting properties and hardness values of ice cream with WP pectin were comparatively closer to those of ice cream with commercial emulsifier. On the other hand, the first dripping time and hardness value of ice cream with PP pectin having 60.25 min and 3.84 N, respectively, were higher than those of commercial ice cream having 53.75 min and 2.14 N, respectively. Practical Application: The utilization of WP and PP, which are good sources for pectin production, benefits both a sustainable environment and a sustainable food industry. Pectin extracted from WP and PP as an emulsifier in ice cream can ensure the production of ice creams with good melting properties. Pectin can be used as a healthy, sustainable, and economical alternative emulsifier in the ice cream industry.

Structural characteristics and gel properties of pectin from citrus physiological premature fruit drop

This study is the first to extract and characterize pectin from citrus physiological premature fruit drop. The extraction yield of pectin reached 4.4 % by acid hydrolysis method. The degree of methoxy-esterification (DM) of citrus physiological premature fruit drop pectin (CPDP) was 15.27 %, indicating it was low-methoxylated pectin (LMP). The monosaccharide composition and molar mass test results showed CPDP was a highly branched macromolecular polysaccharide (β: 0.02, Mw: 2.006 × 10⁵ g/mol) with rich rhamnogalacturonan I domain (50.40 %) and long arabinose and galactose side chain (32.02 %). Based on the fact that CPDP is LMP, Ca²⁺ was used to induce CPDP to form gels. Textural and rheological tests showed that the gel strength and storage modulus of CPDP were higher than commercial citrus pectin (CP) used in this paper due to the lower DM and rich neutral sugar side chains of CPDP. Scanning electron microscope (SEM) results showed CPDP had stable gel network structure.

Binding of ankaflavin with bovine serum albumin (BSA) in the presence of carrageenan and protective effects of Monascus yellow pigments against oxidative damage to BSA after forming a complex with carrageenan

Ankaflavin (AK) is a typical yellow pigment extracted from Monascus-fermented rice with several biological effects; however, its solubility is poor. Thus, research studies of the delivery systems of AK, especially those constructed from protein-polysaccharide complexes, have attracted considerable attention. However, the interactions that exist in the system have rarely been investigated. This work focused on the interactions between AK and bovine serum albumin (BSA) as well as the influence of carrageenan (Car) on the binding of AK to BSA. Results revealed that the quenching of BSA by AK involved the static quenching mechanism. The formed BSA-AK complexes were mainly maintained by hydrophobic forces and AK was located within the hydrophobic cavity of BSA. Compared to free AK or AK only complexed with BSA, a higher absorption intensity of AK was observed for the formed BSA-AK-Car complexes, indicating changes in the microenvironment of AK. This was confirmed by the increase in the α-helix content of BSA after the formation of BSA-AK-Car complexes. Hydrogen bond, van der Waals, and electrostatic interactions were verified to be the primary forces preserving the BSA-AK-Car complexes. Moreover, the antioxidant potential of Monascus-fermented products rich in AK (denoted as Mps), namely BSA-Mps and BSA-Mps-Car was evaluated. The antioxidant activity of Mps was negatively impacted by BSA, while the addition of Car could enhance the antioxidant capacity of BSA-Mps-Car complexes. Meanwhile, Mps showed a protective effect against free radical-induced oxidation damage to BSA, and Car could further improve this effect.

The Ability of Some Polysaccharides to Disaggregate Lysozyme Amyloid Fibrils and Renature the Protein

The deposition of proteins in the form of insoluble amyloid fibril aggregates is linked to a range of diseases. The supramolecular architecture of such deposits is governed by the propagation of β-strands in the direction of protofilament growth. In the present study, we analyze the structural changes of hen egg-white lysozyme fibrils upon their interactions with a range of polysaccharides, using AFM and FTIR spectroscopy. Linear anionic polysaccharides, such as κ-carrageenan and sodium alginate, are shown to be capable to disaggregate protofilaments with eventual protein renaturation. The results help to understand the mechanism of amyloid disaggregation and create a platform for both the development of new therapeutic agents for amyloidose treatment, and the design of novel functional protein-polysaccharide complex-based nanomaterials.

Regulation of Intersubunit Interactions in Homotetramer of Glyceraldehyde-3-Phosphate Dehydrogenases upon Its Immobilization in Protein-Kappa-Carrageenan Gels

Polysaccharides, being biocompatible and biodegradable polymers, are highly attractive as materials for protein delivery systems. However, protein-polysaccharide interactions may lead to protein structural transformation. In the current study, we analyze the structural adjustment of a homotetrameric protein, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), upon its interactions with both flexible coil chain and the rigid helix of κ-carrageenan. FTIR spectroscopy was used to probe the secondary structures of both protein and polysaccharide. Electrostatically driven protein-polysaccharide interactions in dilute solutions resulted in an insoluble complex formation with a constant κ-carrageenan/GAPDH ratio of 0.2, which amounts to 75 disaccharide units per mole of protein tetramer. Upon interactions with both coiled and helical polysaccharides, a weakening of the intersubunit interactions was revealed and attributed to a partial GAPDH tetramer dissociation. In turn, protein distorted the helical conformation of κ-carrageenan when co-gelled. Molecular modeling showed the energy favorable interactions between κ-carrageenan and GAPDH at different levels of oligomerization. κ-Carrageenan binds in the region of the NAD-binding groove and the S-loop in OR contact, which may stabilize the OP dimers. The obtained results highlight the mutual conformational adjustment of oligomeric GAPDH and κ-carrageenan upon interaction and the stabilization of GAPDH's dissociated forms upon immobilization in polysaccharide gels.

κ-Carrageenan Hydrogel as a Matrix for Therapeutic Enzyme Immobilization

During the last few decades, polysaccharide hydrogels attract more and more attention as therapeutic protein delivery systems due to their biocompatibility and the simplicity of the biodegradation of natural polymers. The protein retention by and release from the polysaccharide gel network is regulated by geometry and physical interactions of protein with the matrix. In the present work, we studied the molecular details of interactions between κ-carrageenan and three lipases, namely the lipases from Candida rugosa, Mucor javanicus, and Rhizomucor miehei—which differ in their size and net charge—upon protein immobilization in microparticles of polysaccharide gel. The kinetics of protein release revealed the different capability of κ-carrageenan to retain lipases, which are generally negatively charged; that was shown to be in line with the energy of interactions between polysaccharides and positively charged epitopes on the protein surface. These data create a platform for the novel design of nanocarriers for biomedical probes of enzymatic origin.

Multifaceted Computational Modeling in Glycoscience

Glycoscience assembles all the scientific disciplines involved in studying various molecules and macromolecules containing carbohydrates and complex glycans. Such an ensemble involves one of the most extensive sets of molecules in quantity and occurrence since they occur in all microorganisms and higher organisms. Once the compositions and sequences of these molecules are established, the determination of their three-dimensional structural and dynamical features is a step toward understanding the molecular basis underlying their properties and functions. The range of the relevant computational methods capable of addressing such issues is anchored by the specificity of stereoelectronic effects from quantum chemistry to mesoscale modeling throughout molecular dynamics and mechanics and coarse-grained and docking calculations. The Review leads the reader through the detailed presentations of the applications of computational modeling. The illustrations cover carbohydrate-carbohydrate interactions, glycolipids, and N- and O-linked glycans, emphasizing their role in SARS-CoV-2. The presentation continues with the structure of polysaccharides in solution and solid-state and lipopolysaccharides in membranes. The full range of protein-carbohydrate interactions is presented, as exemplified by carbohydrate-active enzymes, transporters, lectins, antibodies, and glycosaminoglycan binding proteins. A final section features a list of 150 tools and databases to help address the many issues of structural glycobioinformatics.

Alginate-Based Hydrogel as Delivery System for Therapeutic Bacterial RNase

To deliver therapeutic proteins into a living body, it is important to maintain their target activity in the gastrointestinal tract after oral administration. Secreted ribonuclease from Bacillus pumilus (binase) has antitumor and antiviral activity, which makes it a promising therapeutic agent. This globular protein of small molecular weight (12.2 kDa) is considered as a potential agent that induces apoptosis of tumor cells expressing certain oncogenes, including colorectal and duodenum cancer. The most important problem of its usage is the preservation of its structure and target activity, which could be lost during oral administration. Here, we developed alginate microspheres reinforced with divalent cations and analyzed the enzyme release from them. Using methods of scanning electron microscopy, measurements of fluorescence, enzyme catalytic activity, and determination of viability of the duodenum adenocarcinoma tumor cell line, we characterized obtained microspheres and chose calcium as a biogenic ion-strengthening microsphere structure. Among such modified additivities as beta-casein, gelatin, and carbon nanotubes introduced into microspheres, only gelatin showed a pronounced increase in their stability and provided data on the prolonged action of enzyme release from microspheres into tumor cell culture medium during 48 h in an amount of about 70% of the loaded quantity.

Interaction-Induced Structural Transformations in Polysaccharide and Protein-Polysaccharide Gels as Functional Basis for Novel Soft-Matter: A Case of Carrageenans

Biocompatible, nontoxic, and biodegradable polysaccharides are considered as a promising base for bio-inspired materials, applicable as scaffolds in regenerative medicine, coatings in drug delivery systems, etc. The tunable macroscopic properties of gels should meet case-dependent requirements. The admixture of proteins to polysaccharides and their coupling in more sophisticated structures opens an avenue for gel property tuning via physical cross-linking of components and the modification of gel network structure. In this review recent success in the conformational studies of binary protein-polysaccharide gels is summarized with the main focus upon carrageenans. Future perspectives and challenges in rational design of novel polysaccharide-based materials are outlined.

Interaction-induced structural transformation of lysozyme and kappa-carrageenan in binary complexes

The interactions between κ-carrageenan and hen egg-white lysozyme have been studied. In dilute solutions, the insoluble complexes with constant κ-carrageenan/lysozyme ratio of 0.3, or 12 disaccharide units per mole of protein are formed. FTIR-spectroscopy revealed that κ-carrageenan retains its unordered conformation and induces the rise of β-structure in lysozyme. In the complexes formed in concentrated mixtures, κ-carrageenan adopts helical conformation and lysozyme retains its native-like structure. These complexes contain 21 disaccharide units per mole of protein. Molecular modeling showed that flexible coil and rigid double helix of κ-carrageenan have different binding patterns to lysozyme surface. The latter has a strong preference to positively charged spots in lysozyme α-domain while the former also interacts to protein β-domain and stabilizes short-living β-structures. The obtained results confirm the preference of unordered κ-carrageenan to β-structure rich protein regions, which can be further used in the development of carrageenan-based protection of amyloid-like aggregation of proteins.