Sulfated Polysaccharides as a Fighter with Protein Non-Physiological Aggregation: The Role of Polysaccharide Flexibility and Charge Density.

Proteins can lose native functionality due to non-physiological aggregation. In this work, we have shown the power of sulfated polysaccharides as a natural assistant to restore damaged protein structures. Protein aggregates enriched by cross-β structures are a characteristic of amyloid fibrils related to different health disorders.

Complexation of Bromelain, Ficin, and Papain with the Graft Copolymer of Carboxymethyl Cellulose Sodium Salt and -Vinylimidazole Enhances Enzyme Proteolytic Activity.

This study investigates the features of interactions between cysteine proteases (bromelain, ficin, and papain) and a graft copolymer of carboxymethyl cellulose sodium salt with -vinylimidazole. The objective is to understand the influence of this interactions on the proteolytic activity and stability of the enzymes. The enzymes were immobilized through complexation with the carrier.

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.

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.

Carboxymethyl Cellulose-Based Polymers as Promising Matrices for Ficin Immobilization.

The present work is devoted to research on the interaction between carboxymethyl cellulose sodium salt and its derivatives (graft copolymer of carboxymethyl cellulose sodium salt and ,-dimethyl aminoethyl methacrylate) with cysteine protease (ficin). The interaction was studied by FTIR and by flexible molecular docking, which have shown the conjugates' formation with both matrices. The proteolytic activity assay performed with azocasein demonstrated that the specific activities of all immobilized ficin samples are higher in comparison with those of the native enzyme.

Fibrin-Rhamnogalacturonan I Composite Gel for Therapeutic Enzyme Delivery to Intestinal Tumors.

Therapy of colorectal cancer with protein drugs, including targeted therapy using monoclonal antibodies, requires the preservation of the drug's structure and activity in the gastrointestinal tract or bloodstream. Here, we confirmed experimentally the fundamental possibility of creating composite protein-polysaccharide hydrogels based on non-degrading rhamnogalacturonan I (RG) and fibrin as a delivery vehicle for antitumor RNase binase. The method is based on enzymatic polymerization of fibrin in the presence of RG with the inclusion of liposomes, containing an encapsulated enzyme drug, into the gel network.

Novel Biocatalysts Based on Bromelain Immobilized on Functionalized Chitosans and Research on Their Structural Features.

Enzyme immobilization on various carriers represents an effective approach to improve their stability, reusability, and even change their catalytic properties. Here, we show the mechanism of interaction of cysteine protease bromelain with the water-soluble derivatives of chitosan-carboxymethylchitosan, -(2-hydroxypropyl)-3-trimethylammonium chitosan, chitosan sulfate, and chitosan acetate-during immobilization and characterize the structural features and catalytic properties of obtained complexes. Chitosan sulfate and carboxymethylchitosan form the highest number of hydrogen bonds with bromelain in comparison with chitosan acetate and -(2-hydroxypropyl)-3-trimethylammonium chitosan, leading to a higher yield of protein immobilization on chitosan sulfate and carboxymethylchitosan (up to 58 and 65%, respectively).

The dielectric response of hydrated water as a structural signature of nanoconfined lichen melanins.

Lichens are unique symbiotic organisms from a mutually beneficial alliance of fungi and algae/cyanobacteria that successfully survive extreme temperatures and drought conditions. Most probably such extraordinary vitality of lichens is underlain by melanins, one of the main structural and chemical lichen components, and their mutual relationship with residual water. In this paper, we propose mechanisms, which allow lichens to store up the extra water in their structure.

Chitosan Graft Copolymers with -Vinylimidazole as Promising Matrices for Immobilization of Bromelain, Ficin, and Papain.

This work aims to synthesize graft copolymers of chitosan and -vinylimidazole (VI) with different compositions to be used as matrices for the immobilization of cysteine proteases-bromelain, ficin, and papain. The copolymers are synthesized by free radical solution copolymerization with a potassium persulfate-sodium metabisulfite blend initiator. The copolymers have a relatively high frequency of grafting and yields.

Structural and Functional Differences between Homologous Bacterial Ribonucleases.

Small cationic guanyl-preferring ribonucleases (RNases) produced by the species share a similar protein tertiary structure with a high degree of amino acid sequence conservation. However, they form dimers that differ in conformation and stability. Here, we have addressed the issues (1) whether the homologous RNases also have distinctions in catalytic activity towards different RNA substrates and interactions with the inhibitor protein barstar, and (2) whether these differences correlate with structural features of the proteins.

Spectroscopic study of antimicrobial peptides: Structure and functional activity.

Amphibians are a natural source of a large number of peptides with a wide range of functional activities. Here, a complex of spectroscopic methods including NMR-, FTIR-, CD-, and UV-spectroscopy was applied to characterize the structure and functional activity of megin-1, a peptide isolated from amphibian skin. The three-dimensional structure of two forms of the peptide was determined using solution NMR spectroscopy.

Novel biotechnological formulations of cysteine proteases, immobilized on chitosan. Structure, stability and activity.

Bromelain, papain, and ficin are studied the most for meat tenderization, but have limited application due to their short lifetime. The aim of this work is to identify the adsorption mechanisms of these cysteine proteases on chitosan to improve the enzymes' stability. It is known that immobilization can lead to a significant loss of enzyme activity, which we observed during the sorption of bromelain (protease activity compared to soluble enzyme is 49% for medium and 64% for high molecular weight chitosan), papain (34 and 28% respectively) and ficin (69 and 70% respectively).

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.

Spectroscopic, zeta potential and molecular dynamics studies of the interaction of antimicrobial peptides with model bacterial membrane.

Peptide-membrane interactions play a key role in the mechanisms of activity of antimicrobial peptides. Here, methods of fluorescence spectroscopy, zeta potential, and molecular dynamics modeling were used to study the interaction of new antimicrobial peptide megin with model bacterial membrane. The Gibbs free energy of -6 kcal/mol characterizes the interaction of the peptides with liposomes containing DOPE and POPG lipids.

Protein Translational Diffusion and Intermolecular Interactions of Globular and Intrinsically Unstructured Proteins.

The study of intermolecular interactions of proteins has been an important problem for many years. This paper presents an approach to analyze different levels of protein interactions in solutions through a set of the second- and higher-order virial coefficients. The proposed approach is based on the diversified analysis of protein translational collective diffusion and self-diffusion obtained by dynamic light scattering and the pulsed-field gradient NMR (PFG NMR) spectroscopy experimental data.

Direct interaction of fibrinogen with lipid microparticles modulates clotting kinetics and clot structure.

Extensive studies revealed the role of blood lipid microparticles (liposomes, microvesicles) in activation of coagulation cascade. The direct interaction of fibrinogen/fibrin with lipid surfaces and its consequence for hemostasis received much less attention. We observed pronounced changes in both clot morphology and kinetics of fibrin clotting in the presence of artificial liposomes.

Interplay between secondary structure and ion binding upon thermoreversible gelation of κ-carrageenan.

It is widely accepted that cation binding specifically favors chain ordering and gelling of κ-carrageenan. However, current insights into the exact sequence of binding and conformational rearrangements as well as into the structure of binding sites are controversial. In the present work, the FTIR-spectroscopy combined with the computer modelling has been used to reveal the relation between cation binding and the secondary structure transition upon thermoreversible gelation of the κ-carrageenan.

The Native Monomer of Bacillus Pumilus Ribonuclease Does Not Exist Extracellularly.

Supported by crystallography studies, secreted ribonuclease of (binase) has long been considered to be monomeric in form. Recent evidence obtained using native polyacrylamide gel electrophoresis and size-exclusion chromatography suggests that binase is in fact dimeric. To eliminate ambiguity and contradictions in the data we have measured conformational changes, hypochromic effect, and hydrodynamic radius of binase.

Molecular structure and properties of κ-carrageenan-gelatin gels.

Rheological studies, FTIR spectroscopy and a molecular docking approach were used to explore the structural basis of the peculiar physicochemical properties of gelatin gels modified with a κ-carrageenan admixture. Mixed gel properties are affected by the polysaccharide-to-gelatin ratio, Z, and can be divided into two categories. At low ratios, the strength of mixed gels varies insignificantly compared to gelatin due to the similar structures of the gels.

Spatial structures of rhamnogalacturonan I in gel and colloidal solution identified by 1D and 2D-FTIR spectroscopy.

Rhamnogalacturonan I (RG-I), a polysaccharide found in different types of plant cell walls, fulfills specific functions, the structural basis of which remains unclear. Generalized 2D correlation FTIR spectroscopy with dehydration was employed to reveal the structure and interactions in flax RG-I solution and microwave treated gel. Varying water content allowed emphasizing a role of solvent in maintaining different structures.

Effect of Lipid Surface Composition on the Formation and Structure of Fibrin Clots.

We studied the influence of lipid surface composition on the kinetics of fibrin clot formation and its structure. It was shown that lipid surface affects all phases of fibrin polymerization and chances clot morphology. The magnitude and character of the effect depend on the charge and phase state of lipids that determine the interaction of fibrinogen with the lipid surface and its conformational changes, which modulated the process of fibrinogen conversion into fibrin and, as a result, the formation and morphology of the fibrin clot.

Theoretical and Experimental Investigation of the Translational Diffusion of Proteins in the Vicinity of Temperature-Induced Unfolding Transition.

Translational diffusion is the most fundamental form of transport in chemical and biological systems. The diffusion coefficient is highly sensitive to changes in the size of the diffusing species; hence, it provides important information on the variety of macromolecular processes, such as self-assembly or folding-unfolding. Here, we investigate the behavior of the diffusion coefficient of a macromolecule in the vicinity of heat-induced transition from folded to unfolded state.

[Structure and Activity of Fungal Lipases in Bile Salt Solutions].

The changes in structure and catalytic properties of fungal lipases (Candida rugosa, Rhizomucor miehei, Mucor javanicus) were investigated in micellar solutions of bile salts that differ in hydrophilic-lypophilic balance and reaction medium properties. The methods of circular dichroism and tryptophan fluorescence were applied to estimate the changes in peptide structure within complexes with bile salt micelles. Bile salts do not exert a significant influence on the structure of the enzymes under study: in Rh.