Polysaccharide Chains Research Articles

#3270 TRANSPORT AND HYDROLYSIS OF ICODEXTRIN DURING PERITONEAL DIALYSIS

Abstract Background and Aims α-amylase, an enzyme present in plasma and peritoneal tissue, takes part in the process of starch digestion. During peritoneal exchange with icodextrin-based solution, polysaccharide chains are hydrolysed to shorter oligosaccharide chains, influencing osmotic properties of peritoneal dialysate. We estimated peritoneal transport parameters and compared them with hydrolytic clearances using a new model that takes into consideration absorption of icodextrin from the peritoneal cavity and its degradation by α-amylase. Method Frequent dialysate and blood samples were taken in 11 patients (8 icodextrin-naïve, 3 icodextrin-exposed) undergoing 16-hour dwell studies with icodextrin-based dialysis solution and labeled serum albumin (RISA) added as a volume marker. Using data on the intraperitoneal volume and dialysate and blood concentrations of glucose, urea, creatinine, and 7 icodextrin molecular weight (MW) fractions (glucose polymer size classes) and dialysate concentrations of α-amylase the extended three-pore model was applied to estimate individual parameters related to the peritoneal transport induced by dialysis and to hydrolysis of icodextrin by α-amylase. The following MW cut-off values were assumed for icodextrin fractions: up to 1.08, 4.44, 9.89, 21.4, 43.5, 66.7 and over 66.7 kDa, called Fractions 1–7, respectively. The hydrolytic clearances were defined as rate at which dialysate volume is cleared of the fraction by hydrolysis. The time-dependent hydrolytic clearances of icodextrin fractions were calculated and compared with diffusive ones. For the first time the extended three-pore model was validated not only with respect to the peritoneal transport of water and small solutes but also regarding concentration of icodextrin fractions. Results Mean measured and simulated dialysate to plasma concentration ratios for glucose, urea and creatinine are presented in Figure 1, left panel. The peritoneal kinetic of icodextrin (dialysate concentrations of each fraction over its initial concentration) is presented for mean measured data and numerical simulation results in Figure 1, right panel. The results showed that the model provides accurate (mean relative error less than 7%) description of individual patient peritoneal transport kinetics including that of icodextrin fractions in peritoneal dialysate. The comparison of hydrolytic clearances (H) with diffusive transport parameters for icodextrin fractions (PS, reflecting the maximal rates of their clearance by diffusion) showed that in case of shorter polymers (Fractions 1–3) diffusive clearances were higher or similar to hydrolytic ones over the whole dwell time. In case of Fractions 4 and 5, the initial domination of PS slowly decreased during the dwell time, being dominated by hydrolysis processes at the end of the exchange, at least partly due to the changes of intraperitoneal volume and α-amylase concentration. In case of polysaccharides from Fractions 6 and 7, their hydrolytic clearances remained higher than the diffusive ones during whole dwell time. Interestingly, the obtained values of H in icodextrin-exposed patients typically remained below 1.2 mL/min except for Fraction 6, for which H increased from initial value of 0.83±0.30 to 1.43±0.64 mL/min at the end of the peritoneal dwell. On the other hand, the estimated final values of H in icodextrin-naïve patients were on average higher than 1.2 mL/min in all fractions except Fractions 4 and 5. Conclusion The model provided accurate description of peritoneal transport and icodextrin hydrolysis during long icodextrin dwells. The model showed that hydrolytic processes dominate over diffusive ones during whole dwell time in case of Fractions 6 and 7, whereas diffusive processes dominate for Fractions 1–3.

Enhancing enzymatic saccharification of sunflower straw through optimal tartaric acid hydrothermal pretreatment

Sunflower straw, a usually neglected and abundant agricultural waste, has great potential for contributing to environmental protection realizing its high-value of valorization if utilizing properly. Because hemicellulose contains amorphous polysaccharide chains, relatively mild organic acid pretreatment can effectively reduce its resistance. Through hydrothermal pretreatment, sunflower straw was pretreated in tartaric acid (1 wt%) at 180 °C for 60 min to enhance its reducing sugar recovery. After tartaric acid-assisted hydrothermal pretreatment, 39.9% of lignin and 90.2% of xylan were eliminated. The reducing sugar recovery increased threefold, while the solution could be effectively reused for four cycles. The properties of more porous surface, improved accessibility, and decreased surface lignin area of sunflower straw were observed through various characterizations, which explained the improved saccharide recovery and provided a basis for the mechanism of tartaric acid-assisted hydrothermal pretreatment. Overall, this tartaric acid hydrothermal pretreatment strategy greatly provided new impetus for the biomass refinery.

Oxidized Natural Biopolymer for Enhanced Surface, Physical and Mechanical Properties of Glass Ionomer Luting Cement.

This laboratory investigation aimed to synthesize and characterize micron-sized Gum Arabic (GA) powder and incorporate it in commercially available GIC luting formulation for enhanced physical and mechanical properties of GIC composite. Oxidation of GA was performed and GA-reinforced GIC in 0.5, 1.0, 2.0, 4.0 & 8.0 wt.% formulations were prepared in disc-shaped using two commercially available GIC luting materials (Medicem and Ketac Cem Radiopaque). While the control groups of both materials were prepared as such. The effect of reinforcement was evaluated in terms of nano hardness, elastic modulus, diametral tensile strength (DTS), compressive strength (CS), water solubility and sorption. Two-way ANOVA and post hoc tests were used to analyze data for statistical significance (p < 0.05). FTIR spectrum confirmed the formation of acid groups in the backbone of polysaccharide chain of GA while XRD peaks confirmed that crystallinity of oxidized GA. The experimental group with 0.5 wt.% GA in GIC enhanced the nano hardness while 0.5 wt.% and 1.0 wt.% GA in GIC increased the elastic modulus compared to the control. The CS of 0.5 wt.% GA in GIC and DTS of 0.5 wt.% and 1.0 wt.% GA in GIC demonstrated elevation. In contrast, the water solubility and sorption of all the experimental groups increased compared to the control groups. The incorporation of lower weight ratios of oxidized GA powder in GIC formulation helps in enhancing the mechanical properties with a slight increase in water solubility and sorption parameters. The addition of micron-sized oxidized GA in GIC formulation is promising and needs further research for improved performance of GIC luting composition.

Boston ivy-inspired natural-rich binder with strong adhesion for advanced silicon-based anodes

The desirable specific theoretical capacity (3579 mAh g−1) of silicon (Si) renders it beneficial as a next-generation anode for lithium-ion batteries (LIBs). However, the significant volume expansion restricts its commercial application. Here, inspired by natural Boston ivy, an efficient and facile strategy to design a three-dimensional (3D)-crosslinked binder for high-performance Si-based anodes enabled by synergizing “Disk” (small molecules) and “Vine” (long chains) is reported. The small molecule branch-like tannic acid (TA) rich in hydroxyl (−OH) groups tends to have multidimensional hydrogen-bonding interactions with the Si surfaces. Meanwhile, the long chains of polysaccharides, such as carboxymethyl cellulose (CMC) and hyaluronic acid (HA), are beneficial for the large-scale bridging of components in an electrode. Moreover, the in-situ cross-linking of TA and polysaccharides can establish a 3D network to release the inner stress of Si particles. Consequently, this cooperation benefits stable slurry, high adhesive strength, and favorable rate performance. Moreover, when over 100 cycles, the Si anode incorporating tannic-carboxymethyl cellulose (TAC) as the binder delivers a high specific capacity of 2782 mAh g−1. Additionally, favorable practicality is demonstrated by the stable operation of a commercial silicon/graphite (Si/Gr) anode and full-cells.

Synthesis and Characterization of Multi-Reducing-End Polysaccharides.

Site-specific modification is a great challenge for polysaccharide scientists. Chemo- and regioselective modification of polysaccharide chains can provide many useful natural-based materials and help us illuminate fundamental structure-property relationships of polysaccharide derivatives. The hemiacetal reducing end of a polysaccharide is in equilibrium with its ring-opened aldehyde form, making it the most uniquely reactive site on the polysaccharide molecule, ideal for regioselective decoration such as imine formation. However, all natural polysaccharides, whether they are branched or not, have only one reducing end per chain, which means that only one aldehyde-reactive substituent can be added. We introduce a new approach to selective functionalization of polysaccharides as an entrée to useful materials, appending multiple reducing ends to each polysaccharide molecule. Herein, we reduce the approach to practice using amide formation. Amine groups on monosaccharides such as glucosamine or galactosamine can react with carboxyl groups of polysaccharides, whether natural uronic acids like alginates, or derivatives with carboxyl-containing substituents such as carboxymethyl cellulose (CMC) or carboxymethyl dextran (CMD). Amide formation is assisted using the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM). By linking the C2 amines of monosaccharides to polysaccharides in this way, a new class of polysaccharide derivatives possessing many reducing ends can be obtained. We refer to this class of derivatives as multi-reducing-end polysaccharides (MREPs). This new family of derivatives creates the potential for designing polysaccharide-based materials with many potential applications, including in hydrogels, block copolymers, prodrugs, and as reactive intermediates for other derivatives.

Structural factors governing binding of curvature-sensing peptides to bacterial extracellular vesicles covered with hydrophilic polysaccharide chains

Extracellular vesicles (EVs) have attracted an attention as important targets in the fields of biology and medical science because they contain physiologically active molecules. Curvature-sensing peptides are currently used as novel tools for marker-independent EV detection techniques. A structure-activity correlation study demonstrated that the α-helicity of the peptides is prominently involved in peptide binding to vesicles. However, whether a flexible structure changing from a random coil to an α-helix upon binding to vesicles or a restricted α-helical structure is an important factor in the detection of biogenic vesicles is still unclear. To address this issue, we compared the binding affinities of stapled and unstapled peptides for bacterial EVs with different surface polysaccharide chains. We found that unstapled peptides showed similar binding affinities for bacterial EVs regardless of surface polysaccharide chains, whereas stapled peptides showed substantially decreased binding affinities for bacterial EVs covered with capsular polysaccharides. This is probably because curvature-sensing peptides must pass through the layer of hydrophilic polysaccharide chains prior to binding to the hydrophobic membrane surface. While stapled peptides with restricted structures cannot easily pass through the layer of polysaccharide chains, unstapled peptides with flexible structures can easily approach the membrane surface. Therefore, we concluded that the structural flexibility of curvature-sensing peptides is a key factor for governing the highly sensitive detection of bacterial EVs.

Possibilities of sulodexide use in clinical practice

Introduction. Sulodexide is a polymer, the structure of which includes unbranched polysaccharide chains formed by repeating a particular disaccharide unit. This drug was isolated from the endothelium of the pig, and it appeared on the pharmaceutical market in 1974. Sulodexide contains ≈ 80% heparan sulfate (also known as fast-acting heparin) and 20% dermatan sulfate. This drug is produced from the more sulfated waste heparinoids. During production, heparin is chemically decomposed and transformed into the clinical drug Sulodexide. Aim. To estimate the possibilities and prospects of using the drug Sulodexid in the treatment of various diseases. Materials and methods. During this study, we analyzed relevant sources of domestic and foreign literature on the use of the drug Sulodexid in various pathologies. Sources of information included publications from the Russian scientific electronic library integrated with the Russian Science Citation Index, the Medline database, Scopus, Science Direct, Cyberleninka.ru, and the New England Journal of Medicine. Results and discussion. The pharmacological action of the drug is not limited to anticoagulant action, it also has antiaggregant and angioprotective effects. The drug has found application in various fields of medicine, such as pediatrics, surgery, therapy, endocrinology, neurology and proctology. The possibility of wide application is also promoted by the availability of different forms and methods of administration of this drug: intramuscular, infusion and oral, which allows prescribing the drug both in inpatient and outpatient settings. In contrast to other anticoagulants the drug has the most favorable action, since the risk of bleeding is low. Conclusion. In spite of a sufficiently wide use of the study drug in clinical practice, inclusion in the national clinical guidelines, other effects of the drug require further studies. It is difficult to make a conclusion about the efficacy of the drug in the treatment of some diseases, but with further studies, there is a chance of including it in the therapy of different pathological conditions.

Hypermucoviscosity Regulator RmpD Interacts with Wzc and Controls Capsular Polysaccharide Chain Length.

Klebsiella pneumoniae is a leading cause of nosocomial infections, including pneumonia, bacteremia, and urinary tract infections. Treatment options are increasingly restricted by the high prevalence of resistance to frontline antibiotics, including carbapenems, and the recently identified plasmid-conferred colistin resistance. The classical pathotype (cKp) is responsible for most of the nosocomial infections observed globally, and these isolates are often multidrug resistant. The hypervirulent pathotype (hvKp) is a primary pathogen capable of causing community-acquired infections in immunocompetent hosts. The hypermucoviscosity (HMV) phenotype is strongly associated with the increased virulence of hvKp isolates. Recent studies demonstrated that HMV requires capsule (CPS) synthesis and the small protein RmpD but is not dependent on the increased amount of capsule associated with hvKp. Here, we identified the structure of the capsular and extracellular polysaccharide isolated from hvKp strain KPPR1S (serotype K2) with and without RmpD. We found that the polymer repeat unit structure is the same in both strains and that it is identical to the K2 capsule. However, the chain length of CPS produced by strains expressing rmpD demonstrates more uniform length. This property was reconstituted in CPS from Escherichia coli isolates that possess the same CPS biosynthesis pathway as K. pneumoniae but naturally lack rmpD. Furthermore, we demonstrate that RmpD binds Wzc, a conserved capsule biosynthesis protein required for CPS polymerization and export. Based on these observations, we present a model for how the interaction of RmpD with Wzc could impact CPS chain length and HMV. IMPORTANCE Infections caused by Klebsiella pneumoniae continue to be a global public health threat; the treatment of these infections is complicated by the high frequency of multidrug resistance. K. pneumoniae produces a polysaccharide capsule required for virulence. Hypervirulent isolates also have a hypermucoviscous (HMV) phenotype that increases virulence, and we recently demonstrated that a horizontally acquired gene, rmpD, is required for HMV and hypervirulence but that the identity of the polymeric product(s) in HMV isolates is uncertain. Here, we demonstrate that RmpD regulates capsule chain length and interacts with Wzc, a part of the capsule polymerization and export machinery shared by many pathogens. We further show that RmpD confers HMV and regulates capsule chain length in a heterologous host (E. coli). As Wzc is a conserved protein found in many pathogens, it is possible that RmpD-mediated HMV and increased virulence may not be restricted to K. pneumoniae.

Helicity degree of carrageenan conformation determines the polysaccharide and water interactions

The polysaccharide in solution at critical concentration, Cc (g/L), is assimilated to a nano hydrogel (nHG) made of a single polysaccharide chain. Taking as reference the characteristic temperature of 20 ± 2 °C at which kappa-carrageenan (κ-Car) nHG swelling is greater with a Cc = 0.55 ± 0.05 g/L, the temperature of the minimum deswelling in the presence of KCl was found at 30 ± 2 °C for 5 mM with a Cc = 1.15 ± 0.05 g/L but not measurable above 100 °C for 10 mM of which Cc = 1.3 ± 0.05 g/L. Lowering the temperature to 5 °C, contraction of the nHG and further coil-helix transition with self-assembly increases the sample's viscosity, which steadily evolves with time in a logarithmic scale. Accordingly, the relative increment of the viscosity per unit of concentration, Rv (L/g), should increase in agreement with increasing polysaccharide concentration. But the Rv decreases for κ-Car samples above 3.5 ± 0.5 g/L in the presence of 10 mM KCl under steady shear 15 s−1. This reflects a decrease of κ-Car helicity degree knowing that the polysaccharide is rather hydrophilic when its helicity degree is the lowest.

Heteroatom-rich carbon cathodes toward high-performance flexible zinc-ion hybrid supercapacitors

Aqueous zinc-ion hybrid supercapacitors (ZHSs) are attracting increased attention as emerging electrochemical energy storage systems. However, the design of high-performance carbon cathodes for ZHSs remains a challenge. Herein, we report the synthesis of heteroatom-rich carbon cathodes based on a biomass precursor of yeast and a hydrothermal pre-carbonization strategy, realizing high-performance ZHSs. The yeast is composed of polysaccharide chains containing abundant O/N heteroatoms, and a hydrothermal pre-carbonization process is conducive to preserving these heteroatoms in the high-specific-surface-area carbon materials obtained by carbonizing-activating the yeast precursor. As a result, the synthesized carbon materials are endowed with high O/N heteroatom contents (exceeding 13.9 at%), and present superior electrochemical performance in ZHSs, including a high specific capacity of 132 mAh/g, a high energy density of 94.4 Wh/kg and outstanding cycling stability with ∼100% capacity retention after 7000 cycles at 5 A/g. Besides, the heteroatom-rich carbon cathodes show a high capacity retention of 85.3% when their mass loading increases from 3.8 to 12.2 mg/cm2, demonstrating promising application for practical ZHSs. Electrochemical analysis reveals that the O/N heteroatoms promote ion chemical adsorption and thus the electrochemical properties of the carbon cathodes. Furthermore, flexible ZHS devices constructed with the heteroatom-rich carbon cathodes and a biodegradable ZnSO4/dough solid-state electrolyte exhibit excellent flexibility (as reflected by almost unchanged capacity under different bending states and 85% capacity retention after 500 bending cycles) as well as good repairability after dehydration under abnormal environments. This study offers new thinking in designing high-performance carbon cathodes and promotes nonflexible/flexible ZHSs moving towards practical applications.

Modelling of icodextrin hydrolysis and kinetics during peritoneal dialysis

In peritoneal dialysis, ultrafiltration is achieved by adding an osmotic agent into the dialysis fluid. During an exchange with icodextrin-based solution, polysaccharide chains are degraded by α-amylase activity in dialysate, influencing its osmotic properties. We modelled water and solute removal taking into account degradation by α-amylase and absorption of icodextrin from the peritoneal cavity. Data from 16 h dwells with icodextrin-based solution in 11 patients (3 icodextrin-exposed, 8 icodextrin-naïve at the start of the study) on dialysate volume, dialysate concentrations of glucose, urea, creatinine and α-amylase, and dialysate and blood concentrations of seven molecular weight fractions of icodextrin were analysed. The three-pore model was extended to describe hydrolysis of icodextrin by α-amylase. The extended model accurately predicted kinetics of ultrafiltration, small solutes and icodextrin fractions in dialysate, indicating differences in degradation kinetics between icodextrin-naïve and icodextrin-exposed patients. In addition, the model provided information on the patterns of icodextrin degradation caused by α-amylase. Modelling of icodextrin kinetics using an extended three-pore model that takes into account absorption of icodextrin and changes in α-amylase activity in the dialysate provided accurate description of peritoneal transport and information on patterns of icodextrin hydrolysis during long icodextrin dwells.

Structural properties of Phoenix Oolong tea polysaccharide conjugates and the interfacial stability in nanoemulsions.

Tea Polysaccharide conjugate (TPC) is a naturally occurring active substance that is extracted from tea. Due to its benefits in enhancing human immunity and antioxidant effects, TPC is widely used in culinary products. The binding mode of polysaccharides and proteins in TPC, however, hasn't been well studied, it may be closely related to their functional properties, especially emulsification. The molecular weights and monosaccharide compositions of TPC was determined by ion chromatography and high-performance gel permeation chromatography. Although the functional groups of polysaccharides and proteins were confirmed by infrared spectroscopy; the presence of proteins couldn't be detected by SDS-PAGE and UV spectroscopy. It was hypothesized that the hydrophobic groups of the proteins in TPC were wrapped by polysaccharide chains, thus making the proteins undetectable. The rheology and interfacial protein adsorption results show that TPC forms a viscoelastic film at the oil-water interface to prevent the aggregation of oil droplets, thereby enhancing the stability of the emulsion. Based on these structural and emulsifying properties of TPC, the binding mode of polysaccharides and proteins along with their phase behavior at the oil-water interface of the emulsion was speculated. In TPC, the hydrophilic groups of the proteins are linked to polysaccharides by covalent interactions, where the hydrophobic groups are wrapped with the polysaccharide chains with the help of hydrophobic forces to form a hydrophobic core. The unique binding of polysaccharides and proteins in TPC enhances its amphiphilic properties, which can be effectively distributed at the oil-water interface and form stable emulsions. This article is protected by copyright. All rights reserved.

Revisiting the role of electron donors in lytic polysaccharide monooxygenase biochemistry.

The plant cell wall is rich in carbohydrates and many fungi and bacteria have evolved to take advantage of this carbon source. These carbohydrates are largely locked away in polysaccharides and so these organisms deploy a range of enzymes that can liberate individual sugars from these challenging substrates. Glycoside hydrolases (GHs) are the enzymes that are largely responsible for bringing about this sugar release; however, 12 years ago, a family of enzymes known as lytic polysaccharide monooxygenases (LPMOs) were also shown to be of key importance in this process. LPMOs are copper-dependent oxidative enzymes that can introduce chain breaks within polysaccharide chains. Initial work demonstrated that they could activate O2 to attack the substrate through a reaction that most likely required multiple electrons to be delivered to the enzyme. More recently, it has emerged that LPMO kinetics are significantly improved if H2O2 is supplied to the enzyme as a cosubstrate instead of O2. Only a single electron is required to activate an LPMO and H2O2 cosubstrate and the enzyme has been shown to catalyse multiple turnovers following the initial one-electron reduction of the copper, which is not possible if O2 is used. This has led to further studies of the roles of the electron donor in LPMO biochemistry, and this review aims to highlight recent findings in this area and consider how ongoing research could impact our understanding of the interplay between redox processes in nature.

Changes in the structure of polysaccharides under different extraction methods

Changes in the structure of polysaccharides under different extraction methods

Strong and Sustainable Supramolecular Nanofiber Assembling in Acoustic Flow Field

AbstractHierarchical assembly of polysaccharides into nanofiber is at the core of generating advanced biomimetic nanomaterials. However, the artificial synthesis of supramolecular nanofiber from polysaccharides remains an open challenge due to their complicated structure, irregular, and strong interaction. Herein, by mimicking the assembly of natural macromolecules in an out‐of‐equilibrium state, supramolecular nanofiber is successfully fabricated from natural polysaccharides through regular and strong interaction, and a high‐energy and oriented flow field. The high energy of ultrasound can surmount the energy landscape of dynamically stable electrostatic interaction among polysaccharides, while the acoustic‐oriented streaming overcomes the disordered arrangement of macromolecules, thus inducing the orderly arrangement of polysaccharide chains to form kinetically stable nanofibers. The kinetically trapped assembly and the resulting structural evolution can be monitored by scattering and imaging experiments, while the microscopic mechanism can be confirmed by theoretical simulation. Mechanically strong, water‐resistant, and humidity stimulus‐responsive bioplastic film can be fabricated from the supramolecular nanofibers. The discoveries provide critical insights into the assembly of polysaccharides into supramolecular nanofibers and open up many possibilities to prepare advanced nanomaterials from natural polysaccharides.

Biochemical Characterization of an Endoglucanase GH7 from Thermophile Thermothielavioides terrestris Expressed on Aspergillus nidulans

Endoglucanases (EC 3.2.1.4) are important enzymes involved in the hydrolysis of cellulose, acting randomly in the β-1,4-glycosidic bonds present in the amorphous regions of the polysaccharide chain. These biocatalysts have been classified into 14 glycosyl hydrolase (GH) families. The GH7 family is of particular interest since it may act on a broad range of substrates, including cellulose, β-glucan, and xylan, an attractive feature for biotechnological applications, especially in the renewable energy field. In the current work, a gene from the thermophilic fungus Thermothielavioides terrestris, encoding an endoglucanase GH7 (TtCel7B), was cloned in the secretion vector pEXPYR and transformed into the high-protein-producing strain Aspergillus nidulans A773. Purified TtCel7B has a molecular weight of approximately 66 kDa, evidenced by SDS-PAGE. Circular dichroism confirmed the high β-strand content consistent with the canonical GH7 family β-jellyroll fold, also observed in the 3D homology model of TtCel7B. Biochemical characterization assays showed that TtCel7B was active over a wide range of pH values (3.5–7.0) and temperatures (45–70 °C), with the highest activity at pH 4.0 and 65 °C. TtCel7B also was stable over a wide range of pH values (3.5–9.0), maintaining more than 80% of its activity after 24 h. The KM and Vmax values in low-viscosity carboxymethylcellulose were 9.3 mg mL−1 and 2.5 × 104 U mg−1, respectively. The results obtained in this work provide a basis for the development of applications of recombinant TtCel7B in the renewable energy field.

Anionic polysaccharides for stabilization and sustained release of antimicrobial peptides

Chemical and enzymatic in vivo degradation of antimicrobial peptides represents a major challenge for their therapeutic use to treat bacterial infections. In this work, anionic polysaccharides were investigated for their ability to increase the chemical stability and achieve sustained release of such peptides. The investigated formulations comprised a combination of antimicrobial peptides (vancomycin (VAN) and daptomycin (DAP)) and anionic polysaccharides (xanthan gum (XA), hyaluronic acid (HA), propylene glycol alginate (PGA) and alginic acid (ALG)). VAN dissolved in buffer of pH 7.4 and incubated at 37 °C showed first order degradation kinetics with a reaction rate constant kobs of 5.5 × 10-2 day−1 corresponding with a half-life of 13.9 days. However, once VAN was present in a XA, HA or PGA-based hydrogel, kobs decreased to (2.1–2.3) × 10-2 day−1 while kobs was not affected in an alginate hydrogel and a dextran solution (5.4 × 10-2 and 4.4 × 10-2 day−1). Under the same conditions, XA and PGA also effectively decreased kobs for DAP (5.6 × 10-2 day−1), whereas ALG had no effect and HA even increased the degradation rate. These results demonstrate that the investigated polysaccharides (except ALG for both peptides and HA for DAP) slowed down the degradation of VAN and DAP. DSC analysis was used to investigate on polysaccharide ability to bind water molecules. Rheological analysis highlighted that the polysaccharides containing VAN displayed an increase in G’ of their formulations, pointing that the peptides interaction act as crosslinker of the polymer chains. The obtained results suggest that the mechanism of stabilization of VAN and DAP against hydrolytic degradation is conferred by electrostatic interactions between the ionizable amine groups of the drugs and the anionic carboxylate groups of the polysaccharides. This, in turn, results in a close proximity of the drugs to the polysaccharide chain, where the water molecules have a lower mobility and, therefore, a lower thermodynamic activity.

3D stimulated Raman spectral imaging of water dynamics associated with pectin-glycocalyceal entanglement.

Pectin is a heteropolysaccharide responsible for the structural integrity of the cell walls of terrestrial plants. When applied to the surface of mammalian visceral organs, pectin films form a strong physical bond with the surface glycocalyx. A potential mechanism of pectin adhesion to the glycocalyx is the water-dependent entanglement of pectin polysaccharide chains with the glycocalyx. A better understanding of such fundamental mechanisms regarding the water transport dynamics in pectin hydrogels is of importance for medical applications, e.g., surgical wound sealing. We report on the water transport dynamics in hydrating glass-phase pectin films with particular emphasis on the water content at the pectin-glycocalyceal interface. We used label-free 3D stimulated Raman scattering (SRS) spectral imaging to provide insights into the pectin-tissue adhesive interface without the confounding effects of sample fixation, dehydration, shrinkage, or staining.

The lipid linked oligosaccharide polymerase Wzy and its regulating co-polymerase, Wzz, from enterobacterial common antigen biosynthesis form a complex.

The enterobacterial common antigen (ECA) is a carbohydrate polymer that is associated with the cell envelope in the Enterobacteriaceae. ECA contains a repeating trisaccharide which is polymerized by WzyE, a member of the Wzy membrane protein polymerase superfamily. WzyE activity is regulated by a membrane protein polysaccharide co-polymerase, WzzE. Förster resonance energy transfer experiments demonstrate that WzyE and WzzE from Pectobacterium atrosepticum form a complex in vivo, and immunoblotting and cryo-electron microscopy (cryo-EM) analysis confirm a defined stoichiometry of approximately eight WzzE to one WzyE. Low-resolution cryo-EM reconstructions of the complex, aided by an antibody recognizing the C-terminus of WzyE, reveals WzyE sits in the central membrane lumen formed by the octameric arrangement of the transmembrane helices of WzzE. The pairing of Wzy and Wzz is found in polymerization systems for other bacterial polymers, including lipopolysaccharide O-antigens and capsular polysaccharides. The data provide new structural insight into a conserved mechanism for regulating polysaccharide chain length in bacteria.

Effects of polysaccharides from Lyophyllum decastes (Fr.) Singer on gut microbiota via in vitro-simulated digestion and fermentation.

Lyophyllum decastes (Fr.) Singer polysaccharides (LDSPs) have been verified to possess strong biological properties. However, the effects of LDSPs on intestinal microbes and their metabolites have rarely been addressed. The in vitro-simulated saliva-gastrointestinal digestion and human fecal fermentation were used to evaluate the effects of LDSPs on non-digestibility and intestinal microflora regulation in the present study. The results showed a slight increase in the content of the reducing end of the polysaccharide chain and no obvious change in the molecular weight during in vitro digestion. After 24 h in vitro fermentation, LDSPs were degraded and utilized by human gut microbiota, and LDSPs could be transformed into short-chain fatty acids leading to significant (p < 0.05) decrease in the pH of the fermentation solution. The digestion did not remarkably affect the overall structure of LDSPs and 16S rRNA analysis revealed distinct shifts in the gut microbial composition and community diversity of the LDSPs-treated cultures, compared with the control group. Notably, the LDSPs group directed a targeted promotion of the abundance of butyrogenic bacteria, including Blautia, Roseburia, and Bacteroides, and an increase in the n-butyrate level. These findings suggest that LDSPs might be a potential prebiotic to provide a health benefit.