Influence of cations, pH and dispersed phases on pectin emulsification properties

The cooperativity of six cations (Ca²⁺, Mg²⁺, Zn²⁺, Al³⁺, Cr³⁺ and Fe³⁺), three pectins (sugar beet, high and low methyl esterified), three dispersed phases (medium chain triglycerides (MCT), orange oil and hexadecane), time (30 days) and pH (2.0 and 6.0) has been investigated in the formation and stability against coarsening of oil-in-water emulsions. Cations generally influenced emulsion stability in the following order (most stable) Ca²⁺ ​> ​Mg²⁺ ​> ​Al³⁺ ​> ​Cr³⁺ ​> ​Zn²⁺ ​> ​Fe³⁺ (least stable). This order largely coincided with that of the strength of pectin-cation interactions showing that the higher the affinity of cation for pectin the less stable the emulsion. More stable emulsions were formed with sugar beet pectin, which was also unresponsive to the presence of cations, followed by high- and then low-methyl esterified samples. At pH 2.0 all pectins showed their best emulsification performance whereas shifting pH to 6.0 severely impaired emulsification capacity and longer term stability against droplet growth. Smaller droplets were created with hexadecane under all conditions studied followed by MCT and orange oil in agreement with their aqueous solubilities. The present results advance our understanding of the stabilisation of emulsions using pectin and allow us to tailor their functionality for applications in food, pharmaceutical and biomedical industries.

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Cations influence stability in the order: Ca²⁺ ​> ​Mg²⁺ ​> ​Al³⁺ ​> ​Cr³⁺ ​> ​Zn²⁺ ​> ​Fe³⁺.

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Pectins showed best emulsification performance at pH 2.0

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Pectins showed poor emulsification performance at pH 6.0

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Pectin stability order: sugar beet ​> ​high methoxy ​> ​low methoxy pectin.

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Oil stability order at pH 2.0: hexadecane ​< ​medium chain triglycerides ​< ​orange oil.

Hydrolytic Degradation of Heparin in Acidic Environments: Nuclear Magnetic Resonance Reveals Details of Selective Desulfation

Heparin is a complex glycosaminoglycan, derived mainly from pig mucosa, used therapeutically for its anticoagulant activity. Yet, owing largely to the chain complexity, the progressive effects of environmental conditions on heparin structure have not been fully described. A systematic study of the influence of acidic hydrolysis on heparin chain length and substitution has therefore been conducted. Changes in the sulfation pattern, monitored via 2D NMR, revealed initial de-N-sulfation of the molecule (pH 1/ 40 °C) and unexpectedly identified the secondary sulfate of iduronate as more labile than the 6-O-sulfate of glucosamine residues under these conditions (pH 1/ 60 °C). Additionally, the loss of sulfate groups, rather than depolymerization, accounted for most of the reduction in molecular weight. This provides an alternative route to producing partially 2-O-de-sulfated heparin derivatives that avoids using conventional basic conditions and may be of value in the optimization of processes associated with the production of heparin pharmaceuticals.

The identification and characterisation of novel bioactive peptides derived from porcine liver

Bioactive peptides (BAPs) can be derived from a variety of sources; these could be from dietary proteins which are then broken down in the gastrointestinal tract to release BAPs, or they can be isolated from various sources ex vivo. Sources include plant-based proteins such as soy, and chickpeas, and animal proteins from waste from the meat industry and from fish skin. Bioinformatics is also a useful approach to assess the peptides released from digests due to the great number of possible sequences that can be isolated from proteins. Therefore, an in silico analysis of peptides could potentially lead to a more rapid discovery of BAPs. This article investigates a "crude" liver peptide mixture derived from papain hydrolysis of porcine liver and purified peptides derived from the hydrolysates following HPLC fractionation and in silico digestion of the host proteins identified using LC-MS/MS. This allowed the identification of two proteins (cytosol aminopeptidase and haemoglobin subunit alpha) present in the "crude" mixture after LC-MS/MS. In silico hydrolysis of these proteins identified that several peptides were predicted to be both present in the crude mixture using the BIOPEP database and to have potential bioactivity using the Peptide Ranker tool. Peptides (FWG, MFLG and SDPPLVFVG) with the greatest potential bioactivity and which had not previously been reported in the literature were then synthesised. The results indicated that the predicted bioactivity of the synthetic peptides would likely include antioxidant activity. FWG and MFLG derived from the in silico papain hydrolysis of cytosol aminopeptidase showed activity better or comparable to Trolox in the Oxygen Radical Absorbance Capacity (ORAC) assay. The use of these in silico tools, alongside a robust range of biochemical assays which cover a wider range of bioactivities would be a way of improving the discovery of novel bioactive peptides.

Fluorescent Dye Labeling Changes the Biodistribution of Tumor-Targeted Nanoparticles

Fluorescent dye labeling is a common strategy to analyze the fate of administered nanoparticles in living organisms. However, to which extent the labeling processes can alter the original nanoparticle biodistribution has been so far neglected. In this work, two widely used fluorescent dye molecules, namely, ATTO488 (ATTO) and Sulfo-Cy5 (S-Cy5), have been covalently attached to a well-characterized CXCR4-targeted self-assembling protein nanoparticle (known as T22-GFP-H6). The biodistribution of labeled T22-GFP-H6-ATTO and T22-GFP-H6-S-Cy5 nanoparticles has been then compared to that of the non-labeled nanoparticle in different CXCR4+ tumor mouse models. We observed that while parental T22-GFP-H6 nanoparticles accumulated mostly and specifically in CXCR4+ tumor cells, labeled T22-GFP-H6-ATTO and T22-GFP-H6-S-Cy5 nanoparticles showed a dramatic change in the biodistribution pattern, accumulating in non-target organs such as liver or kidney while reducing tumor targeting capacity. Therefore, the use of such labeling molecules should be avoided in target and non-target tissue uptake studies during the design and development of targeted nanoscale drug delivery systems, since their effect over the fate of the nanomaterial can lead to considerable miss-interpretations of the actual nanoparticle biodistribution.

Caffeine release and absorption from caffeinated gums

The objectives of this study were to estimate the impact of chewing time on caffeine release from gum and to understand caffeine pharmacokinetics. Caffeine release increased with chewing time (2 min < 5 min < 10 min). Furthermore, two plasma caffeine concentration peaks were observed suggesting that caffeine absorption occurs both through the oral mucosa and gastrointestinal tract. This is of practical relevance to maximise caffeine doses and to synchronise effort with peak caffeine concentration.

Evaluation of the mucoadhesive properties of chitosan nanoparticles prepared using different chitosan to tripolyphosphate (CS:TPP) ratios

Mucoadhesive molecules such as chitosan, can allow targeting of a particular tissue to prolong residence time and subsequently improve bioavailability. The purpose of this study was to investigate chitosan-tripolyphosphate (CS:TPP) nanoparticles and to evaluate the interaction between nanoparticles of different CS:TPP ratios with mucin using viscosity, particle size analysis and ζ-potential. For all CS:TPP ratios examined, a minimum value of viscosity was reached for a 3:1 CS:TPP ratio, however chitosan nanoparticles at this ratio were not stable (<+30 mV), whereas a CS:TPP ratio of 4:1 displayed the strongest interaction. This suggests a minimum CS:TPP ratio of 4:1 is required to produce stable nanoparticles able to form strong interactions, which is consistent with a greater mucin binding efficiencies at CS:TPP ratios of 4:1 and higher, which were quantified using a colorimetric assay. Further analysis of similar systems could lead potentially to tuneable chitosan nanoparticles for specific applications.

Advances on Bioactive Polysaccharides from Medicinal Plants

In recent decades, the polysaccharides from the medicinal plants have attracted a lot of attention due to their significant bioactivities, such as anti-tumor activity, antioxidant activity, anticoagulant activity, antidiabetic activity, radioprotection effect, anti-viral activity, hypolipidemic and immunomodulatory activities, which make them suitable for medicinal applications. Previous studies have also shown that medicinal plant polysaccharides are non-toxic and show no side effects. Based on these encouraging observations, most researches have been focusing on the isolation and identification of polysaccharides, as well as their bioactivities. A large number of bioactive polysaccharides with different structural features and biological effects from medicinal plants have been purified and characterized. This review provides a comprehensive summary of the most recent developments in physiochemical, structural features and biological activities of bioactive polysaccharides from a number of important medicinal plants, such as polysaccharides from Astragalus membranaceus, Dendrobium plants, Bupleurum, Cactus fruits, Acanthopanax senticosus, Angelica sinensis (Oliv.) Diels, Aloe barbadensis Miller, and Dimocarpus longan Lour. Moreover, the paper has also been focused on the applications of bioactive polysaccharides for medicinal applications. Recent studies have provided evidence that polysaccharides from medicinal plants can play a vital role in bioactivities. The contents and data will serve as a useful reference material for further investigation, production, and application of these polysaccharides in functional foods and therapeutic agents.

Solution conformation and flexibility of capsular polysaccharides from Neisseria meningitidis and glycoconjugates with the tetanus toxoid protein

The structural integrity of meningococcal native, micro-fluidized and activated capsular polysaccharides and their glycoconjugates – in the form most relevant to their potential use as vaccines (dilute solution) - have been investigated with respect to their homogeneity, conformation and flexibility. Sedimentation velocity analysis showed that the polysaccharide size distributions were generally bimodal with some evidence for higher molar mass forms at higher concentration. Weight average molar masses M_w where lower for activated polysaccharides. Conjugation with tetanus toxoid protein however greatly increased the molar mass and polydispersity of the final conjugates. Glycoconjugates had an approximately unimodal log-normal but broad and large molar mass profiles, confirmed by sedimentation equilibrium “SEDFIT MSTAR” analysis. Conformation analysis using HYDFIT (which globally combines sedimentation and viscosity data), “Conformation Zoning” and Wales-van Holde approaches showed a high degree of flexibility – at least as great as the unconjugated polysaccharides, and very different from the tetanus toxoid (TT) protein used for the conjugation. As with the recently published finding for Hib-TT complexes, it is the carbohydrate component that dictates the solution behaviour of these glycoconjugates, although the lower intrinsic viscosities suggest some degree of compaction of the carbohydrate chains around the protein.

A glycoconjugate of Haemophilus influenzae Type b capsular polysaccharide with tetanus toxoid protein: hydrodynamic properties mainly influenced by the carbohydrate

Three important physical properties which may affect the performance of glycoconjugate vaccines against serious disease are molar mass (molecular weight), heterogeneity (polydispersity), and conformational flexibility in solution. The dilute solution behaviour of native and activated capsular polyribosylribitol (PRP) polysaccharides extracted from Haemophilus influenzae type b (Hib), and the corresponding glycoconjugate made by conjugating this with the tetanus toxoid (TT) protein have been characterized and compared using a combination of sedimentation equilibrium and sedimentation velocity in the analytical ultracentrifuge with viscometry. The weight average molar mass of the activated material was considerably reduced (Mw ~ 0.24 × 10(6) g.mol(-1)) compared to the native (Mw ~ 1.2 × 10(6) g.mol(-1)). Conjugation with the TT protein yielded large polydisperse structures (of Mw ~ 7.4 × 10(6) g.mol(-1)), but which retained the high degree of flexibility of the native and activated polysaccharide, with frictional ratio, intrinsic viscosity, sedimentation conformation zoning behaviour and persistence length all commensurate with highly flexible coil behaviour and unlike the previously characterised tetanus toxoid protein (slightly extended and hydrodynamically compact structure with an aspect ratio of ~3). This non-protein like behaviour clearly indicates that it is the carbohydrate component which mainly influences the physical behaviour of the glycoconjugate in solution.

Impact of bread making on fructan chain integrity and effect of fructan enriched breads on breath hydrogen, satiety, energy intake, PYY and ghrelin

Recently, there has been considerable interest in the satiety inducing properties of inulin type fructans (ITF) as a tool for weight management. As a staple food, breads provide an excellent vehicle for ITF supplementation however the integrity of the ITF chains and properties upon bread making need to be assessed. Breads enriched with 12% fructooligosaccharides (FOS) and 12% inulin were baked and the degree of polymerisation of fructans extracted from the breads were compared to those of pure compounds. An acute feeding study with a single blind cross-over design was conducted with 11 participants to investigate the effect of ITF enriched breads on breath hydrogen, self-reported satiety levels, active ghrelin, total PYY and energy intake. Size exclusion chromatography indicated that little or no depolymerisation of inulin occurred during bread making, however, there was evidence of modest FOS depolymerisation. Additionally, ITF enriched breads resulted in increased concentrations of exhaled hydrogen although statistical significance was reached only for the inulin enriched bread (p = 0.001). There were no significant differences between bread types in reported satiety (p = 0.129), plasma active ghrelin (p = 0.684), plasma PYY (p = 0.793) and energy intake (p = 0.240). These preliminary results indicate that inulin enriched bread may be a suitable staple food to increase ITF intake. Longer intervention trials are required to assess the impact of inulin enriched breads on energy intake and body weight.

Sample convection in liquid-state NMR: why it is always with us, and what we can do about it

Many NMR experiments on liquids suffer if the sample convects. This is particularly true for applications, such as the measurement of diffusion, that rely on spatial labelling of spins. It is widely assumed that, in most well-conducted experiments with stable temperature regulation, samples do not convect. Unfortunately this is not the case. It is shown here that typical NMR samples show measurable convective flow for all but a very narrow range of temperatures; convection is seen both above and below this range, which can be as small as a degree or so for a mobile solvent such as chloroform. This convection is driven by both vertical and horizontal temperature gradients. Measurements of convection velocity are presented for a range of samples, sample tubes, probes, and temperatures. Both decreasing sample tube inner diameter and changing sample tube material from glass to sapphire can slow convection markedly, with sapphire tubes being particularly effective. Such tubes are likely to be particularly helpful for accurate measurement of diffusion by NMR.

Characterization of Capsular Polysaccharides and Their Glycoconjugates by Hydrodynamic Methods

Hydrodynamic methods are relevant for the characterization of carbohydrates such as capsular bacterial polysaccharides or glycoconjugates in solution. This chapter focuses on the following hydrodynamic methods: sedimentation velocity analytical ultracentrifugation (SV AUC), dynamic light scattering (DLS), sedimentation equilibrium analytical ultracentrifugation (SE AUC), size exclusion chromatography coupled to multi-angle light scattering (SEC-MALS), and capillary viscometry-intrinsic viscosity measurement. The chapter highlights the general principle of these five methods, describes experimental details, and specifies advances in the last years.

A novel method to estimate the stiffness of carbohydrate polyelectrolyte polymers based on the ionic strength dependence of zeta potential

Polysaccharides have received a great deal of attention from, for example, the food, cosmetic and pharmaceutical industries. Their conformations (flexibility/stiffness) span a wide range of conformational flexibilities with large hydrated volumes, these properties are important in relation to polysaccharide structure-function relationships. Perhaps the simplest parameter available to estimate the dilute solution conformation of polysaccharides is the Smidsrød-Haug stiffness parameter (B) where the stiffness of polyelectrolytes can be estimated by measuring the intrinsic viscosity at a number of different ionic strengths. In this paper we propose an alternative method for estimating the Smidsrød-Haug stiffness parameter (B) using the ionic strength dependency of zeta potential. For this purpose we have studied a number of different polysaccharides.

Solution properties of capsular polysaccharides from Streptococcus pneumoniae

Capsular polysaccharides from ten different serotypes of Streptococcus pneumoniae have been studied with regards their hydrodynamic properties in solution, namely their sedimentation coefficient and molar mass distributions, solution conformations and flexibilities (persistence lengths Lp), important properties for the construction of polysaccharide and glycoconjugate vaccines. Sedimentation and molar mass distributions (obtained by sedimentation velocity and equilibrium analysis in the analytical ultracentrifuge supported by size exclusion chromatography coupled to multi-angle light scattering measurements) were generally unimodal, with weight (mass) average molar masses ranging from 100×10(3) to 1300×10(3) g/mol. Estimates of chain flexibilities from three different procedures applied to intrinsic viscosity, sedimentation coefficient and molar mass data, showed that the polysaccharides from all the serotypes studied had semi-flexible structures in solution with persistence lengths in the range from ∼4 to 9 nm.

Extended Fujita approach to the molecular weight distribution of polysaccharides and other polymeric systems

In 1962 H. Fujita (H. Fujita, Mathematical Theory of Sedimentation Analysis, Academic Press, New York, 1962) examined the possibility of transforming a quasi-continuous distribution g(s) of sedimentation coefficient s into a distribution f(M) of molecular weight M for linear polymers using the relation f(M)=g(s)·(ds/dM) and showed that this could be done if information about the relation between s and M is available from other sources. Fujita provided the transformation based on the scaling relation s=κ(s)M(0.5), where κ(s) is taken as a constant for that particular polymer and the exponent 0.5 essentially corresponds to a randomly coiled polymer under ideal conditions. This method has been successfully applied to mucus glycoproteins (S.E. Harding, Adv. Carbohyd. Chem. Biochem. 47 (1989) 345-381). We now describe an extension of the method to general conformation types via the scaling relation s=κM(b), where b=0.4-0.5 for a coil, ∼0.15-0.2 for a rod and ∼0.67 for a sphere. We give examples of distributions f(M) versus M obtained for polysaccharides from SEDFIT derived least squares g(s) versus s profiles (P. Schuck, Biophys. J. 78 (2000) 1606-1619) and the analytical derivative for ds/dM performed with Microcal ORIGIN. We also describe a more direct route from a direct numerical solution of the integral equation describing the molecular weight distribution problem. Both routes give identical distributions although the latter offers the advantage of being incorporated completely within SEDFIT. The method currently assumes that solutions behave ideally: sedimentation velocity has the major advantage over sedimentation equilibrium in that concentrations less than 0.2mg/ml can be employed, and for many systems non-ideality effects can be reasonably ignored. For large, non-globular polymer systems, diffusive contributions are also likely to be small.

Molecular weight distribution evaluation of polysaccharides and glycoconjugates using analytical ultracentrifugation

We review here the advances that have been made in methodology using the analytical ultracentrifuge for characterising polydisperse polymer systems with a quasi-continuous distribution of molecular weight. These advances include improved ways of defining the weight and z-average molecular weights of a distribution from sedimentation equilibrium experiments and hence the ratio Mz/Mw, off-line calibration of size exclusion chromatography by sedimentation equilibrium and conversion of a sedimentation coefficient distribution into a molecular weight distribution. Although these methods are applicable to other polymeric systems, we focus on polysaccharides, mucins and other glycoconjugates, systems which particularly benefit from the availability of recently available long optical path length cells for the minimisation of complications through thermodynamic non-ideality.

Nano-structure of the laminin γ-1 short arm reveals an extended and curved multidomain assembly

Laminins are multidomain glycoproteins that play important roles in development and maintenance of the extracellular matrix via their numerous interactions with other proteins. Several receptors for the laminin short arms revealed their importance in network formation and intercellular signaling. However, both the detailed structure of the laminin γ-1 short arm and its organization within the complexes is poorly understood due to the complexity of the molecule and the lack of a high-resolution structure. The presented data provide the first subatomic resolution structure for the laminin γ-1 short arm in solution. This was achieved using an integrated approach that combined a number of complementary biophysical techniques such as small angle X-ray scattering (SAXS), analytical ultracentrifugation, dynamic light scattering and electron microscopy. As a result of this study, we have obtained a significantly improved model for the laminin γ-1 short arm that represents a major step forward in molecular understanding of laminin-mediated complex formations.

A simple flowcell for reaction monitoring by NMR

A simple, cheap and flexible flowcell based on a standard 5 mm NMR tube, designed for the monitoring of reactions but of wide applicability, is described. No modification of the NMR instrument is needed, allowing the system to be employed with any conventional NMR probe and magnet. The system is robust and economical in use of reagents, and can be used for studying both homogeneous and heterogeneous reactions.

Constant time gradient HSQC-iDOSY: practical aspects

An improved constant time gradient HSQC-iDOSY pulse sequence is presented, and the corresponding form of the Stejskal-Tanner equation is derived. The pulse sequence is particularly well suited to the problem of analysing mixtures of chemically cognate species, where the high spectral resolution afforded by 1H-13C correlation methods is needed for DOSY experiments to give good diffusion resolution. Its use is illustrated for a mixture of rutin and its aglycone quercetin.

Molecular flexibility of methylcelluloses of differing degree of substitution by combined sedimentation and viscosity analysis

The flexibility/rigidity of methylcelluloses (MCs) plays an important part in their structure-function relationship and therefore on their commercial applications in the food and biomedical industries. In the present study, two MCs of low degree of substitution (DS) 1.09 and 1.32 and four of high DS (1.80, 1.86, 1.88 and 1.93) were characterised in distilled water in terms of intrinsic viscosity [h]; sedimentation coefficient (s020,w) and weight average molar mass (Mw). Solution conformation and flexibility were estimated qualitatively using conformation zoning and quantitatively (persistence length Lp) using the new combined global method. Sedimentation conformation zoning showed an extended coil (Type C) conformation and the global method applied to each MC sample yielded persistence lengths all within the range Lp(1/4)12-17 nm (for a fixed mass per unit length) with no evidence of any significant change in flexibility with DS.

Pectic polysaccharides from Biophytum petersianum Klotzsch, and their activation of macrophages and dendritic cells

The Malian medicinal plant Biophytum petersianum Klotzsch (Oxalidaceae) is used as a treatment against various types of illnesses related to the immune system, such as joint pains, inflammations, fever, malaria, and wounds. A pectic polysaccharide obtained from a hot water extract of the aerial parts of B. petersianum has previously been reported to consist of arabinogalactans types I and II (AG-I and AG-II), probably linked to a rhamnogalacturonan backbone. We describe here further structural characteristics of the main polysaccharide fraction (BP1002) and fractions obtained by enzymatic degradations using endo-alpha-d-(1-->4)-polygalacturonase (BP1002-I to IV). The results indicate that in addition to previously reported structures, rhamnogalacturan type II and xylogalacturonan areas appear to be present in the pectic polymer isolated from the plant. Atomic force microscopy confirmed the presence of branched structures, as well as a polydisperse nature. We further tested whether the BP1002 main fraction or the enzymatically degraded products could induce immunomodulating activity through stimulation of subsets of leukocytes. We found that macrophages and dendritic cells were activated by BP1002 fractions, while there was little response of T cells, B cells, and NK cells. The enzymatic treatment of the BP1002 main fraction gave important information on the structure-activity relations. It seems that the presence of rhamnogalacturonan type I is important for the bioactivity, as the bioactivity decreases with the decreased amounts of rhamnose, galactose, and arabinose. The demonstration of bioactivity by the plant extracts might indicate the mechanisms behind the traditional medical use of the plant.