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The aim of this narrative review was to demonstrate how the notion of allostatic load (AL) relates directly to the mental health disparities observed between Indigenous and non-Indigenous Australians. We also endeavored to synthesize the results of the limited number of studies examining stress and AL in Indigenous Australians in order to explore the potential public health benefits of the AL concept. A range of literature examining health inequalities, psychosocial determinants of mental illness and AL was explored to demonstrate the applicability of stress biology to the significant mental health burden faced by Indigenous Australians. Furthermore, all original studies indexed in MEDLINE that provided quantitative data on primary stress biomarkers in Indigenous Australians were selected for review. Evidence of hypothalamic-pituitary-adrenal axis dysregulation and increased AL is apparent even in the handful of studies examining stress biomarkers in Indigenous Australians. Urinary, salivary, hair and fingernail cortisol, hair cortisone, urinary epinephrine, heart rate variability and the cortisol awakening response are all AL parameters which have been shown to be dysregulated in Indigenous Australian cohorts. Furthermore, associations between some of these biomarkers, self-perceived discrimination, exposure to stressful life events and symptoms of psychiatric disorders in Indigenous Australians have also been demonstrated. The continued assessment of AL biomarkers and their relationship with past traumas, lifetime stressors and socio-economic factors amongst Indigenous Australians is important to addressing the mental health this population. Measurement of AL biomarkers in a culturally appropriate manner may lead to more targeted preventative measures, interventions and policies, which mitigate the effects of stress at both the individual and societal level.

Functional advanced biopolymers have received far less attention than renewable biomass (cellulose, rubber, etc.) used for energy production. Among the most advanced biopolymers known is chitosan. The term chitosan refers to a family of polysaccharides obtained by partial de-N-acetylation from chitin, one of the most abundant renewable resources in the biosphere. Chitosan has been firmly established as having unique material properties as well as biological activities. Either in its native form or as a chemical derivative, chitosan is amenable to being processed—typically under mild conditions—into soft materials such as hydrogels, colloidal nanoparticles, or nanofibers. Given its multiple biological properties, including biodegradability, antimicrobial effects, gene transfectability, and metal adsorption—to name but a few—chitosan is regarded as a widely versatile building block in various sectors (e.g., agriculture, food, cosmetics, pharmacy) and for various applications (medical devices, metal adsorption, catalysis, etc.). This Special Issue presents an updated account addressing some of the major applications, including also chemical and enzymatic modifications of oligos and polymers. A better understanding of the properties that underpin the use of chitin and chitosan in different fields is key for boosting their more extensive industrial utilization, as well as to aid regulatory agencies in establishing specifications, guidelines, and standards for the different types of products and applications.

This study aims to understand the effects of toughness and hardness on two-body wear of nanostructured carbide-free bainitic steels. For this purpose, three different steel grades were austempered at 250 °C to obtain carbide-free bainitic microstructures with different mechanical properties. The mechanical properties were determined in terms of fracture toughness and hardness. The wear tests were carried-out at three different loads with two different types of abrasive papers. The results show that a carbide-free bainitic steel with an optimum combination of hardness and fracture toughness exhibits the highest wear resistance. It has been seen that hardness is not the only parameter in determining the abrasive wear resistance and retained austenite has a beneficial effect on two-body abrasive wear.

The Museum of Physics (University of Turin) was established in 2009 and displays scientific instruments dating from the early 1700s. A monitoring microclimatic campaign has been performed in an exposing hall that houses also part of the collection of the Library of the Department of Physics. The measurements were made using 11 thermo-hygrometers during 13 months inside and outside some showcases, and an outdoor meteorological station on the building top monitored the external weather conditions. Time delays in temperature between outdoor, indoor and inside showcases environments were evaluated. The microclimatic analysis show that the showcases mitigate the daily excursions in temperature and relative humidity and that the showcase microclimatic conditions are dependent on the position in the room. Finally, a new index is proposed to compare the “goodness” of microclimate in the different sites.

In this work, we suggest the use of astronomical laboratory topics in didactic activities. We present two educational experiences, which we offered to last year students of the junior high school and first-year students of the technical-economic high school (ITES). Astronomy attracts the majority of students. Our idea is to use this interest as leverage to show how concepts and tools of Mathematics and Physics are essential; therefore the study of Mathematics and Physics topics becomes more explained and fascinating. For every laboratory activity, we explicate some of the Math, Physics and Astronomical concepts that can be strengthened. Every step was enriched by a brief theoretical presentation of some current research in the astronomical field, to increase the interest of students. We propose to use simple and cheap materials for all the laboratory experiences, and we suggest also using smart-phone applications as physical tools. We present three laboratory activities for the younger students and two laboratory activities for the older ones. For every topic we proposed a pre-test, to check out previous knowledge, and a post-test, to reflect if students have achieved the goals. We report the teacher’s opinion to draw some conclusions about the work done. In the end, we underline some problems and difficulties encountered.

Chitosan-g-N-isopropylacrylamide (NIPAm) water-soluble copolymers were synthesized and characterized by FTIR and (1)H NMR spectroscopies combined with conductometric and potentiometric titrations. Their thermoresponsive, fully reversible, behavior in aqueous solutions was characterized by means of microcalorimetry and rheology. During heating of copolymer solutions there is a well-known endothermic effect, which coincides with a marked increase in G' and a moderate decrement in G'' due to the formation of a hydrophobic network at the expense of the net amount of sol fraction. It was also found that a straight dependence between the values of G' above the LCST and the enthalpies associated with the transition reflecting that the connectivity in the gel network is governed by the net number of formed enthalpic-hydrophobic driven-junctions. Both the LCST and the enthalpy change vary with the ionic strength of copolymer solutions, but no dependence was found with the neutralization of the polyelectrolyte chain.

The review is devoted to synthesis and study of interfacial properties of electrostatic complexes between oppositely charged chitin derivatives and surfactants, so-called surfactant-polyelectrolyte complexes (SPECs). The ordered nanostructure of insoluble SPEC found by small-angle X-ray scattering (SAXS) looks as a physical gel network formed by micelle-like aggregates interconnected by macro-molecular chains. Viscoelastic properties of such gels were studied by means of the Hertz method and interfacial dilational rheology. A new method based on the effect of diffusion-enhanced gelation at the interface of aqueous solutions of oppositely charged polyelectrolytes and surfactants was developed. This method makes it possible to produce microcapsules containing enzymes, i.e. microreactors for enzymatic catalysis.

We compared the enzymatic attack by an active cellulase preparation on native cotton, swollen cotton, and regenerated cellulose. At various time intervals the residual cellulose was analyzed for: weight loss, number-average degree of polymerization, weight-average degree of polymerization, water retention value, and the biometric length distribution of the fibers; morphologic aspects were analyzed at various intervals of time. On the solubilized part glucose and reducing sugars were estimated. All the data obtained at the supramolecular and macromolecular level were consistent with the existence of several enzymic factors responsible for the hydrolysis of these different substrates.

The influence of the nature of the oil phase on the zeta potential and the time course evolution of mean droplet-size of emulsions stabilized with mesquite gum have been investigated. Mesquite gum-stabilized emulsions of d -limonene, n -decane, n -dodecane, n -tetradecane n -hexadecane, and orange oil were prepared in the range of 9–22% w/w mesquite gum concentrations to investigate the emulsion stability by analyzing creaming, zeta potential, and drop size distribution. An electrosteric mechanism of stabilization is proposed to explain the long term stability observed for orange oil–water emulsions in the range of 9–22% w/w mesquite gum concentrations, similar to the one suggested to operate for gum arabic interfaces. Experiments of creaming for the different emulsions, showed that orange oil–water emulsions observed strong stability in time. By contrast, mesquite gum-stabilized emulsions of d -limonene, n -decane, n -dodecane, n -tetradecane, and n -hexadecane produced less stable emulsions. Light scattering measurements were performed to analyse the Ostwald ripening phenomenon on diluted oil in water emulsions stabilized with mesquite gum of n -hexadecane, d -limonene, and orange oil. The averaged hydrodynamic radius showed a linear-like behavior with time except for orange oil drops which kept their size almost constant for more than hundred hours.

The influence of the nature of the oil phase on the viscoelastic properties of emulsions stabilized with mesquite gum has been investigated. Mesquite gum-stabilized emulsions of d-limonene, n-decane, n-dodecane, n-tetradecane n-hexadecane and orange oil were analyzed, the observations showed that the nature of the oil used was determinant for the viscoelastic and gel formation ability of the emulsions. Orange oil-in-water emulsions stabilized with mesquite gum developed a gel-like structure with time, in contrast to the emulsions obtained with alkane oils and with d-limonene. This is rationalized in terms of a weak gel network of protein-polysaccharides molecules interconnecting spherical oil droplets. The gelling behavior of these systems has been described with a model derived from percolation theory.

Background: Millions of individuals are estimated to become infected with dengue virus each year, particularly in tropical and subtropical regions. Mortality is low but infection can lead to a severe form of dengue, characterised by haemorrhage and shock. A safe and effective vaccine against dengue is still not available. Objective: To use the successful construction of dengue type 4 virus (DEN4) cDNA, which yields infectious RNA transcripts, to provide a new approach to the development of safe and effective dengue vaccines. Study design: The 3′ and 5′ noncoding (NC) regions of the genome were targeted to construct DEN4 deletion mutants, because the sequences in these regions are thought to play an important role in the regulation of viral replication. DEN4 cDNA was also employed to construct a viable chimeric virus with dengue type 1, 2 or 3 antigenicity, by substitution of heterotypic structural protein genes. Results: Most viable mutants, recovered from the cDNA constructs, were partially restricted for growth in simian cells as analysed by plaque morphology assay and viral yield analysis. Several 3′ NC deletion mutants which exhibited a range of growth restriction in cell culture were further evaluated for infectivity and immunogenicity in rhesus monkeys. Occurrence and duration of viraemia were reduced for these deletion mutants, compared to the wild type DEN4. Analysis of antibody response to infection in rhesus monkeys also indicated that some of these mutants were attenuated. These DEN4 deletion mutants represent promising live dengue vaccine candidates that merit further clinical evaluation. Chimera DEN1/DEN4 or DEN2/DEN4 which expresses DEN1 or DEN2 antigenicity were also used to infect monkeys. Most monkeys immunised with these chimeric viruses, singly or in combination, developed high titres of neutralising antibodies and were protected against homotypic wild type DEN1 or DEN2 challenge. Conclusions: DEN4 and its derived chimeric viruses of other three dengue serotype specificity, that contain appropriate attenuating mutations, have a potential use in a tetravalent live vaccine against dengue.

The sorption of moisture by ligno-cellulosic materials has a significant influence on their physical properties since it affects both swelling and softening. In order to estimate the adsorption behaviour, an attempt is made to calculate the number and type of water molecules (whether non-freezing bound water or freezing bound water) adsorbed by the polar groups (OH, COO−, SO3−) with counterions (H+, Na+, Ca2+) common in paper products. The analysis is based on sorption experiments using differential scanning calorimetry and thermogravimetric analysis. The main contributors to the adsorption on wood are the hydroxyl groups of the carbohydrates and the lignin. Any adsorption of freezing bound water in the studied moisture range is attributed to ionic groups present in the sample. Differences in adsorption between weak carboxylic acid and strong sulphonic acid systems are explained as being a function of their different degrees of dissociation. The values calculated for the polar groups using model substances are used in an attempt to predict the adsorption for two xylans, a lignin preparation and a sulphonated wood meal of which the composition and the degree of crystallinity are known, assuming a simple law of additivity. The calculated results agree well with the experimental results.

The behavior of gellan during the conformational transition is discussed. This transition corresponds to the formation of a double helix from two separate coils. The influence of the counterion activity on the melting and gelling temperatures of the gels and/or the ordered conformation is also described. The sol-gel transition is studied by conductimetry in the presence of pure monovalent counterions or monovalent divalent mixtures. This method is one of the best ways of characterizing this transition. A two-step mechanism of gelation was demonstrated in the presence of monovalent counterions. In the presence of divalent counterions, at a given ionic strength, the mechanism of gelation and the gel properties depend only on the ratio Y between divalent and monovalent counterions. Three types of gel behavior are described as a function of Y and ionic strength.

Le comportement de solutions aqueuses de methylcellulose (MC) a ete etudie en fonction de la temperature. Les solutions semi-diluees de MC ont la particularite de former un gel lorsqu'elles sont chauffees. Le processus de gelification est reversible mais presente un effet cinetique et une hysterese importants. Differents cycles de temperature ont ete realises et ont demontre la formation progressive d'interactions au sein de l'echantillon. Des etudes en regime dilue ont permis de mettre en evidence l'apparition d'agregats dans les solutions pour des temperatures superieures a 35°C. Par ailleurs, le role de la structure chimique (repartition des substituants et valeur du degre de substitution) sur les proprietes rheologiques a ete etudie. La gelification est ainsi attribuee aux interactions hydrophobes.

The determination of the radius of gyration and intrinsic viscosity as function of molecular weight for xanthan polysaccharide allows for a better understanding of the conformation of this polymer in solution. The native ordered conformation of xanthan, which corresponds to that obtained during its biosynthesis appears to be a single chain characterized by a persistence length of approximately 400 A. In contrast, the renatured ordered conformation restored after the first denaturation of the native conformation exhibits behavior suggesting doublestranded conformation as described previously in the literature. In fact, this conformation seems to correspond to a folded xanthan chain.

Background The goal of rheumatoid arthritis (RA) strategy is to reach remission or at least a low disease activity. When this gaol is reached, no clear guideline exist to manage therapy. Recently, STRASS ( Spacing TNF-blocker injections in RA Study ) provided evidence of step-down therapeutic strategy with adalimumab or etanercept (1). Objectives We investigated if drug dosages and their antidrug antibodies (ADAb) could predict relapse during the 18 months of STRASS study. Methods We assessed 131 serum among the 137 included in STRASS study (60 and 71 for adalimumab and etanercept, respectively). Serum were collected at the time of randomisation. Adalimumab and etanercept blood concentrations and theirs ADAb were assessed by ELISA (Theradiag, Marne-La-Vallee, France). For this study, relapse was defined as DAS28>2.6 with DAS28 increase >0.6 since the previous study visit. Results Characteristics of the 131 patients similar to 137 from the initial STRASS study (data not shown). The median age was 54.5 [48.3–61.8] years. One hundred and two (77%) were female. The median disease duration was 6.5 [4.5–12.4] years. The median DAS28, ESR, and CRP were 2.0 [1.5–2.3], 10 [6–17], and 3 [2–4]mg/mL, respectively. Methotrexate was the main DMARDs used (n=91; 70%). No baseline characteristics were associated with relapse during tapering or not. In patients treated with etanercept, etanercept level was similar in case of relapse or not. Similarly, adalimumab level was comparable in case of relapse or not. However, in patients treated with adalimumab, ADABs was significantly higher in case of relapse compared to no relapse (0.94±0.27 ng/ml vs. 0.27±0.76 ng/ml; P=0.03, respectively). However, this difference was not clinically pertinent. Conclusions No difference was observed in adalimumab or etanercept blood level to predict relapse in RA patients with low disease activity. However, a slight increased of ADAb for adalimumab was observed. Its signification needs further investigation. References Fautrel B, Pham T, Alfaiate T, et al. Step-down strategy of spacing TNF-blocker injections for established rheumatoid arthritis in remission: results of the multicentre non-inferiority randomised open-label controlled trial (STRASS: Spacing of TNF-blocker injections in Rheumatoid ArthritiS Study). Annals of the Rheumatic Diseases 2016; 75: 59–67. Acknowledgement AbbVie provided funding for this study. Analysis was performed independently to AbbVie. Disclosure of Interest None declared

A general formalism for the dynamic scattering properties of cyclic polymers in good solvent conditions is presented. Single-chain dynamics are investigated in the framework of the Oseen tensor model with and without the preaveraging approximation. The chain swelling due to excluded volume interactions is introduced by a renormalization of the internal chain statistics of cyclic polymers. The relaxations of the concentration fluctuations are also described for both ring homopolymers and copolymers. © 1994 John Wiley & Sons, Inc.

cited By 44; International audience; The sorption of moisture by different cellulose derivatives was examined as a function of relative humidity, to evaluate the influence of counter-ions and different charged groups on the moisture adsorption mechanism. Studies were made on cellulosic materials containing sulfate (-O-SO3H) and carboxylic (-COOH) groups in different ionic forms (H+, Li+, Na+, K+ and Ca2+). Uncharged cellulose and amylose were also examined for comparison. It was shown that the choice of counter-ions had a large influence on the moisture uptake by the studied polymers. Moisture adsorption by cellulose containing sulfate acid groups was favoured by the counter-ion H+, rather than, in order of decreasing efficiency, by Li+, Na+, Ca2+ and K+. Two types of differently adsorbed water were found: non-freezing bound water and freezing bound water. Most of the differences in total moisture content were due to differences in the freezing water content. The counter-ion favouring water adsorption in the case of the cellulose containing carboxylic acid groups was Li+, followed, in decreasing order of efficiency, by Na+, K+, Ca2+ and H+. In this case, the differences in total water content were found in both the non-freezing and freezing water. It was furthermore shown that the presence of charged groups was necessary for the adsorption of freezing water when the relative humidity was less than 100%. The large influence of the counter-ions on water adsorption may be associated with the ionic radius (size of the counter-ion), which influences the degree of hydration. Differences in water adsorption for the protonated form may be explained by the observation that carboxylic acids are weak acids with limited dissociation, whereas the stronger sulfate acid groups facilitate a more complete dissociation. © 1994 Butterworth-Heinemann Ltd.

Many water-soluble N -substituted chitosan derivatives have been prepared having the typical -NH-CH 2 - linkage. Both the Michael reaction and alkylation with monochloroacetic acid at pH 8 - 8.5 offer relatively simple ways for their synthesis. Keywords: N-carboxymethyl chitosan; N-dicarboxymethyl chitosan; N-carboxyethyl chitosan; N-carboxybutyl chitosan; N-trimethyl chitosan; 5-methylpyrolidinone chitosan AJSTD Vol.22(3) pp.261-270 (2005)

Background Since biologic therapy development, rheumatoid arthritis (RA) prognosis improves dramatically. Tumor necrosis factor alpha (TNF) is a proinflammatory cytokine that plays an important role in RA pathogenesis. Infliximab (IFX, Remicade®), is a human-murine chimerical monoclonal IgG antibody targeting TNF, approved for RA after inadequate response to conventional synthetic disease modifying antirheumatic drugs (csDMARDs). Clinical improvement is heterogeneous with primary or secondary therapy failure. Furthermore, no factors to predict response are available in the daily practice. Detection of antibody towards IFX (ATI) was described early in the development of this drug. The hypothesis is that ATI reduce IFX concentration associated with a lack of efficacy. Objectives To evaluate methotrexate effects on tumor necrosis factor alpha (TNF) bioactivity and antibody against infliximab (ATI) development in rheumatoid arthritis (RA) patients treated by infliximab (IFX). Methods In a longitudinal multicenter study including 39 RA patients requiring IFX therapy, clinical data and blood sample were recorded at the inclusion (W0), at the 6th week (W6), at the 6th month (W22) and at the 12th month (W54) of treatment. Results IFX trough level increased from W0 to W54 and distribution became heterogeneous at W22 at the time of first ATI detection. From W22, an inverse correlation between IFX trough level and ATI concentrations was observed (p Conclusions This suggests that methotrexate plays a key role on TNF bioactivity and against ATI development Disclosure of Interest None declared

We recorded a series of spectra of sodium hyaluronan (HA) films that were in equilibrium with their surrounding humid atmosphere. The hygrometry of this atmosphere extended from 0 to 0.97% relative humidity. We performed a quantitative analysis of the corresponding series of hydration spectra that are the difference spectra of the film at a defined hygrometry minus the spectrum of the dried film (hygrometry = 0). The principle of this analysis is to use this series of hydration spectra to define a limited number (four) of "elementary hydration spectra" over which we can decompose all hydration spectra with good accuracy. This decomposition, combined with the measurements of the numbers of H(2)O molecules at the origin in these elementary hydration spectra of the three characteristic vibrational bands of H(2)O, allowed us to calculate the hydration number under different relative humidity conditions. This number compares well with that determined by thermogravimetry. Furthermore, the decomposition defines for each hygrometry value which chemical mechanisms represented by elementary hydration spectra are active. This analysis is pursued by determining for the elementary hydration spectra the number of hydrogen bonds established by each of the four alcohol groups found in each disaccharide repeat unit before performing the same analysis for amide and carboxylate groups. These results are later utilized to discuss the structure of HA at various stages of hydration.

The results of the analysis of hydration spectra of Na(+) hyaluronan (HA) performed in a companion study are translated in terms of chemical mechanisms. We find that dried HA is characterized by chains having ordered parts of at least 6 disaccharide repeat units that extend over 60 A. The order is mainly due to C3O3H...O5 and C4O4H...O5 hydrogen bonds that hinder rotations around beta(1-4) and beta(1-3) glycoside bonds. Along one chain there are two-thirds of the N-H amide groups and carboxyl groups that are directly hydrogen bonded, with no water intermediate, to form N-H...(-)O-C=O hydrogen bonds, which are collateral to C3O3H...O5 hydrogen bonds. The existence of these N-H...(-)O-C=O bonds is somewhat in opposition to literature descriptions. In this dry state a "water wire" of 4-5 H(2)O molecules, which are anchored on C=O carboxyl groups and hydrating the Na(+) CO(-) ionic group, establishes hydrogen bonds on other hydrophilic groups of the same chain or other chains and remains embedded in HA, even at 104 degrees C. Hydration occurs at low hygrometry around the remaining one-third of the N-H...(-)O-C=O pairs that are not hydrogen bonded. Each of these N-H and (-)O-C=O groups is hydrated by a nanodroplet of some 25 H(2)O molecules that finds other sites for binding and hydrates 2 disaccharide repeat units. At higher hygrometry bigger nanodroplets hydrate all hydrophilic sites.

This article is the first one in a series dedicated to the study of hyaluronan as observed by IR spectrometry. The goal is to determine its hydration mechanism and the structural changes this mechanism implies. Hyaluronan is a natural polysaccharide that is widely used in biomedical applications and cosmetics. Its macroscopic properties are significantly dependent on its degree of hydration. In this article we record the IR spectrum of a several micron thick dried film and deduce that four or five residual H(2)O molecules remain around each disaccharide repeat unit in the dried film. We then compare the spectra of sodium hyaluronan and its acid form to assign vibrational bands linked to the carboxylate group. We proceed with a qualitative analysis of the spectral changes induced by changes of temperature and hygroscopicity, two independent parameters that act by modifying the hydrogen bond network of the sample. This enables us to assign most of the vibrational bands of the hydrophilic groups and to distinguish the bands that are due to these hydrophilic groups when they are or are not hydrogen bonded. It constitutes a prerequisite for the quantitative analysis of hydration spectra that will be described in the following articles of this series.

Using a variety of rheological techniques, the behavior of hyaluronan (M(w) 0.8-2.2 x 10(6)), cross-linked hyaluronan (hylan) (M(w) 1.8-12.5 x 10(6)), and Healon (M(w) approximately 5 x 10(6)) (a proprietary hyaluronan) was studied over a large range of molecular weights. The object was to study the effect of the cross-links in hylan on the various rheological parameters, in comparison with linear hyaluronan. There are significant differences. The Huggins constant and the critical overlap parameter C*[eta] are considerably lower for hylan and an increase in moduli at low frequencies was observed for hylan compared with the hyaluronan samples at all molecular weights studied. The results point to a difference in structure in dilute solution for hylan due to the ability to form networks, which can be removed by pressure filtration. In contrast, we do not find an increase of the steady shear viscosity and elastic modulus at higher concentrations when a homogeneous entangled network is reached. We attribute this behavior to the semirigid character of the hyaluronan chain and to the predominance of entanglements over the cross-link points present in hylan in the semidilute domain. Due to the higher apparent molecular weights that are possible with hylan structures but not with the hyaluronans currently available, a wider range of applications can be achieved with hylans when viscoelasticity is required, particularly for the viscosupplementation of synovial fluid damaged by osteoarthritis.

Differential scanning microcalorimetry was performed on succinoglycan samples from different sources in order to better understand the thermally induced order-disorder conformational transition of the polysaccharide. The shape of thermograms, as well as the melting temperature, were related to the content or distribution of the succinate groups at least in salt-free solution. With increasing polysaccharide and/or salt concentration, the change in the shape of the thermogram was attributed to a progressive screening of the succinate contribution to the order-disorder conformational transition instead of a change in the transition mechanism. In the presence of salt, contrary to the rheological behavior, the calorimetric results were found to be independent of the thermal history of the samples. This suggests a very low enthalpic contribution of the interchain interactions present in succinoglycan solutions. Possible contributions that could explain some discrepancies with results already published in the literature are discussed.

Publisher Summary This chapter reviews fundamental knowledge on gellan structure and properties. In addition, a few applications in food and non-food industries are discussed. Native gellan behaves as a loose gel in aqueous solutions for polymer concentration larger than 10g/L. At lower concentrations, it forms highly viscous solutions. On the loose gel state, a transition to sol behavior occurs around 60oC, but the moduli are controlled by the levels of salt. Native gellan adopts a double helix conformation characterized by a temperature of conformational change around 75oC; Tm is only slightly displaced when the ionic strength increases. The rheological behavior is largely imposed by polymer concentration and temperature but has no hysteresis over a temperature cycle. After deacylation, gellan forms a stronger gel with hysteresis over a temperature cycle. The conformation is also a double helix with a different conformation compared with the native gellan. The conformational change is located at a temperature Tm much lower than for the native gellan and is very sensitive to the salt excess. At low polymer and ion concentrations, deacylated gellan behaves as a dispersed polymer, but when the ionic strength increases, a coil-to-double helix transition occurs with no ionic selectivity between monovalent counterions. Then, double helices aggregate to form a stiff network. The degree of aggregation is determined by the thermodynamics (temperature, ionic concentration) but also exhibits an ionic selectivity: K+ counterions promote the strongest gelation among monovalent counterions; divalent cations are very effective to promote gelation. Throughout, kinetics of aggregation controls the gel properties.

Publisher Summary This chapter explains the preparation of homogeneously modified methylcelluloses to illustrate the role of the substituent distribution along the chain on the physical properties of the polymers. The mechanism of gelation is described as a two step process in relation with the existence of trimethylated glucose zones necessary to get the first clear loose gel (35°C < T < 60°C). The second step is a phase separation occurring around 60°C with the formation of a turbid strong gel. Alkylchitosans prepared with alkyl chain larger than C8 give very large increase of the viscosity of aqueous dilute solution is also explained; the length of the alkyl chain and the degree of alkylation are very important parameters to control the solution properties. In addition, these amphiphilic polymers have some interfacial properties playing a role on stabilization of foams and emulsions. Subsequently, the synthesis of alkylated chitosans and their properties are described. These polymers are also polyelectrolytes allows to demonstrate the role of the balance between electrostatic repulsions and hydrophobic interactions. Some applications in the food industry are also mentioned.

Background The infliximab (IFX) is a monoclonal chimeric antibody targeting the Tumor Necrosis Factor alpha (TNFα), indicated in the rheumatoid arthritis (RA) treatment. Only two-third of RA patients respond to anti-TNFα therapy. At this time, predictive factors of response to anti-TNFα are missing. Commercial kit for IFX and antibody toward IFX (ATI) detection in the serum is now available Objectives We assessed the development of ATI during one year of IFX treatment in RA patients treated. We also assessed IFX concentrations during the treatment and investigated correlations between the clinical response and IFX concentration and/or ATI development Methods In a longitudinal multicentric study including 40 RA patients requiring IFX therapy, we assessed the TNFα, IFX, and ATI serum concentrations at various time points: before treatment (W0), at the 6th week (W6), at the 6th month (W22) and at the 12th month (W54) of treatment. All blood samples were collected just before the infliximab infusion. The mean age was 54.2±13.28 years old, the RA mean duration was 11.4±7.8 years, the initial DAS 28 was 5.31±0.86. The clinical response was evaluated according to the EULAR criteria. Clinical response was good in 32% and 24% at W22 and W54, respectively; moderate in 47% and 48% at W22 and W 54, respectively; and bad in 21 and 28% at W22 and W54, respectively. Concentrations were determined by a commercial ELISA (LisaTracker, BMD, France). The data were analyzed with Kruskall-Wallis test (ANOVA), then by a multiple comparison Dunnett post-hoc and with a significance threshold P Results The ATI development (concentration upper than 10 μg/ml) was observed early from W6 in 7% of patients but with a low concentrations (lower than 20 μg/ml). However, at W22 and W54, ATI were respectively detected in 45% and 46% of patients. The IFX concentrations increased in time (P We found no correlation between the TNFα concentration and the RA activity assessed by the DAS 28. The initial median serum TNFα concentration was 7.2 pg/ml, increased at W6 to 7.2 pg/ml, and remained high relative at W22 and W54 (P At W22 and W54, we observed detection in the serum detection of IFX or ATI. We did not observe presence of both. At W22 and W54, the ATI distribution was heterogeneous in terms of clinical response (P Conclusions Our study shows an heterogeneity in the ATI development at W22 and W54. However, IFX concentrations were homogenous at W6 and heterogeneous from W22 to W54. This suggests that ATI development contribute to IFX heterogeneity in IFX therapy for RA patients. Disclosure of Interest None Declared

This paper concerns the main properties of water soluble pectins in sol and gel states. First of all, the methods of purification and characteization are discussed. The method of steric exclusion chromatography equipped with different detectors is demonstrated as the most useful to determine the macromolecular characteristics of these polymers; the role of aggregation is pointed out. The worm like chain behaviour of the pectins is developped allowing to predict the dimensions of the chain as soon as the persistence length is known. The experimental data are compared with the theoretical prediction obtained from conformational analysis. The polyelectrolyte properties of pectins are breefly exposed; specially the role of the carboxylic groups distribution along the chain is demonstrated to control the electrostatic properties. The viscometric behaviour depends on the ionic concentration and on the nature of the counterions in relation with electrostatic repulsions. Then, the ionic selectivity is discussed and related to the mechanism of crosslinking with divalent counterions. The sol-gel transition is then examined for LM and HM pectins and the mechanisms described in these two cases. The physical properties of the gels are related to the microstructure of the polymers and few data are examined.

This paper describes the main rheological characteristics of polysaccharide solutions. When there is no specific interaction in solution, they behave as synthetic polymers. The main characteristic concerns their stiffness which causes a large hydrodynamic volume. The ionic charges also induce an increase in viscosity and in the chain dimensions.

Many polysaccharides are recognized as valuable food additives due to their original physicochemical properties. The polymers used for food applications are mainly thickening or gelling polysaccharides. Some are also used to stabilize emulsion or to suspend solid particles1-5

An analysis of dynamic scattering behavior of branched polymers in the high-wave vector region is presented. In particular the first cumulant of the dynamic structure factor Ω(q) is examined. This quantity is calculated using the standard formula which defines Ω(q) within a proportionality constant as a ratio of the generalized mobility M(q) and the static structure factor S(q), where q is the amplitude of the scattering wave vector. The latter quantity has already been calculated by Benoit et al. who obtained a general formula for a branched polymer with an arbitrary architecture. Here, this calculation is extended to the mobility M(q) including hydrodynamic interaction with the angular pre-averaged Oseen tensor. This result may be useful in the cases where the measurement of the first cumulant by quasi-elastic scattering techniques can be made to complete the information obtained by the absolute intensity measurements. © 1994 John Wiley & Sons, Inc.

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