Inter-laboratory analysis of cereal beta-glucan extracts of nutritional importance : An evaluation of different methods for determining weight-average molecular weight and molecular weight distribution

In an interlaboratory study we compare different methods to determine the weight-average molecular weight (Mw) and molecular weight distribution of six cereal beta-glucan isolates of nutritional importance. Size exclusion chromatography (SEC) with multi-angle light scattering (MALS), capillary viscometry, sedimentation velocity analytical ultracentrifugation and one asymmetric flow field-flow fractionation (AF4)-MALS method all yielded similar Mw values for mostly individual chains of dissolved beta-glucan molecules. SEC with post-column calcofluor detection underestimated the Mw of beta-glucan > 500 x 10(3) g/mol. The beta-glucan molecules analysed by these methods were primarily in a random coil conformation as evidenced from individual MarkHouwink-Kuhn-Sakurada (MHKS) scaling coefficients between 0.5 and 0.6 and Wales-Van Holde ratios between 1.4 and 1.7. In contrast, a second AF4-MALS method yielded much larger Mw values for these same samples indicating the presence and detection of beta-glucan aggregates. Storage of the six beta-glucan solutions in the dark at 4 C for 4 years revealed them to be stable. This suggests an absence of storage-induced irreversible aggregation phenomena or chain-scission. Shear forces in SEC and the viscometer capillary and hydrostatic pressure in analytical ultracentrifugation probably led to the reversable dissociation of beta-glucan aggregates into molecularly dissolved species. Thus, all these methods yield true weight-average molecular weight values not biased by the presence of aggregates as was the case in one of the AF4 based methods employed.Peer reviewe

Horizon formation and far-from-equilibrium isotropization in supersymmetric Yang-Mills plasma

Using gauge/gravity duality, we study the creation and evolution of anisotropic, homogeneous strongly coupled $\mathcal N=4$ supersymmetric Yang-Mills plasma. In the dual gravitational description, this corresponds to horizon formation in a geometry driven to be anisotropic by a time-dependent change in boundary conditions.Comment: 4 pages, typos corrected, published versio

The ambivalence of losing weight after bariatric surgery

This study is grounded in a phenomenological lifeworld perspective. It aims at providing rich descriptions of lived experience of the process of losing weight after obesity surgery. Two women participated in in-depth interviews four times each during the first postoperative year. Based on the women's experiences, a meaning structure—the ambivalence of losing weight after obesity surgery—was identified across the women's processes of change. This consisted of five core themes: movement and activity—freedom but new demands and old restraints; eating habits and digestion—the complexity of change; appearance—smaller, but looser; social relations—stability and change; and being oneself—vulnerability and self-assurance. These core themes changed over time in terms of dominance. The experience of ambivalence is discussed according to a phenomenological perspective of the body as lived experience

Morbidly Obese Patients—Who Undergoes Bariatric Surgery?

Treatment seeking patients with severe obesity might choose between specialized medical treatment and surgical treatment. Knowledge of what distinguishes patients that choose either treatment is sparse, with greater understanding also needed on what consequences this choice has for the prevalence, remission and new onset of comorbidities, as well as for the bioavailability of drugs. This has prompted the studies in Gunn Signe Jakobsen and her coauthors work on treatment seeking patients with severe obesity focusing on the prevalence of comorbidities, changes in the use of drugs for hypertension, diabetes and dyslipidaemia, as well as changes in bioavailability of atorvastatin. The methods used in the studies in the thesis; "Bariatric surgery and specialized medical treatment for severe obesity Impact on cardiovascular risk factors and postsurgical pharmacokinetics of atorvastatin "; are a cross-sectional study, a registry based cohort study and a prospective pharmacokinetic study. The results of the studies presented were: - The type and number of comorbidities associated with morbid obesity did not necessarily impact upon choice of treatment, but there was an increased odds for choosing surgery for patients with higher BMI, younger age and earlier onset of obesity. - Patients opting for bariatric surgery as opposed to specialized medical treatment had higher odds of experiencing remission, and significantly lower odds for new-onset of drug treated hypertension, diabetes and dyslipidaemia. Bariatric surgery seemed to not only induce remission but was also effective in preventing disease. - The bioavailability of atorvastatin was increased after bariatric surgery, with a normalization in the long term. This knowledge can give a better understanding of the population of patients seeking treatment for severe obesity and should be included in the shared decision process when helping the patient identify their preferences for treatment of severe obesity in the context of their values

Macromolecular acidic coating increases shelf life by inhibition of bacterial growth

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Cooperative Order−Disorder Transition of Carboxylated Schizophyllan in Water−Dimethylsulfoxide Mixtures

Carboxylated schizophyllan (“sclerox”) is a chemically modified polysaccharide obtained by partial periodate oxidation and subsequent chlorite oxidation of schizophyllan, a water-soluble neutral polysaccharide having a β-1,3-linked glucan backbone and a β-1,6-linked d-glucose residue side chain at every third residue of the main chain. The triple helix of schizophyllan in water has a cooperative order–disorder transition associated with the side chains. The transition is strongly affected by the presence (mole fraction) of dimethylsulfoxide (DMSO). In the present study, the solvent effects on the order–disorder transition of sclerox with different degrees of carboxylation (DS) in water–DMSO mixtures were investigated with differential scanning calorimetry and optical rotation. The transition temperature (Tr) and transition enthalpy (ΔHr) strongly depended on the mole fraction of DMSO (xD). Data were further analyzed with the statistical theory for the linear cooperative transition, taking into account the solvent effect, where DMSO molecules are selectively associated with the unmodified side chains. The modified side chain does not contribute to the transition; hence, ΔHr decreases with increasing DS. The dependence of Tr on the DMSO content becomes weaker than that for unmodified schizophyllan. The theoretical analyses indicated that the number of sites binding with the DMSO molecule and the successive ordered sequence of the ordered unit of the triple helix are changed by carboxylation

Conformation of carboxylated schizophyllan in aqueous solution

Carboxylated schizophyllan (sclerox) samples of different degrees of oxidation were molecularly characterized by size exclusion chromatography equipped with a multi-angle light scattering detector (SEC-MALS) in 0.10 M aqueous NaCl solution. The molar mass distribution obtained by SEC-MALS shows that sclerox of low degree of oxidation is dissolved mainly as the trimer, whereas the trimer and single chain coexist in solution of sclerox of high degree of oxidation. The trimer of sclerox is much more flexible than the fully ordered triple helix of the parent schizophyllan and easily dissociates into single chains upon heating

Degradation kinetics of peptide-coupled alginates prepared via the periodate oxidation reductive amination route

Biomaterials based on peptide-coupled alginates must provide both optimal biological environments and tuneable stability/degradation profiles. The present work investigates the degradation pattern and kinetics of peptide-coupled alginates prepared via the periodate oxidation reductive amination route. Alginates degrade slowly (non-enzymatically) under physiological conditions by acid-catalysed hydrolysis and alkali-catalysed β-elimination, both operating simultaneously but dominated by the latter. While periodate oxidation alone largely increases the rate of β-elimination, substitution restores the susceptibility towards β-elimination to that of the parent alginate. For acid hydrolysis the rate of depolymerization is proportional to the degree of substitution, being approximately one order of magnitude larger than the parent alginate, but still lower than for the corresponding materials with fully reduced dialdehydes. Results also suggest a composition-dependent preference for substitution at C2 or C3. These results demonstrate how the various chemistries introduced by the coupling provide useful means to tune the biodegradability profiles

Influence of amino acids, buffers, and pH on the γ-irradiation-induced degradation of alginates

Alginate-based biomaterials and medical devices are commonly subjected to γ-irradiation as a means of sterilization, either in the dry state or the gel (hydrated) state. In this process the alginate chains degrade randomly in a dose-dependent manner, altering alginates’ material properties. The addition of free radical scavenging amino acids such as histidine and phenylalanine protects the alginate significantly against degradation, as shown by monitoring changes in the molecular weight distributions using SEC-MALLS and determining the pseudo first order rate constants of degradation. Tris buffer (0.5 M), but not acetate, citrate, or phosphate buffers had a similar effect on the degradation rate. Changes in pH itself had only marginal effects on the rate of alginate degradation and on the protective effect of amino acids. Contrary to previous reports, the chemical composition (M/G profile) of the alginates, including homopolymeric mannuronan, was unaltered following irradiation up to 10 kGy