Conformation and cooperative order-disorder transition in aqueous solutions of β-1,3-d-glucan with different degree of branching varied by the Smith degradation

Solvent stabilizing effects on the order-disorder transition of schizophyllan in aqueous mixtures of carboxylic acids

Schizophyllan is a triple helical β-1,3-D-glucan, and shows the cooperative order-disorder transition in the aqueous solution at the triple helix state. In this paper, the solvent stabilizing effects of two carboxylic acids, acetic acid and citric acid, on the cooperative order-disorder transition of aqueous schizophyllan solution were investigated from DSC and SEC-MALS measurements. The transition temperature (Tr) was shifted to higher temperature with increasing the molar fraction of carboxylic acid in the mixture (x). The transition enthalpy (ΔHr) was increased with increasing x. These solvent stabilizing effects indicate that these carboxylic acid molecules were selectively associated with the branched side chains of schizophyllan to stabilize the ordered state. The composition dependencies of Tr and ΔHr were analyzed by the linear cooperative transition theory to estimate the association parameters between the side chains and carboxylic acid. The theoretical parameters obtained were compared with those for the other active substances for the transition to discuss the molecular interactions between the triple helix and carboxylic acid.

A novel method for the direct detection of light stabilizer Tinuvin 622 in polymer additives by gel permeation chromatography combined with multi-angle laser light scattering

Tinuvin 622, an oligomeric light stabilizer, is widely used in plastics to reduce light and heat induced degradation and extend their service life, therefore its detection is of great importance for quality control of plastic products. However, the classical analytical methods of Tinuvin 622, such as chromatography and mass spectrometry, are difficult to achieve direct qualitative and quantitative analysis, and simultaneously to obtain the molecular weight and molecular weight distribution information. Herein, we propose for the first time the combination of gel permeation chromatography with multi-angle laser light scattering as a simple and direct method to detect Tinuvin 622 in polymers and simultaneously to obtain its molecular weight distribution information. The linearity of the method was good in the concentration range of 0.1-5.0 mg/mL Tinuvin 622 with correlation coefficient (R² = 0.9999), and the recoveries of Tinuvin 622 at three addition levels ranged from 94.0% to 98.7%, with relative standard deviations of no more than 1.73%. The proposed method has been successfully used to detect Tinuvin 622 in actual samples of polymer additives. Compared with existing analytical methods, Tinuvin 622 has a single peak shape in our method, which is easy to identify and quantify accurately; more importantly, our method can simultaneously characterize the molecular weight and molecular weight distribution of Tinuvin 622, which makes up for the shortcomings of other approaches and provides a new tool for quality monitoring of polymer additives.

Aminated β-Glucan with immunostimulating activities and collagen composite sponge for wound repair

Immunostimulating activities of yeast β(1 → 3)-D-Glucan (β-Glucan) mainly depended on its structures. However, due to the tight triple helix structure of β-Glucan, its immunostimulating activity is greatly weakened. Therefore, in order to partially unwind the tight triple helix structure of β-glucan and improve its solubility in the medium, we modified it by amination in this study (A-Glu). The results showed that A-Glu could stimulate Raw264.7 macrophages and significantly enhance its TNF-α, IL-6, and IL-10 cytokine expression levels in vitro. A-Glu could also induce a shift of M0 Raw264.7 toward M1, and M2 toward M1. To expand the application of A-Glu in wound repair, the composite sponge consisting of A-Glu and type I collagen via the formation of a stable polyion complex (PIC) was developed. Moreover, the composite sponge could accelerate wound repair significantly. These results reveal that soluble A-Glu as an immunostimulating agent has potential applications in biomedicine.

Association with Imidazole in the Cooperative Order-Disorder Transition in Aqueous Solution of Schizophyllan

Schizophyllan, a triple helical polysaccharide, exhibits cooperative order-disorder transition (CODT) in aqueous solutions. The transition transforms the ordered structure (triple helix I) formed between the branched side chains and solvent molecules into the disordered structure (triple helix II) without dissociation of the triple helix. The CODT behaviors in H₂O-imidazole mixtures containing HCl with different molar ratios of imidazole/HCl were investigated by adiabatic calorimetry and differential scanning calorimetry on two schizophyllan solutions with different molar masses. The transition temperature (T_r) and the transition enthalpy (ΔH_r) significantly depended on both of the mole fractions of imidazole and imidazole/HCl. The composition dependences of T_r and ΔH_r in H₂O-imidazole mixtures were analyzed with linear cooperative transition theory for the solvent-stabilizing effect in the mixture with active compounds. Theoretical analyses confirmed that both imidazole and imidazolium ions in the solutions competitively interact with the side chain of the triple helix.