Synthesis and characterization of 2,3-di-O-alkylated amyloses: hydrophobic substitution destabilizes helical conformation

Tunable structure of chimeric isomaltomegalosaccharides with double α-(1 → 4)-glucosyl chains enhances the solubility of water-insoluble bioactive compounds

Isomaltomegalosaccharides with α-(1 → 4) and α-(1 → 6)-segments solubilize water-insoluble ligands since the former complexes with the ligand and the latter solubilizes the complex. Previously, we enzymatically synthesized isomaltomegalosaccharide with a single α-(1 → 4)-segment at the reducing end (S-IMS) by dextran dextrinase (DDase), but the chain length [average degree of polymerization (DP) ≤ 9] was insufficient for strong encapsulation. We hypothesized that the conjugation of longer α-(1 → 4)-segment afforded the promising function although DDase is incapable to do so. In this study, the cyclodextrin glucanotransferase-catalyzed coupling reaction of α-cyclodextrin to S-IMS synthesized a new α-(1 → 4)-segment at the nonreducing end (N-4S) of S-IMS to form D-IMS [IMS harboring double α-(1 → 4)-segments]. The length of N-4S was modulated by the ratio between α-cyclodextrin and S-IMS, generating N-4Ss with DPs of 7-50. Based on phase-solubility analysis, D-IMS-28.3/13/3 bearing amylose-like helical N-4S with DP of 28.3 displayed a water-soluble complex with aromatic drugs and curcumin. Small-angle X-ray scattering revealed the chain adapted to rigid in solution in which the radius of gyration was estimated to 2.4 nm. Furthermore, D-IMS with short N-4S solubilized flavonoids of less-soluble multifunctional substances. In our research, enzyme-generated functional biomaterials from DDase were developed to maximize the hydrophobic binding efficacy towards water-insoluble bioactive compounds.

A simple strategy for selective photocatalysis degradation of organic dyes through selective adsorption enrichment by using a complex film of CdS and carboxylmethyl starch

Resource utilization of wastes through effective separation is a major challenge in the field of water and wastewater treatment. Photocatalytic degradation is a powerful water treatment technology but has no selectivity in degradation of various coexisting contaminants due to its strong oxidation. In this work, a complex film composed of CdS and carboxylmethyl starch (CdS/CMS) was designed and fabricated using in situ formation method. The morphology, composition, and optical property of this film were investigated in detail by various characterization methods. CdS was well distributed in the starch matrix, and the absorption wavelength of this film was still located in the visible light region. This starch-based complex film was used to remove various organic dyes [methylene blue (MB), crystal violet (CV), and rhodamine B (RhB)] from aqueous solutions by two consecutive processes of adsorption enrichment and photocatalysis degradation. 0.1 g of CdS/CMS film can remove approximately 86.72% of MB and 81.03% of CV in 120 min. CdS/CMS still exhibited evidently selective photocatalysis degradation of MB and CV in MB/RhB and CV/RhB binary systems, respectively, and had nearly no effect on RhB. The cationic groups on MB and CV can effectively interact with negatively carboxyl groups of CMS via electrostatic interactions, causing their good affinities; but the anionic groups on RhB had an electrostatic repulsion to the starch matrix. The considerably different affinities of various dyes to CMS triggered strong adsorption preferences and great selective degradation effectiveness. The selectivity of CdS/CMS could not be influenced by pH and some coexisting inorganic anions. Furthermore, this complex film did not require regeneration and could be reused directly with low removal capacity loss. Therefore, a new and simple strategy was provided to realize the effective separation and recovery of target contaminants in water by photocatalytic degradation technology.

Microsecond kinetics in model single- and double-stranded amylose polymers

Amylose, a component of starch with increasing biotechnological significance, is a linear glucose polysaccharide that self-organizes into single- and double-helical assemblies. Starch granule packing, gelation and inclusion-complex formation result from finely balanced macromolecular kinetics that have eluded precise experimental quantification. Here, graphics processing unit (GPU) accelerated multi-microsecond aqueous simulations are employed to explore conformational kinetics in model single- and double-stranded amylose. The all-atom dynamics concur with prior X-ray and NMR data while surprising and previously overlooked microsecond helix-coil, glycosidic linkage and pyranose ring exchange are hypothesized. In a dodecasaccharide, single-helical collapse was correlated with linkages and rings transitioning from their expected syn and (4)C1 chair conformers. The associated microsecond exchange rates were dependent on proximity to the termini and chain length (comparing hexa- and trisaccharides), while kinetic features of dodecasaccharide linkage and ring flexing are proposed to be a good model for polymers. Similar length double-helices were stable on microsecond timescales but the parallel configuration was sturdier than the antiparallel equivalent. In both, tertiary organization restricted local chain dynamics, implying that simulations of single amylose strands cannot be extrapolated to dimers. Unbiased multi-microsecond simulations of amylose are proposed as a valuable route to probing macromolecular kinetics in water, assessing the impact of chemical modifications on helical stability and accelerating the development of new biotechnologies.

Antioxidant potential of hydroxycinnamic acid glycoside esters

Hydroxycinnamic acids are natural antioxidants found in fruits, vegetables, and cereals. In this study, the antioxidant activity of various types of hydroxycinnamoyl glycoside esters that mimic the structure of polymeric carbohydrates was studied in different model systems prone to oxidation, namely, liposomes and emulsions. In addition, radical scavenging activity against the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical was tested. It was found that the esterification in the primary hydroxyl group of the glycoside resulted in the improved radical scavenging activity of both sinapoyl and feruloyl glycosides compared to conjugation to the secondary hydroxyl group. Increased activity was also observed, particularly in the case of feruloyl glucosides in inhibiting the oxidation of liposomes emulsions. The results showed that sinapic and ferulic acid glycoside esters were as effective or more efficient antioxidants than their free forms. In conclusion, the strength of their antioxidant effect depends on the nature of conjugation.

Partially-methylated amyloses as effective hosts for inclusion complex formation with polymeric guests

Partially 2,3-O-methylated amyloses efficiently form inclusion complexes with polytetrahydrofuran and poly(epsilon-caprolactone) by simply mixing them in DMSO-H(2)O (1 : 9) solution, in contrast to the case of the parent amylose in which the corresponding inclusion complexes are only slightly formed.