A water-soluble neutral polysaccharide (AF1) was extracted from Auricularia (A.) auricula-judae with 0.15 M aqueous NaCl at 80-100 °C. Its chemical components and structure were analyzed by GC, GC-MS, and NMR. AF1 was identified as a β-(1→3)-D-glucan with two β-(1→6)-D-glucosyl residues for every three main chain glucose residues, showing a comb-branched structure. The M(w) values of AF1 in both aqueous solution and DMSO determined by LLS and SEC-LLS were in the narrow range of 2.07-2.15 × 10(6), indicating AF1 existed as single chains in the two solvents. The high intrinsic viscosity [η] of 1753 mL/g and the structure-sensitive parameter ρ (≡R(g)/R(h)) value of 2.3 in water revealed that AF1 existed as stiff chain conformation. Moreover, we directly observed the extended stiff chain conformation by AFM. The branching structure led to the water solubility of AF1, and the intramolecular hydrogen bonds sustained the stiff chain conformation. The rheological results showed that this polysaccharide aqueous solution had higher viscosity than even xanthan, a pronounced thickening agent. This work provided important information for developing new thickeners in food fields, and how neutral polysaccharides can be used as good candidates.

The development of biological high-performance materials fabricated from natural polysaccharides has attracted great attention for a sustainable world. In this work, hollow fibers with high strength were spun from a polysaccharide aqueous solution at a concentration of 0.02 g mL À1 . The polysaccharide was a comb-like b-glucan with short branches isolated from Auricularia auricula-judae, coded as AF1. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) confirmed directly that AF1 existed as a stiff chain conformation in water, and displayed parallel self-orientation behavior. AF1 could selfassemble into well defined hollow nanofibers with diameters less than 100 nm and lengths of tens of micrometers in dilute solution, supported by scanning electron microscopy (SEM). Moreover, AF1 in the disulfonated tetraphenylethene (TPE-SO 3 Na) aqueous solution exhibited strong luminescence, indicating that the TPE-SO 3 Na molecules without luminescence in water were trapped in the cavities of the hollow nanofibers through hydrophobic interactions, leading to the aggregation-induced emission (AIE). The nanofibers were composed of relatively hydrophobic inner-walls and hydrophilic shells in water. Interestingly, SEM and polarized light microscopy verified that the nanofibers fused to form an ordered architecture of lamella and then tended to curl into hollow fibers in relatively concentrated solution.The hollow fibers exhibited excellent tensile strength, biocompatibility, organic solvent resistance and birefringence. A schematic model was proposed to describe the construction of the hollow fibers via the hierarchical self-assembly process. The new materials would have potential applications such as drug release as a new class of fibrous carrier, indicators with fluorescence to detect cell growth in cell transplantation, and biomolecular recognition (e.g., DNA).

Heparan sulfate (HS) is a sulfated polysaccharide exhibiting essential physiological functions. HS 6-O-sulfotransferase (6-OST) transfers a sulfo group to the 6-OH position of glucosamine units to confer a variety of HS biological activities. There are three different isoforms of 6-OST in the human genome. Here, we report crystal structures of the ternary complex of 6-OST with the sulfo donor analog 3′-phosphoadenosine 5′-phosphate and three different oligosaccharide substrates at 1.95 to 2.1 Å resolutions. Structural and mutational analyses reveal amino acid residues that contribute to catalysis and substrate recognition of 6-OST. Unexpectedly, the structures reveal 6-OST engages HS in a completely different orientation than other HS sulfotransferases, and sheds light on the basic HS requirements for specificity. These findings also contribute structural information to understand mutations in human 6-OST isoform 1 associated with the human genetic disease idiopathic hypogonadotrophic hypogonadism characterized by delayed or lack of puberty. Keywords oligosaccharides; heparin; sulfated carbohydrates; crystal structure Heparan sulfates (HS) are sulfated polysaccharides that are found on the surface of mammalian cells attached to core syndecan and glypican proteins and are secreted into the extracellular matrix, associated with perlecan, agrin and collagen XVIII 1, 2 . HS contains a disaccharide repeating unit of glucuronic acid (GlcA) or iduronic acid (IdoA) and glucosamine (GlcN). Both IdoA and GlcN are capable of carrying sulfo groups, while GlcA can be sulfated to a lesser extent. HS play important roles in a wide range of physiological HHS Public AccessAuthor manuscript ACS Chem Biol. Author manuscript; available in PMC 2018 January 20. Author Manuscript Author ManuscriptAuthor Manuscript Author Manuscript and pathophysiological functions including assisting in viral/bacterial infection, inflammatory responses, blood coagulation, angiogenesis, and embryonic development 3 . Notably, HS is implicated in the formation of amyloid plaques contributing to Alzheimer's disease 4 . HS carry out their wide range of functions through interactions with proteins such as growth factors, protease inhibitors, proteases, cytokines, chemokines and morphogens 1, 2, 5 . Many of these interactions rely on distinctive sulfated saccharide sequences in HS for high specificity.The HS 6-O-sulfotransferase isoforms (6-OSTs) are members the HS biosynthetic enzyme family that transfer a sulfo group from 3′-phosphoadenosine 5′-phosphosulfate (PAPS) to the 6-OH of GlcN. HS biosynthesis occurs in the Golgi and endoplasm reticulum and involves glycosyltransferases, an epimerase and several sulfotransferases. A backbone polysaccharide with a disaccharide repeating unit of GlcA and N-acetyl glucosamine (-GlcA-GlcNAc-) is initially synthesized by HS polymerase. The backbone polysaccharide then undergoes a series of modifications ( Supplementary Figure 1) 6 . In general, modification begins with N-deacetylation/N-sulfation by the N-dea...

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Social networking sites (SNS) are helpful for stirring up interactions among users. The number of libraries which adopt SNSs is increasing. However, user engagement is low on many libraries' SNSs. Existing research mainly focuses on the ways SNSs used in libraries and the librarians or users' attitudes towards libraries using SNSs. Little research has been done on how to use SNSs to interact with library users effectively. This study focuses on the interactions between libraries and users on libraries' Facebook, Twitter and Weibo. Four types of interactions are examined, including knowledge sharing, information dissemination, communication and knowledge gathering. A mixed method is applied in this study: quantitative results, generated from the analysis on around 1700 posts sampled from 40 libraries' SNSs, are incorporated with qualitative results concluded from the interviews with 10 librarians. The study finds that among the four types of interactions, knowledge sharing attracts the largest volume of user responses on libraries' SNSs. The study's investigation on the differences of Facebook-like and Twitter-like SNSs and those between academic and public libraries on using SNSs suggests that in order to improve the efficiency of interacting with users on SNSs, there are necessities for libraries to coordinate different types of SNSs and take the properties of their communities under consideration.

L-asparaginase, which catalyses the hydrolysis of L-asparagine to L-aspartate, has attracted the attention of researchers due to its expanded applications in medicine and the food industry. In this study, a novel thermostable L-asparaginase from Pyrococcus yayanosii CH1 was cloned and over-expressed in Bacillus subtilis 168. To obtain thermostable L-asparaginase mutants with higher activity, a robust high-throughput screening process was developed specifically for thermophilic enzymes. In this process, cell disruption and enzyme activity assays are simultaneously performed in 96-deep well plates. By combining error-prone PCR and screening, six brilliant positive variants and four key amino acid residue mutations were identified. Combined mutation of the four residues showed relatively high specific activity (3108 U/mg) that was 2.1 times greater than that of the wild-type enzyme. Fermentation with the mutant strain in a 5-L fermenter yielded L-asparaginase activity of 2168 U/mL.

The thermal stability of polysaccharides under heat treatment is an important factor to their functionality in food and pharmaceutical fields. The stiff branched β-glucan coded as AF1-1 isolated from Auricularia auricula-judae was investigated with viscometry, dynamic light scattering (DLS), and size-exclusion chromatography combined with multiangle laser light scattering (SEC-MALLS) in water at 25 to 170 °C. The chain conformation of AF1-1 in the aqueous solution exhibited a sharp decrease in viscosity, hydrodynamic radius (Rh), and weight-average molecular weight (Mw) at elevated temperature in a narrow range of 140 to 160 °C. It was confirmed that the conformation transitions of the AF1-1 chains from rod-like chains to the flexible occurred during heating to 140-160 °C for 30 min, leading to the coexistence of the flexible chains and stiff chains at 155 °C as a result of the breaking of the intra- and intermolecular hydrogen bonds of the AF1-1 macromolecules. The results from scanning electron microscopy and atomic force microscopy further directly proved that the AF1-1 nanofibers in water were destructed into flexible coils consisting of individual chain at the elevated temperature higher than 155 °C, supporting the conformation transition. The conformational transition from stiff to flexible chains at 140-160 °C was irreversible. However, the chain shape and stiffness of AF1-1 was stable below 140 °C and hardly changed with an increase in the temperature. This was important for the application in the fields of food and pharmaceutical.

l‐asparaginase has high application value in medicine and food industry, but the low yield limits its application. In this study, we designed a synthetic system in Bacillus subtilis to produce l‐asparaginase by improving gene expression and optimizing the fermentation agitation speed. Gene expression was improved by respectively increasing transcription levels and translation speeds through screening promoters and RBS sequences. With the optimal promoter, P43, and the synthetic RBS sequence, the yield obtained in a shake flask was 371.87 U/mL, which was 2.09 times that with the original strain. To further enhance production in a 5‐L fermenter, a multistage agitation speed control strategy was adopted, involving agitation at 600 rpm for the first 12 h, followed by a gradual increase in speed to 900 rpm, which resulted in the highest yield of l‐asparaginase, 5321 U/mL, after 42 h of fermentation.