Dissecting Molecular Aspects of Cell Interactions Using Glycodendrimersomes with Programmable Glycan Presentation and Engineered Human Lectins

Glycodendrimersomes with programmable surface display of glycan, together with artificially engineered galectins, were used to understand the physiological significance of human lectins with homodimeric and tandem‐repeat‐type displays. The mode of topological surface presentation and the density of glycan affected vesicle aggregation mediated by multivalent carbohydrate–protein interactions. The cross‐linking capacity of homodimeric lectins was enhanced by covalent connection of the two carbohydrate‐binding sites. These findings highlight the value of glycodendrimersomes as versatile cell membrane mimetics, and assays provide diagnostic tools for protein functionality. This work also provides guidelines for the design of cell separators, bioactive matrices, bioeffectors, and other biomedical applications.     

Sialic Acid Engineering of Thin Hydrogel Membranes

We report the synthesis of glycosylated hydrogel membranes of poly{[N‐(2‐hydroxypropyl)methacrylamide]‐co‐(2‐hydroxyethyl methacrylate)} with the aim of developing bioactivated polymer substrates for cell culture. 3′‐Sialyllactose, the saccharidic portion of the GM₃ ganglioside involved in cell‐cell recognition over a wide range of biological processes, was chemically modified with an acrylate group and incorporated into the growing macromolecular network of hydrogels by free radical crosslinking copolymerization. The incorporation and accessibility of the sialic acid residues at the hydrogel surface was verified by enzyme linked immunosorbent assay using mouse monoclonal anti‐GM₃, and by electron microscopy after labeling with lectin‐gold nanoparticles. The water content was further characterized by thermogravimetry.

     

Recognition of Amphiphiles with Many Pendent Galactose Residues byRicinus communisAgglutinin

Amphiphiles which carry many pendent galactose residues as side chains were prepared by telomerization of 2-methacryloyloxyethyl β-D-galactopyranoside (MEGal) or 3-(2-methacryloyl aminoethylthio)propylD-galactopyranoside (MEPGal, α:β = 3.9:1) using a lipophilic radical initiator. The galactose-carrying amphiphiles (DP (degree of polymerization) = 15) incorporated in liposomes were recognized by a lectin fromRicinus communis(RCA₁₂₀), which was proven by the increase in turbidity of the liposome suspension after mixing with the lectin. The recognition was largely affected by the distance between the galactose residues and the polymer main chain, and the surface density of the amphiphile in the liposomes. The liposomes containing these galactolipids were not taken up by mouse peritoneal macrophages, probably due to a steric hindrance of polymer main chains from the uptake of D-galactose receptors on the macrophages.     

棉铃虫血淋巴凝集素的性质研究

棉铃虫（Ｈｅｌｉｏｔｈｉｓａｒｍｉｇｅｒａ）血淋巴对人的Ａ、Ｂ、Ｏ型红细胞有同等的凝集活性，对兔、小白鼠、豚鼠、蟾蜍、鲫鱼、鸡红细胞有不同的凝集活性，对山羊红细胞无凝集活性．其凝集活性能被Ｄ－半乳糖明显地抑制．对Ｃａ２＋无依赖性．７０℃处理１５ｍｉｎ凝集活性趋于零．棉铃虫核型多角体病毒的诱导使其活性明显增加．化蛹早期及蛹期凝集活性下降．血淋巴凝集素通过盐析、凝胶过滤和纤维素层析得到分离．它在ＳＤＳ－ＰＡＧＥ中表现为单一带，为糖蛋白，分子量为７．０８×１０４．其蛋白质含量为９８．７４％，糖含量为１．２６％．     

Recent Advances in the Chemical Biology of N-Glycans

Asparagine-linked N-glycans on proteins have diverse structures, and their functions vary according to their structures. In recent years, it has become possible to obtain high quantities of N-glycans via isolation and chemical/enzymatic/chemoenzymatic synthesis. This has allowed for progress in the elucidation of N-glycan functions at the molecular level. Interaction analyses with lectins by glycan arrays or nuclear magnetic resonance (NMR) using various N-glycans have revealed the molecular basis for the recognition of complex structures of N-glycans. Preparation of proteins modified with homogeneous N-glycans revealed the influence of N-glycan modifications on protein functions. Furthermore, N-glycans have potential applications in drug development. This review discusses recent advances in the chemical biology of N-glycans.     

Thiol‐alkyne Chemistry for the Preparation of Micelles with Glycopolymer Corona: Dendritic Surfaces versus Linear Glycopolymer in Their Ability to Bind to Lectins

A poly(tert‐butyl acrylate) (P(tBA)) with a glycodendric endfunctionality with eight glucose moieties was synthesised in four steps via a combination of esterification, thiol‐alkyne conjugation and hetero‐Diels–Alder (HDA) cycloaddition. A linear glycopolymer of similar size and composition was also synthesised in order to compare the protein binding characteristics of the polymer with glycodendritic endfunctionality to the linear glycol blockcopolymer. The two amphiphilic polymers were self‐assembled in water into micelles. These particles were then tested for their ability to bind to Concanavalin A (Con A). In a turbidity assay, the polymer glycodendron exhibited a significantly faster clustering rate to the lectin as compared to the linear glycopolymer. In a precipitation assay, it is found that significantly less glucose residue is required for binding per Con A for the polymer with the glycodendritic endfunctionality.

     

pH‐Responsive Aggregation of Amphiphilic Glyco‐Homopolymer

The first example of amphiphilic glyco‐homopolymers is reported and their aggregation properties as a function of solution pH are studied. Two structurally similar polymers with different hydrophobicity (C8 and C6 alkyl chains) are examined. Both polymers form micelle‐type aggregates in aqueous solution. The size and micro‐environment of the aggregates are found to be strongly dependent on solution pH because of the state of protonation of the tertiary amine group. At acidic pH, swollen multi‐micellar aggregates are formed, presumably because of the electrostatic repulsion among the ammonium ions. At basic pH more compact particles are found, which further co‐assemble to generate either garland type (C8) or fractal‐aggregates (C6).     

High‐Density Glycosylation of Polymer Membrane Surfaces by Click Chemistry for Carbohydrate–Protein Recognition

To biologically mimic the carbohydrate–protein interactions in artificial systems, one of the challenges is to construct a glycosylated surface with a high glycosyl density to yield a notable ‘glycoside cluster effect’. A novel strategy is presented for high density glycosylation of the surface of a microporous poly(propylene) membrane (MPPM) by click chemistry. It is promising that the surface glycosyl density can be well controlled over a wide range and the maximum value is over 10 µmol · cm⁻². The recognition capability of these glycosylated MPPMs to lectins indicates the occurrence of the ‘glycoside cluster effect’ when the glycosyl density on the membrane surface exceeds 0.20 µmol · cm⁻².

     

Glycoprofiling as a novel tool in serological assays of systemic sclerosis: A comparative study with three bioanalytical methods

Systemic sclerosis (SSc) is an autoimmune disease seriously affecting patient’s quality of life. The heterogeneity of the disease also means that identification and subsequent validation of biomarkers of the disease is quite challenging. A fully validated single biomarker for diagnosis, prognosis, disease activity and assessment of response to therapy is not yet available. The main aim of this study was to apply an alternative assay protocol to the immunoassay-based analysis of this disease by employment of sialic acid recognizing lectin Sambucus nigra agglutinin (SNA) to glycoprofile serum samples. To our best knowledge this is the first study describing direct lectin-based glycoprofiling of serum SSc samples. Three different analytical methods for glycoprofiling of serum samples relying on application of lectins are compared here from a bioanalytical point of view including traditional ELISA-like lectin-based method (ELLA), novel fluorescent lectin microarrays and ultrasensitive impedimetric lectin biosensors. Results obtained by all three bioanalytical methods consistently showed differences in the level of sialic acid present on glycoproteins, when serum from healthy people was compared to the one from patients having SSc. Thus, analysis of sialic acid content in human serum could be of a diagnostic value for future detection of SSc, but further work is needed to enhance selectivity of assays for example by glycoprofiling of a fraction of human serum enriched in antibodies for individual diagnostics.