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Polyacrylamide conjugates of glycans have long been widely used in many research areas of glycobiology, mainly for immobilizing glycans in solid-phase assays and as multivalent inhibitors. Pending biotin tag allows immobilizing Glyc-PAA quantitatively on any surface, and acts as a tracer for detection of carbohydrate-binding proteins. However, the scope of already realized capabilities of these probes is immeasurably richer than those listed above. This review is not so much about routine as about less common, but not less significant applications. Also, the data on the glycopolymers themselves, their molecular weight, size and polymer chain flexibility are presented, as well as the methods of synthesis, clusterisation and entropy factor in their interaction with proteins.

Glycosylation of lactosamine acceptors with Kdn thioglycoside donors in the presence of NIS/TfOH as a promoter affords products with both α- and β-ketosidic linkage (2–6' or 2–3') between the Kdn and Gal residues. After deprotection, the synthesized trisaccharides and glycans containing Neu5Ac were printed to a chip and their comparative interaction with human serum antibodies was explored.

Strong discrepancies in published data on the levels and epitope specificities of antibodies against the xenogenic N-glycolyl forms of sialoglycans (Hanganutziu-Deicher Neu5Gcɑ2-3Galβ1-4Glc and related antigens) in healthy donors prompted us to carry out a systematic study in this area using the printed glycan array and other methods. This article summarizes and discusses our published and previously unpublished data, as well as publicly available data from the Consortium for Functional Glycomics. As a result, we conclude that (1) the level of antibodies referred to as anti-Neu5Gc in healthy individuals is low; (2) there are antibodies that seem to interact with Neu5Gc-containing epitopes, but in fact they recognize internal fragments of Neu5Gc-containing glycans (without sialic acids), which served as antigens in the assays used and; (3) a population capable of interacting specifically with Neu5Gc (it does not bind the corresponding NAc analogs) does exist, but it binds the monosaccharide Neu5Gc better than the entire glycans containing it. In other words, in healthy donors, there are populations of antibodies capable of binding the Neu5Gc monosaccharide or the inner core -Galβ1-4Glc, but very few true anti-Neu5Gcɑ2-3Galβ1-4Glc antibodies, i.e., antibodies capable of specifically recognizing the entire trisaccharide.

Previous studies have shown that in the blood of healthy donors (1) there are no natural antibodies against sialylated glycoproteins, which contain Neu5Ac (N-acetylneuraminic acid) as the most widespread form of human sialic acid, and (2) there is a moderate level of antibodies capable of binding unnatural oligosaccharides, where Neu5Ac is beta-linked to a typical mammalian glycan core. In the present study, we investigated antibodies against Neu5Ac in more detail and verified the presence of Kdn (2-keto-3-deoxy-D-glycero-D-galacto-nonulosonic acid) as a possible cause behind their appearance in humans, taking into account the expected cross-reactivity to Kdn glycans, which are found in bacterial glycoconjugates in both the - and -forms. We observed the binding of peripheral blood immunoglobulins to sialyllactosamines (where sialyl is Kdn or neuraminic acid) in only a very limited number of donors, while the binding to monosaccharide Kdn occurred in all samples, regardless of the configuration of the glycosidic bond of the Kdn moiety. In some individuals, the binding level of some of the immunoglobulins was high. This means that bacterial Kdn glycoconjugates are very unlikely to induce antibodies to Neu5Ac glycans in humans. To determine the reason for the presence of these antibodies, we focused on noninfectious pathologies, as well as on a normal state in which a significant change in the immune system occurs: namely, pregnancy. As a result, we found that 2/3 of pregnant women have IgM in the blood against Neu5Ac2-3Gal1-4GlcNAc. Moreover, IgG class antibodies against Neu5Ac2-3Gal1-4GlcNAc and Neu5Ac2-6Gal1-4GlcNAc were also detected in eluates from the placenta. Presumably, these antibodies block fetal antigens.

Polyacrylamide conjugates of glycans have long been widely used in many research areas of glycobiology, mainly for immobilizing glycans in solid-phase assays and as multivalent inhibitors. Pending biotin tag allows immobilizing Glyc-PAA quantitatively on any surface, and acts as a tracer for detection of carbohydrate-binding proteins. However, the scope of already realized capabilities of these probes is immeasurably richer than those listed above. This review is not so much about routine as about less common, but not less significant applications. Also, the data on the glycopolymers themselves, their molecular weight, size and polymer chain flexibility are presented, as well as the methods of synthesis, clusterisation and entropy factor in their interaction with proteins.

The structure of the two-antennary oligoglycines molecules presumes a complex interplay of their bola-amphiphilic nature and the possibility for the onset of Polyglycine II structural motifs in aqueous solutions. These tendencies lead to the appearance of various supramolecular self-assemblies (tectomers). The complex fluid formulations which contain them exhibit high potential for the application of easy fine-tuning procedures. In the present study the possibility for smart regulation of the properties of aqueous solutions of C8H16(-CH2-NH-Gly5)2 (T2-C8-Gly5) is investigated through the variations of pH and changes of the initial incubation time of the systems. A combined investigation protocol, including Dynamic Light Scattering, Profile Analysis Tensiometry, and microscopic Thin-Liquid-Film techniques is developed. The key results are: (i) the size distribution is bimodal in acidic conditions (pH ≤ 6.0) and becomes visibly mono-modal for pH ≥ 7.1; (ii) upon increase of the solution pH the dimensions of the tectomers is shifted towards larger structural entities. These tendencies are enhanced with the raise of the initial incubation time of the aqueous systems. The study permits to draw essential conclusions about the possible coupling mechanism of bulk and interfacial phenomena, and gives key grounds for further fine-tuning of the tectomer-formation phenomena. The obtained results add important new knowledge about the nature of these new materials in view of possible applications in the development of e.g. drug nanocarriers, for extraction of various impurities from water media, etc.

It was previously shown that hemagglutinin residues Thr155, Glu158, and Ser228 are crucial for the recognition of Neu5Gc. In this study, we demonstrated that the ability to bind the Neu5Gc-terminated receptor is related to the amino acid 145: viruses of years 1972-1999 with Lys145 bind to the receptor, whereas viruses with Asn145 do not. Sporadic appearance and disappearance of the ability to bind Neu5Gc oligosaccharides and the absence of Neu5Gc in the composition of human glycoconjugates indicate the non-adaptive nature of this ability. It was previously shown that unlike H1N1 viruses, H3N2 viruses of years 1968-1989 did not distinguish between Neu5Acα2-6Galβ1-4Glc (6'SL) and Neu5Acα2-6Galβ1-4GlcNAc (6'SLN). H3N2 viruses isolated after 1993 have acquired the ability to distinguish between 6'SL and 6'SLN, similarly to H1N1 viruses. We found that the affinity for 6'SLN has gradually increased from 1992 to 2003. After 2003, the viruses lost the ability to bind a number of sialosides, including 6'SL, that were good receptors for earlier H3N2 viruses, and retained high affinity for 6'SLN only, which correlated with the acquisition of new glycosylation sites at positions 122, 133, and 144, as well as Glu190Asp and Gly225Asp substitutions, in hemagglutinin. These substitutions are also responsible for the receptor-binding phenotype of human H1N1 viruses. We conclude that the convergent evolution of the receptor specificity of the H1N1 and H3N2 viruses indicates that 6'SLN is the optimal natural human receptor for influenza viruses.

Antennary oligoglycines are synthetic products, obtained as a result of preliminary molecular design. Equal-length antennae are built of glycine residues joined through the C end to an oligoamine branching core with an amine group at the N terminus exposed outside. The results of systematic research on the properties of aqueous solutions containing two-antennary oligoglycine with four glycine portions are reported. The central feature is the competition between amphiphilic self-assembly and formation of polyglycine II motifs. A combined procedure is developed to characterize bulk and interfacial structures and coatings. It includes registration of bulk aggregates, examination of interfacial layers at solution/air and solution/solid boundaries, drainage, and stability of liquid films. The obtained results provide new insight into the structure-property relationships in these smart fluids and give essential hints about key factors allied to possible applications in medicine, pharmaceuticals, and environmental protection.

Glycan-based suspension array (SGA) is an “in-house” developed multi-target immunoassay, employing commercially available fluorescent microbeads as a solid support for unique chemically synthesized glycopolymers which capture naturally occurring human anti-glycan antibodies. SGA is a sensitive and reliable tool for the high-throughput screening of anti-glycan antibody alterations characteristic for a vast number of human diseases including cancer. However, unspecific background binding, for instance binding of non-target antibodies, is a common obstacle in such immunoassays. In an attempt to reduce unspecific background binding of serum (or plasma) antibodies, we prepared glycosylated microbeads modified with linear poly(ethylene glycols) (PEGs) of different lengths. We compared several kinds of PEG modifications: (a) partial side-chain substitution of glycopolymers by PEGs of different lengths, (b) end-point addition of biotin-linked PEGs to glycopolymer-coupled beads, and (c) linking of heterobifunctional PEGs to the bead surface prior to glycopolymer immobilization. Among the various modifications investigated, the direct modification of the bead surface with linear heterobifunctional PEGs, consisting of 23- and 60PEG-units significantly reduced the background binding. The end-point addition of biotin-linked PEGs, especially in the case of PEG consisting from 50PEG-units, helped to repel non-target binding caused by endogenous biotin. We observed unspecific binding predominantly for antibodies of IgG but of IgM class. The novel design of fluorescent microbeads allows the detection of human anti-glycan antibodies with increased specificity and opens new horizons for practical application of SGA as a diagnostic tool.

Oligoglycines designed in a star-like fashion, so-called tri- and tetraantennary molecules, were found to form highly ordered supramers in aqueous medium. The formation of these supramers occurred either spontaneously or due to the assistance of a mica surface. The driving force of the supramer formation is hydrogen bonding, the polypeptide chain conformation is related to the folding of helical polyglycine II (PG II). Tri- and tetraantennary molecules are capable of association if the antenna length reach 7 glycine (Gly) residues. Properties of similar biantennary molecules have not been investigated yet, and we compared their self-aggregating potency with similar tri- and tetraantennary analogs. Here, we synthesized oligoglycines of the general formula R-Glyn-Х-Glyn-R (X = -HN-(СН2)m-NH-, m = 2, 4, 10; n = 1–7) without pendant ligands (R = H) and with two pendant sialoligands (R = sialic acid or sialooligosaccharide). Biantennary oligoglycines formed PG II aggregates, their properties, however, differ from those of the corresponding tri- and tetraantennary oligoglycines. In particular, the tendency to aggregate starts from Gly4 motifs instead of Gly7. The antiviral activity of end-glycosylated peptides was studied, and all capable of assembling glycopeptides demonstrated an antiviral potency which was up to 50 times higher than the activity of peptide-free glycans.

Assembly of [Gly7-NHCH2-]4C, [Gly7-NHCH2-]3C CH3 and [Gly4NH(CH2)5-]2 peptides on mica surface in aqueous so-lution was studied. The peptides are capable of forming atomically smooth (2.65-4.3 nm in height) layers assembled as polyglycine II. Monomers in the layers are situated normally to the surface. Formation of analogous flat 2D structures also takes place in solution but much more slowly than on mica surface, i.e. negatively charged surface plays an active role promoting the assembly.

An atomistic molecular dynamics (MD) simulation of the adsorption of biantennary oligoglycine [H-Gly4-NH(CH2)5]2 onto a graphite and mica surface is described. The structure of the resultant adsorption layers is analyzed. The secondary structure motifs of peptide blocks are studied by the STRIDE (structural identification) and DSSP (dictionary of the secondary structure of proteins) methods. The results of the study confirm the possibility of forming a polyglycine-II (PGII) structure in the monolayers of biantennary oligoglycines (BAOG) on a graphite surface previously supposed from the data of atomic force microscopy.