Carbohydrate Structure Database: current state and recent developments.

Carbohydrate Structure Database (CSDB) is a curated glycan data collection and a glycoinformatic platform. In this report, its database, analytical, and other components that have appeared for the recent years are reviewed. The major improvements were achieving close-to-full coverage on glycans from microorganisms, launching modules for glycosyltransferases and saccharide conformations, online glycan builder and 3D modeler, NMR simulator, NMR-based structure predictor, and other tools.

Supplementing the Carbohydrate Structure Database with glycoepitopes.

Carbohydrate structures in the Carbohydrate Structure Database have been referenced to glycoepitopes from the Immune Epitope Database allowing users to explore the glycan structures and contained epitopes. Starting with an epitope, one can figure out the glycans from other organisms that share the same structural determinant, and retrieve the associated taxonomical, medical, and other data. This database mapping demonstrates the advantages of the integration of immunological and glycomic databases.

Cataloging natural sialic acids and other nonulosonic acids (NulOs), and their representation using the Symbol Nomenclature for Glycans.

Nonulosonic acids or non-2-ulosonic acids (NulOs) are an ancient family of 2-ketoaldonic acids (α-ketoaldonic acids) with a 9-carbon backbone. In nature, these monosaccharides occur either in a 3-deoxy form (referred to as "sialic acids") or in a 3,9-dideoxy "sialic-acid-like" form. The former sialic acids are most common in the deuterostome lineage, including vertebrates, and mimicked by some of their pathogens. The latter sialic-acid-like molecules are found in bacteria and archaea. NulOs are often prominently positioned at the outermost tips of cell surface glycans, and have many key roles in evolution, biology and disease. The diversity of stereochemistry and structural modifications among the NulOs contributes to more than 90 sialic acid forms and 50 sialic-acid-like variants described thus far in nature. This paper reports the curation of these diverse naturally occurring NulOs at the NCBI sialic acid page (https://www.ncbi.nlm.nih.gov/glycans/sialic.html) as part of the NCBI-Glycans initiative. This includes external links to relevant Carbohydrate Structure Databases. As the amino and hydroxyl groups of these monosaccharides are extensively derivatized by various substituents in nature, the Symbol Nomenclature For Glycans (SNFG) rules have been expanded to represent this natural diversity. These developments help illustrate the natural diversity of sialic acids and related NulOs, and enable their systematic representation in publications and online resources.

Examining the diversity of structural motifs in fungal glycome.

In this paper, we present the results of a systematic statistical analysis of the fungal glycome in comparison with the prokaryotic and protistal glycomes as described in the scientific literature and presented in the Carbohydrate Structure Database (CSDB). The monomeric and dimeric compositions of glycans, their non-carbohydrate modifications, glycosidic linkages, sizes of structures, branching degree and net charge are assessed. The obtained information can help elucidating carbohydrate molecular markers for various fungal classes which, in its turn, can be demanded for the development of diagnostic tools and carbohydrate-based vaccines against pathogenic fungi. It can also be useful for revealing specific glycosyltransferases active in a particular fungal species.

Carbohydrate Structure Database oligosaccharide conformation tool.

Population analysis in terms of glycosidic torsion angles is frequently used to reveal preferred conformers of glycans. However, due to high structural diversity and flexibility of carbohydrates, conformational characterization of complex glycans can be a challenging task. Herein, we present a conformation module of oligosaccharide fragments occurring in natural glycan structures developed on the platform of the Carbohydrate Structure Database. Currently, this module deposits free energy surface and conformer abundance maps plotted as a function of glycosidic torsions for 194 "inter"residue bonds. Data are automatically and continuously derived from explicit-solvent molecular dynamics (MD) simulations. The module was also supplemented with high-temperature MD data of saccharides (2,403 maps) provided by GlycoMapsDB (hosted by GLYCOSCIENCES.de project). Conformational data defined by up to 4 torsional degrees of freedom can be freely explored using a web interface of the module available at http://csdb.glycoscience.ru/database/core/search_conf.html.

Source files of the Carbohydrate Structure Database: the way to sophisticated analysis of natural glycans.

The Carbohydrate Structure Database (CSDB, http://csdb.glycoscience.ru/ ) is a free curated repository storing various data on glycans of bacterial, fungal and plant origins. Currently, it maintains a close-to-full coverage on bacterial and fungal carbohydrates up to the year 2020. The CSDB web-interface provides free access to the database content and dedicated tools. Still, the number of these tools and the types of the corresponding analyses is limited, whereas the database itself contains data that can be used in a broader scope of analytical studies. In this paper, we present CSDB source data files and a self-contained SQL dump, and exemplify their possible application in glycan-related studies. By using CSDB in an SQL format, the user can gain access to the chain length distribution or charge distribution (as an example) in a given set of glycans defined according to specific structural, taxonomic, or other parameters, whereas the source text dump files can be imported to any dedicated database with a specific internal architecture differing from that of CSDB.

CSDB/SNFG Structure Editor: An Online Glycan Builder with 2D and 3D Structure Visualization.

This article describes features, usage, and application of an CSDB/SNFG Structure Editor, a new online tool for quick and intuitive input of carbohydrate and derivative structures using Symbol Nomenclature for Glycans (SNFG). The Editor is built on a platform of the Carbohydrate Structure Database (CSDB) and relies on its online services via the dedicated web-API. The Editor allows building of oligo- and polymeric glycan structures and supports most features of natural glycans, such as underdetermined structures, alternative branches, repeating subunits, SMILES specification of atypical monomers, and others. The vocabulary of building blocks contains 600+ monomeric residues, including 327 monosaccharides. Support for SMILES allows input and visualization of chemical structures of virtually unlimited complexity. On the other hand, the interface follows the recognized GlycanBuilder style easy to novice users. The export feature includes support for CSDB Linear, GlycoCT, WURCS, SweetDB, and Glycam notations, SMILES codes, MOL/PDB atomic coordinate formats, raster and vector SNFG images, and on-the-fly visualization as 2D structural formulas and 3D molecular models. Integration of the Editor into any web-based glycoinformatics project is straightforward and simple, similarly to any other modern JavaScript application.

Production and сharacterization of the exopolysaccharide from strain Paenibacillus polymyxa 2020.

Paenibacillus spp. exopolysaccharides (EPSs) have become a growing interest recently as a source of biomaterials. In this study, we characterized Paenibacillus polymyxa 2020 strain, which produces a large quantity of EPS (up to 68 g/L),and was isolated from wasp honeycombs. Here we report its complete genome sequence and full methylome analysis detected by Pacific Biosciences SMRT sequencing. Moreover, bioinformatic analysis identified a putative levan synthetic operon. SacC and sacB genes have been cloned and their products identified as glycoside hydrolase and levansucrase respectively. The Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectra demonstrated that the EPS is a linear ß-(2→6)-linked fructan (levan). The structure and properties of levan polymer produced from sucrose and molasses were analyzed by FT-IR, NMR, scanning electron microscopy (SEM), high performance size exclusion chromatography (HPSEC), thermogravimetric analysis (TGA), cytotoxicity tests and showed low toxicity and high biocompatibility. Thus, P. polymyxa 2020 could be an exceptional cost-effective source for the industrial production of levan-type EPSs and to obtain functional biomaterials based on it for a broad range of applications, including bioengineering.

CSDB_GT, a curated glycosyltransferase database with close-to-full coverage on three most studied nonanimal species.

We report the accomplishment of the first stage of the development of a novel manually curated database on glycosyltransferase (GT) activities, CSDB_GT. CSDB_GT (http://csdb.glycoscience.ru/gt.html) has been supplemented with GT activities from Saccharomyces cerevisiae. Now it provides the close-to-complete coverage on experimentally confirmed GTs from the three most studied model organisms from the three kingdoms: plantae (Arabidopsis thaliana, ca. 930 activities), bacteria (Escherichia coli, ca. 820 activities) and fungi (S. cerevisiae, ca. 270 activities).

Comparison of Methods for Bulk Automated Simulation of Glycosidic Bond Conformations.

Six empirical force fields were tested for applicability to calculations for automated carbohydrate database filling. They were probed on eleven disaccharide molecules containing representative structural features from widespread classes of carbohydrates. The accuracy of each method was queried by predictions of nuclear Overhauser effects (NOEs) from conformational ensembles obtained from 50 to 100 ns molecular dynamics (MD) trajectories and their comparison to the published experimental data. Using various ranking schemes, it was concluded that explicit solvent MM3 MD yielded non-inferior NOE accuracy with newer GLYCAM-06, and ultimately PBE0-D3/def2-TZVP (Triple-Zeta Valence Polarized) Density Functional Theory (DFT) simulations. For seven of eleven molecules, at least one empirical force field with explicit solvent outperformed DFT in NOE prediction. The aggregate of characteristics (accuracy, speed, and compatibility) made MM3 dynamics with explicit solvent at 300 K the most favorable method for bulk generation of disaccharide conformation maps for massive database filling.

Three-Dimensional Structures of Carbohydrates and Where to Find Them.

Analysis and systematization of accumulated data on carbohydrate structural diversity is a subject of great interest for structural glycobiology. Despite being a challenging task, development of computational methods for efficient treatment and management of spatial (3D) structural features of carbohydrates breaks new ground in modern glycoscience. This review is dedicated to approaches of chemo- and glyco-informatics towards 3D structural data generation, deposition and processing in regard to carbohydrates and their derivatives. Databases, molecular modeling and experimental data validation services, and structure visualization facilities developed for last five years are reviewed.

Structural studies of the pectic polysaccharide from fruits of Punica granatum.

The polysaccharide PGO containing 76 % of uronic acids, was obtained from peels and membranes of Punica granatum fruits by extraction to the aqueous solution of (NH4)2C2O4. The chemical structure of PGO was characterized by enzymatic and partial acid hydrolyses, Smith degradation and 1D/2D NMR spectroscopy. It has been found that PGO consisted mainly of highly methyl-esterified and lowly acetylated pectin. Backbone of the macromolecule was represented by 1,4-α-D-GalpA, 1,4-α-D-GalpA(OMe), 1,4-α-D-GalpA(OAc). The branched region PGO contained minor segments of partially acetylated rhamnogalacturonan-I (RG-I). RG-I side chains were comprised of highly branched 1,5-α-l-arabinan and segments of arabinogalactan type I. In addition to pectins, PGO contained the glucuronoxylans and xyloglucans, indicating a close interaction of these polysaccharides with each other in the cell wall. It was concluded that P. granatum fruit could be a promising source of pectic polysaccharides.

New Features of Carbohydrate Structure Database Notation (CSDB Linear), As Compared to Other Carbohydrate Notations.

The CSDB Linear notation for carbohydrate sequences utilized in the Carbohydrate Structure Database (CSDB) has been improved to meet modern requirements in glycoinformatics. The new features include: the possibility to combine repeating and nonrepeating moieties in one structure; support of carbon-carbon bonds; and usage of SMILES encodings for unambiguous chemical description of glycan structures, including aglycons and atypical components. The new capabilities of CSDB Linear, together with the older ones, allow efficient detection of errors in CSDB and, at the same time, ensure the absence of informatic problems common for human-readable notations. The CSDB Linear implementation provides translation to other carbohydrate notations and multiple procedures for content error checking.

Structure elucidation and gene cluster characterization of the O-antigen of Yersinia kristensenii С-134.

Mild acid degradation of the lipopolysaccharide of Yersinia kristensenii C-134 afforded a glycerol teichoic acid-like O-polysaccharide, which was studied by sugar analysis, O-deacetylation and dephosphorylation along with 1D and 2D NMR spectroscopy. The following structure of the O-polysaccharide was established: This structure is related to those of other Y. kristensenii O-polysaccharides studied earlier. The O-antigen gene cluster of Y. kristensenii С-134 was analyzed and found to be consistent with the O-polysaccharide structure established.

Updates to the Symbol Nomenclature for Glycans guidelines.

The Symbol Nomenclature for Glycans (SNFG) is a community-curated standard for the depiction of monosaccharides and complex glycans using various colored-coded, geometric shapes, along with defined text additions. It is hosted by the National Center for Biotechnology Information (NCBI) at the NCBI-Glycans Page (www.ncbi.nlm.nih.gov/glycans/snfg.html). Several changes have been made to the SNFG page in the past year to update the rules for depicting glycans using the SNFG, to include more examples of use, particularly for non-mammalian organisms, and to provide guidelines for the depiction of ambiguous glycan structures. This Glycoforum article summarizes these recent changes.

Expanding CSDB_GT glycosyltransferase database with Escherichia coli.

In 2017, we reported a new database on glycosyltransferase (GT) activities, CSDB_GT (http://csdb.glycoscience.ru/gt.html), which was built at the platform of the Carbohydrate Structure Database (CSDB, http://csdb.glycoscience.ru/database/index.html) and contained data on experimentally confirmed GT activities from Arabidopsis thaliana. All entries in CSDB_GT are curated manually upon the analysis of scientific publications, and the key features of the database are accurate structural, genetic, protein and bibliographic references and close-to-complete coverage on experimentally proven GT activities in selected species. In 2018, CSDB_GT was supplemented with data on Escherichia coli GT activities. Now it contains ca. 800 entries on E. coli GTs, including ca. 550 entries with functions predicted in silico. This information was extracted from research papers published up to the year 2018 or was obtained by the authors' efforts on GT annotation. Thus, CSDB_GT was extended to provide not only experimentally confirmed GT activities, but also those predicted on the basis of gene or protein sequence homology that could carry valuable information. Accordingly, a new confirmation status-predicted in silico-was introduced. In addition, the coverage on A. thaliana was extended up to ca. 900 entries, all of which had experimental confirmation. Currently, CSDB_GT provides close-to-complete coverage on experimentally confirmed GT activities from A. thaliana and E. coli presented up to the year 2018.

SugarSketcher: Quick and Intuitive Online Glycan Drawing.

SugarSketcher is an intuitive and fast JavaScript interface module for online drawing of glycan structures in the popular Symbol Nomenclature for Glycans (SNFG) notation and exporting them to various commonly used formats encoding carbohydrate sequences (e.g., GlycoCT) or quality images (e.g., svg). It does not require a backend server or any specific browser plugins and can be integrated in any web glycoinformatics project. SugarSketcher allows drawing glycans both for glycobiologists and non-expert users. The "quick mode" allows a newcomer to build up a glycan structure having only a limited knowledge in carbohydrate chemistry. The "normal mode" integrates advanced options which enable glycobiologists to tailor complex carbohydrate structures. The source code is freely available on GitHub and glycoinformaticians are encouraged to participate in the development process while users are invited to test a prototype available on the ExPASY web-site and send feedback.

Glycoinformatics: Bridging Isolated Islands in the Sea of Data.

Glycoinformatics is an actively developing scientific discipline, which provides scientists with the means of access to the data on natural glycans and with various tools of their processing. However, the informatization of glycomics has a long way to go before catching up with genomics and proteomics. In this Viewpoint, we review the current situation in glycoinformatics and discuss its achievements and shortcomings, emphasizing the major drawbacks: the lack of recognized standards, protocols, data indices and tools, and the informational isolation of the existing projects. We reiterate possible solutions of the persistent issues and describe our vision of an ideal glycoinformatics project.

REStLESS: automated translation of glycan sequences from residue-based notation to SMILES and atomic coordinates.

Motivation: Glycans and glycoconjugates are usually recorded in dedicated databases in residue-based notations. Only a few of them can be converted into chemical (atom-based) formats highly demanded in conformational and biochemical studies. In this work, we present a tool for translation from a residue-based glycan notation to SMILES. Results: The REStLESS algorithm for translation from the CSDB Linear notation to SMILES was developed. REStLESS stands for ResiduEs as Smiles and LinkagEs as SmartS, where SMARTS reaction expressions are used to merge pre-encoded residues into a molecule. The implementation supports virtually all structural features reported in natural carbohydrates and glycoconjugates. The translator is equipped with a mechanism for conversion of SMILES strings into optimized atomic coordinates which can be used as starting geometries for various computational tasks. Availability and implementation: REStLESS is integrated in the Carbohydrate Structure Database (CSDB) and is freely available on the web (http://csdb.glycoscience.ru/csdb2atoms.html). Supplementary information: Supplementary data are available at Bioinformatics online.

GRASS: semi-automated NMR-based structure elucidation of saccharides.

Motivation: Carbohydrates play crucial roles in various biochemical processes and are useful for developing drugs and vaccines. However, in case of carbohydrates, the primary structure elucidation is usually a sophisticated task. Therefore, they remain the least structurally characterized class of biomolecules, and it hampers the progress in glycochemistry and glycobiology. Creating a usable instrument designed to assist researchers in natural carbohydrate structure determination would advance glycochemistry in biomedical and pharmaceutical applications. Results: We present GRASS (Generation, Ranking and Assignment of Saccharide Structures), a novel method for semi-automated elucidation of carbohydrate and derivative structures which uses unassigned 13C NMR spectra and information obtained from chromatography, optical, chemical and other methods. This approach is based on new methods of carbohydrate NMR simulation recently reported as the most accurate. It combines a broad diversity of supported structural features, high accuracy and performance. Availability and implementation: GRASS is implemented in a free web tool available at http://csdb.glycoscience.ru/grass.html. Contact: kapaev_roman@mail.ru or netbox@toukach.ru. Supplementary information: Supplementary data are available at Bioinformatics online.