Symbol Nomenclature for Glycans (SNFG)
Standardization in drawing glycan structures is essential for efficient communication. The tools and methodology illustrated here have become widely accepted by the scientific community. Use of these symbols to represent monosaccharides is now strongly recommended for all manuscripts submitted to major journals and other publications.
Citation:
- Symbol Nomenclature for Graphical Representation of Glycans, Glycobiology 25: 1323-1324, 2015. Citation link (PMID 26543186).
- Updates to the Symbol Nomenclature for Glycans guidelines, Glycobiology 29:620-624, 2019. Citation link (PMID 31184695).
Organizations and Publications Adopting SNFG
Software tools supporting SNFG
- 3D-Symbol Nomenclature for Glycans (3D-SNFG): Create 3D atomic models of glycans
Direct weblink | Citation link. - DrawGlycan SNFG: Convert IUPAC input strings to sketches of glycans and glycopeptides
Direct weblink | App download | Citation link. - GlycanBuilder2-SNFG: GlycanBuilder updated to handle SNFG
Direct weblink | App download | Citation link.
Symbol Nomenclature
Downloadable files: Drawing format | Presentation/Slide format | Notes | Examples
Each symbol represents a specific monosaccharide or class of monosaccharides found in nature. Hover over Symbol with pointer to see the full monosaccharide name. Click on a symbol to link to the corresponding PubChem entry. Symbols can also be copied with embedded links from the table using right/control-click or highlight-copy (highlight a symbol, then control-c [on pc], or command⌘-c [on mac]). However links may not copy in some browsers. Symbols with embedded PubChem URLs are therefore also available in the presentation/slide format attachments (see links above the table). A high-quality SVG object file is also provided.
Table 1. Monosaccharide symbol nomenclature
| SHAPE | White (Generic) | Blue | Green | Yellow | Orange | Pink | Purple | Light Blue | Brown | Red |
|---|---|---|---|---|---|---|---|---|---|---|
| Filled Circle |  Hexose |  Glc |  Man |  Gal |  Gul |  Alt |  All |  Tal |  Ido | |
| Filled Square |  HexNAc |  GlcNAc |  ManNAc |  GalNAc |  GulNAc |  AltNAc |  AllNAc |  TalNAc |  IdoNAc | |
| Crossed Square |  Hexosamine |  GlcN |  ManN |  GalN |  GulN |  AltN |  AllN |  TalN |  IdoN | |
| Divided Diamond |  Hexuronate |  GlcA |  ManA |  GalA |  GulA |  AltA |  AllA |  TalA |  IdoA | |
| Filled Triangle |  Deoxyhexose |  Qui |  Rha |  6dGul |  6dAlt |  6dTal |  Fuc | |||
| Divided Triangle |  DeoxyhexNAc |  QuiNAc |  RhaNAc |  6dAltNAc |  6dTalNAc |  FucNAc | ||||
| Flat Rectangle |  Di-deoxyhexose |  Oli |  Tyv |  Abe |  Par |  Dig |  Col | |||
| Filled Star |  Pentose |  Ara |  Lyx |  Xyl |  Rib | |||||
| Filled Diamond |  Deoxynonulosonate |  Kdn |  Neu5Ac |  Neu5Gc |  Neu |  Sia | ||||
| Flat Diamond |  Di-deoxynonulosonate |  Pse |  Leg |  Aci |  4eLeg | |||||
| Flat Hexagon |  Unknown |  Bac |  LDmanHep |  Kdo |  Dha |  DDmanHep |  MurNAc |  MurNGc |  Mur | |
| Pentagon |  Assigned |  Api |  Fru |  Tag |  Sor |  Psi |
Notes
- General: The monosaccharide symbols presented here are from the Third Edition of the Essentials of Glycobiology. They are extended from the symbols in the Second Edition (Figure 1.5, Second Edition) to cover a wider range of monosaccharides found in nature. While previous versions allowed conversion of monosaccharide symbols to black and white representation, this is no longer possible. A listing of abbreviated, full, and complete names of all assigned monosaccharides is shown in Table 3. Selected examples depicting SNFG usage are presented below the footnotes, for various living organisms.
- Drawing recommendations: All downloadable symbols follow CMYK colors as shown in Table 2, which were generated in Adobe Illustrator. Recommended CMYK to RGB conversion is also provided. While there is no hard rule, glycans are typically sketched to orient their non-reducing end in either the left or upward direction.
- Shape, color and symbol orientation: Shapes and colors are completely consistent with stereochemistry only for hexoses, hexosamines, N-acetylhexosamines, hexuronates, and pentoses. Shapes only are consistent for deoxyhexoses, deoxy-N-acetylhexosamines, dideoxyhexoses, and nonulosonates. Avoid rotating the symbols if possible.
- Ring configuration: A colored symbol encodes a defined monosaccharide (including D or L) independent of rotation or mirroring. Pyranose form is assumed by default for all monosaccharides except Api. A few monosaccharides have absolute configurations implicitly specified in their name (D for Abe, Bac, Dha, Kdo, Mur, Par, Tyv; L for Col; DD for Kdn, Neu, Leg, 4eLeg; LL for Pse, Aci). For all other residues, absolute configuration is assumed by default: L for Ara, Fuc, Ido, IdoA, Rha, Alt, AltA, Sor, Api; and D for other monosaccharides.
Less common configurations need to be stated in a figure legend or by adding the letters inside the symbol (e.g., adding D or L to the symbol). Epimers at C8 of nonulosonates can be indicated by adding "8D" or "8L" inside the symbol. Furanose rings can be indicated by adding an italicized "f" inside the symbol, and alditols can be indicated with an italicized "o" inside the symbol. - Linkage presentation: Anomeric notation and destination linkage can be indicated in IUPAC style in figures, with or without a dash and with or without the originating carbon number (but with no commas or spacing) (e.g., Neu5Acα2-3Galβ1-4GlcNAc, Neu5Acα3Galβ4GlcNAc, or equivalents in symbol drawings)
All monosaccharide glycosidic linkages are assumed to originate from C-1—except for 2-ketoses, which are assumed to be linked from C-2. Linkages in the schematics should be sorted to appear in the clockwise order. Optionally, these may also follow the Oxford System that embeds both the specificity and anomericity of the monosaccharide linkages. Dual linkages (e.g., an outgoing linkage from an aldose in open form) can be shown by double lines. Linkages involving carbon-carbon bond (e.g., in C-glycosides) can be shown in different color. An internal phosphodiester can be shown with -P- between the symbols for the linked monosaccharides, with linkage positions if preferred. - Sialic acid: Specific symbols are provided for the core sialic acids Neu5Ac, Neu5Gc, and Kdn, with modifications to be indicated in diagrams (e.g., 9Ac for 9-O-acetylation). A red diamond can be used for any Sia (sialic acid, type unknown, whether Neu5Gc or Neu5Ac, or any of the other >50 forms known to date).
- Carbohydrate modifications: Abbreviations for modifications (e.g., sulfate or O-acetyl esters) follow the style of the Figure 1.5 of the Third Edition of Essentials, using attached letters, with numbers indicating linkage positions, if known (e.g., 9Ac for 9-O-acetyl group; 3S for 3-O-sulfate group; 6P for a 6-O-phosphate group; 8Me for 8-O-methyl group; 9Lt for 9-O-lactyl group; or 4,6Py for 4,6-pyruvyl group, etc.; abbreviations for multiple modifications can be concatenated). The presence of variable amounts of substituents can be indicated using +/- symbol or by indicating % presence if known, e.g. "60% 3Ac" to indicate presence of 3Ac on 60% of a residue or repeating unit.
- Amino substitution: For N-substituted groups it is assumed that there is only one amino group on the monosaccharide, with an already known common position (e.g., NS for N-sulfate group on glucosamine is assumed to be at the 2-position). For amino sugars in which the nitrogen is not at the most common carbon, add a number to the N (e.g., Rha4N is shown as a green triangle with 4N attached). Additionally, atypical acetamido groups may be represented using NAc (e.g. Fuc4NAc is shown using red triangle with 4NAc attached).
- Ambiguous linkage position and glycan mixtures: Brackets (either straight or curly) indicate attachment of specific monosaccharides or structures to any residue within the glycan. Restrictions on the nature of attachment are specified by including linkage data on the bond outside the brackets. Constraints on attachment site are shown using asterisk followed by a number (*#), specified both on the bond and its attachment site(s). Such renderings are used to indicate ambiguity in the structure of a specific glycan. By extension, glycan mixtures may be depicted by including [number range] along the bond as shown in the examples.
- Ambiguous monosaccharides: White symbols based on the standard shapes designate monosaccharides with unknown/undefined stereochemistry (e.g., a white circle designates a hexose, type not defined, or a white diamond, any deoxynonulosonic acid). Other unknown or partially defined monosaccharides may be represented using a white flat hexagon.
- Structures not present in table and non-glycan assignments: Monosaccharides absent in Table 1 or modifications that cannot be represented using the above rules, may be indicated using a single non-italicized letter (A..Z) within an SNFG white symbol, with additional details provided in figure footnote or legends. The choice of white symbol to use should fit the generic type if possible: circle for hexose, triangle for deoxy hexose etc.; otherwise the white pentagon should be used. Any black shape can be used to depict non-monosaccharide structures and detailed definitions should be provided in figure legends. More complicated modifications of the SNFG are discouraged, and if these modifications are made should not be referred to as following the SNFG nomenclature.
Examples of Glycan Symbol Nomenclature
Table 2. CMYK and RGB color assignments
| Color | CMYK settings | RGB settings |
|---|---|---|
| White | 0/0/0/0 | 255/255/255 |
| Blue | 100/50/0/0 | 0/144/188 |
| Green | 100/0/100/0 | 0/166/81 |
| Yellow | 0/15/100/0 | 255/212/0 |
| Light blue | 41/5/3/0 | 143/204/233 |
| Pink | 0/47/24/0 | 246/158/161 |
| Purple | 38/88/0/0 | 165/67/153 |
| Brown | 32/48/76/13 | 161/122/77 |
| Orange | 0/65/100/0 | 244/121/32 |
| Red | 0/100/100/0 | 237/28/36 |
Table 3. Monosaccharide abbreviations and names
| Abbreviation | Short Name | Systematic name |
|---|---|---|
| 4eLeg | 4-Epilegionaminic acid | 5,7-Diamino-3,5,7,9-tetradeoxy-D-glycero-D-talo-non-2-ulopyranosonic acid |
| 6dAlt | 6-Deoxy-L-altrose | 6-Deoxy-L-altropyranose |
| 6dAltNAc | N-Acetyl-6-deoxy-L-altrosamine | 2-Acetamido-2,6-dideoxy-L-altropyranose |
| 6dGul | 6-Deoxy-D-gulose | 6-Deoxy-D-gulopyranose |
| 6dTal | 6-Deoxy-D-talose | 6-Deoxy-D-talopyranose |
| 6dTalNAc | N-Acetyl-6-deoxy-D-talosamine | 2-Acetamido-2,6-dideoxy-D-talopyranose |
| Abe | Abequose | 3,6-Dideoxy-D-xylo-hexopyranose |
| Aci | Acinetaminic acid | 5,7-Diamino-3,5,7,9-tetradeoxy-L-glycero-L-altro-non-2-ulopyranosonic acid |
| All | D-Allose | D-Allopyranose |
| AllA | D-Alluronic acid | D-Allopyranuronic acid |
| AllN | D-Allosamine | 2-Amino-2-deoxy-D-allopyranose |
| AllNAc | N-Acetyl-D-allosamine | 2-Acetamido-2-deoxy-D-allopyranose |
| Alt | L-Altrose | L-Altropyranose |
| AltA | L-Altruronic acid | L-Altropyranuronic acid |
| AltN | L-Altrosamine | 2-Amino-2-deoxy-L-altropyranose |
| AltNAc | N-Acetyl-L-altrosamine | 2-Acetamido-2-deoxy-L-altropyranose |
| Api | L-Apiose | 3-C-(Hydroxymethyl)-L-erythro-tetrofuranose |
| Ara | L-Arabinose | L-Arabinopyranose |
| Bac | Bacillosamine | 2,4-Diamino-2,4,6-trideoxy-D-glucopyranose |
| Col | Colitose | 3,6-Dideoxy-L-xylo-hexopyranose |
| DDmanHep | D-glycero-D-manno-Heptose | D-glycero-D-manno-Heptopyranose |
| Dha | 3-Deoxy-D-lyxo-heptulosaric acid | 3-Deoxy-D-lyxo-hept-2-ulopyranosaric acid |
| Dig | D-Digitoxose | 2,6-Dideoxy-D-ribo-hexopyranose |
| Fru | D-Fructose | D-arabino-Hex-2-ulopyranose |
| Fuc | L-Fucose | 6-Deoxy-L-galactopyranose |
| FucNAc | N-Acetyl-L-fucosamine | 2-Acetamido-2,6-dideoxy-L-galactopyranose |
| Gal | D-Galactose | D-Galactopyranose |
| GalA | D-Galacturonic acid | D-Galactopyranuronic acid |
| GalN | D-Galactosamine | 2-Amino-2-deoxy-D-galactopyranose |
| GalNAc | N-Acetyl-D-galactosamine | 2-Acetamido-2-deoxy-D-galactopyranose |
| Glc | D-Glucose | D-Glucopyranose |
| GlcA | D-Glucuronic acid | D-Glucopyranuronic acid |
| GlcN | D-Glucosamine | 2-Amino-2-deoxy-D-glucopyranose |
| GlcNAc | N-Acetyl-D-glucosamine | 2-Acetamido-2-deoxy-D-glucopyranose |
| Gul | D-Gulose | D-Gulopyranose |
| GulA | D-Guluronic acid | D-Gulopyranuronic acid |
| GulN | D-Gulosamine | 2-Amino-2-deoxy-D-gulopyranose |
| GulNAc | N-Acetyl-D-gulosamine | 2-Acetamido-2-deoxy-D-gulopyranose |
| Ido | L-Idose | L-Idopyranose |
| IdoA | L-Iduronic acid | L-Idopyranuronic acid |
| IdoN | L-Idosamine | 2-Amino-2-deoxy-L-idopyranose |
| IdoNAc | N-Acetyl-L-idosamine | 2-Acetamido-2-deoxy-L-idopyranose |
| Kdn | 3-Deoxy-D-glycero-D-galacto-nonulosonic acid | 3-Deoxy-D-glycero-D-galacto-non-2-ulopyranosonic acid |
| Kdo | 3-Deoxy-D-manno-octulosonic acid | 3-Deoxy-D-manno-oct-2-ulopyranosonic acid |
| Leg | Legionaminic acid | 5,7-Diamino-3,5,7,9-tetradeoxy-D-glycero-D-galacto-non-2-ulopyranosonic acid |
| LDmanHep | L-glycero-D-manno-Heptose | L-glycero-D-manno-Heptopyranose |
| Lyx | D-Lyxose | D-Lyxopyranose |
| Man | D-Mannose | D-Mannopyranose |
| ManA | D-Mannuronic acid | D-Mannopyranuronic acid |
| ManN | D-Mannosamine | 2-Amino-2-deoxy-D-mannopyranose |
| ManNAc | N-Acetyl-D-mannosamine | 2-Acetamido-2-deoxy-D-mannopyranose |
| Mur | Muramic acid | 2-Amino-3-O-[(R)-1-carboxyethyl]-2-deoxy-D-glucopyranose |
| MurNAc | N-Acetylmuramic acid | 2-Acetamido-3-O-[(R)-1-carboxyethyl]-2-deoxy-D-glucopyranose |
| MurNGc | N-Glycolylmuramic acid | 3-O-[(R)-1-Carboxyethyl]-2-deoxy-2-glycolamido-D-glucopyranose |
| Neu | Neuraminic acid | 5-Amino-3,5-dideoxy-D-glycero-D-galacto-non-2-ulopyranosonic acid |
| Neu5Ac | N-Acetylneuraminic acid | 5-Acetamido-3,5-dideoxy-D-glycero-D-galacto-non-2-ulopyranosonic acid |
| Neu5Gc | N-Glycolylneuraminic acid | 3,5-Dideoxy-5-glycolamido-D-glycero-D-galacto-non-2-ulopyranosonic acid |
| Oli | Olivose | 2,6-Dideoxy-D-arabino-hexopyranose |
| Par | Paratose | 3,6-Dideoxy-D-ribo-hexopyranose |
| Pse | Pseudaminic acid | 5,7-Diamino-3,5,7,9-tetradeoxy-L-glycero-L-manno-non-2-ulopyranosonic acid |
| Psi | D-Psicose | D-ribo-Hex-2-ulopyranose |
| Qui | D-Quinovose | 6-Deoxy-D-glucopyranose |
| QuiNAc | N-Acetyl-D-quinovosamine | 2-Acetamido-2,6-dideoxy-D-glucopyranose |
| Rha | L-Rhamnose | 6-Deoxy-L-mannopyranose |
| RhaNAc | N-Acetyl-L-rhamnosamine | 2-Acetamido-2,6-dideoxy-L-mannopyranose |
| Rib | D-Ribose | D-Ribopyranose |
| Sia | Sialic acid | Sialic acid residue of unspecified type |
| Sor | L-Sorbose | L-xylo-Hex-2-ulopyranose |
| Tag | D-Tagatose | D-lyxo-Hex-2-ulopyranose |
| Tal | D-Talose | D-Talopyranose |
| TalA | D-Taluronic acid | D-Talopyranuronic acid |
| TalN | D-Talosamine | 2-Amino-2-deoxy-D-talopyranose |
| TalNAc | N-Acetyl-D-talosamine | 2-Acetamido-2-deoxy-D-talopyranose |
| Tyv | Tyvelose | 3,6-Dideoxy-D-arabino-hexopyranose |
| Xyl | D-Xylose | D-Xylopyranose |
Clicking on the abbreviation leads to the corresponding entry in PubChem
Updates
February 4, 2020
- Rules added for specification of symbol and bond orientation.
November 20, 2019
- SNFG now provides guidelines to depict ambiguous linkages and glycan mixtures using bracket notation.
May 9, 2019
- Footnote 7 modified to accommodate variable modifications.
- More SNFG usage examples added.
January 22, 2019
- SNFG page reorganized with new examples from mammals, yeast, slime mold, insects, bacteria and plants.
- The new examples focus on how to present carbohydrate structures in diverse organisms and ambiguous monosaccharide assignments.
- Number of footnotes reduced from 28 to 10, and thematically organized in order to simplify usage.
- Single non-italicized letter is now allowed in white symbols to help describe monosaccharides that are not part of the SNFG table and that cannot be described using existing footnotes.
- SNFG Discussion Group list updated.
June 5, 2017
- SNFG Discussion Group Listing added.
- White diamond now indicates any deoxynonulosonic acid.
- Flattened diamond introduced for any dideoxynonulosonic acid.
- Additional symbols added for 6dGul, 6dAltNAc, 6dTalNAc, Pse, Leg, Aci and 4eLeg.
- Drawglycan-SNFG and Glycanbuilder 2-SNFG adopted, link to web site provided.
- Updates to Appendix 52A. Organizations and publications adopting SNFG.
- RGB color code provided in addition to CMYK
- Multiple minor corrections and additions to nomenclature and rules of display.
August 31, 2016
- Link to new Appendix 52A. Organizations and Publications Adopting SNFG.
- Red diamond introduced for Sia (sialic acid, type unspecified). White diamond indicates any nonulosonic acid.
- A 3D Symbol Nomenclature for Glycans (3D-SNFG) adopted, link to web site provided.
- Multiple minor corrections and additions to nomenclature and rules of display.