## 2 Structural Characteristics, Classification, and Nomenclature of GSLs
\begin{table}
\begin{tabular}{c c c} \hline \hline
**GSL Series (Symbol)** & **Core Carbohydrate Structure** & **Tissue Specific Distribution** \\ \hline Ganglio (Gg) & Gal81-3 GalNAc81-4 Gal81-4 Glc81-1\({}^{1}\)Cer & In the brain (vertebrates) \\ \hline Isoganglio (iGg) & Gal81-3 GalNAc81-3 Gal81-4 Glc81-1\({}^{1}\)Cer & \\ \hline Lacto (Lc) & Gal81-3 GlcNAc81-3 Gal81-4 Glc81-1\({}^{1}\)Cer & In secretory organs (vertebrates) \\ \hline Neolacto (nLc) & Gal81-4 GlcNAc81-3 Gal81-4 Glc81-1\({}^{1}\)Cer & In certain hematopoietic cells, including leukocytes (vertebrates) \\ \hline Globo (Gb) & GalNAc\(\beta\)1-3 Gal\(\alpha\)1-4 Gal81-4 Glc81-1\({}^{1}\)Cer & In erythrocytes (vertebrates) \\ \hline Isoglobo (iGb) & GalNAc\(\beta\)1-3 Gal\(\alpha\)1-3 Gal\(\beta\)1-4 Glc81-1\({}^{1}\)Cer & In vertebrates \\ \hline Mollu (Mu) & GlcNAc\(\beta\)1-2 Man\(\alpha\)1-3 Man\(\beta\)1-4 Glc81-1\({}^{1}\)Cer & In invertebrates \\ \hline Arthro (At) & GalNAc\(\beta\)1-4 GlcNAc\(\beta\)1-3 Man\(\beta\)1-4 Glc81-1\({}^{1}\)Cer & In invertebrates \\ \hline \hline \end{tabular}
\end{table} 
Table 1: GSL classification according to the core carbohydrate structure. ganglio_-series; the second letter (M, D, T, Q, P) indicates the count of sialic acid units (single, double, triple, quadruple, pentuple) found in the glycans; and the numeral \((1,2,3,4)\) corresponds to their elution sequence in thin-layer chromatography (TLC) (Rf values: GM4 > GM3 > GM2 > GM1), relative to the starting point. The latter property depends on the composition and length of the glycan, and the neutral core oligosaccharides were shown to move farther in TLC as the number increased. The indexes such as a, b, c show the molecular synthesis pathway, with the sialic acids binding position being different for all three pathways: e.g., in GM1b, the residue of sialic acid is linked to a Gal residue on the oligosaccharide chain end, while in the case of GM1a, the inner Gal residue is bound to the sialic acid. \begin{table}
\begin{tabular}{c c} \hline
**Svennerholm Nomenclature** & **IUPAC-IUB Nomenclature** \\ \hline LacCer & Galb4 Glcb1 Cer \\ \hline GA2, G\$g$3 Cer & GalNAcb4 Galb4 Glcb1 Cer \\ \hline GA, G\$4 Cer & Galb3 GalNAcb4 Galb4 Glcb1 Cer \\ \hline nL\$4 Cer & Galb4 GlcNAcb3 Galb4 Glcb1 Cer \\ \hline L\$4 Cer & Galb3 GlcNAcb3 Galb4 Glcb1 Cer \\ \hline GM4 & P3-a-Neu5 Ac-GalCer \\ \hline GM4 & P3-a-Neu5 Ac-GlcCer \\ \hline GM3 & P3-a-Neu5 Ac-LacCer \\ \hline GM3 & P3-a-Neu5 Gc-LacCer \\ \hline GD3 & P3-a-(Neu5 Ac)\({}_{2}\)-LacCer \\ \hline GD3 & P3-a-(Neu5 Ac, Neu5 Gc)\({}_{2}\)-LacCer \\ \hline GD3 & P3-a-(Neu5 Ac, Neu5 Gc)\({}_{2}\)-LacCer \\ \hline GT3 & P3-a-(Neu5 Ac)\({}_{3}\)-LacCer \\ \hline GM2 & P3-a-Neu5 Ac-G\$g$3 Cer \\ \hline GD2 & P3-a-(Neu5 Ac)\({}_{2}\)-G\$g$3 Cer \\ \hline GM1a & P3-a-Neu5 Ac-G\$g$4 Cer \\ \hline GM1b & P3-a-Neu5 Ac-G\$g$4 Cer \\ \hline GalNAc-GM1b & P3-a-Neu5 Ac-G\$g$5 Cer \\ \hline LM1 & P3-a-Neu5 Ac-L\$4 Cer \\ \hline LM1 & P3-a-Neu5 Gc-L\$4 Cer \\ \hline GD1a & P3-a-Neu5 Ac,L\$3-a-Neu5 Ac-G\$g$4 Cer \\ \hline GD1b & P3-a-(Neu5 Ac)\({}_{2}\)-G\$g$4 Cer \\ \hline LD1 & P3-a-(Neu5 Ac)\({}_{2}\)-L\$4 Cer \\ \hline GT1a & P3-a-(Neu5 Ac)\({}_{2}\),P3-a-Neu5 Ac-G\$g$4 Cer \\ \hline GT1b & P3-a-Neu5 Ac,P3-a-(Neu5 Ac)\({}_{2}\)-G\$g$4 Cer \\ \hline GT1c & P3-a-(Neu5 Ac)\({}_{3}\)-G\$g$4 Cer \\ \hline GQ1b & P3-a-(Neu5 Ac)\({}_{2}\),P3-a-(Neu5 Ac)\({}_{2}\)-G\$g$4 Cer \\ \hline GQ1c & P3-a-Neu5 Ac,P3-a-(Neu5 Ac)\({}_{3}\)-G\$g$4 Cer \\ \hline GPIb & P3-a-(Neu5 Ac)\({}_{3}\),P3-a-(Neu5 Ac)\({}_{2}\)-G\$g$4 Cer \\ \hline GPIc & P3-a-(Neu5 Ac)\({}_{2}\),P3-a-(Neu5 Ac)\({}_{3}\)-G\$g$4 Cer \\ \hline \end{tabular}
\end{table} 
Table 2: The Svennerholm system of GSL nomenclature and the IUPAC-IUB Joint Commission nomenclature. Due to the varying degrees of molecular structural insight provided by diverse MS techniques, the Lipid MAPS consortium proposed an extensive classification system in 2005. They also created a comprehensive structural database encompassing biologically significant lipids, GSLs included.