. Author manuscript; available in PMC: 2013 Jan 1.

Published in final edited form as: Mass Spectrom Rev. 2011 Jul 13;31(1):134–178. doi: 10.1002/mas.20342

Table 2.

A schematic representation of the database used for sphingolipids^a

Lipid class	Lipid subclasses	Backbone	Sphingoid backbone (Building block III)	Head group (Building block I)	Side chain (Building block II)	Sum formula	Negative-ion mode	Positive-ion mode	Number of possible species^b
Ceramide (Cer)	non-hydroxy Cer			H	C_mH_2m-2n-1O	C_m+x+3H_{2m-2n+2x-2y+7}O₃N	[M-H]⁻		2214
Ceramide (Cer)	hydroxy Cer				C_mH_2m-2n-1O₂	C_m+x+3H_{2m-2n+2x-2y+7}O₄N			2214
Sphingomyelin (SM)	non-hydroxy SM			C₅H₁₃O₃PN	C_mH_2m-2n-1O	C_m+x+8H_{2m-2n+2x-2y+19}O₆PN₂	[M+Cl]⁻	[M+Li]⁺, [M+Na]⁺	2214
Sphingomyelin (SM)	hydroxy SM				C_mH_2m-2n-1O₂	C_m+x+8H_{2m-2n+2x-2y+19}O₇PN₂			2214
Ceramide phosphoethanola mine (CerPE)	non-hydroxy CerPE			C₂H₆O₃PN	C_mH_2m-2n-1O	C_m+x+5H_{2m-2n+2x-2y+12}O₆PN₂	[M-H]⁻, [M-H+Fmoc]⁻	[M+H]⁺	2214
Ceramide phosphoethanola mine (CerPE)	hydroxy CerPE			C₆H₁₁O₅	C_mH_2m-2n-1O₂	C_m+x+5H_{2m-2n+2x-2y+12}O₇PN₂	[M+Cl]⁻	[M+Li]⁺, [M+Na]⁺	2214
Monohexosyl-ceramide (HexCer)	non-hydroxy HexCer				C_mH_2m-2n-1O₂	C_m+x+9H_{2m-2n+2x-2y+17}O₉N			2214
Monohexosyl-ceramide (HexCer)	hydroxy HexCer				C_mH_2m-2n-1O₂	C_m+x+9H_{2m-2n+2x-2y+17}O₉N			2214
Sulfatide (ST)	non-hydroxy ST	C₃H₆O₂N	C_xH_2x-2y+1	C₆H₁₁SO₈	C_mH_2m-2n-1O	C_m+x+9H_{2m-2n+2x-2y+17}O₁₁NS	[M-H]⁻		2214
Sulfatide (ST)	hydroxy ST				C_mH_2m-2n-1O₂	C_m+x+9H_{2m-2n+2x-2y+17}O₁₂NS			2214
Lactosyl-ceramide (LacCer)	non-hydroxy LacCer			C₁₂H₂₁O₁₀	C_mH_2m-2n-1O	C_m+x+15H_{2m-2n+2x-2y+27}O₁₃N	[M+Cl]⁻	[M+Li]⁺, [M+Na]⁺	2214
Lactosyl-ceramide (LacCer)	hydroxy LacCer			C₅H₁₃O₃PN	C_mH_2m-2n-1O₂	C_m+x+15H_{2m-2n+2x-2y+27}O₁₄N			2214
Lyso-SM Sphingoid backbone				H	H	C_x+8H_2x-2y+21O₅PN₂	[M+Cl]⁻	[M+Li]⁺, [M+Na]⁺	27
Lyso-SM Sphingoid backbone				H	H	C_x+3H_2x-2y+9O₂N	[M+Cl]⁻	[M+H]⁺	27
Sphingoid backbone 1-phosphate				H₂O₃P	H	C_x+3H_2x-2y+10O₅PN	[M-H]⁻		27
Psychosine				C₆H₁₁O₅	H	C_x+9H_2x-2y+19O₇N		[M+H]⁺	27

								Total	26676

The database is constructed based on the building blocks I, II, and III in sphingolipids as indicated in Figure 8 with the variables x, y, m, and n. The variable m represents the number of total carbon atoms of fatty amide chain (m = 12 – 26), the variable n represents the number of total double bonds of the fatty amide chain (n = 0 – 7), the variable x represents the number of total carbon atoms of a partial sphingoid backbone as indicated in Scheme 1 (x = 11 – 19), and the variable y represents the number of total double bonds of the partial sphingoid backbone (y = 0 – 2). The ion modes indicate the ionization mode(s) used to analyze the indicated lipid class in MDMS-based shotgun lipidomics. Gangliosides are not included, as discussed in the text.

The isomers that result from the different locations of double bond(s) are not considered. The number of molecular species are calculated based on the naturally occurring fatty acids that contain the highest degree of unsaturation for acyl chains of 12 – 26 carbon atoms are 12:1, 13:1, 14:3, 15:3, 16:5, 17:3, 18:5, 19:3, 20:6, 21:5, 22:7, 23:5, 24:7, 25:6, and 26:7, respectively, that were previously identified.