Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2021 May 7;218(7):e20202699. doi: 10.1084/jem.20202699

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

© 2021 Cotton et al.

This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms/). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 International license, as described at https://creativecommons.org/licenses/by-nc-sa/4.0/).

PMC Copyright notice

Figure 5. — Length distribution of SMs in cells and skin. (A) Mass spectra of lipids (shown in Fig. S2) derived from HEK293 cells and human skin are shown as MS intensity values for each of 30 possible chain length and saturation variants of SM, where length is the number of methylene units in the fatty acyl and sphingosine chains, and unsat is the number of unsaturations in both chains. (B) The 42/34 ratio is calculated based on the sum of intensity values of C42 SMs divided by the sum of intensity values of C34 SMs for each cell or tissue. Because C42 SMs are inhibitory and C34 SMs are weakly activating for T cells, higher ratios predict stronger inhibitory functions of SM profiles. (A and B) Results are representative of two experiments. (C) Collision-induced dissociation of natural 42:2 SM from HEK293T identified the neutral loss of the choline head group and, through chain cleavage products, the length of the sphingosine as predominantly C24:1 (m/z 390.5) acyl chain and C18:1 sphingosine chain in the synthetic standard and CD1a-eluted molecule. Similar analysis of the 34:2 SM demonstrated a C18 sphingosine chain and a C16 fatty acyl unit (Fig. S2). Thus, chain length variation is determined mainly or exclusively in the fatty acyl unit, so that 42 SMs are formed from VLCFAs and 34 SMs and 36 SMs are made from LCFAs. The position and Z or E stereochemistry are inferred from known lipid structures but cannot be established by MS.