Deuterated, Odd-Chain, & Fluorescent Standards for Sphingolipidomics
Over the past decade sphingolipids have gained enormous recognition as vital and complex components of biological systems. For many years lipids in general, and sphingolipids in particular, have received far less attention than their critical functions deserve. Many reasons contributed to this oversight including the difficulty of extraction and analysis as well as their tremendous diversity in structure and function(1,2). Another problem was the very limited availability of appropriate natural and synthetic
sphingolipid standards. Recently there has been a welcome advance in making standards available, as well as methods, which allow for the relatively quick extraction and analysis of whole classes of sphingolipids from small samples. This advance has greatly accelerated the approach known as sphingolipidomics and has tremendously accelerated the understanding and classification of sphingolipids.
Sphingolipidomics is the determination of the complete sphingolipid profile of a given system and the metabolism and pathways of those sphingolipids. It is the sphingolipid subfield of the greater lipidomic discipline and began to appear as a distinct discipline around 2005(3,4). There are tens of thousands of possible sphingolipids that vary in their polar head groups, acyl chains, and sphingoid bases. The metabolic pathway of these sphingolipids has been extensively studied in an attempt to understand and
treat diseases related to sphingolipids and to use sphingolipids to correct various diseases. Many of these sphingolipids are present in only nanomole to picomole/mg amounts, making detection difficult. However, with the incorporation of soft ionization techniques in mass spectrometry the detection of very small amounts of sphingolipids has been accomplished. The two major approaches of sphingolipidomics studies are the liquid chromatography (LC)-MS based methods and the shotgun lipidomics approach (1). In both methods internal standards for each individual sphingolipid detected would be ideal. However, due to the vast number of possible sphingolipids in a system this is impractical. Therefore the preferred method is to use internal standards for each class of sphingolipid expected to be found in a sample. To meet the need for standards in sphingolipidomic studies sphingolipids have been synthesized that are modified on either the oligosaccharide head, ceramide acyl chain, or the sphingosine tail.
These standards are usually stable isotope, unusual chain length, or fluorescent sphingolipids.
One of the most preferred internal standards for LC-MS and shotgun lipidomic studies are stable isotope labeled standards. These standards can be detected by mass spectrometry while demonstrating nearly identical physical properties with natural sphingolipids. This is very important to ensure similar losses during extraction between the analytes and the internal standards(1). Usually deuterium or 13C atoms are introduced in the acyl chain of the ceramide (see stable isotope sphingolipids below). However
the label can also be introduced in the sphingosine tail allowing for lyso-sphingolipids to be used (see cat. 2079). Another useful internal standard is one that has an acyl or sphingosine chain that has been modified to a length not commonly found in nature, usually C17 or C19 (see odd chain sphingolipids below).
Fluorescent standards have also been developed that can be detected in cultures and in biological systems making them ideal for studies involving the metabolism of sphingolipids (see fluorescent sphingolipids below). These are very advantageous for determining the localization of various sphingolipids in membranes and organelles(5). The NBD fluorescent group attached to hexanoic acid has been shown to be readily taken up by cells and used in the biosynthesis of more complex sphingolipids(6).
In addition to the internal standards mentioned above there is a need for standards that are natural sphingolipids and that can be compared to the analytes detected in samples. Methods have been developed to both synthesize these compounds and to extract them from natural sources. Matreya has many years of experience working with lipids and offers an extensive selection of these naturally occurring compounds. For our complete list please call us at (800) 342-3595 or visit us at www.matreya.com. Our
catalog is also available on our website.
1. Han, X., Jiang X., (2009) Eur J Lipid Sci Technol. 111(1):39–52
2. Futerman, A. and Hannun, Y., (2004) EMBO Reports, 5:777-782
3. Maceyka, M., Milstien, S., Spiegel, S., (2005) Prostaglandins Other Lipid Mediat. 77:15–22. [PubMed: 16099387]
4. Merrill, A.H. Jr., Sullards, M.C., Allegood, J.C., Kelly, S., Wang, E. (2005) Methods 36:207–224. [PubMed: 15894491]
5. Merrill, A.H. Jr., (2011) Chemical Reviews 111:6387-6422
6. Lipsky, N., Pagano, R., (1985) Journal of Cell Biology 100:27-34