Chemical tools for studying the biological function of glycolipids.

Glycolipids play an important role in many biological processes and to this end, synthetic chemists have developed a variety of new techniques and "chemical tools" that allow for the study of glycolipids in vitro and in vivo. The types of probes prepared include fluorescent, radio-labelled, biotinylated and photoreactive ones, as well as others based on liposomes, microarrays and other supramolecular constructs-each of which offers its own advantages, as is discussed. A number of more specialised probes, such as metabolically engineered glycolipids and photopolymerisable glycolipids, have also been prepared in order to investigate various processes including substrate specificities and binding interactions. The purpose of this review is to present the key approaches that can be used for the development of glycolipid probes, organised according to application, and also to discuss the limitations of such strategies, which include the nontrivial task of ensuring that the probe does not adversely influence the biological activity of the parent compound. On the whole, it is exciting to see what can be achieved through the development of chemical probes as tools to study biological processes, and it is envisioned that the reader will be inspired by the large number of superb studies highlighted here and will be encouraged to undertake further work in this research area.