Raft concept

A variety of studies demonstrate a central role for ASM and ceramide in several forms of apoptosis. Ceramide seems to regulate the activity of certain proteins and, thus, may function, in some circumstances, as a second messenger. In addition, the concept of raft modification hy ceramide provides a comprehensive model for cellular effects of ceramide, and perhaps a biophysical explanation for the diverse functions of this lipid. 

This technique for controlling radical polymerizations is based on one of the oldest technique, that of chain transfer, and has often been used in telomeriza-tion [83]. Similar to the concept of degenerative transfer with alkyl iodides [50, 51, 84], reversible addition fragmentation chain transfer with dithio esters (RAFT) [52-55, 85] is successful because the rate constant of chain transfer is faster than the rate constant of propagation. Analogous to both nitroxide-medi-... 

The existence of lipid rafts and their function is still an evolving area of research (D.A. Brown, 2006). Isolation and characterization of detergent-resistant membrane fractions, studies in model systems, and studies with whole cells all support the concept of lipid rafts. However, they have never been observed in eukaryotic cells in the native state, presumably due to their dynamic properties. 

The RAFT-HDA concept relies heavily on the provision of diene-capped polymers, specifically those carrying the reactive cyclopentadienyl (Cp) group. Recently, a mild ambient-temperature approach towards Cp-capped polymers was introduced, whereby the use of nickelocene allowed the transformation of virtually all ATRP-prepared polymers into Cp-capped entities, in quantitative fashion [56]. Notably, the RAFT-HDA approach is not only suited to the preparation of block copolymers (or more complex structures) [57] rather, it has been exploited as a... 

Dynamic covalent chemistry has in recent years complemented tmly noncovalent and metal-bgand chemistries. Jackson and Fulton expanded this concept to block copolymer synthesis. Aldehyde and alkoxyamine functional polymeis prepared by RAFT polymerization react to form oxime bonds, a dynamic link that can be reversed tbrougb equUibriinn perturbations. The block copolymers formed were capable of furtber self-assembly into micellar sttuctures. 

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