Hypothetical membrane domains, called lipid raft domains, have been investigated, using single-molecule tracking. Such domains are formed on-demand upon stimulation-induced clustering of raft-associable receptors. Furthermore, signaling molecules are recruited to such induced rafts transiently (of the order of 0.1 s). Therefore, we propose that raft-related bulk intracellular signals that tend to last over 1000 s might be pulse coded or frequency modulated by the pulse-like digital activation of individual molecules, and that the intensity of the bulk signal might mainly be determined by the number of pulses at a given time.
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