5345
There is broad evidence that association of transmembrane receptors and signalling molecules with lipid rafts / caveolae provides an enriched environment for protein - protein interactions necessary for signal transduction , and a mechanism for the modulation of neurotransmitter and / or growth factor receptor function .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 None