"Structure and function of an acetylcholine receptor" "Structure and function of an acetylcholine receptor" "Structure and function of an acetylcholine receptor" "Structure and function of an acetylcholine receptor" "Structure and function of an acetylcholine receptor" "Structure and function of an acetylcholine receptor" "Structure and function of an acetylcholine receptor" "Structure and function of an acetylcholine receptor" "Structure and function of an acetylcholine receptor" PubMed Central