A lipid particle comprising a lipid having the structure or a salt thereof, wherein: R 1 and R 2 are each independently C 10 -C 20 alkenyl; R 3 is ω-aminoalkyl, ω-(substituted)aminoalkyl, or ω-thiophosphoalkyl, wherein the term "substituted" refers to the replacement of one or more hydrogen radicals with the radical of a substituent selected from the group consisting of halo, alkyl, alkenyl, alkynyl, aryl, heterocyclyl, thiol, alkylthio, oxo, thioxy, arylthio, alkylthioalkyl, arylthioalkyl, alkylsulfonyl, alkylsulfonylalkyl, arylsulfonylalkyl, alkoxy, aryloxy, aralkoxy, aminocarbonyl, alkylaminocarbonyl, arylaminocarbonyl, alkoxycarbonyl, aryloxycarbonyl, haloalkyl, amino, trifluoromethyl, cyano, nitro, alkylamino, arylamino, alkylaminoalkyl, arylaminoalkyl, aminoalkylamino, hydroxy, alkoxyalkyl, carboxyalkyl, alkoxycarbonylalkyl, aminocarbonylalkyl, acyl, aralkoxycarbonyl, carboxylic acid, sulfonic acid, sulfonyl, phosphonic acid, aryl, heteroaryl, heterocyclic, and aliphatic, wherein the substituent may be further substituted with a substituent, selected from the group consisting of amino, alkylamino, dialkylamino, and cyclic amino compounds; and E is C(O)O. or a salt thereof, wherein: R 1 and R 2 are each independently C 10 -C 20 alkenyl; R 3 is ω-aminoalkyl, ω-(substituted)aminoalkyl, or ω-thiophosphoalkyl, wherein the term "substituted" refers to the replacement of one or more hydrogen radicals with the radical of a substituent selected from the group consisting of halo, alkyl, alkenyl, alkynyl, aryl, heterocyclyl, thiol, alkylthio, oxo, thioxy, arylthio, alkylthioalkyl, arylthioalkyl, alkylsulfonyl, alkylsulfonylalkyl, arylsulfonylalkyl, alkoxy, aryloxy, aralkoxy, aminocarbonyl, alkylaminocarbonyl, arylaminocarbonyl, alkoxycarbonyl, aryloxycarbonyl, haloalkyl, amino, trifluoromethyl, cyano, nitro, alkylamino, arylamino, alkylaminoalkyl, arylaminoalkyl, aminoalkylamino, hydroxy, alkoxyalkyl, carboxyalkyl, alkoxycarbonylalkyl, aminocarbonylalkyl, acyl, aralkoxycarbonyl, carboxylic acid, sulfonic acid, sulfonyl, phosphonic acid, aryl, heteroaryl, heterocyclic, and aliphatic, wherein the substituent may be further substituted with a substituent, selected from the group consisting of amino, alkylamino, dialkylamino, and cyclic amino compounds; and E is C(O)O. R 1 and R 2 are each independently C 10 -C 20 alkenyl; R 3 is ω-aminoalkyl, ω-(substituted)aminoalkyl, or ω-thiophosphoalkyl, wherein the term "substituted" refers to the replacement of one or more hydrogen radicals with the radical of a substituent selected from the group consisting of halo, alkyl, alkenyl, alkynyl, aryl, heterocyclyl, thiol, alkylthio, oxo, thioxy, arylthio, alkylthioalkyl, arylthioalkyl, alkylsulfonyl, alkylsulfonylalkyl, arylsulfonylalkyl, alkoxy, aryloxy, aralkoxy, aminocarbonyl, alkylaminocarbonyl, arylaminocarbonyl, alkoxycarbonyl, aryloxycarbonyl, haloalkyl, amino, trifluoromethyl, cyano, nitro, alkylamino, arylamino, alkylaminoalkyl, arylaminoalkyl, aminoalkylamino, hydroxy, alkoxyalkyl, carboxyalkyl, alkoxycarbonylalkyl, aminocarbonylalkyl, acyl, aralkoxycarbonyl, carboxylic acid, sulfonic acid, sulfonyl, phosphonic acid, aryl, heteroaryl, heterocyclic, and aliphatic, wherein the substituent may be further substituted with a substituent, selected from the group consisting of amino, alkylamino, dialkylamino, and cyclic amino compounds; and E is C(O)O. <EOS>