What is described is a lipid particle comprising the compound of formula I ##STR00001##
wherein R.sub.1 consists of alkyl, alkenyl, alkynyl, or cholesteryl; R.sub.2 consists of alkyl or alkenyl; L.sub.1 consists of alkyl, alkylene or alkenyl; X.sub.1 consists of O(CO) or (CO)O; X.sub.2 consists of S or O; L.sub.2 consists of a bond or alkylene; R.sub.3 consists of alkylene; and R.sub.4 and R.sub.5 are the same or different, each consisting of alkyl;
or a pharmaceutical preparation thereof.

What is described is a lipid particle comprising the compound of formula I ##STR00001##
wherein R.sub.1 consists of alkyl, alkenyl, alkynyl, or cholesteryl; R.sub.2 consists of alkyl or alkenyl; L.sub.1 consists of alkyl, alkylene or alkenyl; X.sub.1 consists of O(CO) or (CO)O; X.sub.2 consists of S or O; L.sub.2 consists of a bond or alkylene; R.sub.3 consists of alkylene; and R.sub.4 and R.sub.5 are the same or different, each consisting of alkyl;
or a pharmaceutical preparation thereof.

Amines and amine derivatives that improve the buffering range, and/or reduce the chelation and other negative interactions of the buffer and the system to be buffered. The reaction of amines or polyamines with various molecules to form polyamines with differing pKa's will extend the buffering range, derivatives that result in polyamines that have the same pKa yields a greater buffering capacity. Derivatives that result in zwitterionic buffers improve yield by allowing a greater range of stability.

What are described are compounds of formula II. The compound of formula II ##STR00001##
consists of a compound in which R.sub.1 and R.sub.2 are both a linear alkyl consisting of 1 to 12 carbons, an alkenyl or alkynyl consisting of 2 to 12 carbons; L.sub.1 and L.sub.2 both consist of a linear alkylene or alkenylene consisting of 5 to 18 carbons; X is S; L.sub.3 consists of a bond; R.sub.3 consists of a linear or branched alkylene consisting of 1 to 6 carbons; and R.sub.4 and R.sub.5 are the same or different, each consisting of hydrogen or a linear or branched alkyl consisting of 1 to 6 carbons; or a pharmaceutically acceptable salt thereof.

What are described are compounds of formula II. The compound of formula II ##STR00001##
consists of a compound in which R.sub.1 and R.sub.2 are both a linear alkyl consisting of 1 to 12 carbons, an alkenyl or alkynyl consisting of 2 to 12 carbons; L.sub.1 and L.sub.2 both consist of a linear alkylene or alkenylene consisting of 5 to 18 carbons; X is S; L.sub.3 consists of a bond; R.sub.3 consists of a linear or branched alkylene consisting of 1 to 6 carbons; and R.sub.4 and R.sub.5 are the same or different, each consisting of hydrogen or a linear or branched alkyl consisting of 1 to 6 carbons; or a pharmaceutically acceptable salt thereof.

What is described is a method of synthesis of the compound of formula 1A, ##STR00001##
or a salt thereof, wherein R.sub.3 is a linear or branched alkene of 1, 2, 3, 4, 5 or 6 carbons; R.sub.4 and R.sub.5 are the same or different, each a hydrogen, or a linear or branched alkyl of 1, 2, 3, 4, 5 or 6 carbons; and L.sub.3 is a bond or an alkane of 1, 2, 3, 4, 5 or 6 carbons.

What is described is a method of synthesis of the compound of formula 1A, ##STR00001##
or a salt thereof, wherein R.sub.3 is a linear or branched alkene of 1, 2, 3, 4, 5 or 6 carbons; R.sub.4 and R.sub.5 are the same or different, each a hydrogen, or a linear or branched alkyl of 1, 2, 3, 4, 5 or 6 carbons; and L.sub.3 is a bond or an alkane of 1, 2, 3, 4, 5 or 6 carbons.

A high-molecular-weight compound having a plurality of polymer chains linked through a divalent or higher-valent linking group, in which the divalent or higher-valent linking group has a thiol group and at least one of a thioether structure and a thiourethane structure, and a ratio of an absolute weight-average molecular weight to a relative weight-average molecular weight (absolute Mw/relative Mw) of the high-molecular-weight compound is 1.25 or more; and a method for producing the same are provided.

A high-molecular-weight compound having a plurality of polymer chains linked through a divalent or higher-valent linking group, in which the divalent or higher-valent linking group has a thiol group and at least one of a thioether structure and a thiourethane structure, and a ratio of an absolute weight-average molecular weight to a relative weight-average molecular weight (absolute Mw/relative Mw) of the high-molecular-weight compound is 1.25 or more; and a method for producing the same are provided.

A cationic lipid compound, a preparation method and a use thereof, and a delivery system for mRNA are provided. The cationic lipid compound has a structure represented by formula (I):

##STR00001##

In formula (I): X is O or N; n is 2-4; m is 2-4; a is 0 or 1; R.sub.1 is a chain structure comprising a tertiary amine; R.sub.2 is a linear fatty acyl group or a branched chain fatty acyl group; R.sub.3 is a branched chain fatty acyl group. The cationic lipid compound is used for preparing a delivery system for mRNA.