Typical intestinal bacterial lipid A is 1,4-diphosphate- β 1,6 linked glycosaminodisaccharides as the backbone, and linked 3-hydroxy fatty acids or 3-acyl carboxyl residues with amide and ester bonds. This structure is not common to all gram-negative bacteria. In particular, the above structures are not often encountered in families that are far away from coliform bacteria, such as Bradyrhizobia.

At first, the structure of derived lipid A was considered an "abnormal" lipid A type, and now it is renamed as lipid A variant. For example, Thiobacillus, Rhizobiaceae, Nitrobacter, Brucella, Chromatim Party, Chlorobium N ad son, etc. There are obvious changes in the skeleton structure of LPS, and in its substitution. The lipid A variant has a transitional type (or transformed) form, in Rhodobacter sphaeroides, only part of amide-linked 3-hydroxy fatty acid is replaced by 3-oxymyristic acid. As a lipid, A skeleton polysaccharide, the glycosamine of pigmented bacteria is always accompanied by a small amount of 2,3-diamino-2,3-dideoxy-D-glucose (DAG) connection.

DAG only exists in lipid A skeleton sugar. The uronic acid derivative of 2,3-diamine-2,3-dideoxhexose has been reported as a bacterial antigen (O chain) of different serotypes of Pseudomonas aeruginosa.

3-oxymyristic acid: The presence of 3-oxymyristic acid was first reported in the Listenella anguillarum and erythroid bacteria. Now, in fact, all species and strains of gram-negative bacteria α- 3 branches can be observed.

The endotoxin with the most significant biological effect is heterogeneous LPS, which is often used as the standard to test the cell reaction and carry out research on the therapeutic effect. Its biological activity part of lipid A is composed of β- 1,6 composed of D-glucosamine disaccharide and six saturated fatty acids and two negatively charged phosphate radicals. Changes in the arrangement of these structures, such as the reduction of the number of charges, the reduction of fatty acyl groups, the change of the distribution of fatty acyl chains, and the degree of fatty acyl saturation can lead to the decline of their biological activities. It shows that the change in the primary structure of endotoxin will inevitably affect its physicochemical action. Seydel et al. confirmed that the stereostructure of LPS in endotoxin is closely related to its biological effects. Different three-dimensional structures can produce different effects. Generally speaking, the conical spatial structure often leads to the activation effect of cells, while the cylindrical spatial structure of LPS is often an antagonist of endotoxin to inhibit the activation of cells.