Protein-polysaccharide lipopolysaccharides

In summary, all bacterial cell walls appear to contain short peptides of variable sequence, which cross-link amino-sugar glycan chains to form macromolecular networks important for the integrity of the bacterial cells. Linked to the networks (covalently or otherwise) are a variety of structures including proteins, polysaccharides, lipopolysaccharides, teichoic... 

Myeloma proteins occur in animal tumors of various types. The synthesis of these proteins can be induced in some experimental animals by injection of mineral oil, or the implantation of plastic discs.161 Myeloma proteins were shown to possess antibody activity, with specificity for different types of substances.161 Some of these proteins were found to combine with such carbohydrates as bacterial, cell-wall polysaccharides, lipopolysaccharides, dextrans, levans, and galactans.162 Myeloma proteins that combine with galactans or dextrans possess anti-galactan activity,163,164 or anti-dextran activity,165-167 and have been studied most extensively. 

Polysaccharides may be attached to proteins, in which case they are known as protein-polysaccharides, when they originate from plants, or proteoglycans, when they originate from animals. Polysaccharides may also contain lipid components. Lipopolysaccharides and other mycobacterial constituents are covered in Chap. 6.5 and Chap. 7. 

The field is actually in a good position to contribute to the development of bacterial polysaccharide glycoconjugate vaccines. Numerous fragments of capsular polysaccharides, lipopolysaccharides, or other bacterial carbohydrates have been synthesized and their protein conjugates obtained [87]. 

The next barrier present in gram-negative bacteria is also a continuous, but a much more compact, layer of closely packed macromolecules. This entity, referred to as the outer membrane, consists predominantly of lipopolysaccharides (LPS), proteins, and phospholipids. The proteins have been estimated to contribute to about 50% of the surface area of this layer. The lipid-protein-polysaccharide components of the outer membrane form a matrix which appears in cross section as a typical double-tracked structure, similar to a phospholipid bilayer. This matrix is involved in a multiplicity of interactions of the cell surface with its exterior and interior environment. The outer membrane is known to function as a barrier to a large number of compounds, such as the antibiotics, actinomycin D, penicillin G, polymyxin, and bacitracin. In addition to preventing the entry of certain compounds, the outer membrane can also be viewed as a means of keeping enzymes of the periplasmic space trapped within the domain of the cell. 

Cell wall Peptidoglycan a rigid framework of polysaccharide cross-linked by short peptide chains. Some bacteria possess a lipopolysaccharide- and protein-rich outer membrane. Mechanical support, shape, and protection against swelling in hypotonic media. The cell wall is a porous nonselective barrier that allows most small molecules to pass. 

As may be seen from Table I (see p. 327), MOPC 384 precipitates with the lipopolysaccharides from Proteus mirabilis sp2, Salmonella tranaroa, Escherichia coli 070, and Salmonella telaviv.7s Precipitation with the latter polysaccharide can be inhibited with methyl ct-D-galactopyranoside. No inhibition could be achieved by using p-aminophenyl 1-thio-a-D-galactopyranoside,85 but the specificity of this protein nevertheless appears to be for a-D-linked D-galac-topyranosyl residues. 

Capsular polysaccharides (CPS) and lipopolysaccharides from bacteria are employed for the production of vaccines against human diseases. Initial development of CPS as a vaccine was followed by the development and introduction of conjugate polysaccharide-protein vaccines. The principles leading to both developments are reviewed. 

Since LPS varies in chemical composition from one bacterial species to another, different methods are used for its extraction. LPS is generally extracted from smooth strains of bacteria in a mixture of phenol and water (PW) at 68°C as described by Westphal and Jann (19). After extraction, the solution is allowed to cool and partition. Nearly all proteins remain in the phenol phase or interphase, while polysaccharides, LPS, and nucleic acids remain in the aqueous phase. In some instances, the LPS from certain organisms (i.e. Brucella abortus) remain in the phenol phase. Lipopolysaccharide is extracted from rough strains of bacteria in a mixture of phenol, chloroform, and petroleum ether (PCP) at room temperature as described by Galanos, et (20). After extraction, the chloroform and petroleum ether are removed by rotary evaporation and the LPS is then precipitated from the phenol with water. With some bacteria, PW or PCP will not extract sufficient quantities of LPS (21) and EDTA (22), chloroform-methanol (23), or butanol (11) must be used. 

---