Teichoic acids substitution

The n.m.r, spectra of a number of ribitol teichoic acids substituted with... 

Teiehoic Acids.—The "C n.m.r. spectra of a number of ribitol teichoic acids substituted with glycosyl residues, and of their dephosphorylated repeating units, have been recorded. Identical spectra are obtained for teichoic acids substituted with 2-0- and 4-0-glycosyl residues, so it is not possible to differentiate between these positional isomers by this technique. 

Teichoic acids (TAs), naturally occurring polyphosphates of substituted glycerol (7) or ribitol (2) in the simpler cases, are biopolymers isolated from the cell walls (wall TAs) or membranes [membrane TAs or lipoteichoic acids (LTAs)] of various Grampositive bacteria ... 

Typical wall teichoic acids are the linear polyphosphates of glycerol-1,3 or D-ribitol-1,5. Their average polymerization degree varies from 30 to 40. Carbon atoms at positions 2 and 4 in the ribitol and at position 2 in the glycerol moieties are substituted with sugar residues or with D-alanyl ester groups as shown 7 and 2 8). 

The exterior surface of Gram-positive bacteria is covered by teichoic acids. These are ribitol-phosphate or glycerol-phosphate polymer chains that are frequently substituted by alanine and glycosidically linked monosaccharides (Figure A2.4). They are attached to the peptidoglycan by a phosphate diester link. Teichoic acids can act as receptors to bacteriophages and some appear to have antigenic properties. 

Side branches on teichoic acids are single sugar residues or short oligosaccharides and, again, are often composed of glucose or A-acetylglucos-amine. Unusual or rare amino-sugars are sometimes found and substitution of saccharide branches or main chains with D-alanine is quite common. 

Many teichoic acids are substituted, by way of their hydroxyl groups, with glycosyl residues and D-alanine, and a certain amount is known about the stages at which these are inserted, albeit on the basis of rather few examples. 

The cell walls and membranes of most gram-positive bacteria contain a series of highly anionic polymers. Most important among these is teichoic add, which is a polymer of glucose 1-phosphate or ribitol phosphate. Membrane teichoic acids are based on glucose 1-phosphate and a proportion may be linked to glycolipids to give lipoteichoic acids. The details of these structures and the amount of substitution of the teichoic acids vary with bacterial species. 

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