Induction of metachromasia and circular dichroism in the dye 1,9-dimethyl methylene blue by S. aureus wall teichoic acid.

ABSTRACT

Teichoic acid (TA) isolated from the Gram-positive bacteria Staphylococcus aureus induces blue shifted metachromasia in the dye 1,9-dimethyl methyleneblue (DMMB). Results of conductometric titrations show that DMMB binds to TA with 11 stoichiometry. Unlike DNA, this TA does not induce a definite metachromatic band in the dye acridine orange. S. aureus TA also induces strong circular dichroism (CD) in this dye with molar ellipticity value of the order of 10(4). This induction of CD in DMMB supports our earlier inference that TA in dilute solution at neutral pH has a helical conformation, and is not a random coil polymer.