Sialic acid doesn't have one single formula, as it encompasses a family of over 50 different derivatives. However, the most common naturally occurring sialic acid is N-acetylneuraminic acid (Neu5Ac).
Common Forms of Sialic Acid and Their Formulas:
The major naturally occurring sialic acids include:
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N-Acetylneuraminic acid (Neu5Ac): This is the most prevalent form. Its molecular formula is C11H19NO9.
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N-Glycolylneuraminic acid (Neu5Gc): This form is similar to Neu5Ac but has a glycolyl group instead of an acetyl group. Its molecular formula is C11H19NO10.
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2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (Kdn): Also known as deaminoneuraminic acid, Kdn lacks the N-acetyl or N-glycolyl group. Its molecular formula is C9H14O8.
Therefore, while the question asks for the formula, it is more accurate to provide the formulas of the most common sialic acids, as there isn't one definitive answer. Each form has a slightly different molecular structure and thus, a different formula.
