Thiogalactosides are a type of chemical compound that contain a sulfur atom in place of an oxygen atom in the galactoside structure. They are often used in biological research to study the function of certain enzymes and proteins, particularly those involved in carbohydrate metabolism. These compounds can act as substrates for specific enzymes, allowing scientists to investigate how these enzymes interact with sugars. Thiogalactosides are particularly relevant in studies involving E. coli and other microorganisms, where they help in understanding the mechanisms of glycosylation and cell signaling.