The nucleoside analogue MANT GDP has a modified ribose group. The compactness of the MANT fluorophore and its attachment site allows nucleoside analogues to have little interference with nucleotide-protein interactions. Because MANT fluorescence is sensitive to the environment of the fluorophore, nucleotide-protein interactions can be directly detected. MANT nucleotides are important probes for detecting the structure and enzymatic activity of nucleotide-binding proteins.