A new class of shape-modified nucleosides is introduced. These novel “fleximers” feature the purine ring systems of adenosine, inosine, and guanosine split into their individual imidazole and pyrimidine components (as in 1−3). This structural modification serves to introduce flexibility into the nucleoside while still retaining the elements essential for recognition. As a consequence, these novel fleximers should find use as bioprobes for investigating enzyme−coenzyme binding sites as well as nucleic acid and protein interactions. Their design and synthesis are described.