Paclitaxel: Difference between revisions

Paclitaxel has the molecular formula C₄₇H₅₁NO₁₄ and has a molecular weight of 853.92 Da, a melting point of 213°C and a boiling point of 218-222°C. <scene name='80/809872/Sami_scene_4/2'>Paclitaxel</scene> is a complex diterpene having a taxane ring with a four-membered oxetane ring and an ester side chain at position C-13. Microtubules are long, hollow cylinders made up of polymerized α- and β- tubulin dimers and are approximately 24 nm in diameter. <ref>DOI: 10.1016/S0960-9822(95)00180-1</ref> <scene name='80/809872/Sami_scene_6/1'>α and β tubulin</scene> <ref>DOI: 10.2210/pdb5SYF/pdb</ref> The walls of microtubules consist of a lattice of tubulin heterodimers that are arranged head-to-tail to form protofilaments. The α- and β- tubulin dimers polymerize end-to-end and associate laterally to form a single microtubule. The two subunits are 50% identical in terms of amino acids, with each subunit having a molecular weight of 50 kDa. Tubulin polymerizes end to end, with the β- subunits of one tubulin dimer, binding to the α- subunit of the next dimer. This results in a protofilament containing one end with an α- subunit exposed, and one end with a β- subunit exposed. These ends are designated (-) and (+), respectively. The protofilaments align parallel to one another according to polarity, therefore in a microtubule, there is one end with only  β- subunits (+), and the other end with only α- subunits (-). Elongation occurs at both ends, however, it is a lot more rapid at the (+) end.