1. Cyclobutane exists predominantly in a " butterfly " conformation.

2. Aim To improve the synthetic procedure of bromomethyl cyclobutane .

3. UV-B-induced cyclobutane pyrimidine dimmers (CPD) in the DNA of rice seedlings were measured using ELISA with specific monoclonal antibody.

4. On the other hand , cyclobutane pyrimidine dimmer ( CPD ) just has an effect of cell cycle arrest.

5. Photoreactivating enzyme (DNA photolyase) repairs DNA by utilizing the energy of visible light to break the cyclobutane ring of the dimer.

6. Ten of them were identified. They are ethylene, propylene, isobutane, cyclobutane, three isomeric butenes, methyl ethyl ether, ethyl isopropyl ether, and ethyl acetate.

7. In this paper, recent progresses in model studies of cyclobutane pyrimidine dimer photolyases and (6-4) photoproduct photolyases have been reviewed.