Compositions and methods for the photocleavage of DNA and similar molecules are disclosed. The compositions are solutions having 1) an oligomer having a sugar-phosphate backbone; 2) an organic oxyradical precursor compound which is capable of generating an organic oxyradical a) by direct photo-excitation or b) by accepting an electron from a dye and upon receiving the electron, releasing an organic oxyradical. The composition can also contain a dye that is capable of absorbing light and transferring an electron to the oxyradical precursor. The method includes the step of forming the above solution and then exposing the solution to light of a wavelength so as to generate an oxyradical which cleaves the sugar-phosphate backbone.