Radiation damage to living cells is initiated via a variety of molecular lesions which mostly result from the attacks of secondary species generated by raw high-energy quanta. Since the seminal experiments of Sanche's group demonstrate that low-energy electron (LEE) attachment to DNA can incur strand breaks through resonant processes, copious amounts of research have been devoted to study the dissociative electron attachment (DEA) to biomolecules initiated from resonance anionic states. Biomolecules include nucleobases, sugars, phosphates, amino acids, et al. The five-membered ring is a commonly occurring biomolecular structure that also plays anactive role in various biochemical processes. My work in this dissertation shows DEA can induce ring opening for aromatic five-membered ring compounds, such as isoxazole, oxazole, and thiazole. Especially, for isoxazole the observation that all the ring opening pathways are conducted through O-N bond cleavage. This observation is of special interest to pharmaceutical engineering because the biotransformation of several isoxazole substructure containing drugs are found downstream from O-N bond cleavage.  Besides the five-member ring compounds, the LEE destructive impact on peptide linkage has been studied through DEA to peptide model molecules, such as formamideand its methylated derivatives. Peptide bond cleavage induced by DEA clearly demonstrates bond selectivity, which is susceptible when the LEE energy falls between 5to 8 eV. Resonance states responsible for the cleavage are found by my stabilization calculations which show that an anti-bonding force is exerted on the peptide bond by the attached electron through forming a π* type orbital around this bond. In addition to the conventional DEA study through measuring the anion yields, an experimental methodology called stepwise electron spectroscopy for detection of neutral products from DEA was proposed and successfully applied to detect and characterize neutrals formed via DEA to CCl4. This experimental procedure can be extended to investigate more radicals resulting from DEA processes.