SecA ATPase is a critical member of the Sec system, which is important in the translocation of membrane and secreted polypeptides/proteins in bacteria. Small molecule inhibitors can be very useful research tools as well as leads for future antimicrobial agent development. Based on previous virtual screening work, we optimized the structures of two hit compounds and obtained SecA ATPase inhibitors with IC50 in the single digit micromolar range. These represent the first low micromolar inhibitors of bacterial SecA and will be very useful for mechanistic studies. Post synthetic modification is an important and efficient way of DNA functionalization especially in DNA aptamer selection. In this research, the feasibility of norbornene (Neo) modified thymidine triphosphate incorporation was described. Besides, substituted tetrazines have been found to undergo facile inversed electron demand Diels-Alder reactions with "tunable" reaction rates. This finding paves the way to utilize tetrazine conjugation reactions for not only DNA but also other labeling work.