Aptamer transcription factor inhibition, molecular model. This is an RNA (ribonucleic) aptamer (green), inhibiting the effect of a transcription factor (blue and yellow). Nucleic acid aptamers are structures engineered to affect genetic and biochemical processes. The aptamer is shown both as a ribbon and ball-and-stick structure and as a surface (solid) structure. This is the NF-kB transcription factor, which mediates the response to inflammation. It is part of the response to both inflammatory cytokines, as well as inflammation caused by pathogens or the response to pathogens.