On the cover: Intermolecular ionic interactions between lipid A and human TLR4 are key interactions in the human TLR4/MD-2/LPS cocrystal structure. Color scheme: TLR4 is white and light purple (surface view), MD-2 is yellow and brown (surface view), and the lipid A portion of LPS is green and red (stick view). The graphics were created in PyMol. Meng, J., M. Gong, H. Björkbacka, and D. T. Golenbock. 2011. Genome-wide expression profiling and mutagenesis studies reveal that lipopolysaccharide responsiveness appears to be absolutely dependent on TLR4 and MD-2 expression and is dependent upon intermolecular ionic interactions. J. Immunol. 187: 3683–3693.