Tunable Coassembly\nof Octaarginine with Thiazolyl\nBenzenesulfonamides Exerts Variable Antibacterial Activity

The\ncationic peptide octaarginine (R8) is a prominent cell-penetrating\npeptide and has been extensively researched as a carrier of diverse\ncell-destined cargo. In this work, we describe the coassembly of R8\nwith small molecule thiazolyl benzenesulfonamide (TBS) derivatives.\nPhysical complexation of R8 with three TBS derivatives across a range\nof weight ratios results in the formation of a distinctive set of\nnano- and microstructures. A detailed structural characterization\nof the R8:TBS-derivative coassemblies has been performed by a combination\nof FTIR, XRD, SEM, and DSC. The major functional groups that facilitate\ncoassembly include sulfonamide SO<sub>2</sub> and NH groups of the\nTBS derivatives, and the guanidinium of R8, via a combination of cation-π\nand hydrogen-bonding interactions. The R8:4F-TBS coassembly displays\nsingular topological features compared to R8:4Br-TBS and R8:4CH<sub>3</sub>-TBS complexes. These differences are attributed to the changes\nin the preferred orientation of the guanidino groups of R8 with respect\nto the π-surface of TBS derivatives. The modulation of forces\nof interaction across the R8:TBS-derivative coassemblies aligns with\ntheir respective thermal stabilities. The single-crystal structure\nof bare 4F-TBS has been subjected to Hirshfeld and 2D fingerprinting\nanalysis and indicates notable variations from the crystal packing\nof the R8:4F-TBS coassembly. The structural differences among the\nR8:TBS-derivative coassemblies correlate with distinctive profiles\nof antibacterial activity in each case. The coassembled structures\nexert a variable extent of bacterial membrane disruption and damage\nbased on the unique disposition of R8 and the potency of small molecule\nin each case. The aqueous suspension of R8:4F-TBS displays significant\nouter membrane disruption and bacterial killing compared with the\nother complexes. This work successfully demonstrates the hitherto\nunreported potential for coassembly of cell-penetrating peptides with\nother entities. The coassembly of R8 with small molecules highlights\nan attractive strategy for tuning the functional properties of each\ncomponent.