Cell-penetrating peptides show promise in the treatment of certain infections and cancers. The mechanisms by which such peptides transverse the membrane are not fully understood. As part of a program focused on labeling amino acids with fluorescent antimicrobial groups, we found that the electronic excited state of a naphthalimide-arginine conjugate (Boc-Arg(naph)-OH) has a remarkably low pKa of ~0.9. Natural arginine residues (pKa = 12.5) are positively charged at physiological pH and are essentially never found in contact with the hydrophobic core of lipid bilayers. The goal of this project is to manipulate the electrical charge of this arginine fluorophore using irradiation by visible light, thereby controlling its membrane incorporation. Assays of calcein leakage from POPC liposomes, under both light and dark conditions, will be presented.

Excited-state properties of fluorescent arginine: Toward light-promoted cellular penetration

253rd National Meeting (2017)

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