title: Nitrodibenzofuran: A One- and Two-Photon Sensitive Protecting Group That Is Superior to Brominated Hydroxycoumarin for Thiol Caging in Peptides.
abstract: Photoremovable protecting groups are important for a wide range of applications in peptide chemistry. Using Fmoc-Cys(Bhc-MOM)-OH, peptides containing a Bhc-protected cysteine residue can be easily prepared. However, such protected thiols can undergo isomerization to a dead-end product (a 4-methylcoumarin-3-yl thioether) upon photolysis. To circumvent that photoisomerization problem, we explored the use of nitrodibenzofuran (NDBF) for thiol protection by preparing cysteine-containing peptides where the thiol is masked with an NDBF group. This was accomplished by synthesizing Fmoc-Cys(NDBF)-OH and incorporating that residue into peptides by standard solid-phase peptide synthesis procedures. Irradiation with 365 nm light or two-photon excitation with 800 nm light resulted in efficient deprotection. To probe biological utility, thiol group uncaging was carried out using a peptide derived from the protein K-Ras4B to yield a sequence that is a known substrate for protein farnesyltransferase; irradiation of the NDBF-caged peptide in the presence of the enzyme resulted in the formation of the farnesylated product. Additionally, incubation of human ovarian carcinoma (SKOV3) cells with an NDBF-caged version of a farnesylated peptide followed by UV irradiation resulted in migration of the peptide from the cytosol/Golgi to the plasma membrane due to enzymatic palmitoylation. Overall, the high cleavage efficiency devoid of side reactions and significant two-photon cross-section of NDBF render it superior to Bhc for thiol group caging. This protecting group should be useful for a plethora of applications ranging from the development of light-activatable cysteine-containing peptides to the development of light-sensitive biomaterials.
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: M Mohsen
authors.initials: MM
authors.lastname: Mahmoodi
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Abate-Pella
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Tom J
authors.initials: TJ
authors.lastname: Pundsack
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Charuta C
authors.initials: CC
authors.lastname: Palsuledesai
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Philip C
authors.initials: PC
authors.lastname: Goff
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Blank
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Distefano
mesh_terms: D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000494:pharmacology; D001572:Benzofurans / Q000737:chemistry*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D003374:Coumarins / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry; D003600:Cytosol / Q000378:metabolism; D013186:Farnesyl-Diphosphate Farnesyltransferase / Q000037:antagonists & inhibitors; D005260:Female; D006056:Golgi Apparatus / Q000378:metabolism; D054879:Halogenation; D006801:Humans; D007202:Indicators and Reagents; D010051:Ovarian Neoplasms / Q000188:drug therapy; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry* / Q000494:pharmacology; D055668:Photochemical Processes; D017785:Photons; D060327:Solid-Phase Synthesis Techniques; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D000970:Antineoplastic Agents; D001572:Benzofurans; D003374:Coumarins; D007202:Indicators and Reagents; D010455:Peptides; D013438:Sulfhydryl Compounds; C067509:3-nitrodibenzofuran; D013186:Farnesyl-Diphosphate Farnesyltransferase; D003545:Cysteine