2 research outputs found
Synthesis and Charge-Transfer Dynamics in a Ferrocene-Containing Organoboryl aza-BODIPY Donor–Acceptor Triad with Boron as the Hub
A <i>N</i>,<i>N</i>′-bisÂ(ferroceneacetylene)Âboryl
complex of 3,3′-diphenylazadiisoindolylmethene was synthesized
by the reaction of an <i>N</i>,<i>N</i>′-difluoroboryl
complex of 3,3′-diphenylazadiisoindolylmethene and ferroceneacetylene
magnesium bromide. The novel diiron complex was characterized by a
variety of spectroscopic techniques, electrochemistry, and ultrafast
time-resolved methods. Spectroscopy and redox behavior was correlated
with the density functional theory (DFT) and time-dependent DFT calculations.
An unexpected degree of coupling between the two Fc ligands was observed.
Despite a lack of conjugation between the donor and acceptor, the
complex undergoes very rapid (τ = 1.7 ± 0.1 ps) photoinduced
intramolecular charge separation followed by subpicosecond charge
recombination to form a triplet state with a lifetime of 4.8 ±
0.1 μs
Nitrodibenzofuran: A One- and Two-Photon Sensitive Protecting Group That Is Superior to Brominated Hydroxycoumarin for Thiol Caging in Peptides
Photoremovable
protecting groups are important for a wide range
of applications in peptide chemistry. Using Fmoc-CysÂ(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-CysÂ(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