Narrow Results

Continuous-wave linear-absorption spectroscopy based on THz radiation generated by solid-state photomixers has been applied to the investigation of the dynamics of biomolecules in polyethylene matrices and to line shape studies of HF for diagnostics of semiconductor etching plasmas. The THz spectra of biotin and myoglobin have been obtained using a variable-temperature, cryogenic sampling system. The spectrum of biotin displays a small number of discrete absorptions over the temperature range from 4.2 K to room temperature while the spectrum of myoglobin has no obvious resonance structure at the >10% fractional absorption level. Spectral predictions from the lowest energy ab initio conformations of biotin are in poor agreement with experiment, suggesting the need to include condensed-phase environmental interactions for qualitative predictions of the THz spectrum. Vibrational anharmonicity is used to model the line shapes that result from drastic changes in vibrational sequence level populations of biotin over this temperature range. Anharmonicity factors (χ_eω_e/ω_e) at the levels of 0.1% to 0.8% are obtained from non-linear least squares fits of the observed resonances and illustrate their important for refining model predictions. Application of the photomixer system to line shape studies in etching plasmas has been used to study the formation efficiency and translational temperature of HF at 1.2 THz under different operating conditions. These results will aid in understanding the chemistry of industry-standard fluorocarbon and oxygenated fluorocarbon etching plasmas.

The easily accessible 2,17-bis-chlorosulfonated 5,10,15-trispentafluorophenylcorrole is demonstrated as a highly versatile synthon for the preparation of corroles with functional groups that may be used for advanced applications and materials. Examples presented here are useful for donor-acceptor dyads, water-solubility inducing carbohydrates, chirality-inducing sugars and amino acids, and biotin-avidin technology.

Silicon (IV) phthalocyanines bearing one or two biotin groups on the axially positions were synthesized, and these novel phthalocyanines were characterized by elemental analysis and standard spectroscopic techniques such as FT-IR, ${}^{\mathrm{\text{1}}}$H NMR, UV-vis and MALDI-TOF. The synthesized compounds are the first examples of axially biotin substituted silicon (IV) phthalocyanines. These phthalocyanines were designed as targeting photosensitizers for the treatment of cancer by photodynamic therapy (PDT) technique. The phthalocyanine ring was selected for its photosensitizer ability and the biotin group was selected as a targeting agent for increasing accumulation of these photosensitizers in tumor cells. The photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen generation) properties of the target silicon(IV) phthalocyanines were investigated in DMSO. The photosensitizing efficiency of the studied phthalocyanines was tested against human cervical cancer (HeLa) cells at different photosensitizer concentrations. Both axially mono- and bis-biotin substituted silicon(IV) phthalocyanines present high photocytotoxicity against HeLa cancer cells with the cell survival degree ranging from 13% to 50%. The photosensitivity and the intensity of damage were found to be directly related to the concentration of the used photosensitizers. According to the obtained results, both silicon(IV) phthalocyanine derivatives could be promising as photosensitizers for treatment of cancer by PDT technique.

An isothiocyanato-functionalized phthalocyanine (Pc) was synthesized in good yield from the corresponding amine-substituted Pc. This Pc reacted with ethanolamine, biotin hydrazine, and biotin diethylamine under mild conditions (room temperature in DMF or DMSO in the presence of TEA) to produce the corresponding thiourea products in 60–75% yields. All Pcs showed intense Q absorptions in DMF around 677 nm, emissions centered at 683 nm, and fluorescence quantum yields in the range 0.18–0.27. The Pcs were phototoxic to human carcinoma HEp2 cells (IC${}_{50}$$\sim$ 7 at 1.5 J/cm${}^2)$ and localized in multiple organelles, including the lysosomes, Golgi and ER. One biotin-Pc conjugate was injected via tail vein into nude mice bearing HT-29 tumors and demonstrated selective localization in the tumor tissue.

Because streptavidin is a homotetramer, it can bind multiple biotinylated ligands and cause target aggregation. To allow biotin detection without clustering, we previously engineered monomeric streptavidin (mSA) that is structurally similar to a single streptavidin subunit. Introducing the S25H mutation near the binding site increases the biotin dissociation half-life t_1/2 to 83 minutes. The slowly dissociating mutant, mSA2, is useful in imaging studies because it allows stable labeling of biotinylated targets. We show that mSA2 conjugated with Alexa 488 binds biotinylated receptors on HEK293 with high specificity, and bound mSA2–Alexa488 does not dissociate significantly during an imaging study lasting 50 minutes. As a structural monomer, mSA2 can be fused to other proteins to create bifunctional molecules. We tested the use of mSA2 in proximity dependent biotinylation, in which mSA2 is fused to a peptide or a protein that binds a protein of interest (POI) and is used to recruit photoactivatable biotin (PA-biotin) to the target molecule. Once the resulting cluster of interacting proteins is subjected to UV-initiated distance-dependent biotinylation, subsequent affinity purification of biotinylated proteins on streptavidin beads can identify protein molecules that interact with POI. In addition to proteins that directly interact with the mSA2 fusion, mSA2 also induces biotinylation of other proteins that are associated through a series of noncovalent interactions. We show that mSA2 fused to an antibody recognition domain can be recruited to the kinase Erk-2 using a commercially available antibody and induce biotinylation of a known Erk-2 substrate, GST-Elk-1. Therefore, mSA2 can be used to implement proximity dependent biotinylation and detect transient enzyme-substrate interactions.

An isothiocyanato-functionalized phthalocyanine (Pc) was synthesized in good yield from the corresponding amine-substituted Pc. This Pc reacted with ethanolamine, biotin hydrazine, and biotin diethylamine under mild conditions (room temperature in DMF or DMSO in the presence of TEA) to produce the corresponding thiourea products in 60–75% yields. All Pcs showed intense Q absorptions in DMF around 677 nm, emissions centered at 683 nm, and fluorescence quantum yields in the range 0.18–0.27. The Pcs were phototoxic to human carcinoma HEp2 cells (IC₅₀ ~ 7 at 1.5 J/cm²) and localized in multiple organelles, including the lysosomes, Golgi and ER. One biotin-Pc conjugate was injected via tail vein into nude mice bearing HT-29 tumors and demonstrated selective localization in the tumor tissue.

Continuous-wave linear-absorption spectroscopy based on THz radiation generated by solid-state photomixers has been applied to the investigation of the dynamics of biomolecules in polyethylene matrices and to line shape studies of HF for diagnostics of semiconductor etching plasmas. The THz spectra of biotin and myoglobin have been obtained using a variable-temperature, cryogenic sampling system. The spectrum of biotin displays a small number of discrete absorptions over the temperature range from 4.2 K to room temperature while the spectrum of myoglobin has no obvious resonance structure at the >10% fractional absorption level. Spectral predictions from the lowest energy ab initio conformations of biotin are in poor agreement with experiment, suggesting the need to include condensed-phase environmental interactions for qualitative predictions of the THz spectrum. Vibrational anharmonicity is used to model the line shapes that result from drastic changes in vibrational sequence level populations of biotin over this temperature range. Anharmonicity factors (χ_eω_e/ω_e) at the levels of 0.1 % to 0.8 % are obtained from non-linear least squares fits of the observed resonances and illustrate their important for refining model predictions. Application of the photomixer system to line shape studies in etching plasmas has been used to study the formation efficiency and translational temperature of HF at 1.2 THz under different operating conditions. These results will aid in understanding the chemistry of industry-standard fluorocarbon and oxygenated fluorocarbon etching plasmas.