Copper-Catalyzed Arylation of 1\u3cem\u3eH\u3c/em\u3e-Perfluoroalkanes

A general method has been developed for arylation of readily available 1H-perfluoroalkanes. The method employs aryl iodide and 1H-perfluoroalkane reagents, DMPU solvent, TMP2Zn base, and a copper chloride/phenanthroline catalyst. Preliminary mechanistic studies are reported

Mechanistic studies of anti-hyperpigmentary compounds: elucidating their inhibitory and regulatory actions.

Searching for depigmenting agents from natural sources has become a new direction in the cosmetic industry as natural products are generally perceived as relatively safer. In our previous study, selected Chinese medicines traditionally used to treat hyperpigmentation were tested for anti-hyperpigmentary effects using a melan-a cell culture model. Among the tested chemical compounds, 4-ethylresorcinol, 4-ethylphenol and 1-tetradecanol were found to possess hypopigmentary effects. Western blot analysis, reverse transcriptase polymerase chain reaction (RT-PCR), cyclic adenosine monophosphate (cAMP) assay, protein kinase A (PKA) activity assay, tyrosinase inhibition assay and lipid peroxidation inhibition assay were performed to reveal the underlying cellular and molecular mechanisms of the hypopigmentary effects. 4-Ethylresorcinol and 4-ethylphenol attenuated mRNA and protein expression of tyrosinase-related protein (TRP)-2, and possessed antioxidative effect by inhibiting lipid peroxidation. 1-Tetradecanol was able to attenuate protein expression of tyrosinase. The hypopigmentary actions of 4-ethylresorcinol, 4-ethylphenol and 1-tetradecanol were associated with regulating downstream proteins along the PKA pathway. 4-Ethylresorcinol was more effective in inhibiting melanin synthesis when compared to 4-ethylphenol and 1-tetradecanol

Mechanistic studies of plasma polymerization

Plasma polymerization is a solventless method for depositing polymeric layers onto any substrate at room temperature. This technique comprises excitation, fragmentation, and polymerization of precursor molecules by an electrical discharge. Although widely used, the fundamental molecular processes associated with plasma polymerization are not fully understood. Basic plasma / polymer interactions were studied by investigating the surface treatment of polytetrafluoroethylene (PTFE) using inert and reactive gas discharges. Depending upon the feed gas employed, chemical, UV, or ion beam modification of the PTFE surface were found to be important. Argon glow discharge treatment was found to result in similar physicochemical phenomena at the PTFE surface to that observed during argon ion beam studies, thereby supporting the relative importance of ion bombardment during noble gas plasma modification. In high power discharges it has been shown that extensive ion bombardment of PTFE can lead to the simultaneous sputtering and plasma polymerization of ejected species onto an adjacent substrate. The chemical nature of the resultant fluorocarbon deposits for various gases was found to correlate to the earlier surface treatment studies. Another way of carrying out plasma polymerization is to use pulsed plasmas; these offer the advantage of greater retention of monomer structure within the plasma polymer matrix. In the case of maleic anhydride less fragmentation of the precursor, reduced beam damage of the polymer, and radically initiated polymerization was observed by increasing the off-period of the pulse. Similarly the structural characteristics of 2- iodothiophene plasma polymers were found to be influenced by the electrical discharge power and pulsing parameters leading to a gradual destruction of the aromatic ring structure

Mechanistic studies on DNA damage by minor groove binding copper–phenanthroline conjugates

Copper–phenanthroline complexes oxidatively damage and cleave nucleic acids. Copper bis-phenanthroline and copper complexes of mono- and bis-phenanthroline conjugates are used as research tools for studying nucleic acid structure and binding interactions. The mechanism of DNA oxidation and cleavage by these complexes was examined using two copper–phenanthroline conjugates of the sequence-specific binding molecule, distamycin. The complexes contained either one or two phenanthroline units that were bonded to the DNA-binding domain through a linker via the 3-position of the copper ligand. A duplex containing independently generated 2-deoxyribonolactone facilitated kinetic analysis of DNA cleavage. Oxidation rate constants were highly dependent upon the ligand environment but rate constants describing elimination of the alkali-labile 2-deoxyribonolactone intermediate were not. Rate constants describing DNA cleavage induced by each molecule were 11–54 times larger than the respective oxidation rate constants. The experiments indicate that DNA cleavage resulting from β-elimination of 2-deoxyribonolactone by copper–phenanthroline complexes is a general mechanism utilized by this family of molecules. In addition, the experiments confirm that DNA damage mediated by mono- and bis-phenanthroline copper complexes proceeds through distinct species, albeit with similar outcomes

Mechanistic studies of photoelectrochemical systems

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Mechanistic studies of metal carbonyls

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