David E. Lewis

A fluorescent sensor for Cu2+ at the sub-ppm level

Abstract Two 4-(aminoalkyl)aminonaphthalimide compounds which exhibit fluorescence enhancement and associated spectral changes in the presence of Cu2+, Mn2+ and Ni2+ are reported. The compounds are believed to undergo intramolecular quenching by the distal nitrogen on the 4-substituent. When metal ions are present, this quenching mechanism is partially or wholly removed due to complexation of the metal ions with the 4-substituent. The two compounds are particularly sensitive to Cu2+ such that concentrations in the 0–1 ppm range are sufficient to effect complete restoration of the naphthalimide fluorescence.

NMR, Mass Spectrometry and Chemical Evidence Reveal a Different Chemical Structure for Methanobactin That Contains Oxazolone Rings

Methanobactin (mb) is a small copper-binding peptide produced by methanotrophic bacteria and is intimately involved in both their copper metabolism and their role in the global carbon cycle. The structure for methanobactin comprises seven amino acids plus two chromophoric residues that appear unique to methanobactin. In a previously published structure, both chromophoric residues contain a thiocarbonyl attached to a hydroxyimidazolate ring. In addition, one is attached to a pyrrolidine ring, while the other is attached to an isopropyl ester. A published X-ray determined structure for methanobactin shows these two chromophoric groups forming an N2S2 binding site for a single Cu(I) ion with a distorted tetrahedral geometry. In this report we show that NMR, mass spectrometry, and chemical data reveal a chemical structure that is significantly different than the previously published one. Specifically, the 1H and 13C NMR assignments are inconsistent with an N-terminal isopropyl ester and point instead to a 3-methylbutanoyl group. Our data also indicate that oxazolone rings instead of hydroxyimidazolate rings form the core of the two chromophoric residues. Because these rings are directly involved in the binding of Cu(I) and other metals by methanobactin and are likely involved in the many chemical activities displayed by methanobactin, their correct identity is central to developing an accurate and detailed understanding of methanobactins many chemical and biological roles. For example, the oxazolone rings make methanobactin structurally more similar to other bacterially produced bactins and siderophores and suggest pathways for its biosynthesis.

4-alkylamino-3-bromo-N-alkyl-1,8-naphthalimides: new photochemically activatable antiviral compounds

The synthesis of several 3-bromo-4-alkylamino-N-alkyl-1,8-naphthalimides is described. These compounds have been shown to be effective, non-oxygen based photochemical inactivators of enveloped viruses, including herpes simplex virus and HIV.

Synthesis and bromination of 4-alkylamino-N-alkyl-1,8-naphthalimides

4-Alkylamino-N-alkyl-1,8-naphthalimides were prepared from 4-chloro-1,8-naphthalic anhydride and from 4-amino-1,8-naphthalimide. It was found that the amino nitrogen of 4-amino-N-alkyl-1,8-naphthalimides is nucleophilic enough to participate in nucleophilic displacement reactions without the need for added base, despite being a vinylogous amide. Bromination of 4-alkylamino-N-alkyl-1,8-naphthalimides using molecular bromine was found to occur in the absence of a Lewis acid catalyst, and to be regiospecific, yielding only the 3-bromo isomer. Extended reaction times and the use of excess bromine result in dealkylation of the 4-alkylamino substituent, but no polybromination of the naphthalimide ring system.

Reactions of Active Methylene Compounds with Benzhydrol During Solvolysis in Formic Acid

Formic acid reacts with benzhydrol to give benzhydryl formate, which reacts with active methylene compounds in refluxing formic acid to give either C-alkylation or Ritter reaction products. The product formed is determined by the equilibrium enol content of the active methylene compound. These reaction conditions avoid the use of halogenated reaction solvents, and the pure products are isolated without recourse to chromatography.

Constituents of thai medicinal plants - iv new nitrogenous compounds - odorine and odorinol

Two new nitrogenous compounds were isolated from the leaves of Aglaia odorata. Their structures were elucidated by spectral evidences as odorine (1) and odorinol (2).

Gel electrophoretic studies of photochemical cross-linking of type I collagen with brominated 1,8-naphthalimide dyes and visible light

Insoluble Type I collagen from bovine Achilles tendon (Sigma C9879) was suspended in a 3 mM solution of the dye diEd66Br dissolved in Cremophor ELR (BASF) to give a molecular concentration ratio. Fifty-microliter aliquots in 5-mm-diameter wells were exposed to 458 J/cm2 (225 mW/cm2, 1800 sec) of 457.9-nm light from an argon ion laser; similar aliquots with and without dye were kept in the dark to serve as controls. Following pelleting of the collagen by centrifugation and 3x washing in phosphate-buffered saline, aliquots of light-treated and control sample pellets were (1) digested in collagenase (Sigma C9891) or (2) extracted in 0.5 M acetic acid, followed by centrifugative ultrafiltration (10-kd cutoff) in 0.01 M acetic acid. Aliquots of the supernatant of the acid-extracted collagen also were digested in pepsin. Electrophoretic protein migration in 8% to 25% gradient polyacrylamide gels following SDS solubilization disclosed numerous, densely packed, essentially contiguous protein bands. These studies indicate that the dye and light treatment of insoluble Type I collagen (1) results in cross-linking of collagen molecules and (2) does not denature the trimer conformation sufficiently to enable significant digestion by pepsin.

Photochemical bonding of skin with 1,8-naphthalimide dyes

Our ongoing studies out to one year postoperatively of healing in sheep menisci and condylar articular cartilage prompt the study of photochemical bonding of other connective tissues with our 1,8-naphthalimide dyes. Here we report our ex-vivo experiments in photochemical bonding of the dermis of rabbit dorsal skin with 1,8-naphthalimide dyes, in which effects of varying the externally applied pressure during the welding and of the addition of an albumin-collagen protein filler are studied.

Elimination of Molecular Hydrogen and Methane from Collision-Activated Alkoxide Negative Ions in the gas Phase. Anab initioand Isotope Effect Study

Ab initio calculations indicate that the collisional induced losses of molecular hydrogen from the ethoxide negative ion and methane from the t- butoxide negative ion to be stepwise processes in which the key intermediates are [H-… MeCHO ] and [Me-…Me2CO] respectively. Deuterium kinetic isotope effects observed for these and other alkoxide negative ions are in accord with the operation of a stepwise reaction.

Pre-treatment options for halophytic microalgae and associated methane production

Methane production from lipid extracted, pre-treated disrupted and non-pretreated Tetraselmis spp. microalgae was investigated. The results demonstrated that 122 mL per g VS methane was produced for the lipid extracted Tetraselmis spp., demonstrating that lipid free Tetraselmis can be effectively digested in an anaerobic environment. A total of 252 mL per g VS and 248 mL per g VS of methane was reported for non-disrupted and pre-treated disrupted Tetraselmis sp. respectively. It was also observed that the microbial community caused cell lysis of Tetraselmis spp. during the anaerobic digestion process. Cell lyses can offer a direct conversion pathway of intact Tetraselmis spp. for energy production, thus negating the need for pre-treatment.