A new three-phase argon plasma arc was developed for analytical emission spectroscopy. The power supplied to the plasma arc utilized a simple circuit with three-phase as line voltage stepped down via a transformer to 104Vrms. A three concentric quartz tubing assembly was determined to be the optimum configuration for supplying...
Lycopodium alkaloids have shown widespread and noteworthy biological activity, consisting of over 250 known natural products. Moreover, their structural complexity and diversity have attracted considerable attention from numerous laboratories including our own. Recently, we have developed a unified approach that would provides access to numerous, previously unprepared C₁₀-functionalized lycopodium alkaloids....
At Site-300, Lawrence Livermore National Laboratory (LLNL), CA,
trichloroethene (TCE) is present along with tetraalkoxysilanes such as tetrabutoxysilane
(TBOS) and tetrakis(2-ethylbutoxy) silane (TKEBS), as subsurface contaminants.
Intrinsic transformation of TCE to cis-dichloroethene (c-DCE) was observed in the
groundwater at locations co-contaminated with TBOS or TKEBS. Attenuation of TBOS
and TKEBS...
Studies were carried out to determine the absolute stereochemistry of
botryococcene (1). The natural product was degraded to two sets of 'y- and 8-
valerolactones. All enantiomeric variations of these lactones were synthesized in
optically pure form starting from (S)- and (R)-methyloxiranes. 1H NMR correlation of
natural and synthetic materials...
A series of compounds, 7-8 and 20-25, were tested as competitive inhibitors of 2,5-dihydroxyacetanilide epoxidase I (DHAE I) and DHAE II. A Hammett plot was constructed for each enzyme to determine the effect of electron density on inhibition. DHAE I gave a linear, highly correlated plot (r²=0.91) that signifies the...
Sulfide is an important species to measure in environmental water samples. The
spectrophotometric detection method for reduced sulfur species (sulfide) based on
generation of methylene blue was adapted to work in an apparatus utilizing microfluidic
PDMS mixing and observation cells with flow channels in the 100 μm range. The
benefits...
In this investigation the addition of hydrogen bromide
to 3-methylcyclohexene has been studied in order to see if
the theory of hyperconjugation could be extended to include
olefins of this type. Since the olefin has an equal number
of hydrogens on both carbons carrying the double bond, a
mixture of...
Mass Spectrometry has emerged as an analytical core technique in omics sciences, in particularly mass spectrometry has advanced the fields of proteomics, metabolomics and lipidomics in recent years. Mass spectrometric techniques have enabled the characterization and determination of abundance levels of a wide range of biomolecules at molecular and system-wide...
A novel acyl protecting group for cytosine and adenine has been prepared
from 4-( chloromethyl) benzoic acid. Reaction of the acid with morpholine produces
4-( 4-morpholinyl )methyl benzoic acid which is converted to it's acid chloride
with thionyl chloride. This may be used to acylate cytidine and adenosine under
standard...
Mitochondria provide energy for biological cells to function, but this process is also a source of oxygen radicals that are capable of damaging nearby proteins. Mitochondrial protein damage can eventually lead to cell death, especially in the case of heart cells, where mitochondria are present in the highest concentrations. As...
Toxoflavin, a toxic secondary metabolite produced by a variety of bacteria, has been implicated as a causative agent in food poisoning and a virulence factor in phytopathogenic bacteria. This toxin is produced by the tox operon in Burkholderia glumae, in which the encoded protein, ToxD, was previously characterized as essential...
Sequential alkylation of Hagemann's ester with methyl and
methallyl halides has been studied. Treatment of Hagemann's ester
with methyl iodide and sodium ethoxide gave a mixture of 21 and 25
in a ratio of 4:1. Alkylation of 21 with methallyl chloride and potassium
t-butoxide afforded a mixture of 37 and...
The unique capability of carbon-based ion-selective electrode (ISE) to perform highly sensitive anodic stripping voltammetry, while maintaining all the properties of an ISE, is demonstrated in terms of sensitivity, detection limit, response time and selectivity. Square wave anodic stripping voltammetry involves deposition and dissolution steps of metal ions, which means...
An instrument was developed which performs analysis of the
oxygen content of air by means of a commercial polarographic oxygen
electrode. The oxygen analyzer is part of a portable instrument
which converts the current from the oxygen electrode into a pulse
whose width is proportional to the oxygen concentration. This...
A synthetic approach toward the two major fragments of cathedulin K-19,
euonyminol (4) and dimethyl cathate (69), was investigated. Synthesis of
dimethyl cathate was accomplished in 3 steps starting from 73. Efforts directed
towards the synthesis of euonyminol, a highly oxygenated dihydroagarofuran
sesquiterpene, was advanced to a stage in which...
The change in the oscillation frequency in the current of
an atmospheric helium glow discharge is a sensitive detector
for gas chromatography. The response of the detector is in
the femtomole and picomole range for nonane and decane. The
effluent of a capillary column is directed into a glow
discharge...