Faculty Research
BRAD BAKER
Development and deployment of chemical flux measurement technology
Gas Chromatography
Mass Spectroscopy
SUSAN CRAWFORD
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Fall 2004 l Capital University Journal Research Notes
Article Appearing in the above Journal noting research work. |
Talk about efficient. At the same time chemistry professor Susan Crawford is tracking the cause of a toxin lurking in drinking water from the Sacramento Delta, a second experiment she's conducting with absorbent materials called zeolites may turn out to be a possible solution.
More than 22 million people depend on Delta water, but before it can be used it gets chlorinated. Unfortunately, Crawford says, the good work of chlorination sometimes results in another problem. “When you chlorinate Delta water, dissolved organic or DOC—carbons associated with peat and other remnants of the land around the Delta—form trihaolmethanes or THMs, such as chloroform, which is considered a carcinogen.”
Working with the U.S. Geological Survey, Crawford uses a variety of sophisticated equipment including nuclear magnetic resonance and infrared spectroscopy to test water samples. She looks at the samples before and after chlorination to see what happens when the THMs form, looking for a link. “We're trying to determine if there's something similar between the DOC and the amount of THMs formed,” she says. “Can it be traced to a site, such as near a peat island? Does it happen at a certain time of year, such as during tilling, during flooding or when irrigation takes place?
“There's a tendency to blame agriculture. But it may be something that occurs in the Delta naturally such as plant decomposition,” Crawford says, noting that before taking a radical, disruptive step such as modifying farming practices in the region, scientists need to be pretty sure of the culprit.
If the source turns out to be a naturally occurring process, Crawford thinks she has a possible solution. Zeolites.
Crawford has been studying the filtering qualities of zeolites for years, including the ability of some zeolites to transform harmful materials into less dangerous ones. The porous rock materials are extremely absorbent, grabbing and holding waste products sort of like a molecular sponge.
If it turns out that the carbon in the Delta can't be controlled at the source, Crawford thinks zeolites might be an effective way to absorb the chloroform from the water.
In yet another project with Sac State's Office of Water Programs, Crawford is also looking at whether zeolites might be able to play a role in removing metals from storm water that runs off area roads.
Londa Borer:
- Preparation of platinum complexes of bile acids as possible antitumor agents
- Preparation of copper and nickel complexes as models for enzymes.
- Adapting experiments for use in elementary and high school science classrooms.
- Student Retention
- Academic Advising
ROY DIXON
General Research Interests:
Interest is in areas of analytical chemistry, primarily in analytical separations, and in environmental chemistry, particularly atmospheric chemistry.
Specific Research Projects:
Development of New Aerosol-based Detectors for High Performance Liquid Chromatography (HPLC)
Aerosol-based detectors function in three steps: nebulization of the HPLC effluent, evaporation of the solvent leaving aerosol particles containing analytes, and detection of the aerosol, with the last step depending on the type of aerosol-based detector. Evaporative light scattering detection (ELSD) has been employed in commercially-available detectors with light scattering used for aerosol detection. More recently, the use of condensation nucleation counters, which count particles larger than about 3 to 10 nm diameter has resulted in a more sensitive detection method known as condensation nucleation light scattering detection (CNLSD). Aerosol-based detection methods are considered to be "universal".
We have been investigating the construction of sensitive and potentially economical HPLC detectors using aerosol charging as the mechanism for detecting the aerosol. The name aerosol charge detection (ACD) has been given to the first method we have developed. The first ACD instrument was built using home-built and commercial nebulizers, a spray chamber, heated tubing and an Electrical Aerosol size Analyzer (EAA) for aerosol detection. For a picture of the detector click here (the detector is is to the left of me). In the flow injection analysis (FIA) mode (i.e. without a chromatography column) and using water as the solvent, detection limits around 10 ppb have been achieved with linear response is observed from 0.1 to around 10 to 100 ppm (depending on the nebulizer used). When using typical HPLC solvents, the sensitivity is limited somewhat by non-volatile impurities present in solvents (even HPLC grade solvents). It is possible to improve the signal to noise under these circumstances by removing small particles in the EAA before detection. Detection limits of about 20 ppb (similar to CNLSD and more sensitive than ELSD) and good reponse linearity have been observed for weakly retained compounds separated using reverse-phase liquid chromatography. This detection method has been documented in the Dixon and Peterson paper in the publications section of my homepage. To see an example chromatogram set (using both AC detection and UV detection) showing the separation and detection of 5 ppm ammonium sulfate, uracil, sulfanilamide, nicotinamide, and adenosine, click here .
Current work is focused on creation of related detectors utilizing other mechanism of aerosol charging to be constructed from scratch (not using the EAA) and involving Bill DeGraffenreid (CSUS Physics Department). Work also has been undertaken to use ACD for practical applications. The main emphasis has been on developing methods to use HPLC-ACD for analysis of dicarboxylic acids and carbohydrates. Some of this work is described below. We also are interested in ACD with FIA and simple separations to segregate non-volatile mass in samples into different classes.
Application of ACD to Analyzing Atmospheric Aerosols
Atmospheric aerosols are known to adversely affect health, to decrease visibility, and to affect the earth's climate. Although it is known that a significant fraction of the aerosol mass is carbon-containing, relatively little work has been done to determine the composition of the organic fraction. The main emphasis in past work has been to measure compounds using gas chromatography. Gas chromatography can only be used for compounds which can be successfully volitilized (only a fraction of the organic compounds present in atmospheric aerosols).
We have been working to apply aerosol-based detectors to the analysis of bulk atmospheric aerosol samples. Aerosol-based detectors can be used in the FIA mode with different aerosol extraction methods to obtain information on the mass concentration of various fractions of the organic aerosol. HPLC with aerosol-based detectors can be used to determine the concentration of specific organic compounds. We have been measuring levoglucosan and related carbohydrates in atmospheric aerosols in samples from the Central Valley of California with a smaller number of samples from New Mexico, Montana, and the Sierra Nevada mountains to estimate the effects of biomass combustion smoke on aerosol levels in collaboration with state agencies and other researchers. Fine aerosol levoglucosan concentrations of up to about 10 µ g/m 3 have been observed in winter in communities strongly affected by wood burning. We also are measuring levoglucosan in air downwind of the following fires:
Star Fire (Lake Tahoe Region), August/Sept., 2001. This should provide a link to a satellite picture showing this fire from a NOAA website .
Southern Oregon fires of August, 2002. This should provide a link to a satellite picture showing these fires from a NOAA website.
Forrest fires around Missoula, Montana, August, 2003. This should provide a link to a satellite picture showing these fires from a NOAA website .
A second project involving the analysis of atmospheric aerosols has been to use FIA-ACD and simple extraction and separation methods to analyze aerosol samples. Aerosol samples have been collected with filters and with an impactor which segregates the aerosol by particle size. We have been working on developing methods to extract some of the compounds in the aerosols and to estimate the soluble compound concentration (using FIA-ACD). The ultimate goal will be to better characterize the composition of atmospheric aerosols. Different solvents can be used to assess whether large fractions of the aerosol are inorganic or organic and for organics, polar or non-polar. Most of the work completed has been in developing methods.
Mary McCarthy Hintz:
Vitamin D and Breast Cancer
Recent in vivo and in vitro evidence indicates that Vitamin D inhibits the growth of some cancers. Some synthetic analogs of Vitamin D inhibit cellular proliferation more potently than Vitamin D itself. It appears that the structure of these analog s prevents them from being inactivated in the cancer cell, as Vitamin D is. Vitamin D 24-hydroxylase is the first enzyme to act in the Vitamin D inactivation pathway. As such, this protein is potentially oncogenic, because its overexpression could lead to Vitamin D deficiency in cancer cells, which would suppress growth inhibition. My laboratory is assessing the relationship betwee amplification of CYP24, expression of Vitamin D 24-hydroxylase, and resistance to the anti-prolfertive effects of Vitamin D in breast cancer cell lines.
Ethnopharmacognosy and Breast Cancer
Katherine McReynolds
Synthesis of anionic anti-HIV agents
Evaluation of anti-HIV agents using ELISA
Synthesis of novel dendrimer architectures
Computational chemistry studies of dendrimers and glycodendrimers
Linda Roberts:
My research involves structural studies of apolipoprotein A-I (apo A-I). This protein is the major constituent
of high density lipoprotein (HDL), which is responsible for removing excess cholesterol from
the body. High levels of HDL are linked to lowered risk for coronary artery
disease. Currently, I am conducting structural studies of chemically
and genetically modified forms of apo A-I either bound to lipid or free in solution using fluorescence
and circular dichroism spectroscopy, and limited proteolysis. I have had the
great fortune to be able to involve a number of undergraduates in
this research and we have presented
our results at national meetings of the Biophysical Society and
the Protein Society. Pictured
at left is the ribbon structure of apolipophorin III. This protein
is found in the blood of the
African locust (Locust migratoria). The structure was solved to
2.5 angstroms by Hazel Holden's
group (Breiter et al., Biochemistry 30, 603, 1991). Notice that
the protein consists of
five helices. It is likely that the other apolipoproteins, including
apo A-I, also form helical bundles
in solution. A recent structure from David Borhani and coworkers
(Borhani et al., Proc.
Natl. Acad. Sci. 94, 12291-12296, 1997) of an apo A-I amino-terminal
deletion mutant,
delta 1-43, shown below, suggests that extensive helical structure
is present in this protein.
Note that the shape of this protein is very different, however,
from that of apolipophorin.
We believe that this protein represents the lipid-bound, rather
than the lipid-free,
structure of apo A-I (Rogers et al., Biochemistry 36, 288-300, 1997).
