Dr. Mary Walczak: The "Surfaces Group" is focused on characterizing self-assembled amphiphillic structures and understanding the forces between molecules in such arrangements. The project is fundamentally collaborative; it is a joint effort between myself and Dr. Anne Walter (Biology Dept.) and has engaged undergraduate student researchers with home departments of chemistry, biology, physics and mathematics. We are funded through the Collaborative Research at Undergraduate Institutions (C-RUI) program of the National Science Foundation, a relatively new program targeting projects at the interface of the traditional scientific disciplines.
Our work derives from our fundamental interest in amphiphillic (both water-loving and water-hating) molecules arranged in two-dimensional structures: microemulsions, monolayers and vesicles. A fundamental question is whether reactivity of molecules at the surfaces of these structures changes from reactivity of isolated molecules. To address this question we have prepared microemulsions (e.g., palmitic acid molecules around a hexadecane core) and spectrophotometrically determined the pH of the resulting solution utilizing an acid/base indicator dye. By treating the system as simultaneous equilibria, the pKa of the palmitic acid can be calculated and compared with the pKa of free fatty acids. We have found that the pKa of palmitic acid increases by at least 1 pKa unit when it is in a microemulsion. We are now performing experiments aimed at ascertaining the importance of hydrogen bonding and electrostatics in the decreased reactivity of the acid.
Another fundamental question we have is about segregation in self-assembled structures. If a monolayer or vesicle is composed of two different types of molecules (e.g., methyl- or acid-terminated alkanethiols or PC and sphyngomylein) are the compositions homogeneous or do molecules segregate? We are addressing this question using several techniques to date, including fluorescence spectroscopy, atomic force microscopy (AFM), and differential scanning calorimetry.
A third area of focus is the determination of how phospholipase enzymes act on substrates. Some projects have focused on characterizing enzyme activity on vesicle substrates. In the future we plan to follow phospholipid bilayers attached to flat surfaces using AFM. To this end, we have begun investigating ways of putting phospholipid bilayers onto mica or gold surfaces. Both these substrates are easily obtained as atomically flat surfaces, which makes them ideal for AFM applications.
Students who work in the Surfaces Group will have the opportunity to
examine these and related questions that are found at the interface of
biology, chemistry, physics and mathematics. If you would like to find
out more talk with Mary Walczak, Anne Walter or one of the Surfaces Group
students (currently Matt Brahs, Melissa Brand, John Craighead, Dave Gilmer,
Kate Helgen, Kiran Pandey, Aimee Potasek, Laura Schilling, Emina Stojkovic,
or Justin Wheeler). More information can also be found on our web page:
www.stolaf.edu/other/surfaces
Dr. Jeff Dahlseid:
I am interested in engaging students in my quest to understand how
changes in the stability and translation of messenger RNA (mRNA) regulate
the expression of genes. My present research focuses on a specialized mRNA
degradation pathway in bakersí yeast as a model system. The nonsense mediated
mRNA decay pathway (NMD) has been characterized primarily for accelerating
the degradation of mutant mRNAs that contain premature translation termination
signals. NMD is thought to thereby diminish the effect of the truncated
polypeptides that would otherwise accumulate, which includes uncontrolled
cell growth (cancer). It is now clear that NMD is also part of the natural
repertoire for regulating gene expression. Recent experiments show that
6-9% of the natural mRNAs in yeast accumulates when NMD is inactivated.
We have identified several mRNAs affected by NMD that are interesting because
they encode proteins, which affect chromosome function at either the centromere
or telomere. The mRNAs we have characterized thus far do not appear to
be degraded by NMD, but rather accumulate through increased synthesis when
NMD is inactivated. Our working hypothesis is that one or more protein
regulators are responsible, and that these regulators are translated from
mRNA substrates of NMD. We are presently characterizing three candidate
substrate mRNAs of NMD that might encode a protein regulator of gene expression.
Future projects in the lab include; 1) assay the promotor activity of
genes affected by NMD using the green fluorescence protein as a reporter,
to identify promotors regulated by NMD (and thereby candidate genes for
mRNA substrates of NMD), 2) using RNA blotting methods to measure decay
rates of mRNAs that are strong candidates for direct substrates of NMD,
3) use genetic approaches to identify candidate genes for mRNA substrates
of NMD (which should also encode protein regulators of genes indirectly
affected by NMD), and 4) create recombinant DNAís (plasmids) suitable for
expression and characterize the degradation of natural mRNA substrates
of NMD (assuming we identify one).
Research Opportunities with Dr.
Paul Jackson
During the summer of 2000 there are numerous opportunities for interested
students to work with me on projects related to separation science, environmental
analysis, and organic synthesis. Project 1: Reversed-phase liquid
chromatography (RPLC) is used in over 2/3 of all liquid chromatographic
separation protocols. Unfortunately stationary phase pH stability is a
severe limitation in RPLC method development work. This project seeks to
compare and contrast the chemical stability (pH) of various commercial
RPLC stationary phases and make recommendations to end users about the
conditions under which specific phases should be used. Project 2:
Wetlands play a vital role in the natural world; they provide an excellent
water filtration system and a bridging habitat for both aquatic and terrestrial
species. Work on this project focuses on the development of analysis methods
in which organic components in wetland waters may be surveyed and quantitated.
Complexities abound when analyzing natural samples; the sampling protocol
as well as the sample matrix provide challenges to be overcome. Samples
will be taken from the Skoglund wetland, the city of Northfield, and throughout
Rice County. Project 3: The chemical and physical processes that
result in a RPLC separation are not completely understood. The design and
use of a novel stationary phase ligand chemically grafted onto porous silica
particles would provide insights into the separations process. Since the
ligand has yet to be created, the project will use molecular modeling to
guide any synthetic effort. Project 4: Evaluation and development
of laboratory experiences designed to introduce students having little
background in chemistry to environmental chemistry.
Research Opportunities with Dr.
Gary Miessler: Organometallic Chemistry of Molybdenum
After my sabbatical leave, I am now interested in resuming my research
in organometallic chemistry. Primarily I would like to develop syntheses
of new complexes of molybdenum that contain dithiolene ligands in addition
to organic ligands such as CO and h 5-C5H5.
Some important molybdenum-containing enzymes have dithiolene ligands, and
as a new direction for my research I hope to synthesize complexes that
might serve as models for the metal sites in such enzymes. In addition,
I am interested in testing new ways to prepare molybdenum complexes of
the now well-known buckminsterfullerene (C60, alias "buckyball")
using both thermal and photochemical routes.
Dr. John Walters will
be working with, Joe Lohmeyer ë00, during the spring semester (not in the
summer) to develop robotic methods for standard addition analysis of natural
waters for three or four selected trace metals by atomic absorption spectrometry.
Sample pretreatment by robotic methods will include microfiltration, acidification,
and matrix buffering. Prior screening by RP/HPLC also will be done to help
ascertain some kinds of organic matrix variability. Samples will be prepared
for standard addition analysis robotically. LabVIEW® virtual instrumentation
will be developed to report out the standard addition results automatically.
Success in the work will lead to its inclusion in the instrumental analysis
laboratory collection of experiments to be published on the web.
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