These are some of the research opportunities you can have through the Department of Chemistry and Physical Sciences.
Research in the Nicholson Group focuses on aspects of organic reaction development and novel experiments for undergraduate teaching labs. Undergraduate research students in my group are focused currently on the applications of 3D printing in the design of small volume lab devices to innovate learning while minimizing waste in the teaching lab. Students are also carying out research aimed at identifying biological systems that can carry out appropriate asymmetric enzymatic reactions to study stereochemistry in the undergraduate organic laboratory as well as reactions that can be carried out to demonstrate transfer or loss of that stereochemistry in a teaching context.
The muon is an elementary particle in the same family as the electron, first discovered in cosmic rays but now commonly manufactured in particle accelerators. Muons come in both positive and negative charge types. With a lifetime of 2 microseconds, muons might seem too short-lived to be of any practical use, but after injection into materials they can provide many different kinds of useful information through their decay into electrons or positrons. Positive and negative muons have completely different behaviors in matter: the positive muon typically captures an electron to form muonium, a light isotope of the hydrogen atom, which can then react with molecules in its surroundings to form a free radical, while the negative muon is itself typically captured by a nucleus into a low orbit, screening one unit of charge and temporarily creating an atom one place to the left on the periodic table. Positive and negative muons in matter are studied at several accelerator facilities around the world - in Japan, Canada, and the U.K., among other places - using methods collectively known as µSR spectroscopy.
Currently active projects in this area include:
From the bulk down to a scale of a few hundred nanometers, the properties of materials do not vary much with the size of the particles from which they are composed, but below this scale there are changes that can involve structural preferences and physical and electronic properties: this is the world of nanoparticles, larger than molecules, but smaller than - and different from - bulk matter. Various factors influence these size-dependent phenomena, including structural effects near the particle surface and the transition from bulk-like to molecule-like quantum states. We have experience in making and studying several kinds of nanoparticles, including silica, metal oxide, and compound semiconductor materials.
Carbon compounds are the archetypes of covalently-bonded molecules, and are at the heart of simple views of chemical bonding; carbon atoms in molecules can usually be characterized as sp3 (tetrahedral), sp2 (trigonal), or sp (linear). Allotropes of elemental carbon include the bulk forms diamond (sp3) and graphite (sp2), as well as a proliferation of fullerenes, nanotubes, and other molecular forms where factors such as symmetry, surface curvature, and elimination of dangling bonds play roles in determining the preferred structures.
Currently active projects in this area include:
Atoms and molecules behave in accordance with the laws of quantum mechanics. Quantum chemistry is the branch of chemistry dedicated to the prediction of molecular structures and physical properties by solving the relevant quantum mechanical equations. This requires highly numerically intensive calculations, and is done with the help of computers. While modern personal computers are capable of carrying out quantum chemical calculations, the intensiveness of the calculations increases rapidly with the size of the molecule and the sophistication of the approach. We use in-house computational resources located within the Simmons-Purdie Data Center at Â鶹ÊÓƵAPK (including a new GPU-based server), as well as national supercomputing infrastructure (XSEDE) where necessary.
For medium-sized molecules, density functional theory (DFT) is a set of methods that allows molecular structures, energies, and electron density distributions to be calculated with reasonable computational effort.
Currently active projects in this area include:
In our laboratory we use modular spectroscopic equipment to carry out several different types of measurements, including fluorescence spectroscopy with excitation from diode-pumped solid-state lasers of various wavelengths.
One strand of research studies light-induced reactions occurring in solutions containing dyes in the class known as xanthenes (which includes fluorescein, Eosin Y, and Rose Bengal) and molecules containing conjugated carbon chains (polymethines and polyenes). These reactions are thought to be mediated by singlet oxygen generated via spin exchange from the xanthene triplet state. Research on these systems includes rate law measurements and product identification.
Currently active projects in this area include:
Nuclear magnetic resonance spectroscopy is commonly encountered by students of organic chemistry as a technique for qualitative identification of molecules. However, this only scratches the surface of the capabilities of NMR, which has applications ranging from physics to biochemistry. Among the most interesting possibilities offered by the method are the use of different pulse sequences to study sources of spin relaxation including translational diffusion and interactions of the probe spin with paramagnetic species.
As an example, pulsed field-gradient NMR offers a suite of methods for the study of molecular diffusion dynamics in solution. The basic technique is a spin echo sequence in which an additional field gradient pulse along the z axis is applied before and after the 180° pulse. The first pulse generates a position-dependent phase along the z direction which is only exactly reversed by the second pulse if no diffusion of the nuclei has occurred. In the presence of diffusion, the spin echo is weakened by an amount dependent on the field gradient. Mapping the echo intensity as a function of field gradient in a 2D spectrum leads to the form of spectroscopy known as DOSY (“diffusion-ordered spectroscopy”). We apply these methods to the study of molecular transport in self-organized nanoenvironments such as micelles.
Currently active projects in this area include:
The purpose of this study is to evaluate the applicability of electrospray laser desorption ionization (ELDI) mass spectrometry imaging (MSI) to interrogate tablet formulations for the spatial distributions of ingredients. ELDI combines laser ablation via an ultraviolet laser with electrospray ionization to create spatially resolved molecular images. The general ablation setup and process of ELDI-MSI can be seen in Figure 1. Mass spectrometry imaging is a non-targeted technique allowing the concurrent detection of different classes of small molecules from a solid sample surface. This is ideal for the analysis of pharmaceutical preparations. Five Marian undergraduate students are working on this project.
While we have previously shown that ELDI-MSI on pills is possible (Figure 2) we are currently working to expand the capabilities of the method to further explore agglomeration of the active ingredient, and the form by which the active ingredient exists in the pill with high accuracy. Here at Marian, we are building our ELDI-MSI setup with a brand new Q-Spark 266 nm nanosecond high-power laser (RPMC Lasers) coupled with our Thermo Scientific LTQ XL linear ion trap mass spectrometer. This is the same instrument used by many pharmaceutical companies for routine analysis. The ultimate goal of this project is to diagnose agglomeration of the active ingredient in tablets with MSI molecular images and determine the percentage of the active ingredient existing in the crystalline versus amorphous forms. This project is funded by AbbVie Inc., North Chicago, IL. All samples are provided by AbbVie.
Figure 1. General setup of ELDI-MSI method. The pill sample is mounted on a glass slide which is rastered by a xyz micro-translational stage under a static laser beam.
Figure 2. ELDI-MSI of acetaminophen tablets. A) “Filler” compound at m/z 112.0844. A steady signal across the entire tablet surface was observed for these filler compounds. The MS-images in B, C, D, and E show the spatial distributions of acetaminophen [M+H]+ at different crystallinity percentages, with the same normalized heat map intensity scale.
This study will look at changes in the spatial distributions of small metabolites in plant leaves due to external stimuli. Sugars, flavonoids, amino acids, and organic acids among other small molecules will be tracked across the study. Past data can be seen in Figure 3 below from the previous publication: https://doi.org/10.3389/fpls.2018.01348. This project will begin in summer 2019.
Figure 3. Four different anthocyanins in a coleus leaf as affected by light exposure after 28 days of one half of the leaf illuminated (left) and the other half shaded (right).
Check back soon for more information about this project!
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