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1.  Oxidation of Ethidium using TAML Activators: A Model for High School Research Performed in Partnership with University Scientists 
Journal of chemical education  2013;90(3):326-331.
A chemical research program at a public high school has been developed. The full-year Advanced Chemical Research class (ACR) in the high school enrolls 20 to 30 seniors each year, engaging them in long-term experimental projects. Through partnerships involving university scientists, ACR high school students have had the opportunity to explore a number of highly sophisticated original research projects. As an example of the quality of experimental work made possible through these high school–university partnerships, this article describes the development of a novel method for the oxidation of ethidium bromide, a mutagen commonly used in molecular biology. Data collected from ACR alumni show that the ACR program is instrumental in encouraging students to pursue careers in scientific fields and in creating life-long problem-solvers.
PMCID: PMC3622257  PMID: 23585695
High School/Introductory Chemistry; Curriculum; Interdisciplinary/Multidisciplinary; Laboratory Instruction; Hands-On Learning/Manipulatives; Inquiry-Based/Discovery Learning; Problem Solving/Decision Making; Oxidation/Reduction; Green Chemistry; UV-Vis Spectroscopy
2.  Assaying proline hydroxylation in recombinant collagen variants by liquid chromatography-mass spectrometry 
BMC Biotechnology  2012;12:51.
The fabrication of recombinant collagen and its prescribed variants has enormous potential in tissue regeneration, cell-matrix interaction investigations, and fundamental biochemical and biophysical studies of the extracellular matrix. Recombinant expression requires proline hydroxylation, a post-translational modification which is critical for imparting stability and structure. However, these modifications are not native to typical bacterial or yeast expression systems. Furthermore, detection of low levels of 4-hydroxyproline is challenging with respect to selectivity and sensitivity.
We have developed a new liquid chromatography-mass spectrometry (LC-MS) method to evaluate proline hydroxylation in recombinant collagen. This assay was tested in different Saccharomyces cerevisiae expression systems to evaluate the effect of gene ratio between prolyl-4-hydroxylase and collagen on the extent of hydroxylation. These systems used a human collagen III gene that was synthesized de novo from oligonucleotides. The LC-MS assay does not require derivatization, uses only picomoles of sample, and can measure proline hydroxylation levels in recombinant and native collagen ranging from approximately 0% to 40%. The hydroxylation values obtained by LC-MS are as accurate and as precise as those obtained with the conventional method of amino acid analysis.
A facile, derivatization-free LC-MS method was developed that accurately determines the percentage of proline hydroxylation in different yeast expression systems. Using this assay, we determined that systems with a higher collagen-to-hydroxylase gene copy ratio yielded a lower percentage of hydroxylation, suggesting that a specifically balanced gene ratio is required to obtain higher hydroxylation levels.
PMCID: PMC3443662  PMID: 22901055
Hydroxyproline; Liquid chromatography-mass spectrometry; LC-MS assay; Recombinant collagen
3.  Catalytic Reduction of Dioxygen to Water with a Monomeric Manganese Complex at Room Temperature 
There have been numerous efforts to incorporate dioxygen into chemical processes because of its economic and environmental benefits. The conversion of dioxygen to water is one such example, having importance in both biology and fuel cell technology. Metals or metal complexes are usually necessary to promote this type of reaction and several systems have been reported. However, mechanistic insights into this conversion are still lacking, especially the detection of intermediates. Reported herein is the first example of a monomeric manganese(II) complex that can catalytically convert dioxygen to water. The complex contains a tripodal ligand with two urea groups and one carboxyamidopyridyl unit—this ligand creates an intramolecular hydrogen-bonding network within the secondary coordination sphere that aids in the observed chemistry. The manganese(II) complex is five-coordinate with an N4O primary coordination sphere; the oxygen donor comes from the deprotonated carboxyamido moiety. Two key intermediates were detected and characterized: a peroxo-manganese(III) species (1). The formulation of 1 was based on spectroscopic and analytical data, including an X-ray diffraction analysis. Reactivity studies showed dioxygen was catalytically converted to water in the presence of reductants, such as diphenylhydrazine and hydrazine. Water was confirmed as a product in greater than 90% yield. A mechanism was proposed that is consistent with the spectroscopy and product distribution, in which the carboxyamido group switches between a coordinated ligand and a basic site to scavenge protons produced during the catalytic cycle. These results highlight the importance of incorporating intramolecular functional groups within the secondary coordination sphere of metal-containing catalysts.
PMCID: PMC3381988  PMID: 21425844
4.  A Monomeric MnIII—Peroxo Complex Derived Directly from Dioxygen 
The binding and activation of dioxygen by transition metal complexes is a fundamentally and practically important process in chemistry. Often the initial steps involve formation of peroxometal species that is difficult to observe because of their inherent reactivity. The interaction of dioxygen with a manganese(II) complex (1) of bis[(N’-tert-butylurealy)-N-ethyl]-(6-pivalamido-2-pyridylmethyl)amine was investigated, leading to the detection of a new intermediate that is a peroxomanganese(III) complex (2). This complex is high-spin (S = 2) with a g-value of 8.2 and D = -2.0(5) as determined by parallel-mode electron paramagnetic resonance spectroscopy. The coordination of a peroxo ligand was established using Fourier transform infrared spectroscopy that reveals a new signal at 885 cm-1 for 2 when formed from 16O2—this band shifts to 837 cm-1 when 18O2 is used in the preparation. Moreover, electrospray ionization mass spectra contain a strong ion at an m/z of 576.2703 for the 16O-isotopomer that shifts to 580.2794 in the 18O-isotopomer. Complex 2 also is capable of oxidatively deformylating aldehydes, which is a known reaction of peroxometal complexes. The similarities of 2 to the peroxo intermediates in cytochrome P450 are noted.
PMCID: PMC2647946  PMID: 18570414
5.  Synthesis, Screening, and Sequencing of Cysteine-Rich One-Bead One-Compound Peptide Libraries 
Cysteine-rich peptides are valued as tags for biarsenical fluorophores and as environmentally important reagents for binding toxic heavy metals. Due to the inherent difficulties created by cysteine, the power of one-bead one-compound (OBOC) libraries has never been applied to the discovery of short cysteine-rich peptides. We have developed the first method for the synthesis, screening, and sequencing of cysteine-rich OBOC peptide libraries. First, we synthesized a heavily biased cysteine-rich OBOC library, incorporating 50% cysteine at each position (Ac-X8-KM-TentaGel). Then, we developed conditions for cysteine alkylation, cyanogen bromide cleavage, and direct MS/MS sequencing of that library at the single bead level. The sequencing efficiency of this library was comparable to a traditional cysteine-free library. To validate screening of cysteine-rich OBOC libraries, we reacted a library with the biarsenical FlAsH and identified beads bearing the known biarsenical-binding motif (CCXXCC). These results enable OBOC libraries to be used in high-throughput discovery of cysteine-rich peptides for protein tagging, environmental remediation of metal contaminants, or cysteine-rich pharmaceuticals.
PMCID: PMC2646870  PMID: 18656989

Results 1-5 (5)