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Full-Text Articles in Physical Sciences and Mathematics

Circular Dichroism Spectroscopy In The Undergraduate Curriculum, Adam R. Urbach Sep 2010

Circular Dichroism Spectroscopy In The Undergraduate Curriculum, Adam R. Urbach

Chemistry Faculty Research

Circular dichroism spectropolarimetry (CD) is a method of optical spectroscopy that seems in most practical ways like UV−visible spectroscopy. The main difference between the two methods is that CD, instead of measuring the absorbance of light as a function of wavelength, measures the difference in absorbance of left versus right circularly polarized light as a function of wavelength. A CD spectrum is an observation of the structure of a chiral compound; it often serves as a “fingerprint” of the structure of biological molecules such as proteins and nucleic acids. For this reason, CD has been broadly applied in biochemistry and …


Enhanced Oxygen Activation Over Supported Bimetallic Au-Ni Catalysts, Bert D. Chandler, Cormac G. Long, John D. Gilbertson, Christopher J. Pursell, G. Vijayaraghavan, K. J. Stevenson May 2010

Enhanced Oxygen Activation Over Supported Bimetallic Au-Ni Catalysts, Bert D. Chandler, Cormac G. Long, John D. Gilbertson, Christopher J. Pursell, G. Vijayaraghavan, K. J. Stevenson

Chemistry Faculty Research

New bimetallic Ni-Au supported nanoparticle catalysts were prepared by using dendrimer templated nanoparticles. Amine-terminated generation 5 polyamidoamine (PAMAM) dendrimers were anchored to a commercial silica with a siloxane linked anhydride. The dendrimer was then alkylated and used to template Ni-Au nanoparticles, which were subsequently extracted into organic solution as thiol monolayer protected clusters (MPCs). Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) indicated bimetallic nanoparticles of about 2 nm in size. Nanoparticles were deposited onto P-25 TiO2, and the capping thiol ligands were removed under flowing H2. DRIFTS infrared spectra of adsorbed CO showed only Au on the catalyst …


Ultrafast Optical Study Of Small Gold Monolayer Protected Clusters: A Closer Look At Emission, S. Hei Yau, O. Varnavski, John D. Gilbertson, Bert D. Chandler, G. Ramakrishna, T. Goodson May 2010

Ultrafast Optical Study Of Small Gold Monolayer Protected Clusters: A Closer Look At Emission, S. Hei Yau, O. Varnavski, John D. Gilbertson, Bert D. Chandler, G. Ramakrishna, T. Goodson

Chemistry Faculty Research

Monolayer-protected metal nanoclusters (MPCs) were investigated to probe their fundamental excitation and emission properties. In particular, gold MPCs were probed by steady-state and time-resolved spectroscopic measurements; the results were used to examine the mechanism of emission in relation to the excited states in these systems. In steady-state measurements, the photoluminescence of gold clusters in the range of 25 to 140 atoms was considerably stronger relative to larger particle analogues. The increase in emission efficiency (for Au25, Au55, and Au140 on the order of 10-5) over bulk gold may arise from a different mechanism …


Conformational Dynamics Of Single Pre-Mrna Molecules During In Vitro Splicing, J. Abelson, M. Blanco, M. A. Ditzler, F. Fuller, P. Aravamudhan, M. Wood, T. Villa, D. E. Ryan, J. A. Pleiss, Corina Maeder, C. Guthrie Apr 2010

Conformational Dynamics Of Single Pre-Mrna Molecules During In Vitro Splicing, J. Abelson, M. Blanco, M. A. Ditzler, F. Fuller, P. Aravamudhan, M. Wood, T. Villa, D. E. Ryan, J. A. Pleiss, Corina Maeder, C. Guthrie

Chemistry Faculty Research

The spliceosome is a complex small nuclear RNA (snRNA)-protein machine that removes introns from pre-mRNAs via two successive phosphoryl transfer reactions. The chemical steps are isoenergetic, yet splicing requires at least eight RNA-dependent ATPases responsible for substantial conformational rearrangements. To comprehensively monitor pre-mRNA conformational dynamics, we developed a strategy for single-molecule FRET (smFRET) that uses a small, efficiently spliced yeast pre-mRNA, Ubc4, in which donor and acceptor fluorophores are placed in the exons adjacent to the 5′ and 3′ splice sites. During splicing in vitro, we observed a multitude of generally reversible time-and ATP-dependent conformational transitions of individual pre-mRNAs. The …


Solid-Phase Synthesis Of Peptide−Viologen Conjugates, Joseph J. Reczek, Elisa Rebolini, Adam R. Urbach Mar 2010

Solid-Phase Synthesis Of Peptide−Viologen Conjugates, Joseph J. Reczek, Elisa Rebolini, Adam R. Urbach

Chemistry Faculty Research

This paper presents a robust method for the conjugation of viologens to peptides using an amide coupling strategy that is compatible with standard Fmoc solid-phase peptide synthesis. Methodology is presented for monitoring the milligram scale process quantitatively by UV spectroscopy. This chemistry enables the synthesis of a broad range of asymmetric viologens in high yield at room temperature and is compatible with a wide range of functional groups, including amine, guanidinyl, thiol, carboxylic acid, phenol, and indole.