Physical Sciences and Mathematics Commons^™

Electrostatic Assembly Of A Redox Catalysis System For Detection Of Glutamate, Alice Harper, Mark Anderson

Mark R. Anderson

Interfacial assemblies capable of determining glutamate by redox catalysis are prepared by electrostatic assembly of alternating layers of ferrocene poly(allylamine) polymer and glutamate oxidase on a gold electrode. Deposition of the polymer was confirmed in cyclic voltammetry measurements by the presence of a surface wave corresponding to the oxidation of the ferrocene group. In the presence of glutamate in the adjacent electrolyte solution, the current increases and approaches a pseudosteady state, consistent with redox catalysis. Electrodes modified with glutamate oxidase had a linear response to glutamate up to 0.0045 M with sensitivity of 20 μA/cm2 and a limit of detection …

Nano And Microscale Adhesion Energy Measurement For Au-Au Contacts In Microswitch Structures, Nima Rahbar, Zong Zong, Yifang Cao, Wole Soboyejo

Nima Rahbar

This paper presents a study of adhesion energies that are relevant to Au–Au microswitch contacts at the nano- and micronscales. Adhesionmeasurements are obtained from cantilevered Aumicroelectromechanical system(MEMS)microswitch structures with varying lengths. Scanning electron microscopymeasurements of the microbeam profiles are combined with fracture mechanics model for the estimation of the adhesion energy. Adhesion contact and pull-off experiments are combined with theoretical models for the extraction of adhesion energies associated with Au-coated atomic force microscopy tips and Aumicroswitch substrates. Finite element method simulation was also performed to account for crack-tip shielding contributions from asperities in contact between Au–Au microscale cantilevered MEMS structure. …

Physical And Structural Basis For The Strong Interactions Of The -Impy- Central Pairing Motif In The Polyamide F-Impyim, K. Buchmueller, S. Bailey, D. Matthews, Z. Taherbhai, J. Register, Z. Davis, Chrystal Bruce, C. O'Hare, J. Hartley, M. Lee

Chrystal D. Bruce

The polyamide f-ImPyIm has a higher affinity for its cognate DNA than either the parent analogue, distamycin A (10-fold), or the structural isomer, f-PyImIm (250-fold), has for its respective cognate DNA sequence. These findings have led to the formulation of a two-letter polyamide “language” in which the -ImPy- central pairings associate more strongly with Watson−Crick DNA than -PyPy-, -PyIm-, and -ImIm-. Herein, we further characterize f-ImPyIm and f-PyImIm, and we report thermodynamic and structural differences between -ImPy- (f-ImPyIm) and -PyIm- (f-PyImIm) central pairings. DNase I footprinting studies confirmed that f-ImPyIm is a stronger binder than distamycin A and f-PyImIm and …

Formation And Stabilization Of Persistent Free Radicals, Barry Dellinger, Slawomir Lomnicki, Lavrent Khachatryan, Zofia Maskos, Randall W. Hall, Julien Adounkpe, Cheri Mcferrin, Hieu Truong

Randall W. Hall

Structure And Enhanced Reactivity Rates Of The D 5 H Sc3n@ C80 And Lu3n@ C80 Metallofullerene Isomers: The Importance Of The Pyracylene Motif, Ting Cai, Liaosa Xu, Mark Anderson, Zhongxin Ge, Tianming Zuo, Xuelei Wang, Marilyn Olmstead, Alan Balch, Harry Gibson, Harry Dorn

Mark R. Anderson

In this paper we report enhanced reactivity of the D5h isomers in comparison with the more common Ih isomers of Sc3N@C80 and Lu3N@C80 toward Diels−Alder and 1,3-dipolar tritylazomethine ylide cycloaddition reactions. Also, the structure of the D5h isomer of Sc3N@C80 has been determined through single-crystal X-ray diffraction on D5h-Sc3N@C80·Ni(OEP)·2benzene (OEP = octaethylporphyrin). The Sc3N portion of D5h-Sc3N@C80 is strictly planar, but the plane of these four atoms is tipped out of the noncrystallographic, horizontal mirror plane of the fullerene by 30°. The combination of short bond length and high degree of pyramidization for the central carbon atoms of the pyracylene …

High-Resolution Raman Spectra With Femtosecond Pulses: An Example Of Combined Time- And Frequency-Domain Spectroscopy, Sukhendu Nath, Diana Urbanek, Sean Kern, Mark Berg

Sean J. Kern

Frequency-domain spectroscopy requires long pulses, whereas time-domain spectroscopy requires short pulses. This Letter demonstrates both theoretically and experimentally that simultaneous detection in frequency and time generates well-resolved spectra using intermediate-length pulses. In the case of coherent Raman spectroscopy, typical femtosecond pulses lie between the time and frequency domains. To demonstrate this method, a high-resolution Raman spectrum of nitrobenzene is obtained from 60 fs pulses. Phase control, pulse shaping, or pulses of widely differing duration are not required.

Projects That Assist With Content In A Traditional Organic Chemistry Course, John Esteb, John Magers, Luanne Mcnulty, Anne Wilson

John Esteb

Projects that engage undergraduate students in content-based courses, such as organic chemistry, must relate to the material and provide useful tools for the divergent needs of the students. There are few examples of these types of projects in the literature. Herein, we describe two projects, the reaction notebook and the end-of-semester synthesis activity. Each project is designed to stimulate student ownership of the material and leads to engagement with the content of the course.

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Kinetic Deuterium Isotope Effects On The Reactions Of 2-(4-Methoxyphenyl)Oxirane In Water Solutions, Ram Mohan, Victoria Ukachukwu, Dale Whalen

Ram S. Mohan

The rates of reaction of 2-(4-methoxyphenyl)oxirane (4-methoxystyrene oxide), trans-3-deutereo-2-(4-methoxyphenyl)oxirane and 3,3-dideutereo-2-(4-methoxyphenyl)oxirane in water solutions were measured as functions of pH. Kinetic deuterium isotope effects for the reactions of the mono- and di-deuterated (4-methoxyphenyl)oxiranes were determined for both the acid-catalyzed hydrolysis to diols and the pH-independent reactions leading mostly to rearranged aldehyde and involving a 1,2-hydrogen migration. The inverse kinetic deuterium isotopes for acid-catalyzed hydrolyses of the deuterated (4-methoxyphenyl)oxiranes to diols are consistent with rate-limiting epoxide ring opening. The magnitudes of the normal kinetic deuterium isotope effects on the pH-independent reactions of deuterated 4-methoxyphenyloxiranes are significantly smaller than the deuterium …