Graduation Year

2013

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Chemistry

Major Professor

Julie Harmon

Keywords

BEDO-TTF, Dielectric Analysis, Differential Scanning Calorimetry, Induction Based Fluidics, Peptide Mass Fingerprinting

Abstract

With the emergence of Matrix Assisted Laser Desorption/Ionization-Time-of-flight as a tool for diagnosis of diseases via proteomics, there is an increasing need for greater sensitivity. Analysis of peptides by MALDI-TOF-MS is affected by sample formulation and spotting onto a MALDI target. This dissertation investigates a novel MALDI sample preparation technique, Induction Based Fluidics (IBF), for depositing precise volumes (pL to nL) of samples onto the target. We have seen that while using IBF, the induced electric field accompanying deposition enhances matrix crystallization yielding smaller crystals with more homogeneity, as compared to conventional manual micropipette (MP) depositions. An investigation of the signal-to-noise (S/N) for IBF deposition of tryptic digested Bovine Serum Albumin (BSA) showed a significant improvement in the signal-to-noise ratio for 0.5 and 0.25 pmol/µL BSA sample compared to equivalent MP depositions. The S/N enhancement for IBF and MP depositions of BSA were studied using à-cyano-4-hydroycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB) matrices, and CHCA showed better results than DHB .

The exciting results obtained by IBF prompted us to probe sample morphology more fully and to relate morphology to the detections level and hopefully, to increase the utility of MALDI-TOF-MS for detection of a larger range of peptides. Morphology results were correlated to sensitivity limits using both dispensing techniques. Because of dissimilar rates of evaporation, different or uneven deposition thickness, or crystal lattice morphology, discontinuous crystallization patterns were observed for MP depositions. However, IBF deposited samples occupied less planar area with uniform distribution of crystals, thereby reducing sample crystal heterogeneity and laborious hunt for a "sweet" or "hot" spot to produce high quality spectra. The application of IBF was extended to the tryptic digested BSA protein using peptide mass fingerprinting. IBF deposition resulted in a larger number of detectable peptides as well as higher sequence coverage as compared to equivalent MP depositions.

In last few decades, advanced research and potential applications in the field of microelectronics have spurred interest in the development of reticulated doped polymer films. Bis (ethylenedioxy) tetrathiafulvalene (BEDO-TTF)/Polycarbonate (PC) films were synthesized and characterized for use in hand-held real time explosives sensors, capable of detecting nitro-based compounds (nitroaromatics, nitoamines and nitroesters), which are the main components of Improvised Explosive Devices or IEDs. Reticulated doped polymer films were prepared by exposing solid solutions of BEDO-TTF in PC to iodine to form conductive charge transfer complexes. The resulting films exhibited room temperature conductivities ranging from 6.33-90.4*10-5 S cm-1. The colored iodine complexes in the film were reduced by cyclic voltammetry yielding conductive, colorless, transparent films. Dielectric analysis (DEA) was used to probe relaxations in neat PC and BEDO-TTF/PC showed that BEDO-TTF plasticized the PC and decreased the glass transition temperature. Two secondary relaxations appeared in PC films, whereas the transitions merged in the doped film. DEA also revealed conductivity relaxations above 180°C, which were characterized by the electric modulus formalism and showed that BEDO-TTF increased the alternating current, (AC) conductivity in PC.

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