Login

Publications  •  Project Statistics

Glossary  •  Schools  •  Disciplines
People Search: 
   
Title/Abstract Search: 

Dissertation Information for Steven J. Lawson

NAME:
- Steven J. Lawson

DEGREE:
- Ph.D.

DISCIPLINE:
- Chemistry

SCHOOL:
- Emory University (USA) (2001)

ADVISORS:
- Kermit K. Murray

COMMITTEE MEMBERS:
- Vincent P. Conticello
- Joseph B. Justice Jr.

MPACT Status: Fully Complete

Title: Infrared matrix-assisted laser desorption ionization mass spectrometry with liquid and ice matrices

Abstract: "In this work, the development of liquid and ice IR-MALDI matrices has been explored, and applications for these matrices have been developed. Solvent-based IR-MALDI matrices can be used in the liquid state for continuous flow (on-line) MALDI or frozen into the solid state for off-line MALDI analyses. Continuous flow MALDI was demonstrated with infrared laser desorption and an ethanol matrix. A capillary was used to deliver an analyte solution to a metal frit embedded in a sample stage. Typical flow rates were 1.7 ìL/min. An optical parametric oscillator tuned to 2.8 ìm was used for desorption and ionization, and mass analysis was achieved with a 1 m linear time-of-flight mass spectrometer. Flow injection studies were performed with low picomolar quantities of insulin and myoglobin in solutions containing 0.1 to 1.0% glycerol in ethanol. A design for a better continuous flow probe was proposed. The improved probe should be simpler to use compared with prototype probes. In addition, the new probe has a replaceable frit, which reduces dead volume compared with the prototype probe and allows capillary tubing with the narrowest bores to be used.

Mass spectra of oligonucleotides were obtained from frozen mixed matrices. The frozen matrices consisted of glycerol in dimethyl sulfoxide (DMSO) and were kept in the solid state using a cold MALDI ion source which can be refrigerated with liquid nitrogen. Oligonucleotides analyzed from mixed, frozen DMSO matrices produced MALDI mass spectra with little matrix background. With small oligonucleotides, mass resolution was sufficient to resolve salt adducts, and a detection limit of 0.50 ìM was established. Oligonucleotides as large as 50-mers were also desorbed and ionized from a frozen DMSO matrix. With oligonucleotides of this size, integration of ion intensities improved spectral interpretation. Double stranded DNA was investigated in a mixed liquid matrix of glycerol and water. These matrices, however, did not need to be frozen due to high glycerol content. When analyzed in such a matrix, a 50 base pair DNA spectrum was obtained. This spectrum exhibited abundant matrix background and low mass resolution. However, singly protonated ds-DNA ion intensity was identified in the spectrum, though peak assignment was difficult. Desorption and ionization of polymerase chain reaction amplified DNA was also attempted using a glycerol/water matrix, but mass spectra could not be obtained. Reasons for poor IR-MALDI performance with the PCR products such as GC (guanine-eytosine) and salt content of the DNA and the temporal width of the laser pulse were postulated.

Mixed liquid matrices are of promise to MALDI mass spectrometry. These matrices are equally applicable to off-line and on-line MALDI. Future work will center around further development of mixed matrices for on-line macromolecular analysis by continuous flow MALDI. An effective continuous flow interface is expected which, among other applications, may be useful for on-line oligonucleotide analysis by IR-MALDI."

MPACT Scores for Steven J. Lawson

A = 0
C = 0
A+C = 0
T = 0
G = 0
W = 0
TD = 0
TA = 0
calculated 2008-04-07 07:57:07

Advisors and Advisees Graph