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Articles 181 - 186 of 186

Full-Text Articles in Biochemistry, Biophysics, and Structural Biology

Capillary Liquid Chromatography Using Micro Size Particles, Yanqiao Xiang Jul 2004

Capillary Liquid Chromatography Using Micro Size Particles, Yanqiao Xiang

All Theses and Dissertations

High speed and/or high efficiency separations can be realized using small particles (~ 1 ┬Ám) in liquid chromatography (LC). However, due to the large pressure drop caused by small particles, conventional LC pumping systems cannot satisfy the pressure requirements needed to drive the mobile phase through the column. Use of ultrahigh pressure, elevated temperature, or both can overcome these pressure limitations and allow the use of very small particles for high speed and/or high efficiency separations.

In this dissertation, the use of ultrahigh pressures with and without elevated temperatures in capillary LC is described. Very fast separations of various ...


Velocity And Temperature Characterization Of The First Vacuum Stage Expansion In An Inductively Coupled Plasma - Mass Spectrometer, William Neil Radicic May 2004

Velocity And Temperature Characterization Of The First Vacuum Stage Expansion In An Inductively Coupled Plasma - Mass Spectrometer, William Neil Radicic

All Theses and Dissertations

The inductively coupled plasma - mass spectrometer (ICP-MS) is the analytical instrument of choice for trace element detection and quantification. Despite the popularity of ICP-MS, significant degradation in sensitivity and precision occurs as the result of matrix and instrument-induced effects. The sources of these effects are not well understood, characterized, or correlated to particular plasma operating condition settings or matrix compositions and involve both neutral and charged species. The purpose of this study is to characterize the behavior of metastable Ar (I) atom and Ca (II) ion through the measurement of Doppler velocities and fluorescence line width "temperatures."

For the characterization ...


N9 Alkylation And Glycosylation Of Purines; A Practical Synthesis Of 2-Chloro-2'-Deoxyadenosine, Minghong Zhong May 2004

N9 Alkylation And Glycosylation Of Purines; A Practical Synthesis Of 2-Chloro-2'-Deoxyadenosine, Minghong Zhong

All Theses and Dissertations

(a) The Robins reagent [2-acetamido-6-O-(diphenylcarbamoyl)purine] was utilized for glycosylation under Lewis acid conditions. Regioselectivity of glycosylation depends on the glycosyl donor and its 2-O- or 2-N-protecting group. Regioselective N9 glycosylation of 2-acetamido-6-O-(diphenylcarbamoyl)purine with problematic glucosamine has been accomplished by protecting the amino function as a phthalimido group with consequent stabilization of the oxocarbenium cation, and lowering the activation energy by introduction of trichloroacetimidate at the anomeric carbon.

(b) 6-Heteroaryl functions [6-(1,2,4-triazol-4-yl) and 6-(imidazol-1-yl)] were introduced into purine derivatives for regioselective N9 alkylation. The regiospecificity of alkylation mainly results from steric effects due ...


Fluorescence Detectors For Proteins And Toxic Heavy Metals, Uchenna Prince Paul Apr 2004

Fluorescence Detectors For Proteins And Toxic Heavy Metals, Uchenna Prince Paul

All Theses and Dissertations

An inexpensive detector for proteins is described. The detection technique was based on two-photon excitation intrinsic protein fluorescence using a visible 532 nm diode-pumped nano laser as the excitation source. Proteins that exhibit intrinsic fluorescence must contain at least one tryptophan, tyrosine, or phenylalanine residue in their amino acid sequences. The detector was characterized and was found to have a detection limit of 4 micro-molar for tryptophan, 22 micro-molar for tyrosine and 500 micro-molar for phenylalanine. Bovine serum albumin, a serum protein with 3 tryptophan residues in its amino acid sequence was also used to characterize the detector. It was ...


Analysis Of Clinically Important Compounds Using Electrophoretic Separation Techniques Coupled To Time-Of-Flight Mass Spectrometry, Zlatuse Durda Peterson Apr 2004

Analysis Of Clinically Important Compounds Using Electrophoretic Separation Techniques Coupled To Time-Of-Flight Mass Spectrometry, Zlatuse Durda Peterson

All Theses and Dissertations

Capillary electrophoretic (CE) separations were successfully coupled to time-of-flight mass spectrometric (TOFMS) detection for the analysis of three families of biological compounds that act as mediators and/or indicators of disease, namely, catecholamines (dopamine, epinephrine, norepinephrine) and their O-methoxylated metabolites (3-methoxytyramine, norepinephrine, and normetanephrine), indolamines (serotonin, tryptophan, and 5-hydroxytryptophan), and angiotensin peptides. While electrophoretic separation techniques provided high separation efficiency, mass spectrometric detection afforded specificity unsurpassed by other types of detectors.

Both catecholamines and indolamines are present in body fluids at concentrations that make it possible for them to be determined by capillary zone electrophoresis coupled to TOFMS without employing ...


Comprehensive Isotachophoresis-Capillary Electrophoresis Coupled To Time-Of-Flight Mass Spectrometry, Christopher Ryan Bowerbank May 2001

Comprehensive Isotachophoresis-Capillary Electrophoresis Coupled To Time-Of-Flight Mass Spectrometry, Christopher Ryan Bowerbank

All Theses and Dissertations

Isotachophoresis (ITP) coupled to capillary zone electrophoresis (CE) in a comprehensive manner was used to separate mixture components in both insufficient and sufficient concentrations without heart-cutting or splitting. Examples of comprehensive ITP-CE involving multiple CE injections of preconcentrated ITP zones are demonstrated. In the comprehensive arrangement, all of the sample in the first dimension (ITP) is subjected to analysis in the second dimension (CE), without significant sample loss or decrease in sample detectability resulting from removal of a portion of the sample. This is especially important for analytes at low concentrations which may form a single mixed zone instead of ...