Publications by authors named "Karen E Butler"

4 Publications

  • Page 1 of 1

Utilizing Ion Mobility-Mass Spectrometry to Investigate the Unfolding Pathway of Cu/Zn Superoxide Dismutase.

Front Chem 2021 9;9:614595. Epub 2021 Feb 9.

Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, United States.

Native mass spectrometry has emerged as a powerful tool for structural biology as it enables the evaluation of molecules as they occur in their physiological conditions. Ion mobility spectrometry-mass spectrometry (IMS-MS) has shown essential in these analyses as it allows the measurement of the shape of a molecule, denoted as its collision cross section (CCS), and mass. The structural information garnered from native IMS-MS provides insight into the tertiary and quaternary structure of proteins and can be used to validate NMR or crystallographic X-ray structures. Additionally, due to the rapid nature (millisecond measurements) and ability of IMS-MS to analyze heterogeneous solutions, it can be used to address structural questions not possible with traditional structural approaches. Herein, we applied multiple solution conditions to systematically denature bovine Cu/Zn-superoxide dismutase (SOD1) and assess its unfolding pathway from the holo-dimer to the holo-monomer, single-metal monomer, and apo-monomer. Additionally, we compared and noted 1-2% agreement between CCS values from both drift tube IMS and trapped IMS for the SOD1 holo-monomer and holo-dimer. The observed CCS values were in excellent agreement with computational CCS values predicted from the homo-dimer crystal structure, showcasing the ability to use both IMS-MS platforms to provide valuable structural information for molecular modeling of protein interactions and structural assessments.
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http://dx.doi.org/10.3389/fchem.2021.614595DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7900566PMC
February 2021

Enhanced protocol for quantitative N-linked glycomics analysis using Individuality Normalization when Labeling with Isotopic Glycan Hydrazide Tags (INLIGHT)™.

Anal Bioanal Chem 2020 Nov 26;412(27):7569-7579. Epub 2020 Aug 26.

Department of Chemistry, North Carolina State University, Raleigh, NC, 27695, USA.

The analysis of N-linked glycans using liquid chromatography and mass spectrometry (LC-MS) presents significant challenges, particularly owing to their hydrophilic nature. To address these difficulties, a variety of derivatization methods have been developed to facilitate improved ionization and detection sensitivity. One such method, the Individuality Normalization when Labeling with Isotopic Glycan Hydrazide Tags (INLIGHT)™ strategy for labeling glycans, has previously been utilized in the analysis of N- and O-linked glycans in biological samples. To assess the maximum sensitivity and separability of the INLIGHT™ preparation and analysis pipeline, several critical steps were investigated. First, recombinant and nonrecombinant sources of PNGase F were compared to assess variations in the released glycans. Second, modifications in the INLIGHT™ derivatization step were evaluated including temperature optimization, solvent composition changes, reaction condition length and tag concentration. Optimization of the modified method resulted in 20-100 times greater peak areas for the detected N-linked glycans in fetuin and horseradish peroxidase compared with the standard method. Furthermore, the identification of low-abundance glycans, such as (Fuc)(Gal)(GlcNAc)(Man)(NeuAc) and (Gal)(GlcNAc)(Man)(NeuAc), was possible. Finally, the optimal LC setup for the INLIGHT™ derivatized N-linked glycan analyses was found to be a C18 reverse-phase (RP) column with mobile phases typical of RPLC.
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http://dx.doi.org/10.1007/s00216-020-02892-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7541788PMC
November 2020

Evaluation of Nicotine and the Components of e-Liquids Generated from e-Cigarette Aerosols.

J Anal Toxicol 2018 Oct;42(8):537-543

Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA.

Electronic cigarettes (e-cigs) deliver nicotine in an aerosol to the user that simulates the smoke of traditional cigarettes purportedly without the pathology of inhaling tobacco smoke due to the absence of combustion. Advanced versions of e-cigs enable the user to potentially moderate the concentration of drug in the aerosol by selecting from a range of voltages on the power supply. A method was developed to trap the aerosol produced by a KangerTech AeroTank, 1.8 Ω preassembled atomizer in order to analyze the concentration of nicotine and to evaluate the constituents of the aerosol at various voltages on the power supply. A 12-mg/mL formulation of nicotine in 50:50 propylene glycol (PG):vegetable glycerin (VG) was used to produce aerosol at 3.9, 4.3 and 4.7 V. The aerosol was trapped in a simple glass assemblage and analyzed by a 3200 Q Trap HPLC-MS-MS. The dose of nicotine delivered in the aerosol at 3.9, 4.3 and 4.7 V was determined to be 88 ± 12 μg, 91 ± 15 μg and 125 ± 22 μg. The average recovery of nicotine in the trap across the voltages was 99.8%. The glass trap system was an effective device for collecting the aerosol for analysis and an increase in drug yield was observed with increasing voltage from the power supply on the e-cig. The glass trap system was also used in combination with a 100-μm solid-phase microextraction fiber to capture the aerosol and analyze it via DART-MS and GC-MS. Four commercial e-liquids labeled to contain nicotine were aerosolized at 4.3 V. The pharmacologically active ingredient, nicotine, as well as PG, VG and a number of flavoring agents found in these formulations were identified.
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http://dx.doi.org/10.1093/jat/bky056DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6203128PMC
October 2018

Evaluation of Two Commercially Available Cannabidiol Formulations for Use in Electronic Cigarettes.

Front Pharmacol 2016 29;7:279. Epub 2016 Aug 29.

Department of Forensic Science, Virginia Commonwealth University, Richmond, VAUSA; Department of Pathology, Virginia Commonwealth University, Richmond, VAUSA; Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VAUSA.

Since 24 states and the District of Columbia have legalized marijuana in some form, suppliers of legal marijuana have developed Cannabis sativa products for use in electronic cigarettes (e-cigarettes). Personal battery powered vaporizers, or e-cigarettes, were developed to deliver a nicotine vapor such that smokers could simulate smoking tobacco without the inherent pathology of inhaled tobacco smoke. The liquid formulations used in these devices are comprised of an active ingredient such as nicotine mixed with vegetable glycerin (VG) and/or propylene glycol (PG) and flavorings. A significant active ingredient of C. sativa, cannabidiol (CBD), has been purported to have anti-convulsant, anti-nociceptive, and anti-psychotic properties. These properties have potential medical therapies such as intervention of addictive behaviors, treatments for epilepsy, management of pain for cancer patients, and treatments for schizophrenia. However, CBD extracted from C. sativa remains a DEA Schedule I drug since it has not been approved by the FDA for medical purposes. Two commercially available e-cigarette liquid formulations reported to contain 3.3 mg/mL of CBD as the active ingredient were evaluated. These products are not regulated by the FDA in manufacturing or in labeling of the products and were found to contain 6.5 and 7.6 mg/mL of CBD in VG and PG with a variety of flavoring agents. Presently, while labeled as to content, the quality control of manufacturers and the relative safety of these products is uncertain.
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http://dx.doi.org/10.3389/fphar.2016.00279DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5002419PMC
September 2016