Publications by authors named "Daud Sharif"

Article Synopsis
  • cVSSI and HDX-MS were used to study various DNA forms, including G-quadruplexes, triplex, and duplex DNA, revealing their conformational properties.
  • G-quadruplex DNA showed a 12% to 21% range in deuterium uptake, with different topologies having varying stability and protection levels of hydrogens.
  • The findings suggest that G-quadruplex structures exhibit unique hydrogen protection characteristics, and the study sets the stage for future research on DNA conformations and flexibility.
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N-methyladenosine (mA) is the most prominent epitranscriptomic modification to RNA in eukaryotes, but it's role in adaptive changes within the gestational environment are poorly understood. We propose that gestational exposure to nano titanium dioxide (TiO) contributes to cardiac mA methylation in fetal offspring and influences mitochondrial gene expression. 10-week-old pregnant female FVB/NJ wild-type mice underwent 6 nonconsecutive days of whole-body inhalation exposure beginning on gestational day (GD) 5.

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Rationale: Many different structure analysis techniques are not capable of probing the heterogeneity of solution conformations. Here, we examine the ability of in-droplet hydrogen-deuterium exchange (HDX) to directly probe solution conformer heterogeneity of a protein with mass spectrometry (MS) detection.

Methods: Two vibrating capillary vibrating sharp-edge spray ionization (cVSSI) devices have been arranged such that they generate microdroplet plumes of the analyte and D O reagent, which coalesce to form reaction droplets where HDX takes place in the solution environment.

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Field-free capillary vibrating sharp-edge spray ionization (cVSSI) is evaluated for its ability to conduct native mass spectrometry (MS) experiments. The charge state distributions for nine globular proteins are compared using field-free cVSSI, field-enabled cVSSI, and electrospray ionization (ESI). In general, for both positive and negative ion mode, the average charge state () increases for field-free cVSSI with increasing molecular weight similar to ESI.

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Article Synopsis
  • A new ionization technique called vibrating sharp-edge spray ionization (cVSSI) has been combined with corona discharge to improve atmospheric pressure chemical ionization (APCI) capabilities.
  • This optimized process significantly enhances ion signal intensity, reduces matrix effects, and limits ion suppression, achieving up to a 10-fold increase in signal for certain analytes like cocaine.
  • The technique shows remarkable improvements, with ion signal levels increasing drastically for aqueous samples and better signal-to-noise ratios, making it advantageous for field analyses and direct measurements from samples like cotton swabs.
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Multidevice capillary vibrating sharp-edge spray ionization (cVSSI) source parameters have been examined to determine their effects on conducting hydrogen/deuterium exchange (HDX) experiments. Control experiments using select compounds indicate that the observed differences in mass spectral isotopic distributions obtained upon initiation of HDX result primarily from solution-phase reactions as opposed to gas-phase exchange. Preliminary studies have determined that robust HDX can only be achieved with the application of same-polarity voltage to both the analyte and the deuterium oxide reagent (DO) cVSSI devices.

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The relative contributions to ionization efficiency by three molecular chemical properties have been examined for field-free and field-enabled capillary vibrating sharp-edge spray ionization (cVSSI) using mass spectrometry (MS) analysis. Ion intensities have been recorded for model compounds under each operational ionization mode as well as for aqueous and nonaqueous (methanol) solvent systems. Multiple regression analysis suggests that for field-free cVSSI, ion intensity is mostly associated with the log of the base dissociation constant (p) and proton affinity (PA) for both aqueous and methanol solutions.

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The first 17 amino acid residues of Huntingtin protein (Nt17 of htt) are thought to play an important role in the protein's function; Nt17 is one of two membrane binding domains in htt. In this study the binding ability of Nt17 peptide with vesicles comprised of two subclasses of phospholipids is studied using electrospray ionization - mass spectrometry (ESI-MS) and molecular dynamics (MD) simulations. Overall, the peptide is shown to have a greater propensity to interact with vesicles of phosphatidylcholine (PC) rather than phosphatidylethanolamine (PE) lipids.

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