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Full-Text Articles in Physical Sciences and Mathematics
Formation Of Gaseous Peptide Ions From Electrospray Droplets: Competition Between The Ion Evaporation Mechanism And Charged Residue Mechanism., Elnaz Aliyari, Lars Konermann
Formation Of Gaseous Peptide Ions From Electrospray Droplets: Competition Between The Ion Evaporation Mechanism And Charged Residue Mechanism., Elnaz Aliyari, Lars Konermann
Chemistry Publications
The transfer of peptide ions from solution into the gas phase by electrospray ionization (ESI) is an integral component of mass spectrometry (MS)-based proteomics. The mechanisms whereby gaseous peptide ions are released from charged ESI nanodroplets remain unclear. This is in contrast to intact protein ESI, which has been the focus of detailed investigations using molecular dynamics (MD) simulations and other methods. Under acidic liquid chromatography/MS conditions, many peptides carry a solution charge of 3+ or 2+. Because of this pre-existing charge and their relatively small size, prevailing views suggest that peptides follow the ion evaporation mechanism (IEM). The IEM …
Mobile Protons Limit The Stability Of Salt Bridges In The Gas Phase: Implications For The Structures Of Electrosprayed Protein Ions., Lars Konermann, Elnaz Aliyari, Justin H Lee
Mobile Protons Limit The Stability Of Salt Bridges In The Gas Phase: Implications For The Structures Of Electrosprayed Protein Ions., Lars Konermann, Elnaz Aliyari, Justin H Lee
Chemistry Publications
Electrosprayed protein ions can retain native-like conformations. The intramolecular contacts that stabilize these compact gas-phase structures remain poorly understood. Recent work has uncovered abundant salt bridges in electrosprayed proteins. Salt bridges are zwitterionic BH+/A- contacts. The low dielectric constant in the vacuum strengthens electrostatic interactions, suggesting that salt bridges could be a key contributor to the retention of compact protein structures. A problem with this assertion is that H+ are mobile, such that H+ transfer can convert salt bridges into neutral B0/HA0 contacts. This possible salt bridge annihilation puts into question the …
Sulfolane-Induced Supercharging Of Electrosprayed Salt Clusters: An Experimental/Computational Perspective., Leanne M Martin, Lars Konermann
Sulfolane-Induced Supercharging Of Electrosprayed Salt Clusters: An Experimental/Computational Perspective., Leanne M Martin, Lars Konermann
Chemistry Publications
It is well-known that supercharging agents (SCAs) such as sulfolane enhance the electrospray ionization (ESI) charge states of proteins, although the mechanistic origins of this effect remain contentious. Only very few studies have explored SCA effects on analytes other than proteins or peptides. This work examines how sulfolane affects electrosprayed NaI salt clusters. Such alkali metal halide clusters have played a key role for earlier ESI mechanistic studies, making them interesting targets for supercharging investigations. ESI of aqueous NaI solutions predominantly generated singly charged [NanI(n-1)]+ clusters. The addition of sulfolane resulted in abundant …
Gas Phase Protein Folding Triggered By Proton Stripping Generates Inside-Out Structures: A Molecular Dynamics Simulation Study., Alexander I M Sever, Lars Konermann
Gas Phase Protein Folding Triggered By Proton Stripping Generates Inside-Out Structures: A Molecular Dynamics Simulation Study., Alexander I M Sever, Lars Konermann
Chemistry Publications
The properties of electrosprayed protein ions continue to be enigmatic, owing to the absence of high-resolution structure determination methods in the gas phase. There is considerable evidence that under properly optimized conditions these ions preserve solution-like conformations and interactions. However, it is unlikely that these solution-like conformers represent the "intrinsic" structural preferences of gaseous proteins. In an effort to uncover what such intrinsically preferred conformers might look like, we performed molecular dynamics (MD) simulations of gaseous ubiquitin. Our work was inspired by recent gas phase experiments, where highly extended 13+ ubiquitin ions were transformed to compact 3+ species by proton …
Crown Ether Effects On The Location Of Charge Carriers In Electrospray Droplets: Implications For The Mechanism Of Protein Charging And Supercharging., Haidy Metwally, Lars Konermann
Crown Ether Effects On The Location Of Charge Carriers In Electrospray Droplets: Implications For The Mechanism Of Protein Charging And Supercharging., Haidy Metwally, Lars Konermann
Chemistry Publications
"Native" electrospray ionization (ESI) mass spectrometry (MS) aims to transfer proteins from solution into the gas phase while maintaining solution-like structures and interactions. The ability to control the charge states of protein ions produced in these experiments is of considerable importance. Supercharging agents (SCAs) such as sulfolane greatly elevate charge states without significantly affecting the protein structure in bulk aqueous solution. The origin of native ESI supercharging remains contentious. According to one model, SCAs trigger unfolding within ESI droplets. In contrast, the "charge trapping model" envisions that SCAs impede the ejection of charge carriers (e.g., NH4+ or Na …
Molecular Dynamics Simulations On Gas-Phase Proteins With Mobile Protons: Inclusion Of All-Atom Charge Solvation., Lars Konermann
Molecular Dynamics Simulations On Gas-Phase Proteins With Mobile Protons: Inclusion Of All-Atom Charge Solvation., Lars Konermann
Chemistry Publications
Molecular dynamics (MD) simulations have become a key tool for examining the properties of electrosprayed protein ions. Traditional force fields employ static charges on titratable sites, whereas in reality, protons are highly mobile in gas-phase proteins. Earlier studies tackled this problem by adjusting charge patterns during MD runs. Within those algorithms, proton redistribution was subject to energy minimization, taking into account electrostatic and proton affinity contributions. However, those earlier approaches described (de)protonated moieties as point charges, neglecting charge solvation, which is highly prevalent in the gas phase. Here, we describe a mobile proton algorithm that considers the electrostatic contributions from …
Salt And Water Uptake In Nanocon!Nement Under Applied Electric Field: An Open Ensemble Monte Carlo Study, F. Moucka, D. Bratko, A. Luzar
Salt And Water Uptake In Nanocon!Nement Under Applied Electric Field: An Open Ensemble Monte Carlo Study, F. Moucka, D. Bratko, A. Luzar
Chemistry Publications
Permeation of electrolytes in nanoporous materials underlies many applications in energy and materials technologies. Wetting of apolar nanopores can be enhanced by electric !eld, attracting water and ions from unperturbed electrolyte bath. We study absorption of water and NaCl in the pores by Expanded Ensemble Grand Canonical Monte Carlo simulation, which implements particle insertions and deletions through incremental changes in particles’ coupling with the system. We determine the uptake of water and ions in the pores, and concomitant changes in pore thermodynamics, as functions of !eld strength in the pore and salinity in the external bath. Pressure increase and reduction …