Gas phase protein ions

Top PDF Gas phase protein ions:

Using Ion Mobility Spectrometry to Study Protein Conformations in the Gas Phase

Using Ion Mobility Spectrometry to Study Protein Conformations in the Gas Phase

In terms of ESI techniques, there are two options existing to convert solution phase analytes to gaseous ions. Regular ESI operates at the flow rate in the µL/min range, using a metal emitter capillary. 30, 58 NanoESI operates with a much smaller spray capillary (Figure 1-3), giving rise to flow rate of less than 100 nL/min. 59 NanoESI was first proposed by Wilm, Mann and coworkers. 60-61 They pointed out that achieving a low flow rate can be beneficial in many ways. The initial droplets from nanoESI have diameters of less than 200 nm due to the smaller capillary orifice, which are about 100 to 1000 times smaller than in regular ESI. 60 In the aspect of operation, the potential applied on the capillary is around 0.5-1.5 kV, which is significantly lower than regular ESI, although it always needs an auxiliary pressure to initiate and maintain a steady flow of solution. 62 Considering such low flow rate and small volume of initial droplets, nanoESI can be associated with several advantages. First of all, less sample is required. Only 1-2 µL of sample is loaded directly into the gold-coated glass capillaries. 63 Solution is drawn through the capillary without a conventional syringe pump. Secondly, ionization efficiency is improved, which is supported by a series of experiments. 64-67 The ionization efficiency can be characterized as the ratio between the number of detected analyte molecules and the total number of ions in the solution delivered to the ionization source. 68 It is commonly accepted
Show more

112 Read more

Amphipols outperform dodecylmaltoside micelles in stabilizing membrane protein structure in the gas phase

Amphipols outperform dodecylmaltoside micelles in stabilizing membrane protein structure in the gas phase

Analysis of DDM and A8-35 solubilized Mhp1 and GalP by use of ESI-IMS-MS resulted in peaks corresponding to each MP, as well as those originating from protein-bound lipids retained from the puri fi cation procedure (Figures 4a,c and 5a,c). Collision energies had to be set to much higher levels than for both of the OMPs (with the Trap T-wave collision energy having to be raised to 180 V) before resolvable protein peaks were observed. Both phosphatidylethanolamine (PE) and cardiolipin (CL) were identi fi ed by lipid extraction and further analysis by ESI-MS/MS in negative ion mode (data not shown), common components of the E. coli inner membrane from which the MPs were isolated. 77 In the case of the DDM solubilized proteins (Figures 4a,b and 5a,b), a narrow range of charge states was observed in the spectra. In contrast, a much broader range of charge state ions was observed in the ESI- IMS-MS spectra of A8-35 solubilized Mhp1 and GalP (Figures 4c,d and 5c,d), with more lowly charged species present, indicating the gas phase conformations of the proteins also contain more compact/folded species. Analysis of the measured CCSs of the observed ions reinforces this, with the lowly charged ions liberated from the A8-35 trapped protein samples having CCSs which indicate they are of relatively compact structure, unlike the ions observed upon analysis of the DDM solubilized protein (Figures 4e and 5e). The lowest observed charge state ions for A8-35 trapped Mhp1 (7+) had a measured CCS of 3916 Å 2 , within 3.9% of the CCS predicted from the X-
Show more

9 Read more

Protein Conformations in the Gas Phase Probed by Mass Spectrometry and Molecular Dynamics Simulations

Protein Conformations in the Gas Phase Probed by Mass Spectrometry and Molecular Dynamics Simulations

The preceding considerations refer to traditional drift tube IM-MS. However, many commercial instruments (including the one used for the current work) employ travelling wave voltages with nitrogen as buffer gas. A TWIMS device contains a series of ring electrodes that constitute a traveling wave ion guide (TWIGs). Opposite radio frequency (RF) potentials are applied to the electrodes to prepare a radial potential barrier which traps the ions in the radial direction. In addition, ”waves” of direct current voltage (DC) are superimposed onto the RF voltage, in order to propel the ions through the TWIMS device in the axial direction. The DC voltage maxima jump from ring to ring, thereby “peristaltically” pushing the ions along. Ions with large CCSs experience occasional “rollover” events, i.e., they will fall behind the wave crest, and then get swept along with the subsequent crest. In this way, ions with different mobilities migrate through the TWIMS at different velocities which enables their separation 34 . Figure 1.6. shows the schematics of a TWIMS separator 35-36 .
Show more

77 Read more

From Solution Into the Gas Phase: Studying Protein Hydrogen Exchange and Electrospray Ionization Using Molecular Dynamics Simulation

From Solution Into the Gas Phase: Studying Protein Hydrogen Exchange and Electrospray Ionization Using Molecular Dynamics Simulation

Pulsed mode analyzers accept packets of ions from an upstream ion gate or directly from a pulsed ion source such as MALDI. This type of analyzer includes time-of-flight (TOF) analyzers, Orbitrap analyzers, and Fourier transform ion cyclotron resonance (FTICR) analyzers. The latter two operate under a similar principle, whereby ions are trapped in a harmonic oscillating orbit passing close to a detector and inducing a current, which is recorded and later deconvoluted using a Fourier transformation to identify the individual m/z ratios of species in the ion packet. Orbitrap instruments use an electric field to accomplish this task 34 , while FTICR instruments use a strong magnetic field. 35 Both can achieve very high resolutions and mass accuracy, but require long acquisition times to do so for large analytes, making them somewhat less useful for coupling to continuous flow sources such as ESI. Superconducting magnets needed for the highest resolution ion cyclotron resonance instruments are also very expensive to cool and maintain.
Show more

114 Read more

Gas phase stability of Protein Ions in a Cyclic Ion Mobility Spectrometry Traveling Wave Device

Gas phase stability of Protein Ions in a Cyclic Ion Mobility Spectrometry Traveling Wave Device

subsequent segments/funnels is switched; only the ions with mobilities resonant with the field switching frequency can proceed to the following segments while others are lost. An IM spectrum is obtained by scanning the field switching frequency. Several developments of high resolution IM instrumentation have been facilitated by travelling wave (T-Wave, TW) technology 33 which relies on a series of voltage pulses which propel ions across the device. T-Wave technology eliminates problems related to high voltages, required for the traditional, linear field DT-IM apparatus. A T- Wave based, multi-pass separator (cyclic IM) was first introduced by Giles et al., 34 and separation at path length over 50m was demonstrated. 35 Further advances in a T-Wave technology include structures for lossless ion manipulation (SLIM), notably by Smith et al. 36 A multi-pass SLIM device has allowed IM separations over an extremely long path length (~1km). 37 Other recent developments in IM technology include tandem methods. Two-stage IM technique was first presented by Koeniger et al. 38,39 where an instrument featuring two drift tubes allowed separation in the first IM stage, mobility selection, activation and separation of product ions in the second stage. This was further expanded to three-stage IM method by Merenbloom et al. 40 More recently, the multi-stage IM technology was combined with a multi-pass cyclic IM separator by Giles et al., 35 allowing for IMS n – type workflows.
Show more

33 Read more

Simulation of two phase oil gas flow in 
		pipeline

Simulation of two phase oil gas flow in pipeline

performed using a flow loop with a test section of 50.8- mm ID and 18.9-m-long horizontal pipe. The range of superficial liquid and gas velocity are 0.01 m/s to 3.0 m/s and 0 to 7.0 m/s, respectively. The existing flow patterns: stratified smooth, stratified wavy, elongated bubble, slug, dispersed bubble and annular, were observed for the studied flow conditions. Most of the experimental points observed in this study correspond to slug flow. The stratified smooth region decreases when the oil viscosity increases. Liquid viscosity increase delays the formation of an eddy at the liquid slug front, thus increasing the region of the elongated bubble flow. Gas bubble entrainment in the elongated bubble region increases when oil viscosity increases. For the lower oil viscosities (39 cP and 60 cP), transition from intermittent flow to dispersed bubble flow occurs at higher superficial gas velocities in comparison with higher oil viscosities (108 cP and 166 cP). Annular flow was only observed for the highest oil viscosity (166 cP).
Show more

6 Read more

Gas phase interstitial modification of rare earth intermetallics

Gas phase interstitial modification of rare earth intermetallics

In the initial stage of nitrogenation, stress and strain lead to an expanded particle centre with increased Curie temperature but negative K1.. This "soft centre", which is found in part[r]

6 Read more

The properties of gas-phase multiply-charged ions

The properties of gas-phase multiply-charged ions

Before ions enter the velocity filter they are accelerated to a relatively high translational energy, typically of the order of 250 eV. The necessity for such an acceleration is that dicationic lifetimes are often of the order of a microsecond or less. Hence, without this acceleration, the transit times of the species in the ion beam to the source region of the spectrometer are of the same order as the dicationic lifetimes. So, to reduce the number of dications lost through natural unimolecular decay, the ions are accelerated to reduce their transit times from the ion source to the collision region. Additionally, higher energy ion beams are easier to handle, as perturbing effects from stray electric fields are less significant. However, despite the above arguments in favour of high energy ion beams, the upper limit to the laboratory frame collision energy used in the research presented in this thesis is of the order of 15 eV. The reason for this limit is that we expect the bond-forming reactivity of molecular dications to be favoured at low collision energies, typically lower than 15 eV in the laboratory frame. In addition to this, at laboratory frame collision energies in excess of 15 eV, the detection efficiency of the experimental arrangement will be markedly reduced as a result of the product ion’s transverse velocity component. The detection efficiency is discussed in greater detail in the next Chapter. Hence, before the ions pass into the interaction/source region of the TOFMS, they must be decelerated to the desired collision energy. The deceleration is achieved with the use of appropriate ion deceleration optics.
Show more

159 Read more

A Mathematical Study of Gas phase Hot atom Reactions

A Mathematical Study of Gas phase Hot atom Reactions

in general, the heavier the mass of the radical attached to the activated atom, the smaller the net recoil energy required for bond rupture.. Also presented in Table I, as a percent of E[r]

207 Read more

Ultraviolet Laser Based Gas Phase Fluorination of Polystyrene

Ultraviolet Laser Based Gas Phase Fluorination of Polystyrene

The sample then was irradiated with the excimer laser with a pulse fluence of 10 mJ/cm2 and an accumulated fluence of 30 J/cm2, the precursor pressure was set to 65 mbar.. All samples ex[r]

10 Read more

First Detection of Gas-phase Methanol in a Protoplanetary Disk

First Detection of Gas-phase Methanol in a Protoplanetary Disk

The young star, TW Hya, was observed on 2015 January 02 with 39 antennas and baselines from 15 to 350 m ( project 2013.1.00902.S, P. I. C. Walsh ) . The quasars J1256-0547 and J1037-2934 were used for bandpass and phase calibration, respectively, and Titan was used for amplitude calibration. The Band 7 ( B7 ) methanol transitions listed in Table 1 were targeted using a channel width of 122 kHz ( corresponding to 0.12 km s − 1 ) . A continuum-only spectral window at 317 GHz ( with a total bandwidth of 2 GHz ) was also covered. The total on-source observation time was 43 minutes. All data were self- calibrated prior to imaging using CASA version 4.3 and the continuum band at 317 GHz, and using a timescale of 20 s (≈ 3 times the integration step ) . This increased the dynamic range of the continuum data by a factor of »30. Self-calibration using the continuum around the methanol lines between »304 and 307 GHz gave almost indistinguishable results. The rms noise level achieved for the 317 GHz continuum following imaging with CLEAN ( Briggs weighting, robust = 0.5 ) was 0.10 mJy beam −1 , with a peak signal-to-noise ratio ( S / N ) of 4200. The continuum synthesized beam was 1 2 × 0 6 ( -  86 ) . The line data were imaged without CLEANing ( using natural weight- ing ) following self-calibration and continuum subtraction, with a slight overgridding in velocity resolution ( 0.15 km s −1 ) . The rms achieved in the dirty channel maps was »4 mJy beam − 1 per velocity channel at all four frequencies.
Show more

7 Read more

Structural applications of gas phase ion molecule reactions

Structural applications of gas phase ion molecule reactions

A variety of mass spectrometers have been used to study lour projects, involving three different applications of gas phase* ion- molecule reactions. Firstly, the use of the vinyl methyl ether radical cation for the location of olefinic bonds (NEUIRAL STHUJCIURE DETERMINATION) has been improved by altering the mode of production of the reagent ion. The scope and application of this technique have been reviewed. Secondly, the structures of various C^H^O and C 4 H 5 N+ ' ions (ION STRUCTURE DETERMINATION) have been studied. Reactions specific for the structures (i) CHg-O-CfMSlg + and (ii) have been identified and anployed to detect the presence of C 2 HgO+ ‘ ions of these structures formed from a variety of precursors. These results provide an insight into the mechanisms of sane gas phase elimination reactions and allow this method to be compared with those providing analogous information. Reactions have been sought to characterise the structure of C^HgN ions generated from five different neutral precursors. Such reactions proved not to be identifiable readily, with the exception of a reaction involving 1 .3-butadiene. which appears to be specif ic for the pyrrole molecular ion structure. Finally, the beginning of the application of the technique of Mass Spectrometry/Mass Spectranetry to the detection of gibberellins in mixtures (MIXTURE ANALYSIS) is described. The results of a survey of the chemical ionisation of the gibberellins are
Show more

200 Read more

Parents of two-phase flow and theory of “gas-lift”

Parents of two-phase flow and theory of “gas-lift”

Description of formulas for calculations and designs for gas-lift reactors also serve gas lift model in the laboratory of the Department of Power System Engineering. The model in the first stage is used as media for water and air dispersion modeling using bubble type two-phase flow, which is in terms of the operation of nuclear reactors advantageous. Measurements on the model will be compared with the method Chexal - Lellouche [14]. In addition, there is a comparison of experimental data with numerical simulations.

9 Read more

Gas Phase Train in Upstream Oil & Gas Fields: PART-I Model Development

Gas Phase Train in Upstream Oil & Gas Fields: PART-I Model Development

5. CONCLUSIONS AND FUTURE CHALLENGES Large scale series processes are rather common in the upstream oil & gas industry. Consequently, representative models are a key demand for control and automation engineers to test and verify different control approaches and strategies. The intention of this ’PART I’ paper is to deliver simple and easy to understand process models based on transfer functions for a complex gas processing operations. Processes like gas sweetening and gas dehydra- tion are deemed as difficult control tasks for both process and control engineers. Henceforth the presented model is aimed to ease these control challenges by providing an authentic framework for engineers to design, analyse and evaluate different control solutions. The model provides good opportunity for control engineers to test different variety of process disturbances, malfunctions, and load changes on the process operation and verify its significance in order to design a precise control system. Control system thats able to solve a major control challenge problem the disturbance growth effecting the series connected processes in LSS.
Show more

8 Read more

Gas-phase surface oxidation and chlorination of carbon nanotubes

Gas-phase surface oxidation and chlorination of carbon nanotubes

Table 15 summarizes the peak area % by chemical species for the control (24A) and powdered SWCNT samples treated from 1 to 90 min (24B-24M in Table 13) which revealed low saturation levels of Cl after treatment due to the high oxygen concentration present on these samples before UV photo-chlorination with HCl gas. There is a steady increase in the Cl concentration up to a saturation level of ca. 5.8 at%. The amount of detected oxygen increased with treatment time but not in a linear or proportional relationship. The concentration of oxygen is higher than that of chlorine and thus, resulted in low saturation levels of Cl onto the sample’s surface. The data shows that only a very small amount of the C-C*Cl 2 and/or O-C=O moieties are present and are not
Show more

90 Read more

Removal of gas-phase benzene in an immobilized photocatalytic reactor

Removal of gas-phase benzene in an immobilized photocatalytic reactor

oxidation process appears to be a highly effective technology to decompose high concentrations of VOCs to harmless end products such as H 2 O and CO 2 at ambient temperatures [2]. Recently, the gas-phase elimination of VOCs in photo reactors using suitable photocatalyst such as TiO 2 has re- ceived increased attention in process industries [3]. TiO 2 irradiating with UV or near UV light re- sults in the formation of electron-hole pairs on the catalyst surface. These electrons and holes interact with adsorbed species producing highly reactive hydroxyl radicals which in turn initiate redox re- actions to decompose VOCs. It is known from the literature elsewhere that, shorter the wavelength more is the degradation potential of VOCs in the photoreactor.
Show more

8 Read more

Air-sea transfer of gas phase controlled compounds

Air-sea transfer of gas phase controlled compounds

The transfer velocity of methanol (as well as sensible heat) was determined during the AMT-22 and the HiWinGS cruises. Acetone was measured with enough precision to derive its transfer velocity only on the HiWinGS cruise. The experimental settings and methods have been described in detail previously [1, 19, 20]. Very briefly, concentrations of both compounds in the atmosphere and surface ocean were quantified by a PTR-MS. For the majority of the cruise, the PTR-MS was operated in atmospheric mode and sampling at a rate just above 2 Hz. Winds and motion were measured by a sonic anemometer (Gill 7th International Symposium on Gas Transfer at Water Surfaces IOP Publishing IOP Conf. Series: Earth and Environmental Science 35 (2016) 012011 doi:10.1088/1755-1315/35/1/012011
Show more

9 Read more

Solid phase protein chemical synthesis

Solid phase protein chemical synthesis

The method was illustrated with the synthesis of a 94 or 135 amino acids polypeptides by ligating sequentially four or five peptide segments respectively. The synthesis of the 94 amino acids polypeptide is depicted in Fig. 15. The first SEA off segment was anchored chemoselectively to the solid support through its N-terminus using the copper-catalyzed or the strain-promoted alkyne azide cycloaddition reaction, i.e. CuAAC[155,156] and SPAAC[251] respectively. For this, the first SEA off peptide segment was modified on the N-terminus with an azide-functionalized Esec handle using the method developed by Aucagne and coworkers ([175], see entry 7 of Table 2), while the solid support was modi- fied by a terminal alkyne or a cyclooctyne derivative. The ethylsulfonyl-2-ethyloxycarbonyl moiety of Esec linker can be cleaved with aqueous base (pH ~ 11) as already discussed in the previous sections. It is stable in the neutral or mildly acidic conditions used for the elongation cycle, while its lability in basic conditions is exploited for monitoring the elon- gation process or for cleaving off the target polypeptide by treatment of the peptidyl resin with aqueous base. The overall isolated yield of the target 94 amino acids polypeptide was 6.5% including the HPLC purification step. Nine chemical steps were performed on the sol- id phase, meaning an average yield per step of 74%. A similar average yield per step was reported for the assembly of five peptide segments.
Show more

62 Read more

On Some Applications of Nanoparticles Synthesized in the Gas Phase by Magnetron Discharges

On Some Applications of Nanoparticles Synthesized in the Gas Phase by Magnetron Discharges

For the seventies, scientists focused their researches to find techniques to produce high quality films. One of the ideas, for example, was to generate an ionized cluster beam (ICB) formed by inert gas condensation (IGC) from evaporation of material. This method generates non-agglomerated nanoparticles to be deposited onto any substrate. However, the synthesis of spherical and well-dispersed nanoparticles remains, today, a major technological issue. Several trials have been performed with magnetron sputtering that has the advantage of producing very pure atomic vapour from a wide variety of solid materials or composites, and therefore in this configuration offers the possibility to synthesize nanopar- ticles in a gaz phase with potential numerous applications. In this paper, we describe several results of our laboratory and we show how it is possible to synthesize non-agglomerated nanoparticles with a narrow size distribution in the nm range. Detailed examples of Ag, TiO 2 , Au, Y, C, Co and Fe are given. We illustrate their current use in applications
Show more

6 Read more

Show all 10000 documents...