Gas-phase Collisions Research Articles

Study by crossed beams and ab initio techniques of an environmentally interesting process: Gas-phase high energy collisions between N2O(1Σ+) and Li+(1S0)

The environmentally relevant gas phase collisions between ground states N2O molecules and lithium ions have been studied by crossed-beams techniques and fluorescent emissions. Total emission cross-sections for Li(2Pu) and Li(2Dg) formation in the 0.100–5.00keV laboratory energy range have been measured in absolute units. Different potential energy surfaces involved in the non-adiabatic electron transfer processes have been calculated at the ab initio complete active space interaction configuration (CASCI) level of theory in the collinear configuration system. These gave information on different excited states including those asymptotically correlating the prominent process leading to the formation of Li(2Pu) and N2O+. Also, a detailed full dimensional analysis of the systems’ ground PES has been made at the perturbation second order Möller–Plesset (MP2) level. From the ab initio calculations and using simple model analytical equations for excitation functions a qualitative interpretation of the measured data for the dominant non-adiabatic process is given.

Charge-neutralization effect of the tail regions on the histone H2A/H2B dimer structure.

It is well known that various modifications of histone tails play important roles in the regulation of transcription initiation. In this study, some lysine (Lys) and arginine (Arg) residues were acetylated and deiminated, respectively, in the histone H2A/H2B dimer, and charge-neutralization effects on the dimer structure were studied by native mass spectrometry. Given that both acetylation and deimination neutralize the positive charges of basic amino acid residues, it had been expected that these modifications would correspondingly affect the gas-phase behavior of the histone H2A/H2B dimer. Contrary to this expectation, it was found that Arg deimination led to greater difficulty of dissociation of the dimer by gas-phase collision, whereas acetylation of Lys residues did not cause such a drastic change in the dimer stability. In contrast, ion mobility-mass spectrometry (IM-MS) experiments showed that arrival times in the mobility cell both of acetylated and of deiminated dimer ions changed little from those of the unmodified dimer ions, indicating that the sizes of the dimer ions did not change by modification. Charge neutralization of Arg, basicity of which is higher than Lys, might have triggered some alteration of the dimer structure that cannot be found in IM-MS but can be detected by collision in the gas phase.

Measuring the Heat Capacity of Large Isolated Molecules via Gas-Phase Collisions: C60

We present a novel method to measure the heat capacity of isolated molecules or clusters. Neutral molecules emerge from an effusive source at known temperature. They are heated in a single sticking collision with an atomic ion of known kinetic energy; the breakdown curve of the adduct ion is measured as a function of collision energy. The procedure is repeated for different source temperatures. The heat capacity of the neutral molecule equals the change in the breakdown energy divided by the change in source temperature. The method avoids potential sources of systematic errors inherent to other approaches that involve multiple collisions. The accuracy of the method is demonstrated by colliding an effusive beam of C60 with a monoenergetic beam of Na+ which produces endohedral Na@C60+. The value obtained for the heat capacity of C60 at 535 ± 35 °C agrees with theoretical ones within the experimental uncertainty of 11%.

EXPERIMENTAL AND COMPUTATIONAL STUDIES OF THE FORMATION MECHANISM OF PROTONATED INTERSTELLAR DIAZINES

Studies of interstellar chemistry have grown in number and complexity by both observations and laboratory measurements, and nitrogen-containing aromatics have been implicated as important interstellar molecules. In this paper, the gas-phase collision induced dissociation (CID) processes of protonated pyridazine (1,2-diazine), pyrimidine (1,3-diazine), and pyrazine (1,4-diazine) cations (C4H5N2 +) are investigated in detail both experimentally and theoretically. The major neutral loss for all three CID processes is HCN, leading to the formation of C3H4N+ isomers; our density functional theory (DFT) calculations support and elucidate our experimental results. The formation of C3H4N+ isomers from the reaction of abundant interstellar acrylonitrile (CH2CHCN) and H+is also studied employing DFT calculations. Our results lead to a novel mechanism for interstellar protonated diazine formation from the consecutive reactions of CH2CHCN+ H+ + HCN. Moreover, our results motivate the continuing search for interstellar C3H4N+ isomers as well as polycyclic aromatic N-containing hydrocarbons (PANHs).

Strategy to improve the quantitative LC-MS analysis of molecular ions resistant to gas-phase collision induced dissociation: application to disulfide-rich cyclic peptides.

Due to observed collision induced dissociation (CID) fragmentation inefficiency, developing sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) assays for CID resistant compounds is especially challenging. As an alternative to traditional LC-MS/MS, we present here a methodology that preserves the intact analyte ion for quantification by selectively filtering ions while reducing chemical noise. Utilizing a quadrupole-Orbitrap MS, the target ion is selectively isolated while interfering matrix components undergo MS/MS fragmentation by CID, allowing noise-free detection of the analyte's surviving molecular ion. In this manner, CID affords additional selectivity during high resolution accurate mass analysis by elimination of isobaric interferences, a fundamentally different concept than the traditional approach of monitoring a target analyte's unique fragment following CID. This survivor-selected ion monitoring (survivor-SIM) approach has allowed sensitive and specific detection of disulfide-rich cyclic peptides extracted from plasma.

Polymer amide as an early topology.

Hydrophobic polymer amide (HPA) could have been one of the first normal density materials to accrete in space. We present ab initio calculations of the energetics of amino acid polymerization via gas phase collisions. The initial hydrogen-bonded di-peptide is sufficiently stable to proceed in many cases via a transition state into a di-peptide with an associated bound water molecule of condensation. The energetics of polymerization are only favorable when the water remains bound. Further polymerization leads to a hydrophobic surface that is phase-separated from, but hydrogen bonded to, a small bulk water complex. The kinetics of the collision and subsequent polymerization are discussed for the low-density conditions of a molecular cloud. This polymer in the gas phase has the properties to make a topology, viz. hydrophobicity allowing phase separation from bulk water, capability to withstand large temperature ranges, versatility of form and charge separation. Its flexible tetrahedral carbon atoms that alternate with more rigid amide groups allow it to deform and reform in hazardous conditions and its density of hydrogen bonds provides adhesion that would support accretion to it of silicon and metal elements to form a stellar dust material.

Performance of a high-resolution mid-IR optical-parametric-oscillator transient absorption spectrometer.

We report on a mid-IR optical parametric oscillator (OPO)-based high resolution transient absorption spectrometer for state-resolved collisional energy transfer. Transient Doppler-broadened line profiles at λ = 3.3 μm are reported for HCl R7 transitions following gas-phase collisions with vibrationally excited pyrazine. The instrument noise, analyzed as a function of IR wavelength across the absorption line, is as much as 10 times smaller than in diode laser-based measurements. The reduced noise is attributed to larger intensity IR light that has greater intensity stability, which in turn leads to reduced detector noise and better frequency locking for the OPO.

Membrane proteins bind lipids selectively to modulate their structure and function.

Previous studies have established that the folding, structure and function of membrane proteins are influenced by their lipid environments1-7 and that lipids can bind to specific sites, for example in potassium channels8. Fundamental questions remain however regarding the extent of membrane protein selectivity toward lipids. Here we report a mass spectrometry (MS) approach designed to determine the selectivity of lipid binding to membrane protein complexes. We investigate the mechanosensitive channel of large conductance (MscL), aquaporin Z (AqpZ), and the ammonia channel (AmtB) using ion mobility MS (IM-MS), which reports gas-phase collision cross sections. We demonstrate that folded conformations of membrane protein complexes can exist in the gas-phase. By resolving lipid-bound states we then rank bound lipids based on their ability to resist gas phase unfolding and thereby stabilize membrane protein structure. Results show that lipids bind non-selectively and with high avidity to MscL, all imparting comparable stability, the highest-ranking lipid however is phosphatidylinositol phosphate, in line with its proposed functional role in mechanosensation9. AqpZ is also stabilized by many lipids with cardiolipin imparting the most significant resistance to unfolding. Subsequently, through functional assays, we discover that cardiolipin modulates AqpZ function. Analogous experiments identify AmtB as being highly selective for phosphatidylglycerol prompting us to obtain an X-ray structure in this lipid membrane-like environment. The 2.3Å resolution structure, when compared with others obtained without lipid bound, reveals distinct conformational changes that reposition AmtB residues to interact with the lipid bilayer. Overall our results demonstrate that resistance to unfolding correlates with specific lipid-binding events enabling distinction of lipids that merely bind from those that modulate membrane protein structure and/or function. We anticipate that these findings will be influential not only for defining the selectivity of membrane proteins toward lipids but also for understanding the role of lipids in modulating function or drug binding.

Size-Controllable and Low-Cost Fabrication of Graphene Quantum Dots Using Thermal Plasma Jet

We report a size-controllable and low-cost fabrication method of graphene quantum dots (GQDs) using a thermal plasma jet. A carbon atomic beam was generated by injecting a large amount (2.5 L/min) of ethylene gas continuously into Ar plasma. The beam was then flowed through a carbon tube (5-20 cm in length) attached to the anode and then dispersed into a chamber. Carbon materials including GQDs were made by a gas phase collision reaction. The production rate of carbon soot was 40 g/h for a 2.5 L/min injection rate. Almost all of the carbon soot dispersed in ethanol by sonication, while isolated GQDs were dispersed in ethanol by stirring with a stirring rod. The weight percent of GQDs in carbon soot, based on the amount extracted in ethanol, was about 10%. This means that the production rate of GQDs was about 4 g/h. The average size of GQDs, with a relatively narrow size distribution, was controlled by varying the length of the carbon tube attached. It was about 10, 14, and 19 nm when the length was 5, 10, and 20 cm, respectively. The electric structure based on the photoluminescence data of our GQDs had a singlet ground state and was in good agreement with that of carbyne. Our GQDs will disperse in organic solvents such as toluene, but not in water. The dispersion properties also support that our GQDs have carbyne-like edges. We proposed that the PL peaks observed can be attributed to electronic transitions between energy levels of the GQDs having carbyne-like edges.

Conformational Ordering of Biomolecules in the Gas Phase: Nitrogen Collision Cross Sections Measured on a Prototype High Resolution Drift Tube Ion Mobility-Mass Spectrometer

Ion mobility-mass spectrometry measurements which describe the gas-phase scaling of molecular size and mass are of both fundamental and pragmatic utility. Fundamentally, such measurements expand our understanding of intrinsic intramolecular folding forces in the absence of solvent. Practically, reproducible transport properties, such as gas-phase collision cross-section (CCS), are analytically useful metrics for identification and characterization purposes. Here, we report 594 CCS values obtained in nitrogen drift gas on an electrostatic drift tube ion mobility-mass spectrometry (IM-MS) instrument. The instrument platform is a newly developed prototype incorporating a uniform-field drift tube bracketed by electrodynamic ion funnels and coupled to a high resolution quadrupole time-of-flight mass spectrometer. The CCS values reported here are of high experimental precision (±0.5% or better) and represent four chemically distinct classes of molecules (quaternary ammonium salts, lipids, peptides, and carbohydrates), which enables structural comparisons to be made between molecules of different chemical compositions for the rapid “omni-omic” characterization of complex biological samples. Comparisons made between helium and nitrogen-derived CCS measurements demonstrate that nitrogen CCS values are systematically larger than helium values; however, general separation trends between chemical classes are retained regardless of the drift gas. These results underscore that, for the highest CCS accuracy, care must be exercised when utilizing helium-derived CCS values to calibrate measurements obtained in nitrogen, as is the common practice in the field.

Experimental evaluation of the gas-phase collision cross-section of effusive Au beam with noble gases: The effect of size and flux

We find that the effusive atomic beam of Au atoms is deflected away by collision with noble gas atoms crossing in a perpendicular geometry with a beam flux of >1 × 1016/cm2s. The ratio of defected Au atoms is found to increase proportional to the flux of noble gases. In addition, the effective cross-section for the collision between Au and noble gases (Ne, Ar, Xe) is measured to increase in an order of Ne < Ar < Xe. As a result of the increased collision probability, the deflection ratio of Au beam in the noble gases is measured to be enhanced for the Au flux in the range of 1 × 1011–1013Au/cm2s. Our results show that the gas-phase collision can be reliably determined by measuring the deflection ratio. The experimentally determined collision cross-section also explains the variation in the deflection ratio among various noble gases and the importance of a long-range van der Waals interaction between Au and noble gases in the deflection efficiency.

Bond‐Forming Reactions of Small Triply Charged Cations with Neutral Molecules

Time-of-flight mass spectrometry reveals that atomic and small molecular triply charged cations exhibit extensive bond-forming chemistry, following gas-phase collisions with neutral molecules. These experiments show that at collision energies of a few eV, I(3+) reacts with a variety of small molecules to generate molecular monocations and molecular dications containing iodine. Xe(3+) and CS2(3+) react in a similar manner to I(3+), undergoing bond-forming reactions with neutrals. A simple model, involving relative product energetics and electrostatic interaction potentials, is used to account for the observed reactivity.

MALDI-TOF MS: Much More than only Protein Analysis!

Carbohydrates and particularly lipids represent molecules with significant structural variabilities: this is stemming from (a) the headgroups, (b) the different fatty acyl residues and (c) the linkage types (acyl-acyl-, alkyl-acyl-, and alkenyl-acyl-). Therefore, analytical methods to clarify these aspects are of immense significance. As the amount of the available biological material is normally limited, suitable methods should also exhibit reasonable sensitivities. It is our aim to introduce MALDI (matrix-assisted laser desorption and ionization) MS (mass spectrometry) [1] (often but not necessarily with a time-offlight (TOF) mass analyzer) as a simple and sensitive analytical method that helps to overcome many problems related to carbohydrate and particularly lipid analysis [2]. Although the history of MS dates back to the end of the nineteenth century, applications of MS to the structural analysis of biomolecules are rather new: the MS analysis of such complex molecules (often in combination with high polarity and low volatility) became only possible with the invention of “soft ionization” methods such as electrospray ionization (ESI) and “MALDI” [3]. Both techniques are nowadays widely used, whereby the focus is often on the investigation of proteins - normally subsequent to enzymatic digestion of the (unknown) protein into characteristic peptides, the MS of which enables the elucidation of the protein sequence and further structural properties [4]. It is a characteristic property of “soft ionization” MS that there is only a small extent of analyte fragmentation and, thus, the intact ions of the analyte of interest can be observed. This is a pronounced difference in comparison to the classical “electron ionization” (EI) technique. Although MALDI MS has many advantages it should be noted that the analysis of small molecules (for instance, free fatty acids) is still a problem - despite many improvements that could be recently achieved [5]. This problem with small molecules can be easily understood when the principle of MALDI MS is considered: MALDI MS is based on laser ionization, whereby normally UV lasers (emitting often at λ=337 nm) are used. Since not all potential analytes exhibit a sufficient absorption at this wavelength, a “matrix” must be used [1]. This matrix is normally a small organic molecule (such as 2,5-dihydroxybenzoic acid (DHB)) [6] that absorbs the laser energy, is evaporated and simultaneously carries the analyte into the gas phase (high vacuum). In the gas phase collisions between the analyte and cations (such as H + or Na + ), that are either already present in the lipid extract of interest or artificially added, occur leading to ion generation. As the mass of the observed (positive) ions is slightly higher than the mass of the analyte, these are normally termed “adducts” or “quasimolecular” ions. Of course, analytes with acidic groups are also detectable as negative ions. Since the matrix is normally in considerable excess over the analyte (at least 100:1), it is not surprising that the smaller mass range is dominated by matrix ions [7]. This is the reason why the small mass range is normally not shown when MALDI spectra are discussed. Despite this drawback, however, there are a lot of advantages: 1. The necessary sample preparation is simple and fast - and comprises often only the mixing of the analyte with the matrix and the deposition of this mixture onto the sample carrier, the “target”.

Gas-phase collision induced dissociation mechanisms of peptides: Theoretical and experimental study of N-formylalanylamide fragmentation

In order to shed light on the fragmentation mechanisms occurring during the collision induced dissociation (CID) of peptides in the gas phase, we have studied a model system, the N-formylalanylamide (HCO-Ala-NH2), by coupling experimental and theoretical methods. In particular, we have addressed two different questions arising in such experiments: (i) what is (are) the structure(s) of the ion before collision, and (ii) what are the fragmentation mechanisms occurring after collision with the target gas. For the first question, we coupled the potential energy surface (PES) study done by means of density functional theory (DFT), with Infra Red Multiple Photon Dissociation (IRMPD) spectroscopy. For the second problem, which is actually the main topic of the present work, we coupled quantum mechanics plus molecular mechanics (QM+MM) direct chemical dynamics simulations with tandem mass spectrometry (MS/MS). In addition, in order to better delineate the fragmentation mechanisms and validate those proposed by simulations, isotopic labeling experiments using 2H and 13C were performed. Thanks to the interplay between simulations and experiments, it was possible to successfully identify the fragmentation pathways leading to b1, y1, a1 and immonium ions. Our mechanisms support the “mobile proton” picture that is supposed to trigger the peptide fragmentation in the gas phase, confirming, from a chemical dynamics point of view, previous theoretical and experimental studies on similar systems.

Quantitative high-speed burned gas temperature measurements in internal combustion engines using sodium and potassium fluorescence

When sodium- and potassium-containing fuel additives are used in internal combustion engines, the bright fluorescence that sodium and potassium atoms emit in the burned gas zone offers a large potential for spectroscopic combustion analysis. To utilize this potential quantitatively, it is crucial to fully understand all physical and chemical processes involved. This includes (1) the temperature dependence of the fluorescence intensity due to gas-phase collisions, (2) the pressure, temperature and equivalence ratio effects on thermodynamic equilibria in the burned gas zone and (3) pressure and temperature-dependent line shapes for quantitative correction of fluorescence reabsorption. High-speed imaging of sodium and potassium fluorescence in a spark-ignited, direct injection, single-cylinder research engine was conducted under well-controlled homogeneous operating conditions at equivalence ratios ranging from 0.71 to 1.43, cylinder pressure from 3 to 15 bar and burned gas temperatures from 1,700 to 2,600 K. This study demonstrates that the influence of pressure, temperature and equivalence ratio on the fluorescence signals of sodium and potassium is understood quantitatively and establishes the potentials and limitations of this tool for burned gas temperature measurements with high temporal and two-dimensional spatial resolution in a homogeneously operated internal combustion engine.

Crossed molecular beams study of inelastic non-adiabatic processes in gas phase collisions between sodium ions and ZnBr2 molecules in the 0.10–3.50 keV energy range

Inelastic electronically non-adiabatic reactions between Na(+) ions and neutral ZnBr(2) molecules, both in their electronic ground state, have been studied using crossed beams techniques and measuring the decaying emission radiation of the excited species produced. The fluorescent emission corresponding to Na(3 (2)P) produced by a charge transfer reaction was observed, as well as that corresponding to the decay of Zn(4s 5s (3)S), generated by dissociation of the neutral target molecule, to Zn(4s 4p (3)P). The phosphorescent decaying emission of Zn*(4s 4p (3)P) to the zinc ground state was also observed. For each emission process, the cross section energy dependences have been measured in the 0.10-3.50 keV energy range in the laboratory system. The ground electronic state of the (NaZnBr(2))(+) collision system has been characterized by ab initio chemical structure calculations at the second order Möller-Plesset perturbation level of theory using pseudo-potentials. By performing restricted open shell Hartree-Fock calculations for C(2v) geometries, four singlet and four triplet potential energy surfaces of the system have been calculated and used to interpret qualitatively the observed reactions. A simple two-state dynamical model is presented that allows an estimation of the maximum values for measured cross sections at high collision energies to be made.

Capillary and Coulombic Effects on the Gas Phase Structure of Electrosprayed Concanavalin A Ions and Its Clusters Cn+z(n= 1–6)

Ion mobility spectrometry (IMS) coupled to mass spectrometry (MS) is used to study the gas phase collision cross section Ω(z, n) in CO(2) of multimers C(n) (n = 1-4, 6) of concanavalin A, whose tetramer C(4) has a crystal structure resembling four tetrahedrically arranged globules. C(n)(+z) ions electrosprayed from aqueous solutions of triethylammonium formate (Et(3)AF) are moderately charged (up to z = 6 and 17 for n = 1 and 6) and produce narrow mobility peaks. Charge states down to z = 1 obtained with a charge-reducing radioactive (63)Ni source are studied for the dimer and the tetramer via pure IMS (no MS). The mobilities are independent of pH in the range 6-8, controlled by addition of triethylamine to the Et(3)AF. The measured compactness group Ω(z, n)/n(2/3) is practically independent of n and z, whereas mobility calculations with clusters of touching spheres show that it should vary with n by 20-30% for a variety of scattering models. This contrast suggests that, irrespective of ambiguities on the scattering model, all multimers adopt globular shapes, precluding in particular a tetrahedral tetramer. Acetic acid solutions (87 mM aqueous) yield ions with substantially higher z, mostly with broad mobility distributions. Exceptionally high z tetramers (z = 25-29) and trimers have narrowly defined mobilities with compact but nonspherical shapes. Addition of 2-4 mM Et(3)AF to the 87 mM aqueous acetic acid solution yields narrowly defined mobilities almost identical at all z values to those from the Et(3)AF buffer, although with higher charge states showing also a transition to nonspherical shapes. We conclude that all gas phase clusters charged below a Rayleigh-like charge, z(R), are globular without regard to solution conditions, some undergoing a sharp shape transition at a critical z = z(R). We confirm that gas phase protein cross sections differ from those expected from the crystal structure, with a trend to compact probably driven by their high surface energy (and opposed by Coulombic stresses). The Rayleigh-like shape transitions seen are similar to those arising in linear homopolymers, although not as sharply defined. They yield a surface energy for protein matter almost as high as the surface tension of water. This quantitative conclusion is corroborated by prior data on cytochrome c and apomyoglobin (also showing a critical shape transition) as well as measurements of the maximum charge versus mass in aggregates of dipeptides.

Structural Mass Spectrometry: Rapid Methods for Separation and Analysis of Peptide Natural Products

A significant challenge in natural product discovery is the initial discrimination of discrete secondary metabolites alongside functionally similar primary metabolic cellular components within complex biological samples. A property that has yet to be fully exploited for natural product identification and characterization is the gas-phase collision cross section, or, more generally, the mobility-mass correlation. Peptide natural products possess many of the properties that distinguish natural products, as they are frequently characterized by a high degree of intramolecular bonding and possess extended and compact conformations among other structural modifications. This report describes a rapid structural mass spectrometry technique based on ion mobility-mass spectrometry for the comparison of peptide natural products to their primary metabolic congeners using mobility-mass correlation. This property is empirically determined using ion mobility-mass spectrometry, applied to the analysis of linear versus modified peptides, and used to discriminate peptide natural products in a crude microbial extract. Complementary computational approaches are utilized to understand the structural basis for the separation of primary metabolism derived linear peptides from secondary metabolite cyclic and modified cyclic species. These findings provide a platform for enhancing the identification of secondary metabolic peptides with distinct mobility-mass ratios within complex biological samples.

The diatomic dication CuZn2+ in the gas phase

In the present combined experimental and theoretical study we report the observation of the novel gas-phase dication CuZn(2+) and provide some theoretical insight into the electronic binding of this exotic metastable molecule and its formation mechanism. Using mass spectrometry we have detected four isotopomer signals of CuZn(2+) at half-integer m/z values for ion flight times of about 14 μs. CuZn(2+) was unambiguously identified by its isotopic abundance. High-current energetic Ar(+) ion bombardment of a brass surface was used for its production. Subsequent dication formation was found to take place in the ion extraction region of our mass spectrometer several tens of microns in front of the sputtered brass surface. The dication formation mechanism appears to be resonant electron transfer in soft gas-phase collisions between sputter-ejected singly charged CuZn(+) molecular ions and incoming Ar(+) projectiles. This conclusion is supported by our theoretical study that obtained an ionization energy of CuZn(+) of 15.75 eV, in excellent agreement with both the experimental and calculated ionization energy of Ar (15.76 and 15.67 eV, respectively). The ground state of CuZn(2+) is found to be a metastable one with a very shallow potential well at an internuclear equilibrium distance of about 2.7 Å the dissociation energy being very difficult to estimate. Interestingly, spin-orbit corrections are found to be necessary to get an adequate description of the metastable state of CuZn(2+), whereas relativistic corrections have no effects on neutral CuZn nor on CuZn(+).

Back to deuterium: Utility of 2H-labeled peptides for targeted quantitative proteomics

Multiple reaction monitoring mass spectrometry coupled with stable isotope dilution has become the method of choice for quantifying target proteins in complex biological samples. It quantifies signature peptides based on the sequential detection of peptide precursor ions and their fragments generated upon gas-phase collision. Heavy-isotope (13C and/or 15N) labeled peptides or proteomes are commonly used as internal reference standards for quantitation. However, use of these standards is becoming expensive when large numbers/amounts of reference peptides are needed. The search for low-cost, labeled references for proteomic quantitation such as those with 2H-labels is an object of constant pursuit. In order to take the cost advantage of 2H-labels, this work examines whether or not the known chromatographic separation of 2H-based peptides from the native counterparts affects the peptide quantitation using multiple reaction monitoring mass spectrometry. Experimental results from model peptides and proteome digests indicate that targeted mass spectrometry quantitation of the 2H- and 13C/15N-based peptides are comparable.