Atomic Mass Units Research Articles

Syntheses of Alkylated Aromatic Model Compounds To Facilitate Mass Spectral Characterization of Heavy Oils, Resids, and Bitumens

This study summarizes the synthesis of model compounds. Long-chain alkyl multi-ring heteroaromatics are the synthetic targets. These compounds are considered analogues of similar compounds that are present at abundant levels in petroleum crude oils, resids, heavy oils, deasphalted oils, asphaltenes, and bitumens, and they are responsible for coke formation and other processing problems. Model compounds are not readily available. Some models have been synthesized to approximate the physical and chemical behavior of real asphaltenes, but the structures are not completely consistent with the current structural understanding. The composition of petroleum crudes, resids, heavy oils, and bitumens has been a subject of intense research for years. The structure of these coke-forming molecules is generally thought to be an aromatic core of critical molecular weight and number of fused aromatic rings. This critical ring number is around 4–5 fused aromatic rings, which bear alkyl side chains and heteroatoms. This general structural view is still being improved. During coking, these side chains thermally cleave off of the aromatic core and leave the coker as volatile liquids and gas. The aromatic cores are thermally stable, and they are not volatile. They remain in the coker until they condense and form low-value coke. The purpose of this research was to synthesize model compounds representing the molecular structure of the coke-forming molecules. These compounds will be used to model the behavior of resids, heavy oils, and bitumens to understand their processing chemistry and their physical and chemical properties. Model compounds that reasonably represent the structural data with boiling point ranges that map directly onto the boiling point ranges of real heavy oils, resids, and bitumens have been successfully synthesized. Important structural features are emphasized in these models, such as high molecular weight [∼1000 atomic mass units (amu)] with multi-ring aromatic cores, long alkyl side chains, and the inclusion of sulfur and nitrogen. These model compounds can be used to calibrate analytical methods to provide response factors for quantitative characterization of alkylated aromatics in real petroleum fractions and to better understand thermal chemistry kinetics.

High-Performance Thin-Layer Chromatography Using Automated Multiple Development for the Separation of Heavy Petroleum Products According to Their Number of Aromatic Rings

Automated multiple development (AMD) is a gradient elution technique for high-performance thin-layer chromatography (HPTLC), in which successive runs are performed with decreasing solvent strength and increasing developing distance. A method for obtaining separations or distributions of heavy petroleum products according to their number of aromatic rings has been developed using AMD together with caffeine-impregnated silica gel HPTLC layers and selective detection by fluorescence scanning densitometry. A gradient of dichloromethane–heptane, starting from a composition of 70:30 (v/v) to 65:35 (v/v), in 34 elution steps with a migration of 2 mm per step, over a total migration distance of 68 mm, has been used. Calibration of elution has been carried out using polycyclic aromatic compounds (PACs) with a molecular weight (MW) from 200 to 1000 atomic mass units (amu), which have been separated under the described conditions. Other parameters on AMD separation have also been discussed, such as the effect of mob...

Non-enzymatically derived minor lipids found in Escherichia coli lipid extracts

Electrospray ionization mass spectrometry is a powerful technique to analyze lipid extracts especially for the identification of new lipid metabolites. A hurdle to lipid identification is the presence of solvent contaminants that hinder the identification of low abundance species or covalently modify abundant lipid species. We have identified several non-enzymatically derived minor lipid species in lipid extracts of Escherichia coli; phosphatidylmethanol, ethyl and methyl carbamates of PE and N-succinyl PE were identified in lipid extracts of E. coli. Phosphatidylmethanol (PM) was identified by exact mass measurement and collision induced dissociation tandem mass spectrometry (MS/MS). Extraction in the presence of deuterated methanol leads to a 3 atomic mass unit shift in the [M–H] − ions of PM indicating its formation during extraction. Ethyl and methyl carbamates of PE, also identified by exact mass measurement and MS/MS, are likely to be formed by phosgene, a breakdown product of chloroform. Addition of phosgene to extractions containing synthetic PE significantly increases the levels of PE-MC detected in the lipid extracts by ESI-MS. Extraction in the presence of methylene chloride significantly reduced the levels of these lipid species. N-succinyl PE is formed from reaction of succinyl-CoA with PE during extraction. Interestingly N-succinyl PE can be formed in an aqueous reaction mixture in the absence of added E. coli proteins. This work highlights the reactivity of the amine of PE and emphasizes that careful extraction controls are required to ensure that new minor lipid species identified using mass spectrometry are indeed endogenous lipid metabolites. This article is part of a Special Issue entitled: Lipodomics and Imaging Mass Spectrometry.

Adsorption of xenon ions onto defects in organic surfaces: Implications for the origin and the nature of organics in primitive meteorites

Noble gases trapped in primitive meteorites are quantitatively hosted by a poorly defined organic phase, labeled phase Q. Xenon is enriched in heavy isotopes by +1.30 ± 0.06% per atomic mass unit (amu, 1 σ) in phase Q relative to solar. To understand the origin of this fractionation, we have performed adsorption experiments of xenon atoms and ions, ionized in a radiofrequency plasma. Within the reaction vessel, anthracite was heated and the resulting smoke deposited onto the walls of the vessel, resulting in carbon-rich films. Xenon was trapped in the carbon films either as ions in the ionization zone of the vessel, or as neutral atoms outside this zone. Xenon trapped as ionic Xe is tightly bound and is enriched by +1.36 ± 0.05%/amu (1 σ) in heavy isotopes, reproducing the isotopic fractionation of xenon trapped in phase Q relative to solar. Neutral xenon is more loosely trapped, is in much lower concentration, and is not isotopically fractionated. Ionized conditions allow the constant xenon isotopic composition observed in meteorite during stepwise heating release to be reproduced. Furthermore, the trapping efficiency of Xe + estimated from these experiments is consistent with the high xenon concentration measured in phase Q of primitives meteorites. Xenon was not trapped in the film by implantation because the energies of the incident Xe atoms and ions were far too low (<1 eV). From the difference of behavior between ionic and neutral forms, we propose that xenon ions were trapped via chemical bonding at the surface of the newly created C-rich film. The observed mass-dependent fractionation of xenon is unlikely to have occurred in the gas phase. It is more probably related to variations in chemical bonding strengths of Xe isotopes as chemical bonds involving heavy Xe isotopes are more stable than those involving light ones. For young stars, including the young Sun, photons emitted in the far UV energy range able to ionize noble gases (<100 nm) were orders of magnitude more abundant than for the Present-day Sun, allowing efficient ionization of gaseous species. A way to achieve Q-noble gas fractionation and trapping was UV irradiation by nearby young stars from O/B association of the surface of growing organic grains in the outer part of the solar system or by the young Sun at the edge of the disk.

The Cryogenic Storage Ring and its application to molecular ion recombination physics

The Cryogenic Storage Ring (CSR), presently under construction at the Max-Planck-Institute for Nuclear Physics, will allow the storage of large ionic molecules under optimum experimental conditions. The electrostatic beam optics and the presence of a low-energy electron cooler will allow highly-precise recombination experiments with molecular ions of 160 atomic mass units per charge state. The all-cryogenic design of the storage ring will provide unprecedented vacuum conditions and assure long storage times even for very heavy ion beams. Suppression of the black body radiation background of the beam pipe in combination with electron cooling will give access to internal ion temperatures of 10K and allow state-selective experiments on infrared-active species, impossible in present-day room-temperature storage rings. We give an overview of the CSR project, point out the scientific opportunities arising from its unique design, and give an outlook on possible first molecular recombination experiments after commissioning of the storage ring.

Characterization and relative response factor determination of process related impurity in Naproxen by nuclear magnetic resonance spectroscopy

In the impurity profile of naproxen around 0.6% unknown polar impurity was detected by high performance liquid chromatography (HPLC). The product ion spectrum of the impurity and Naproxen was recorded in LCMS/MS and the fragmentation pattern of the impurity was observed to be similar to the fragmentation pattern of Naproxen with only a difference of two atomic mass units. The high resolution mass spectrum (HRMS) of the impurity displayed a protonated molecular ion at m/z 229.0863, which corresponds to the pseudomolecular formula C14H13O3+. Based on LC/MS/MS, HRMS, 1D and 2D NMR data, the structure of the impurity was characterized as 2-(6-methoxynaphthalen-2-yl)acrylic acid. The acrylic acid impurity was synthesized in the laboratory and co injected in HPLC to confirm the retention time. RRF of the impurity was determined by 1H NMR method and also by conventional HPLC slope method and the RRF values are found to be 6.11 and 5.64, respectively. The values are comparable and 1H NMR method of RRF determination is complimentary and can be effectively used as an alternative method to conventional HPLC method especially in early stages of development when availability of impurity standards is not possible.

Deciphering sulfoglycolipids of Mycobacterium tuberculosis

For 4 decades, in vivo and in vitro studies have suggested that sulfoglycolipids (SGLs) play a role in the virulence or pathogenesis of the tubercle bacilli. However, the SGL structure and biosynthesis pathway remain only partially elucidated. Using the modern tools of structural analysis, including MALDI-time-of-flight MS, MS/MS, and two-dimensional NMR, we reevaluated the structure of the different SGL acyl (di-, tri-, and tetra-acylated) forms of the reference strain Mycobacterium tuberculosis H37Rv, as well as those produced by the mmpL8 knockout strains previously described to intracellularly accumulate di-acylated SGL. We report here the identification of new acyl forms: di-acylated SGL esterified by simple fatty acids only, as well as mono-acylated SGL bearing a hydroxyphthioceranoic acid, which were characterized in the wild-type strain. In a clinical strain, a complete family of mono-acylated SGLs was characterized in high abundance for the first time. For the mmpL8 mutant, SGLs were found to be esterified i) by an oxophthioceranoic acid, never observed so far, and ii) at nonconventional positions in the case of the unexpected tri-acylated forms. Our results further confirm the requirement of MmpL8 for the complete assembly of the tetra-acylated forms of SGL and also provide, by the discovery of new intermediates, insights in terms of the possible SGL biosynthetic pathways.

Stabilization of HIV-1 Envelope in the CD4-bound Conformation through Specific Cross-linking of a CD4 Mimetic

CD4 binding on gp120 leads to the exposure of highly conserved regions recognized by the HIV co-receptor CCR5 and by CD4-induced (CD4i) antibodies. A covalent gp120-CD4 complex was shown to elicit CD4i antibody responses in monkeys, which was correlated with control of the HIV virus infection (DeVico, A., Fouts, T., Lewis, G. K., Gallo, R. C., Godfrey, K., Charurat, M., Harris, I., Galmin, L., and Pal, R. (2007) Proc. Natl. Acad. Sci. U.S.A. 104, 17477-17482). Because the inclusion of CD4 in a vaccine formulation should be avoided, due to potential autoimmune reactions, we engineered small sized CD4 mimetics (miniCD4s) that are poorly immunogenic and do not induce anti-CD4 antibodies. We made covalent complexes between such an engineered miniCD4 and gp120 or gp140, through a site-directed coupling reaction. These complexes were recognized by CD4i antibodies as well as by the HIV co-receptor CCR5. In addition, they elicit CD4i antibody responses in rabbits and therefore represent potential vaccine candidates that mimic an important HIV fusion intermediate, without autoimmune hazard.

LC/MS analysis of stratum corneum lipids: ceramide profiling and discovery

Ceramides (CERs) in the upper layer of the skin, the stratum corneum (SC), play a key role in the skin barrier function. In human SC, the literature currently reports 11 CER subclasses that have been identified. In this paper, a novel quick and robust LC/MS method is presented that allows the separation and analysis of all known human SC CER subclasses using only limited sample preparation. Besides all 11 known and identified subclasses, a 3D multi-mass chromatogram shows the presence of other lipid subclasses. Using LC/MS/MS with an ion trap (IT) system, a Fourier transform-ion cyclotron resonance system, and a triple quadrupole system, we were able to identify one of these lipid subclasses as a new CER subclass: the ester-linked ω-hydroxy fatty acid with a dihydrosphingosine base (CER [EOdS]). Besides the identification of a new CER subclass, this paper also describes the applicability and robustness of the developed LC/MS method by analyzing three (biological) SC samples: SC from human dermatomed skin, human SC obtained by tape stripping, and SC from full-thickness skin explants. All three biological samples showed all known CER subclasses and slight differences were observed in CER profile.

Exploring the Inhibition of CTX-M-9 by β-Lactamase Inhibitors and Carbapenems

Currently, CTX-M β-lactamases are among the most prevalent and most heterogeneous extended-spectrum β-lactamases (ESBLs). In general, CTX-M enzymes are susceptible to inhibition by β-lactamase inhibitors. However, it is unknown if the pathway to inhibition by β-lactamase inhibitors for CTX-M ESBLs is similar to TEM and SHV β-lactamases and why bacteria possessing only CTX-M ESBLs are so susceptible to carbapenems. Here, we have performed a kinetic analysis and timed electrospray ionization mass spectrometry (ESI-MS) studies to reveal the intermediates of inhibition of CTX-M-9, an ESBL representative of this family of enzymes. CTX-M-9 β-lactamase was inactivated by sulbactam, tazobactam, clavulanate, meropenem, doripenem, ertapenem, and a 6-methylidene penem, penem 1. K(i) values ranged from 1.6 ± 0.3 μM (mean ± standard error) for tazobactam to 0.02 ± 0.01 μM for penem 1. Before and after tryptic digestion of the CTX-M-9 β-lactamase apo-enzyme and CTX-M-9 inactivation by inhibitors (meropenem, clavulanate, sulbactam, tazobactam, and penem 1), ESI-MS and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) identified different adducts attached to the peptide containing the active site Ser70 (+52, 70, 88, and 156 ± 3 atomic mass units). This study shows that a multistep inhibition pathway results from modification or fragmentation with clavulanate, sulbactam, and tazobactam, while a single acyl enzyme intermediate is detected when meropenem and penem 1 inactivate CTX-M-9 β-lactamase. More generally, we propose that Arg276 in CTX-M-9 plays an essential role in the recognition of the C(3) carboxylate of inhibitors and that the localization of this positive charge to a "region of the active site" rather than a specific residue represents an important evolutionary strategy used by β-lactamases.

Architecture of a Full-length Retroviral Integrase Monomer and Dimer, Revealed by Small Angle X-ray Scattering and Chemical Cross-linking

We determined the size and shape of full-length avian sarcoma virus (ASV) integrase (IN) monomers and dimers in solution using small angle x-ray scattering. The low resolution data obtained establish constraints for the relative arrangements of the three component domains in both forms. Domain organization within the small angle x-ray envelopes was determined by combining available atomic resolution data for individual domains with results from cross-linking coupled with mass spectrometry. The full-length dimer architecture so revealed is unequivocally different from that proposed from x-ray crystallographic analyses of two-domain fragments, in which interactions between the catalytic core domains play a prominent role. Core-core interactions are detected only in cross-linked IN tetramers and are required for concerted integration. The solution dimer is stabilized by C-terminal domain (CTD-CTD) interactions and by interactions of the N-terminal domain in one subunit with the core and CTD in the second subunit. These results suggest a pathway for formation of functional IN-DNA complexes that has not previously been considered and possible strategies for preventing such assembly.

현미 및 백미의 저장기간에 따른 지방산가 및 향기 패턴 분석

This study was conducted to compare the quality of the brown rice (BR) and milled rice (MR) during storage. To assess quality, BR and MR were analysed by their fat acidity and flavor pattern using a SMart Nose. BR was stored for 30 days at , and analysed after 5, 15, 20, and 30 days of storage. MR produced in 2005, 2009, and 2010 were also tested. The fat acidity of both rice groups was increased with extended storage and the fat acidity of BR was more rapidly increased than that of MR in general. The flavor patterns from the SMart Nose results were analyzed by the principal component analysis (PCA). The major groups of atomic mass unit (amu) for good discrimination contribution were from 41 to 85 amus. The PCA1 and PCA2 of BR were 95.64% and 2.78%, respectively when the samples were categorized by storage period. The PCA1 and PCA2 of MR were 81.18% and 13.85%, respectively when the samples were compared by production year. Both rice groups could be practically differentiated into flavor patterns by volatile properties for storage period. With regard to the correlation between fat acidity and flavor pattern, we could find that increasing storage period increased fat acidity value and changed flavor pattern from SMart Nose. Accordingly, SMart Nose could be successfully used for easy screening and quality evaluation of stored rice.

The Scales of Time, Length, Mass, Energy, and Other Fundamental Physical Quantities in the Atomic World and the Use of Atomic Units in Quantum Mechanical Calculations

This article is divided into two parts. In the first part, the atomic unit (au) system is introduced and the scales of time, space (length), and speed, as well as those of mass and energy, in the atomic world are discussed. In the second part, the utility of atomic units in quantum mechanical and spectroscopic calculations is illustrated with examples. It is shown that the system of atomic units can greatly facilitate calculations and unit conversions. In addition, a number of topics that can be fruitfully treated with the au system, including photoelectric effect, hydrogen atom and different Rydberg constants, positronium atom, atomic mass unit, nuclear binding energy, nuclear reaction energetics, annihilation and mass-energy interconversions, femtosecond and attosecond spectroscopies, quantum-size effects, excitons in semiconductors, and so forth are presented and discussed.

High-altitude charged aerosols in the atmosphere of Titan

Observations by several instruments onboard the Cassini spacecraft revealed the existence of heavy hydrocarbon and nitrile species with masses of several thousand atomic mass units in the ionosphere of Titan. These very large molecules are in fact aerosols. The goal of this paper is to compute the concentrations of the charged aerosols in the upper atmosphere (950–1200 km) of Titan. The charging of these aerosols has been studied using the charge balance equations, where positive ions, negative ions, electrons, neutral and charged aerosols are included. Number concentrations of charged aerosols are compared with those observed by the Cassini instruments. The present work estimates the aerosol mass density as 1–10 kg/m 3, which is within the predicted range. The results show that the aerosols must be smaller than 10 nm in order to have reasonable agreement with observations by the Cassini Plasma Spectrometer.

Transesterification in the Microbial Degradation of Phthalate Esters

Our previous study revealed that phthalate esters (PEs), a group of suspected endocrine-disrupting chemicals, acquire estrogenic activities by ring 4hydroxylation. In addition, the estrogenic activities are modified depending on alkyl chain structures (chain length and branching), which can be altered in the environmental conditions such as microbial degradation. Therefore, it is important to determine the environmental fate of these alkyl chains to evaluate the biological impact of PEs on humans and wildlife. PEs are known to undergo biodegradation via sequential hydrolysis, resulting in the formation of monoester and dicarboxylic acid forms. In this study, dipropyl phthalate chosen as one of PEs was cultivated with Acinetobacter lwoffii, a known PE-degrading bacterium, in the presence of a limited amount of CH3 OH as aP E-solvent. As ar esult, several unknown biotransformation products were detected. The products were characterized as methyl propyl phthalate, dimethyl phthalate, and monomethyl phthalate, suggesting that environmental PEs are processed through novel biotransformation pathways. The products can be produced both by esterification of monoester forms and transesterification of diester forms. However, when monobutyl phthalate—a monoester of dibutyl phthalate—was used as a substrate, esterified products were not detected, indicating phthalate methyl esters were formedvia transesterification. A stable-isotopetracer experimentusing CD3OH insteadof CH3OH revealed the production of phthalate methyl esters, the molecular ions of which shifted by 3 or 6 atomic mass units. These results revealed that PE was bacterially trans

Polyatomic interferences in plutonium determination in the femtogram range by double-focusing sector-field ICP-MS

The determination of very low concentrations of plutonium, in the femtogram per millilitre range, in environmental samples using ICP-MS can be interfered by polyatomic species containing heavy elements, from hafnium to bismuth. Mass-to-charge ratios of these polyatomic species are very close to the ones of the plutonium isotopes and cannot be separated from them in the low resolution mode currently used for trace analysis. In this paper, we present an evaluation of the extent and impact of these interferences on the background at masses of plutonium isotopes 239Pu and 240Pu, based on measurement of environmental samples for three years using a double-focusing sector-field ICP-MS. We demonstrate that these molecular interferences, especially the ones involving lead, mercury, and iridium through species PbO2+, ArHg+, IrO3+, must be considered as the additional background induced by these interferences (on average for all interferences respectively ∼1.2 and ∼1.9 counts s−1 at 239 and 240 atomic mass units) is often higher than the instrumental background measured with deionised water acidified at 2% by ultra-pure grade HNO3 (∼0.4 counts s−1), and are generally of the same order as other usual sources of background for low-level plutonium analysis by ICP-MS, i.e.242Pu tracer isotopic impurities, 238U hydrides and peak tail. Thus, if not corrected, these polyatomic interferences may lead to false detection of femtogram amounts of plutonium or overestimation of results. The extents of formation of the main polyatomic species are highly variable from one analysis to the other, over one or two orders of magnitude, depending on instrumental settings. Chemical purification procedures are very efficient in eliminating the greater part of heavy elements present in the initial samples. However, these procedures also bring heavy elements into the final sample solutions through contamination by the atmosphere, glassware and reagents.

About the plausible contribution of field ionization in the mechanism of the formation of dyes of ions under conditions of laser desorption/ionization from a nanostructurized graphite surface

An approach is proposed for the estimation of the contribution of field ionization (FI) to the mechanism of dye ion formation under the conditions of laser desorption/ionization (LDI) from a nanostructurized graphite surface. As test systems, rough graphite layers with dyes, e.g., imidazophenazine derivatives applied to them were chosen; these ensure FI in a strong electric field. The dyes form three neutral precursors upon reduction and various types of ions in different ionization methods. It was found that the mass distribution within the group of peaks formed by the initial dye molecule and the products of its reduction in the positive ion mode upon LDI from a rough graphite surface is shifted to lower masses by one atomic mass unit in comparison to the distribution recorded for LDI from a smooth metal support. The analysis of plausible pathways of ion formation has shown that such a shift may be due to the superposition of ions formed by the FI mechanism on a graphite substrate with a number of ions formed by protonation in LDI with no dependence on the support type. In the negative ion mode, the registration of LDI dye spectra succeeded only if the graphite substrates used favored negative FI and electron emission enhanced by the field.

Increased Power for the Analysis of Label-free LC-MS/MS Proteomics Data by Combining Spectral Counts and Peptide Peak Attributes

Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomics provides a wealth of information about proteins present in biological samples. In bottom-up LC-MS/MS-based proteomics, proteins are enzymatically digested into peptides prior to query by LC-MS/MS. Thus, the information directly available from the LC-MS/MS data is at the peptide level. If a protein-level analysis is desired, the peptide-level information must be rolled up into protein-level information. We propose a principal component analysis-based statistical method, ProPCA, for efficiently estimating relative protein abundance from bottom-up label-free LC-MS/MS data that incorporates both spectral count information and LC-MS peptide ion peak attributes, such as peak area, volume, or height. ProPCA may be used effectively with a variety of quantification platforms and is easily implemented. We show that ProPCA outperformed existing quantitative methods for peptide-protein roll-up, including spectral counting methods and other methods for combining LC-MS peptide peak attributes. The performance of ProPCA was validated using a data set derived from the LC-MS/MS analysis of a mixture of protein standards (the UPS2 proteomic dynamic range standard introduced by The Association of Biomolecular Resource Facilities Proteomics Standards Research Group in 2006). Finally, we applied ProPCA to a comparative LC-MS/MS analysis of digested total cell lysates prepared for LC-MS/MS analysis by alternative lysis methods and show that ProPCA identified more differentially abundant proteins than competing methods.

The Isolation and Characterization of Glycosylated Phosphoproteins from Herring Fish Bones

Past studies of bone extracellular matrix phosphoproteins such as osteopontin and bone sialoprotein have yielded important biological information regarding their role in calcification and the regulation of cellular activity. Most of these studies have been limited to proteins extracted from mammalian and avian vertebrates and nonvertebrates. The present work describes the isolation and purification of two major highly glycosylated and phosphorylated extracellular matrix proteins of 70 and 22 kDa from herring fish bones. The 70-kDa phosphoprotein has some characteristics of osteopontin with respect to amino acid composition and susceptibility to thrombin cleavage. Unlike osteopontin, however, it was found to contain high levels of sialic acid similar to bone sialoprotein. The 22-kDa protein has very different properties such as very high content of phosphoserine (∼270 Ser(P) residues/1000 amino acid residues), Ala, and Asx residues. The N-terminal amino acid sequence analysis of both the 70-kDa (NPIMA(M)ETTS(M)DSKVNPLL) and the 22-kDa (NQDMAMEASSDPEAA) fish phosphoproteins indicate that these unique amino acid sequences are unlike any published in protein databases. An enzyme-linked immunosorbent assay revealed that the 70-kDa phosphoprotein was present principally in bone and in calcified scales, whereas the 22-kDa phosphoprotein was detected only in bone. Immunohistological analysis revealed diffusely positive immunostaining for both the 70- and 22-kDa phosphoproteins throughout the matrix of the bone. Overall, this work adds additional support to the concept that the mechanism of biological calcification has common evolutionary and fundamental bases throughout vertebrate species.

Erratum: Bin+ cluster ion sources for investigation of a covalently immobilized mixed film composed of oligonucleotides and poly(2‐hydroxyethyl methacrylate) brushes

This paper was published online on 20 May 2010 (DOI: 10.1002/sia.3431). Subsequent to online publication the authors wish to make the following correction: A small detail has been omitted in the Instrumentation a sub-section of Experimental Section, which will clarify the procedure further. The amended Instrumentation sub-section is presented below with the authors' revisions in bold face: Instrumentation ToF-SIMS experiments were done at Surface Interface Ontario, University of Toronto. The instrument used was an ION-TOF TOFSIMS IV (Muenster, Germany), which was operated in static mode. The primary ion source was a Bin+ cluster ion primary source with a potential of 25 keV and a maximum current of 1 pA. Ion currents of 1 pA was used for Bi+, about 0.4 pA was used for Bi3+, and about 0.05 pA was used for Bi5+. The experiments that used the same ion source were at the same current. A spot area of 500 µm × 500 µm was sampled and the spectra were obtained in high-mass resolution mode.[4] Both negative and positive ion modes were investigated and a mass range from 0 to 500 atomic mass units (amu) was scanned for collection of SIMS spectra. The raw ToF-SIMS data were processed by IonSpec Application software, version 4.5.0.0 by ION-TOF GmbH (1996–2002).