bluuebunny/crossref_metadata_2025 huggingface dataset:
Trisomy 13 and trisomy 18 in a defined population: epidemiological, genetic and prenatal observations
Authors: Parker M. J. , Budd J. L. S. , Draper E. S. , Young I. D.
Published: October 2003

Objectives

To establish precise incidence figures for trisomy 13 and trisomy 18 in the former Trent region, to identify current prenatal diagnostic practice, and to assess the potential impact of the introduction of recently devised prenatal diagnostic practices.

Methods

An audit of all cases of trisomy 13 and trisomy 18 ascertained through the records of the Trent Congenital Anomalies Register and the Trent Regional Cytogenetic Laboratories.

Results

Forty‐four cases of trisomy 13 and 88 cases of trisomy 18 were ascertained. Advanced maternal age effects were observed. Of all cases, 64% were first detected through chromosomal analysis initiated because of abnormalities noted on fetal anomaly scanning in the second trimester, whereas only 3% of cases were detected through the serum‐screening programme currently offered for Down syndrome. In 11% of cases, the diagnosis was first suspected after birth. Twelve percent of couples chose to continue pregnancy following chromosomal confirmation of a suspected diagnosis.

Conclusion

The introduction of a highly sensitive prenatal diagnostic screening programme would have a major impact on the timing and proportions of all trisomy 13 and 18 cases diagnosed in pregnancy as gauged by current practice. It is important that health professionals involved in prenatal counselling be aware that, as with Down syndrome and anencephaly, around 12% of prospective parents of a child with trisomy 13 or 18 choose to continue rather than terminate the pregnancy. Copyright © 2003 John Wiley & Sons, Ltd.
Maternal weight correction of maternal serum PAPP‐A and free β‐hCG MoM when screening for trisomy 21 in the first trimester of pregnancy
Authors: Spencer Kevin , Bindra Renu , Nicolaides Kypros H.
Published: October 2003

Objective

To assess the suitability of either the log‐linear or reciprocal‐linear regression procedure for maternal weight correction of biochemical marker MoMs in the first trimester.

Methods

Data from two prospective first‐trimester OSCAR screening programmes including 32 010 women with first‐trimester maternal serum‐free β‐hCG and PAPP‐A measured by the Kryptor analyser was analysed by regression analysis to provide parameters for the log‐linear and reciprocal‐linear MoM correction procedures. Assessment was made by goodness of fit to the data. The impact on detection rate and false‐positive rate of the different correction procedures was assessed using statistical modelling with biochemical markers alone.

Results

Both log‐linear and reciprocal‐linear correction were shown to fit the data well. For free β‐hCG, the log‐linear procedure was marginally superior to the reciprocal‐linear procedure (r2 = 0.986 v 0.980), whilst for PAPP‐A the reciprocal‐linear procedure was marginally better (r2 = 0.991 v 0.985). Log‐linear correction reduced the variance for both markers more than did the reciprocal‐linear procedure. For free β‐hCG, the sd was reduced from 0.2675 to 0.2605 and for PAPP‐A, it was reduced from 0.2545 to 0.2336. Correcting for maternal weight was shown to reduce the population false‐positive rate from 7.0 to 6.5%, whilst maintaining the same detection rate at a risk cut‐off of 1 in a 100. At individual levels, a two‐fold variation in risk was demonstrated depending upon the individual's weight.

Conclusions

To provide accurate individual patient‐specific risks for trisomy 21, maternal weight must be taken into account and should be a mandatory data item for screening programmes. Maternal weight correction in the first trimester using free β‐hCG and PAPP‐A can be best achieved using the log‐linear procedure. Copyright © 2003 John Wiley & Sons, Ltd.
Mild pyelectasis: evaluating the relationship between gestational age and renal pelvic anterior–posterior diameter
Authors: Odibo Anthony O. , Marchiano Dominic , Quinones Joanne N. , Riesch Deborah , Egan Jim F. X. , Macones George A.
Published: October 2003

Objective

To determine the relationship between gestational age and renal pelvic anterior–posterior diameter and the feasibility of developing gestational age–specific thresholds for the diagnosis of mild pyelectasis.

Methods

Cross‐sectional study of 420 singleton fetuses between 16 and 39 weeks' gestation. The mean renal AP diameter as a function of gestational age was determined using fractional polynomial regression models and centile plots were generated. Assessment of goodness of fit for each regression model was performed.

Results

There was a positive correlation between gestational age and renal pelvic AP diameter (Pearson's Correlation Coefficient 0.65). Using the derived mean and standard deviations of renal AP diameter, gestational‐age specific 95% reference levels were generated. The sensitivity, specificity, positive, and negative predictive values of using the gestational age‐specific cutoffs for predicting persistent postnatal renal anomaly were 80%; 99%; 29%; and 99% respectively.

Conclusion

There is a positive correlation between gestational age and renal pelvic AP diameters. Reliable gestational age‐specific renal AP thresholds for diagnosis of pyelectasis are provided. Copyright © 2003 John Wiley & Sons, Ltd.
NMR, solvation and theoretical investigations of conformational isomerism in 2‐X‐cyclohexanones (X=NMe2, OMe, SMe and SeMe)
Authors: Freitas Matheus P. , Tormena Cláudio F. , Garcia Janaína C. , Rittner Roberto , Abraham Raymond J. , Basso Ernani A. , Santos Francisco P. , Cedran Jaime C.
Published: October 2003

The conformational equilibria of 2‐N,N‐dimethylamino‐ (1), 2‐methoxy‐ (2), 2‐methylthio‐ (3) and 2‐methylselenocyclohexanone (4) were determined in various solvents by measurement of the 3JH‐2,H‐3 couplings. The observed couplings were analyzed using theoretical and solvation calculations to give both the conformer energies in the solvents studied plus the vapor‐phase energies and the coupling constants for the distinct conformers. These gave the conformer energies and couplings of 2–4. The intrinsic couplings for the 2‐N,N‐dimethylamino compound were determined by the molecular mechanics PCMODEL program. The axial conformation in 1 is the most polar and also more stable in DMSO solution (Eeq−Eax=0.05 kcal mol−1) and the pure liquid, while the equatorial conformer predominates in the remaining solvents studied (except in CCl4, where self‐association is observed). In the methoxy ketone (2) the equatorial conformation is more stable in the vapor (Eeq−Eax=−0.30 kcal mol−1) and in all solvents. The opposite behavior is shown by 3 and 4, where the axial conformation is the more stable one in the vapor phase (Eeq−Eax=1.60 and 2.95 kcal mol−1 for 3 and 4, respectively) and is still the prevailing conformer in solution. The axial predominance for 3 and 4 is attributed to hyperconjugation between the electron lone pair of the hetero‐substituent and the π*CO orbital. This interaction is stronger for 3 and 4 than in the case of 1 and 2, where the ‘gauche effect’ in the equatorial conformation should be more effective in stabilizing this conformation. Copyright © 2003 John Wiley & Sons, Ltd.
Mechanism and structure–reactivity correlation in the homogeneous, unimolecular elimination kinetics of 2‐substituted ethyl methylcarbonates in the gas phase
Authors: Chuchani Gabriel , Marquez Edgar , Herize Armando , Domínguez Rosa María , Tosta María , Brusco Doris
Published: October 2003

The gas‐phase elimination kinetics of 2‐substituted ethyl methylcarbonates were determined in a static reaction system over the temperature range of 323–435°C and pressure range 28.5–242 Torr. The reactions are homogeneous, unimolecular and follow a first‐order rate law. The kinetic and thermodynamic parameters are reported. The 2‐substituents of the ethyl methylcarbonate (CH3OCOOCH2CH2Z, Z=substituent) give an approximate linear correlation when using the Taft–Topsom method, log(kZ/kH)=−(0.57±0.19)σα+(1.34±0.49)σR− (r=0.9256; SD=0.16) at 400°C. This result implies the elimination process to be sensitive to steric factors, while the electronic effect is unimportant. However, the resonance factor has the greatest influence for a favorable abstraction of the β‐hydrogen of the Cβ—H bond by the oxygen carbonyl. Because ρα is significant, a good correlation of the alkyl substituents of carbonates with Hancock's steric parameters was obtained: log(kR/kH) versus ESC for CH3OCOOCH2CH2R at 400°C, R=alkyl, δ=−0.17 (r=0.9993, SD=0.01). An approximate straight line was obtained on plotting these data with the reported Hancock's correlation of 2‐alkyl ethylacetates. This result leads to evidence for the β‐hydrogen abstraction by the oxygen carbonyl and not by the alkoxy oxygen at the opposite side of the carbonate. The carbonate decompostion is best described in terms of a concerted six‐membered cyclic transition state type of mechanism. Copyright © 2003 John Wiley & Sons, Ltd.
Exothermic thermal reaction of dopamine with 3,5‐dinitrobenzoic acid
Authors: Ito Yoshikatsu , Arimoto Satoru
Published: October 2003

Pyrolysis of the crystalline 1 : 1 molecular complex DAċdnba, which was prepared from cocrystallization of dopamine (DA) and 3,5‐dinitrobenzoic acid (dnba), was studied. This cocrystal decomposed violently at the melting‐point, leading to the formation of a black solid along with a tiny amount of 3‐amino‐5‐nitrobenzoic acid (1). The pyrolysis reaction was followed by differential scanning calorimetry (DSC) and one large exothermic peak was observed at the decomposition temperature. In view of the DSC patterns for cocrystal DAċdnba and other compounds, it seems that both a catechol moiety and an amino group of DA in addition to a strong electron acceptor such as dnba are required for the appearance of the exothermic peak. On the basis of (a) elemental analysis of the black solid and (b) other pyrolysis experiments for cocrystals PAċdnba (PA: β‐phenylethylamine), BAċdnba (BA: benzylamine), DMDAċdnba (DMDA: O,O′‐dimethyldopamine) and DHBAċdnba (DHBA: 3,4‐dihydroxybenzylamine), it is assumed that the black solid was formed mainly through elimination of more than one molecule of water from one molecule of DAċdnba. Copyright © 2003 John Wiley & Sons, Ltd.
Nonexponential decay of reactive intermediates: new challenges for spectroscopic observation, kinetic modeling and mechanistic interpretation
Authors: Carpenter Barry K.
Published: October 2003

A thermally generated reactive intermediate is generally presumed to consist of a population with a distribution of lifetimes characterized by a single, well‐defined parameter, τ. The decay of an instantaneously generated population, whose conversion to products occurred by parallel unimolecular steps, would be expected to be defined by a simple, single‐exponential expression: A(t)=A0 exp(−t/τ), where A(t) is the population at time t, and A0 is the population at t=0. In this model, the lifetime is also related to the first‐order rate constants, ki, for the unimolecular product‐forming steps; specifically τ = (Σiki)−1. The ratio of the products is equal to the ratio of the rate constants for their formation. Given an accurate potential energy surface (PES) for the reaction, one would expect to be able to compute the values of the ki under the specified reaction conditions, and hence both the lifetime of the intermediate and the ratio of products. This simple picture, which has formed the basis for most mechanistic investigation of reactive intermediates, and most kinetic modeling of reactions in which they are involved, has been challenged in recent years by molecular dynamics (MD) simulations, which have predicted that a variety of thermally generated intermediates should exhibit bimodal or even multimodal lifetime distributions. In several cases the shortest lifetime populations have been found to lead to products in a ratio quite different from that for the longer‐lived populations, and also quite unlike that expected from RRKM or transition state theory calculations based on the same PES used for the MD simulations. This commentary reviews the origins of this behavior and discusses the challenges of designing experiments to test the predictions. Copyright © 2003 John Wiley & Sons, Ltd.
Kinetics and mechanisms of the gas‐phase elimination of N‐phenylglycine and its ethyl ester
Authors: Domínguez Rosa M. , Tosta Maria , Chuchani Gabriel
Published: October 2003

The elimination kinetics of the title compounds were determined over the temperature range 290.4–420.3°C and pressure range 14.5–44.0 Torr. The reactions, carried out in seasoned vessels and in the presence of the free radical inhibitor toluene, are homogeneous, unimolecular and follow a first‐order rate law. The rate coefficient is expressed by the following Arrhenius equation: for N‐phenylglycine ethyl ester, log [I1 (s−1)]=(12.13±0.38)− (193.6±4.9) kJ mol−1 (2.303 RT)−1; and for N‐phenylglycine, log [k1 (s−1)]=(12.95±0.52)−(177.4±5.8) kJ mol−1 (2.303 RT)−1. Both substrates yield mainly N‐methylaniline and a small amount of aniline. N‐Phenylglycine as a neutral amino acid decomposes 130 times faster than its ethyl ester at 380°C. The mechanisms of these elimination reactions are presented and discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Anharmonic contributions to the nuclear relaxation first hyperpolarizability for push–pull molecules
Authors: Squitieri Emilio
Published: October 2003

The nuclear relaxation first hyperpolarizability of a push–pull molecule was studied using the simple valence‐bond charge‐transfer model and analytical evaluation of electrical properties method. A relationship between the nuclear relaxation and electronic contributions to the first hyperpolarizability was derived, which incorporates the harmonic and anharmonic terms associated with the ground‐state potential energy. We show that the anharmonic contribution is as important as that of the harmonic contribution and it follows the trend of the electronic contribution. Copyright © 2003 John Wiley & Sons, Ltd.
Preparation and chiral recognition ability of cellulose 3,5‐dimethylphenylcarbamate immobilized on silica gel through radical polymerization
Authors: Kubota Takateru , Yamamoto Chiyo , Okamoto Yoshio
Published: October 2003

Polysaccharide‐immobilized chiral stationary phases (CSPs) were prepared by the polymerization of cellulose 3,5‐dimethylphenylcarbamate, having a polymerizable vinyl group, such as 4‐vinylphenylcarbamate or 2‐methacryloyloxyethylcarbamate, at the 6‐position, with a vinyl monomer, such as styrene, isoprene, t‐butyl acrylate, or t‐butyl methacrylate, on silica gel under various conditions. Their chiral recognition abilities were then evaluated with high‐performance liquid chromatography. The immobilized cellulose 3,5‐dimethylphenylcarbamate remained on the silica gel even if washed with tetrahydrofuran, which could dissolve the cellulose derivative. The chiral recognition abilities of the immobilized CSPs were similar to those of the coated CSPs when the vinyl monomer content was low. The chiral recognition abilities of the obtained immobilized CSPs slightly depended on the vinyl monomers. The immobilization of the cellulose derivatives was more efficiently attained on the silica gel modified with a vinyl compound. The cellulose derivatives, randomly having a vinyl group at the 2‐, 3‐, or 6‐position of the glucose unit, were prepared by a one‐pot reaction. The immobilization efficiency of these derivatives was slightly lower than that of the derivative with the vinyl group at the 6‐position. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3703–3712, 2003
Liquid‐crystalline stereoregular polyketone prepared from a mesogenic vinylarene and carbon monoxide
Authors: Kawashima Yasutoyo , Nozaki Kyoko , Hiyama Tamejiro , Yoshio Masafumi , Kanie Kiyoshi , Kato Takashi
Published: October 2003

Isotactic and syndiotactic polyketones were synthesized by the alternating copolymerizations of a mesogenic vinylarene, 4‐cyano‐4′‐[8‐(4‐vinylphenyl)octyl‐1‐oxy]biphenyl, with carbon monoxide, and this revealed the influence of backbone tacticity on their thermal properties. The isotactic polyketone was an amorphous polymer that did not show any mesophase, whereas the syndiotactic polyketone exhibited liquid crystallinity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3556–3563, 2003
Further progress in atom transfer radical polymerizations conducted in a waterborne system
Authors: Li Mei , Matyjaszewski Krzysztof
Published: October 2003

An improved atom transfer radical polymerization (ATRP) process was developed for use in a waterborne miniemulsion system. To conduct a successful ATRP in a heterogeneous waterborne system, it is of great importance to ensure control over the polymerization process while preserving colloidal stability. Efforts devoted to optimization of reaction conditions and improvement in the overall productivity of the process allowed the development of a novel, practical initiation system for ATRP suitable for use in a miniemulsion procedure that can provide copolymers of well‐defined composition (e.g., block copolymers) and topologies (e.g., multiarm polymer). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3606–3614, 2003
Control of polymer topology through late‐transition‐metal catalysis
Authors: Guan Zhibin
Published: October 2003

An Erratum has been published for this article in J Polym Sci Part A: Polym Chem (2004) 42 213

In this article, recent examples are reviewed of late‐transition‐metal catalysis applied to polymer topology control. By the judicious selection or design of late‐transition‐metal catalysts, polymers with a broad range of topologies, including linear, short‐chain‐branched, hyperbranched, dendritic, and cyclic topologies, have been successfully synthesized. A distinctive advantage of the catalyst approach is that polymers with complex topologies can be prepared in one pot from simple commercial monomers. A fundamental difference of the catalyst approach with respect to other approaches is that the polymer topology is controlled by the catalysts instead of the monomer structure. In our own laboratory, we have successfully used two strategies to control the polymer topology with late‐transition‐metal catalysts. In the first strategy, hyperbranched polymers are prepared by the direct free‐radical polymerization of divinyl monomers through control of the competition between propagation and chain transfer with a cobalt chain‐transfer catalyst. In the second strategy, polyethylene topology is successfully controlled by the regulation of the competition between propagation and chain walking with the Brookhart PdII‐α‐bisimine catalyst. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3680–3692, 2003
Fuzzy TOPSIS approach for failure mode, effects and criticality analysis
Authors: Braglia Marcello , Frosolini Marco , Montanari Roberto
Published: October 2003

In this paper, an alternative multi‐attribute decision‐making approach for prioritizing failures in failure mode, effects and criticality analysis (FMECA) is presented. The technique is specifically intended to overcome some of the limitations concerning the use of the conventional US MIL‐STD‐1629A method. The approach is based on a fuzzy version of the ‘technique for order preference by similarity to ideal solution’ (TOPSIS).The use of fuzzy logic theory allows one to avoid the intrinsic difficulty encountered in assessing ‘crisp’ values in terms of the three FMECA parameters, namely chance of failure, chance of non‐detection, and severity. With the proposed approach, the definition of a knowledge base supported by several qualitative rule bases is no longer required. To solve the fundamental question of ranking the final fuzzy criticality value, a particular method of classification is adopted, allowing a fast and efficient sorting of the final outcome. An application to an important Italian domestic appliance manufacturer and a comparison with conventional FMECA are reported to demonstrate the characteristics of the proposed method. Finally, a sensitivity analysis of the fuzzy judgement weights has confirmed that the proposed approach gives a reasonable and robust final priority ranking of the different causes of failure. Copyright © 2003 John Wiley & Sons, Ltd.
Implementing Evaluation of the Measurement Process in an Automotive Manufacturer: a Case Study
Authors: Knowles Graeme , Vickers Gordon , Anthony Jiju
Published: October 2003

Reducing process variability is presently an area of much interest in manufacturing organizations. Programmes such as Six Sigma robustly link the financial performance of the organization to the degree of variability present in the processes and products of the organization. Data, and hence measurement processes, play an important part in driving such programmes and in making key manufacturing decisions. In many organizations, however, little thought is given to the quality of the data generated by such measurement processes. By using potentially flawed data in making fundamental manufacturing decisions, the quality of the decision‐making process is undermined and, potentially, significant costs are incurred. Research in this area is sparse and has concentrated on the technicalities of the methodologies available to assess measurement process capability. Little work has been done on how to operationalize such activities to give maximum benefit. From the perspective of one automotive company, this paper briefly reviews the approaches presently available to assess the quality of data and develops a practical approach, which is based on an existing technical methodology and incorporates simple continuous improvement tools within a framework which facilitates appropriate improvement actions for each process assessed. A case study demonstrates the framework and shows it to be sound, generalizable and highly supportive of continuous improvement goals. Copyright © 2003 John Wiley & Sons, Ltd.
Development of a FTA versus Parts Count Method Model: Comparative FTA
Authors: Arcidiacono G.
Published: October 2003

This study adopts a special Fault Tree Analysis (FTA) method called Comparative FTA to compare the reliability of an electronic braking system with its mechanical counterpart. To this end two Top Events, ‘Ineffective parking braking’ and ‘Wheels jamming during emergency braking’, were analysed. One of the limitations of classic FTA is that the setting up of the tree diagram requires the long‐term involvement—one to two months according to Fiat Auto—of specialists of the system being studied. For this reason, therefore, when dealing with relatively complex systems, classic FTA is only used when safety is involved. This paper introduces a simplified FTA model based on the same principle as the Parts Count Method, which limits its attention to the new branches, thereby avoiding the study of all the branches of the tree, in order to make FTA management easier and to encourage its use. The probability that a Top Event takes place is therefore evaluated by studying the different causes which diversify the solutions considered. This approach is a lean practice to minimize the resources and the time of the analysis. It has guaranteed very satisfactory results and, therefore, Fiat Auto has introduced the practice in their Corporate Instructions. Copyright © 2003 John Wiley & Sons, Ltd.
Identification of plant sterols in hexaploid and tetraploid wheats using gas chromatography with mass spectrometry
Authors: Pelillo Marco , Iafelice Giovanna , Marconi Emanuele , Caboni Maria Fiorenza
Published: October 2003

Free sterols from hexaploid and tetraploid free‐threshing wheats (Triticum aestivum L. and T. durum Desf.) and from their respective hulled wheats (T. spelta L. and T. dicoccon Schrank) were analysed by gas chromatography with mass spectrometry. The qualitative analysis of sterols showed a similar pattern either between hexaploid (T. aestivum, T. spelta) and tetraploid (T. durum, T. dicoccon) wheats or between free‐threshing (T. aestivum, T. durum) and hulled (T. spelta, T. dicoccon) wheats. However, quantitative differences were found between tetraploid and hexaploid wheats, in that free sterol amounts in tetraploid wheats were 40% higher than in hexaploid ones. The mass spectra of the sterols were classified into four groups, taking into account the structural features of rings A and B. Typical mass spectral fragmentations of the four classes, and additional evidence related to the side chain of each molecule, were investigated together with their chromatographic behaviour, allowing identification of all the detected sterols. Copyright © 2003 John Wiley & Sons, Ltd.
Analytical method for the quantitative determination of urinary ethylenethiourea by liquid chromatography/electrospray ionization tandem mass spectrometry
Authors: Sottani Cristina , Bettinelli Maurizio , Fiorentino Maria Lorena , Minoia Claudio
Published: October 2003

A direct, rapid and selective method for the quantitative determination of the ethylenethiourea (ETU) in human urine has been validated and is reported in the present study. It allows the accurate quantification of ETU in this complex matrix without the use of any internal standard as the sample cleanup is effective enough for the removal of interferences that could lead to ion suppression in the electrospray ionization (ESI) source. This simple and rapid purification system, based on the use of a Fluorosil phase of a BondElut® column followed by a liquid‐liquid extraction procedure, achieves mean extracted recoveries, assessed at three different concentrations (2.5, 10.0, and 25.0 μg/L), always more than 85%. High‐performance liquid chromatography (HPLC) with positive ion tandem mass spectrometry, operating in selected multiple reaction monitoring (MRM) mode, is used to quantify ETU in human urine. The assay is linear over the range 0–50 μg/L, with a lower limit of quantification (LOQ) of 1.5 μg/L and a coefficient of variation (CV) of 8.9%. The lower limit of detection (LOD) is assessed at 0.5 μg/L. The overall precision and accuracy were determined on three different days. The values for within‐ and between‐day precision are ≤ 8.3 and 10.1%, respectively, and the accuracy is in the range 97–118%. The relative uncertainties for the LOQ and QC concentrations have been estimated to be 18 and 8%, respectively. The assay was applied to quantify ETU in human urine from growers that regularly handle ethylenebisdithiocarbamate pesticides in large crop plantations. The biological samples were collected at the start and end of the working day, and the ETU urine levels were found to vary between 1.9 and 8.2 μg/L. Copyright © 2003 John Wiley & Sons, Ltd.
Effects of hydrolysis on the δ13C values of individual amino acids derived from polypeptides and proteins
Authors: Jim Susan , Jones Vicky , Copley Mark S. , Ambrose Stanley H. , Evershed Richard P.
Published: October 2003

This study investigates the effects of hydrolysis on the δ13C values of individual amino acids (IAAs) derived from polypeptide standards, and modern and ancient bone collagen. All IAAs were derivatised to their trifluoroacetyl/isopropyl (TFA/IP) esters for δ13C determination using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Firstly, authentic single poly amino acid standards (SPAAs; n = 5) were hydrolysed for 4, 10, 24 and 48 h. As expected, IAA yields increased as a function of hydrolysis time. Significantly, it was only after 24 h of hydrolysis that IAA δ13C values were statistically identical to bulk SPAA values for all five standards. The accuracy of IAA δ13C values was thus shown to be a function of yield; however, poly phenylalanine demonstrated accurate IAA δ13C values with yields of only 1.4 and 4.3%, after 24 and 48 h of hydrolysis time, respectively. Authentic mixed poly amino acid standards (MPAAs; n = 5) comprising two different amino acids were then hydrolysed for 24 h. Percentage recoveries ranged from 36–95%. Estimates of bulk MPAA δ13C values calculated from measured IAA δ13C values agreed within experimental error with measured bulk MPAA values for three out of the five standards. Finally, the experimental procedure was applied to modern rat (MBCs; n = 20) and ancient ovi‐caprine and bovine (ABCs; n = 27) bone collagen samples where the δ13C values of 12 out of its 18 constituent amino acids were determined. Estimated bulk MBC and ABC δ13C values were calculated from constituent amino acid δ13C values using mass balance. With the exclusion of three ABC samples, calculated bulk bone collagen δ13C values (δ13CBCcal) were shown to correlate extremely well with measured bone collagen values (δ13CBCmes) for both modern and ancient samples, where R2 = 0.91 and 0.84, respectively. Significantly, the variation between calculated and measured bone collagen values (Δ13CBCcal‐BCmes) exhibited similar ranges for both MBC (from −2.6 to +1.2‰) and ABC (from −2.7 to +2.2‰) samples, providing evidence for the preservation of intact collagen in the ancient samples. These results demonstrate that the experimental procedures employed in the acid hydrolytic cleavage of peptides or proteins to their constituent amino acids does not involve significant isotopic fractionation. Copyright © 2003 John Wiley & Sons, Ltd.
Induced in‐source fragmentation for the selective detection of organic bound iodine by liquid chromatography/electrospray mass spectrometry
Authors: Putschew Anke , Jekel Martin
Published: October 2003

The detection of unknown organic compounds, e.g., transformation products of known trace pollutants in environmental samples, is a difficult task which can be simplified if the compounds of interest are characterized by a functional group or a heteroatom which can selectively be detected. For the detection of iodinated benzene derivatives, used as X‐ray contrast media, we have studied whether such compounds can be selectively detected by negative ion (NI) electrospray ionization via iodide as a product ion of in‐source fragmentation, generated by applying a high cone voltage. It was found that selective detection of iodinated benzene derivatives is possible by liquid chromatography/negative ion electrospray ionization (LC/NI‐ESI) if the compounds are destroyed before entering the mass spectrometer. To our knowledge this is the first report of the use of NI in‐source fragmentation MS for analyses traditionally performed with inductively coupled plasma (ICP)‐MS. The novel application of NI in‐source fragmentation MS is a tool for those who do not possess the facilities to perform ICP‐MS. Furthermore, NI‐ESI at varying cone voltages provides both structural information and elemental detection, whereas ICP‐MS can only provide elemental detection. Copyright © 2003 John Wiley & Sons, Ltd.
Chromatographic and mass spectral studies of perfluorooctanesulfonate and three perfluorooctanesulfonamides
Authors: Kuehl D. W. , Rozynov B.
Published: October 2003

The chromatographic and mass spectral characteristics of perfluorooctanesulfonate (PFOS) and three nitrogen‐substituted perfluorooctanesulfonamides have been obtained. A methyl/phenyl mixed‐phase fused‐silica capillary column was used for gas chromatographic (GC) analyses, while a C18 reversed‐phase microbore column was used for liquid chromatographic (LC) analyses. Mass (MS) and tandem mass (MS/MS) spectra were generated using electron ionization (EI), argon CE, methane positive and negative ion CI, and ES ionization modes. EI spectra of the amides showed ions characteristic of both the fluorinated hydrocarbon and the sulfonamide portion of the molecules. The fragmentation pathway was studied using hydrogen/deuterium exchange, and was thought to involve a cyclic intermediate ion. Formation of molecular ions by CE and protonated molecule ions by CI to obtain molecular weight information was only partially successful. Negative ion ES‐MS spectra provided intense [M–H]− anions for the amides, and an [M–K]−anion for PFOS from which molecular weight information could be obtained, while ES‐MS/MS produced product ions that could be used to detect the presence of these compounds in biological or environmental samples. Published in 2003 by John Wiley & Sons, Ltd.
Phosphate buffers in capillary electrophoresis/mass spectrometry using atmospheric pressure photoionization and electrospray ionization
Authors: Nilsson S. L. , Andersson C. , Sjöberg P. J. R , Bylund D. , Petersson P. , Jörntén‐Karlsson M. , Markides K. E.
Published: October 2003

Capillary electrophoresis (CE) has been combined with atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) for mass spectrometric (MS) detection. Separation conditions using potassium phosphate buffer and ammonium formate buffer have been compared for analysis of eleven pharmaceutical bases. The results showed improvements in separation efficiency and peak symmetry when phosphate buffer was used. The low flow in CE may enable utilization of these advances with MS detection. Compared with ESI, the APPI technique provided a cluster‐free background. The enhanced signal‐to‐noise ratio in the total ion current (TIC) and the reduced spectral background indicated that the APPI process is less affected by non‐volatile salts in the CE buffers. This results in a wider range of choice of CE buffers in CE/MS analysis when APPI is the ionization method. Copyright © 2003 John Wiley & Sons, Ltd.
Comparative study of matrix‐assisted laser desorption/ionization and gas chromatography for quantitative determination of cocoa butter and cocoa butter equivalent triacylglycerol composition
Authors: Guyon F. , Absalon Ch. , Eloy A. , Salagoity M. H. , Esclapez M. , Medina B.
Published: October 2003

The triacylglycerol (TAG) composition study of cocoa butter (CB) and cocoa butter equivalents (CBEs) has been performed by gas chromatography (GC) and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS). These two techniques provided comparable results. The advantage of the MALDI technique was the detection of each compound comprising the triacylglycerol classes (Cn). Moreover, comparison of the data obtained by these two techniques indicated that TAG relative percentages could be obtained quantitatively with the MALDI technique. These techniques have been applied for the composition determination of CB + CBE mixtures. Encouraging results showed that it is possible to quantify an admixture containing as little as 4% of CBE. Copyright © 2003 John Wiley & Sons, Ltd.
Characteristic fragmentation behavior of phosphoamino acid conjugates with 3′‐azido‐3′‐deoxythymidine by electrospray ionization tandem mass spectrometry
Authors: Xiao Qiang , Ju Yong , Zhao Yufen , Cui Yuxin
Published: October 2003

The conjugates of phosphoamino acids with 3′‐azido‐3′‐deoxythymidine were synthesized and their structures were determined by various spectral methods. In positive and negative ion electrospray mass spectrometry (ESI‐MS), the fragmentation pathways were investigated in conjunction with tandem mass spectrometry (MS/MS). The results showed that there were very different characteristic fragment ions in the positive ion MS/MS spectra and the negative ion MS/MS spectra. Copyright © 2003 John Wiley & Sons, Ltd.
Linear quadrupoles with added octopole fields
Authors: Sudakov Michael , Douglas D. J.
Published: October 2003

Two methods of adding relatively small octopole fields to the main quadrupole field of quadrupoles and linear ion traps with cylindrical rods are investigated. The first, ‘stretching’ the quadrupole by moving two rods out from the axis, produces a combination of higher order fields with similar magnitudes in which the octopole field is not necessarily the greatest. The quadrupole field strength is changed significantly and a large potential appears on the axis. The second method uses rod pairs of different diameters. It adds octopole components of up to several percent while all other higher order fields remain small. An axis potential is also added, but it is only a few percent of the radio‐frequency (RF) voltage and approximately equal to the strength of the octopole field. The axis potential can be removed by moving the larger rod pair out from the axis or applying unbalanced RF to the electrodes. Copyright © 2003 John Wiley & Sons, Ltd.
Electrospray ion‐trap multistage mass spectrometry for characterisation of co‐monomer compositional distribution of bacterial poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) at the molecular level
Authors: Adamus Grażyna , Sikorska Wanda , Kowalczuk Marek , Noda Isao , Satkowski Michael M.
Published: October 2003

We report an electrospray ionisation multistage mass spectrometry (ESI‐MSn) method that utilises molecular mass information for determination of sequence distribution and chemical structure of mass‐selected macromolecules of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) biopolyester, PHBH. On the basis of ESI‐MSn studies of PHBH oligomers obtained by partial alkaline depolymerisation of natural PHBH containing 13–14 mol% of hydroxyhexanoate (HH) units, the microstructure of this bacterial copolyester was assessed up to the level of 28 repeat units. The subtle structural details of the PHBH were evaluated based on sequencing of individual macromolecular ions thus showing the utility of this technique for the analysis of biological copolyester macromolecules. It was confirmed that both HH and hydroxybutyrate (HB) units of the PHBH copolymer are randomly distributed. Copyright © 2003 John Wiley & Sons, Ltd.
Quantitative analysis of small pharmaceutical drugs using a high repetition rate laser matrix‐assisted laser/desorption ionization source
Authors: Hatsis Panos , Brombacher Stephan , Corr Jay , Kovarik Peter , Volmer Dietrich A.
Published: October 2003

In this work, a high repetition rate laser matrix‐assisted laser desorption/ionization (MALDI) source is studied on a quadrupole‐time‐of‐flight (QqTOF) and a triple quadrupole (QqQ) mass spectrometer for rapid quantification of small pharmaceutical drugs. The high repetition rate laser allows an up to 100‐fold higher pulse frequency as compared with regular MALDI lasers, resulting in much larger sample throughput and number of accumulated spectra. This increases the reproducibility of signal intensities considerably, with average values being around 5% relative standard deviation after taking into account the area ratio of the analyte to an internal standard. Experiments were conducted in MS/MS mode to circumvent the large chemical background due to MALDI matrix ions in the low mass range. The dynamic range of calibration curves on the QqTOF mass spectrometer extended over at least two orders of magnitude, whereas on the QqQ it extended over at least three orders of magnitude. Detection limits ranged from 60–400 pg/μL on the QqTOF and from 6–70 pg/μL on the QqQ for a series of benzodiazepines. The benzodiazepine content of commercial pill formulations was quantified, and less than 5% error was obtained between the present method and the manufacturer's certified values. Furthermore, a high sample throughput was achieved with this method, so that a single MALDI spot could be quantitatively scanned in as little as 15 s, and an entire 96‐well MALDI plate in 24 min. Copyright © 2003 John Wiley & Sons, Ltd.
Quantification of the ratio of positional isomer dilinoleoyl‐oleoyl glycerols in vegetable oils
Authors: Jakab A. , Jablonkai I. , Forgács E.
Published: October 2003

The distribution of fatty acids in a triacylglycerol is of great importance from nutritional, biochemical, quality and technological points of view. The ratio of triacylglycerol positional isomers containing two linoleic acid (18:2) and one oleic acid (18:1) moieties—namely, 1(3),2‐dilinoleoyl‐3(1)‐oleoyl glycerol (LLO) and 1,3‐dilinoleoyl‐2‐oleoyl glycerol (LOL)—were quantified in grape seed, olive, pumpkin seed, soybean, sunflower and wheat germ oils by high‐performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (HPLC/APCI‐MS) in selected ion monitoring (SIM) mode. Relative LOL contents (LOL/(LLO+LOL)) of the oils were calculated from the mass abundances of the [LL]+ and [LO]+ diacylglycerol fragment ions ([M+H–RCOOH]+) using a calibration curve. The calibration curve of the relative diacylglycerol mass abundances was measured in SIM mode. The relative LOL contents were found to be relatively consistent for each oil variety. The relative LOL content in grape seed, sunflower, pumpkin seed, soybean and wheat germ oils accounted for 44.2 ± 2.6, 26.8 ± 3.2, 16.7 ± 4.6, 15.9 ± 2.9 and 13.9 ± 4.3%, respectively. Only olive oils contained practically 100% of the LLO isomer. These results indicate that the unsaturated fatty acids such as linoleic and oleic acids have ‘non‐random’ distribution patterns in various oils. Copyright © 2003 John Wiley & Sons, Ltd.
Production and fragmentation of multiply charged ions in ‘electron‐free’ matrix‐assisted laser desorption/ionization
Authors: Frankevich Vladimir , Zhang Juan , Dashtiev Maxim , Zenobi Renato
Published: October 2003

An unusually large fraction of multiply charged ions is observed in ‘electron‐free’ matrix‐assisted laser desorption/ionization (MALDI). Here we investigate how the yield of multiply charged ions depends on experimental parameters in MALDI. It is found to increase if measures are taken to limit the number of electrons in the plume, for example, by using non‐metallic MALDI targets or low laser pulse energies. The ionization energy of the matrix is another important parameter that affects the yield of multiply charged ions: matrices with high ionization energies lead to greater intensities of multiply charged ions. It is furthermore proposed that some of the fragment ions observed in MALDI are due to reactions of analyte with electrons in the plume. The possibility of electron capture dissociation of multiply charged ions produced by MALDI is shown. Copyright © 2003 John Wiley & Sons, Ltd.
Automated multiple‐layer spotting for matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry of synthetic polymers utilizing ink‐jet printing technology
Authors: Meier Michael A. R. , de Gans Berend‐Jan , van den Berg Antje M. J. , Schubert Ulrich S.
Published: October 2003

Recently, a new multiple‐layer matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) sample spotting technique for poly(ethylene glycol), offering improved analysis possibilities, was described. In this contribution the application of ink‐jet printing to automated, multiple‐layer MALDI‐TOFMS sample preparation of synthetic polymers is presented, allowing accurate deposition of matrix, additive and analyte solutions. The new sample preparation technique was evaluated for poly(ethylene glycol) as well as poly(methyl methacrylate) standards, and optimized settings for both synthetic polymers have been obtained. Copyright © 2003 John Wiley & Sons, Ltd.
PEAKS: powerful software for peptide de novo sequencing by tandem mass spectrometry
Authors: Ma Bin , Zhang Kaizhong , Hendrie Christopher , Liang Chengzhi , Li Ming , Doherty‐Kirby Amanda , Lajoie Gilles
Published: October 2003

A number of different approaches have been described to identify proteins from tandem mass spectrometry (MS/MS) data. The most common approaches rely on the available databases to match experimental MS/MS data. These methods suffer from several drawbacks and cannot be used for the identification of proteins from unknown genomes. In this communication, we describe a new de novo sequencing software package, PEAKS, to extract amino acid sequence information without the use of databases. PEAKS uses a new model and a new algorithm to efficiently compute the best peptide sequences whose fragment ions can best interpret the peaks in the MS/MS spectrum. The output of the software gives amino acid sequences with confidence scores for the entire sequences, as well as an additional novel positional scoring scheme for portions of the sequences. The performance of PEAKS is compared with Lutefisk, a well‐known de novo sequencing software, using quadrupole‐time‐of‐flight (Q‐TOF) data obtained for several tryptic peptides from standard proteins. Copyright © 2003 John Wiley & Sons, Ltd.
Phenol, chlorobenzene and chlorophenol isomers: resonant states and dissociative electron attachment
Authors: Khatymov Roustem V. , Muftakhov Mars V. , Mazunov Victor A.
Published: October 2003

This paper reports a study of resonant dissociative electron attachment (DEA) to the phenol, chlorobenzene, p‐, m‐, and o‐chlorophenol molecules. On the basis of spectroscopic and thermochemical approaches the resonant states of the molecular negative ions (NIs) and the structures of some dissociative decay products are assigned. In the electron energy range up to 3 eV, DEA processes are determined by the two 2[π*]‐shape resonances resulting mainly in formation of [MH]− and/or Cl− ions. At higher electron energies the energy correlation between peaks in the negative ion effective yield curves and bands of UV spectra allowed identification of the core‐excited resonances. The peculiarities of Cl− ion formation and the vibrational fine structure on the effective yield curves of the [MH]− ions are discussed. The mass spectrometric procedures for measurement of relative cross sections for NI formation are described. Copyright © 2003 John Wiley & Sons, Ltd.
A method for reducing the time required to match protein sequences with tandem mass spectra
Authors: Craig Robertson , Beavis Ronald C.
Published: October 2003

An algorithm for reducing the time necessary to match a large set of peptide tandem mass spectra with a list of protein sequences is described. This algorithm breaks the process into multiple steps. A rapid survey step identifies all protein sequences that are reasonable candidates for a match with a set of tandem mass spectra. These candidates are then used as models, which are refined by detailed analysis of the set of tandem mass spectra for evidence of incomplete enzymatic hydrolysis, non‐specific hydrolysis and chemical modifications of amino acid residues resulting from either post‐translational modifications or sample handling. Compared with current one‐step methods for matching proteins to mass spectra, this multiple‐step method can decrease the time required for the calculation by several orders of magnitude. Copyright © 2003 John Wiley & Sons, Ltd.
Trypsin digestion of proteins on intact immobilized pH gradient strips for surface matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric analysis
Authors: Iyer Srinivas , Olivares José
Published: October 2003

Isolelectric focusing (IEF) of proteins on immobilized pH gradient (IPG) strips is an integral part of two‐dimensional (2D) electrophoresis‐based proteomics. Proteins can be effectively analyzed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) on the intact strip itself, leading to the creation of a virtual 2D map giving pI and MW information, bypassing the second dimension SDS‐PAGE. Further, trypsin digestion of proteins on the strip can significantly aid the identification of IPG‐separated proteins. However, the small size of the peptides leads to diffusion along and outside the gel matrix. In this study, we describe a simple spray‐based procedure to perform ‘on‐strip’ trypsin digestion of proteins embedded in IPG strips. Examination of intact myoglobin and its tryptic peptides shows that post‐digestion diffusion of tryptic peptides is significantly minimized using this approach. Copyright © 2003 John Wiley & Sons, Ltd.