bluuebunny/crossref_metadata_2025_split huggingface dataset:
High affinity capture surface for matrix‐assisted laser desorption/ionisation compatible protein microarrays
Authors: Koopmann Jens‐Oliver , Blackburn Jonathan 
Published: February 2003

AbstractA surface for the capture of biotin‐tagged proteins on matrix‐assisted laser desorption/ionisation (MALDI) targets has been investigated. Binding of a poly‐L‐lysine poly(ethylene glycol)‐biotin polymer to glass and gold surfaces has been demonstrated using dual wavelength interferometry. Biotinylated proteins were captured onto this surface using tetrameric neutravidin as a multivalent bridging molecule. Biotin tagging of proteins was achieved by chemical biotinylation or by expressing a protein with a biotinylation consensus sequence in E. coli. The specificity of the surface for biotin‐tagged proteins allowed the purification of biotin‐tagged glutathione‐S‐transferase from a bacterial lysate directly onto a MALDI target. Subsequently, the protein was digested on the MALDI target and a protein fingerprint analysis confirmed its presence directly, but no E. coli proteins were detected. Therefore, we conclude that this surface is highly specific for the capture of biotin‐labelled proteins and has low non‐specific binding properties for non‐biotinylated proteins. Furthermore, protein–protein interactions using biotinylated lectins were investigated, and the selective capture of the glycoprotein fetuin with wheat germ agglutinin was demonstrated. Also, immobilised Arachis hypogea agglutinin recognised a minor asialo component of this glycoprotein on the array. The high affinity immobilisation of proteins onto this surface allowed effective desalting procedures to be used which improved the desorption of high molecular weight proteins. Another aspect of this surface is that a highly ordered coupling of the analyte can be achieved which eliminates the search for the sweet spot and allows the creation of densely packed protein microarrays for use in mass spectrometry. Copyright © 2003 John Wiley & Sons, Ltd.
Mass spectrometric investigation of N‐sulfonylated purine nucleic bases and nucleosides
Authors: Srzić Dunja , Rožman Marko , Krizmanić Irena , Žinić Biserka 
Published: February 2003

AbstractThe gas/phase behaviour of N‐sulfonylated purine nucleic bases and nucleosides towards electron impact (EI) and matrix‐assisted laser desorption/ionization (MALDI) occurring in a ion trap of a Fourier transform ion cyclotron resonance mass spectrometer is investigated. The influence of the storage time on the protonated molecule ([M+H]+) abundance under EI conditions confirms that the formation of these ions proceeds through ion/molecule reactions. Using stored‐waveform inverse Fourier transform (SWIFT) selective isolation of M+. or H3O+, self‐chemical ionization, M+./M, and chemical ionization, H3O+/M, are detected. Investigation of specific EI expulsion of SO2, SO2H and/or SO2H2 from M+. and/or [M+H]+ shows that oxygen protonation in SO2 proceeds faster than nitrogen protonation. Expulsion of SO2 from molecular ions is not observed in MALDI mass spectra of nucleosides. Copyright © 2003 John Wiley & Sons, Ltd.
Use of S‐pentafluorophenyl tris(2,4,6‐trimethoxyphenyl)phosphonium acetate bromide and (4‐hydrazino‐4‐oxobutyl) [tris(2,4,6‐trimethoxyphenyl)phosphonium bromide for the derivatization of alcohols, aldehydes and ketones for detection by liquid chromatography/electrospray mass spectrometry
Authors: Barry Samantha J. , Carr Richard M. , Lane Stephen J. , Leavens William J. , Manning Calvin O. , Monté Soraya , Waterhouse Ian 
Published: February 2003

AbstractThe synthesis of S‐pentafluorophenyl tris(2,4,6‐trimethoxyphenyl)phosphonium acetate bromide (TMPP‐AcPFP) and the novel compound (4‐hydrazino‐4‐oxobutyl) [tris(2,4,6‐trimethoxyphenyl)phosphonium bromide (TMPP‐PrG) is described and the use of these compounds as derivatizing reagents for alcohols, aldehydes and ketones evaluated. Methods have been developed for the pre‐column derivatization of alcohols using TMPP‐AcPFP and for aldehydes and ketones using TMPP‐PrG. The reactions were investigated by the use of a variety of individual test compounds containing the target functional groups. The TMPP acetyl ester and TMPP propyl hydrazone derivatives formed with their respective target analytes produced an enhanced response in electrospray ionization mass spectrometry (ESI‐MS), and reproducible chromatography. The use of these two reagents to derivatize and facilitate detection of alcohols (including sugars and steroids), aldehydes and ketones (including steroids) by LC/ESI‐MS was investigated. Copyright © 2003 John Wiley & Sons, Ltd.
Individual variability in Tityus serrulatus (Scorpiones, Buthidae) venom elicited by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Pimenta Adriano M. C. , Almeida Flavia De Marco , de Lima Maria Elena , Martin‐Eauclaire Marie France , Bougis Pierre E. 
Published: February 2003

AbstractVenom variability in specimens of Tityus serrulatus scorpion was assessed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) analyses. An expanded time lag venom extraction protocol was carried out using ten scorpions to study individual variations that might occur due to different rates in protein expression and/or processing. The first extraction of venom was made from the animals after 20 days of starvation, which allowed the venom gland to be filled up. The second extraction event was carried out 24 hours after the first one. The third was 8 days after the first extraction. By means of MALDI‐TOF analyses, important variations were observed in venoms of a single specimen extracted at different times, especially in latter extraction events. These variations are most probably related to dynamics in cell gland production. Since T. serrulatus is a parthenogenetic species, sexual variations are naturally excluded and we did not expect intra‐specific variations, which was confirmed. Knowledge of individual venom variability is extremely important to avoid misunderstandings in the use of venom proteomic analysis as a taxonomic tool. Copyright © 2003 John Wiley & Sons, Ltd.
A novel nanoflow interface for atmospheric pressure ionization mass spectrometry
Authors: Hirabayashi Atsumu 
Published: February 2003

AbstractA novel spray‐ionization technique for nanoflow liquid chromatography/mass spectrometry (nLC/MS) has been developed by modifying the sonic spray ionization (SSI) technique. A solution from a tapered fused‐silica capillary is sprayed by a gas flow coaxial to the capillary, and ions produced are analyzed with an ion‐trap mass spectrometer. The ion intensity is shown to have a steep threshold at a low gas velocity and to be much less dependent on the gas velocity than that of conventional SSI, in which the ion intensity is strongly dependent on the gas velocity and reaches its maximum at sonic velocity. Thus, we conclude that the concentration of charge in the solution at the tapered capillary tip with an inner diameter of 15 μm is almost at saturation so that charged droplets are produced from the solution by electrical force, rather than by sheer stress due to the gas flow. The ions are readily produced from these charged droplets. Preliminary results are compared with results obtained with a miniaturized electrospray unit. Copyright © 2003 John Wiley & Sons, Ltd.
Determination of perfluorooctane sulfonate in river water by liquid chromatography/atmospheric pressure photoionization mass spectrometry by automated on‐line extraction using turbulent flow chromatography
Authors: Takino Masahiko , Daishima Shigeki , Nakahara Taketoshi 
Published: February 2003

AbstractA simple, fast and sensitive liquid chromatography/atmospheric pressure photoionization mass spectrometry (LC/APPI‐MS) method, with automated on‐line extraction using turbulent flow chromatography (TFC), was developed for the determination of perfluorooctane sulfonate (PFOS) in river water. In this method, following an on‐line extraction by injection onto a column under TFC conditions, PFOS is back‐flushed onto a reversed‐phase column via on‐line column switching, and resolved chromatographically at a laminar flow rate of 1 mL min−1. Using this tandem LC‐LC/APPI‐MS system the extraction, separation and selective detection of PFOS in river water could be achieved with satisfactory selectivity and sensitivity. The limit of detection (LOD) (S/N = 3) and the limit of quantitation (LOQ) (S/N = 10)were 5.35 and 17.86 pg mL−1. The described procedure was very simple since no off‐line sample preparation was required, total analysis time being 18.75 min. Copyright © 2003 John Wiley & Sons, Ltd.
A simple method for fabrication of silver‐coated sheathless electrospray emitters
Authors: Chen Yet‐Ran , Her Guor‐Rong 
Published: February 2003

AbstractA simple and time‐saving procedure is proposed for preparing a silver‐coated fused‐silica capillary tip. The tapered capillary tip was coated with silver using an acrylic‐based silver conductive pen. The fabrication of a silver‐coated fused‐silica capillary tip takes less than 5 minutes. The silver‐coated fused‐silica capillary tip is rugged and durable for sheathless capillary electrophoresis/electrospray mass spectrometry and also for microspray applications. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of protein profiles of genetically modified potato tubers by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Careri M. , Elviri L. , Mangia A. , Zagnoni I. , Agrimonti C. , Visioli G. , Marmiroli N. 
Published: February 2003

AbstractTraceability of genetically modified (GM) foods demands the development of appropriate reliable techniques in order to identify and quantify peptide or nucleic acid residues in GM plants and food products through the food chain. In this study the applicability of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) was demonstrated for the characterization of proteins of transformed and untransformed potato (Solanum Tuberosum L.) tubers. In GM tubers the expression level of the G1‐1 gene, which regulates transition from dormancy to sprouting tubers, was inhibited by antisense technology. The analysis of antisense transformed lines showed that several of them exhibited a significant delay in sprouting relative to the control lines, in accordance with a decrease in the transcript level. Preliminary attempts to compare the protein patterns obtained from transformed and control lines using traditional electrophoresis were not able to reveal differences in the low‐kDa range. Instead, MALDI‐TOFMS applied to total peptide extract without any purification was able to distinguish spectral patterns of transformed and untransformed lines. In particular, several characteristic peaks from m/z 4373 to 4932 were detected only in the mass spectra of GM tuber samples. Copyright © 2003 John Wiley & Sons, Ltd.
Stability of multivariable fractional polynomial models with selection of variables and transformations: a bootstrap investigation
Authors: Royston P. , Sauerbrei W. 
Published: February 2003

AbstractSauerbrei and Royston have recently described an algorithm, based on fractional polynomials, for the simultaneous selection of variables and of suitable transformations for continuous predictors in a multivariable regression setting. They illustrated the approach by analyses of two breast cancer data sets. Here we extend their work by considering how to assess possible instability in such multivariable fractional polynomial models. We first apply the algorithm repeatedly in many bootstrap replicates. We then use log‐linear models to investigate dependencies among the inclusion fractions for each predictor and among the simplified classes of fractional polynomial function chosen in the bootstrap samples. To further evaluate the results, we define measures of instability based on a decomposition of the variability of the bootstrap‐selected functions in relation to a reference function from the original model. For each data set we are able to identify large, reasonably stable subsets of the bootstrap replications in which the functional forms of the predictors appear fairly stable. Despite the considerable flexibility of the family of fractional polynomials and the consequent risk of overfitting when several variables are considered, we conclude that the multivariable selection algorithm can find stable models. Copyright © 2003 John Wiley & Sons, Ltd.
Confidence intervals for the binomial parameter: some new considerations
Authors: Reiczigel Jenö 
Published: February 2003

AbstractSeveral methods have been proposed to construct confidence intervals for the binomial parameter. Some recent papers introduced the ‘mean coverage’ criterion to evaluate the performance of confidence intervals and suggested that exact methods, because of their conservatism, are less useful than asymptotic ones. In these studies, however, exact intervals were always represented by the Clopper–Pearson interval (C–P). Now we focus on Sterne's interval, which is also exact and known to be better than the C–P in the two‐sided case. Introducing a computer intensive level‐adjustment procedure which allows constructing intervals that are exact in terms of mean coverage, we demonstrate that Sterne's interval performs better than the best asymptotic intervals, even in the mean coverage context. Level adjustment improves the C–P as well, which, with an appropriate level adjustment, becomes equivalent to the mid‐P interval. Finally we show that the asymptotic behaviour of the mid‐P method is far poorer than is generally expected. Copyright © 2003 John Wiley & Sons, Ltd.
Generalized covariance‐adjusted canonical correlation analysis with application to psychiatry
Authors: Kowalski J. , Tu X. M. , Jia G. , Perlis M. , Frank E. , Crits‐Christoph P. , Kupfer D. J. 
Published: February 2003

AbstractThe lack of control over covariates in practice motivates the need for their adjustment when measuring the degree of association between two sets of variables, for which canonical correlation is traditionally used. In most studies however, there is also a lack of control over the attributes of responses for the sets of variables of interest. In particular, a portion of the response variable may be continuous and the other discrete. For such settings, the traditional partial canonical correlation approach is restrictive, since a covariate‐adjustment for a set of continuous variables is assumed. By ignoring the assumption of continuous variates and proceeding with a partial canonical correlation analysis in the presence of continuous and discrete variates, results in canonical correlation estimates that are not consistent. In this paper we generalize the traditional partial canonical correlation approach to covariate‐adjustment by allowing the response variables to contain continuous, as well as discrete, variates. The methodology is illustrated with a psychiatric application for examining which sleep variables relate to which depressive symptoms, as measured by commonly used constructs that presents with both continuous and discrete outcomes. Copyright © 2003 John Wiley & Sons, Ltd.
Methods for categorizing a prognostic variable in a multivariable setting
Authors: Mazumdar Madhu , Smith Alex , Bacik Jennifer 
Published: February 2003

AbstractThe literature is filled with examples of categorization of a continuous prognostic variable in a univariable setting followed by the addition of this categorical variable to an existing multivariable model. Typically, an ‘optimal’ cutpoint for a new prognostic variable is obtained through a systematic search relating the variable to the outcome in an univariable manner. The corresponding categorical variable is then fitted in a multivariable model along with other already established prognostic covariates to assess the additional value of the new variable. This prompts the question whether the cutpoint search should have been performed in the same multivariable setting where it will ultimately be used. In this paper, we extend the univariable cutpoint search methods (split‐sample approach and two‐fold cross‐validation approach) to the multivariable setting using ‐2×log‐likelihood statistic as the correlative measure. A Monte Carlo simulation study demonstrates that both methods are more efficient in detecting the true cutpoint and in estimating the effect size under the multivariable setting as opposed to the univariable setting. The cross‐validation method performs better than the split‐sample method in univariable as well as multivariable scenarios. For the cross‐validation method in the multivariable setting, there is still a substantial loss of power when a cutpoint model is used in cases where there is a continuous relationship between the covariate and the outcome. An example is provided to illustrate the value of the multivariable cross‐validation approach. Copyright © 2003 John Wiley & Sons, Ltd.
Bias due to missing exposure data using complete‐case analysis in the proportional hazards regression model
Authors: Demissie Serkalem , LaValley Michael P. , Horton Nicholas J. , Glynn Robert J. , Cupples L. Adrienne 
Published: February 2003

AbstractWe studied bias due to missing exposure data in the proportional hazards regression model when using complete‐case analysis (CCA). Eleven missing data scenarios were considered: one with missing completely at random (MCAR), four missing at random (MAR), and six non‐ignorable missingness scenarios, with a variety of hazard ratios, censoring fractions, missingness fractions and sample sizes. When missingness was MCAR or dependent only on the exposure, there was negligible bias (2–3 per cent) that was similar to the difference between the estimate in the full data set with no missing data and the true parameter. In contrast, substantial bias occurred when missingness was dependent on outcome or both outcome and exposure. For models with hazard ratio of 3.5, a sample size of 400, 20 per cent censoring and 40 per cent missing data, the relative bias for the hazard ratio ranged between 7 per cent and 64 per cent. We observed important differences in the direction and magnitude of biases under the various missing data mechanisms. For example, in scenarios where missingness was associated with longer or shorter follow‐up, the biases were notably different, although both mechanisms are MAR. The hazard ratio was underestimated (with larger bias) when missingness was associated with longer follow‐up and overestimated (with smaller bias) when associated with shorter follow‐up. If it is known that missingness is associated with a less frequently observed outcome or with both the outcome and exposure, CCA may result in an invalid inference and other methods for handling missing data should be considered. Copyright © 2003 John Wiley & Sons, Ltd.
A comparison of group sequential methods for binary longitudinal data
Authors: Spiessens Bart , Lesaffre Emmanuel , Verbeke Geert 
Published: February 2003

AbstractInterim analyses are conducted to allow for early termination of the trial, for ethical as well as economical reasons. Here we consider interim analyses in repeated measurements studies where the measurements are binary. Two methods for analysing this kind of data are compared according to their operating characteristics. A subject‐specific approach based on the logistic random‐effects model is compared with the population‐averaged approach based on the generalized estimating equations. The comparison is illustrated with simulations using a randomized clinical trial for toenail fungal infection. Copyright © 2003 John Wiley & Sons, Ltd.
The effect of maternal hypothermia on the fetal heart rate
Authors: Aboud E. , Neales K. 
Published: February 2003

AbstractFetal bradycardia is a recognized response to maternal hypothermia but has not previously been reported in conjunction with diabetes. A 30‐year‐old insulin‐dependent diabetic was admitted at 35 weeks gestation for control of her diabetes. She developed maternal hypothermia and hypoglycemia and the fetal heart rate fell to 100 beats per minute (b.p.m.). However, the fetal heart rate gradually returned to normal after rewarming the patient.
Customised gravidogram and fetal growth chart in a South African population
Authors: van Bogaert L.‐J. 
Published: February 2003

AbstractObjective:To investigate whether gravidograms and fetal growth curves should be customized, i.e. tailor made for a specific ethnic group.Methods:a cross‐sectional study of 800 pregnant Xhosa women attending antenatal care in the Eastern Cape Province (South Africa). The data measured was used to compare the correlation between the symphysis–fundus height measurement (SFHM) and the sonographic estimate of gestational age (SEGA), as well as the intra‐uterine fetal growth curve with existing gravidograms and fetal growth charts.Results:There was a good correlation between the SFHM and the SEGA:r=0.91 (P<0.0001). The correlation between the SFHM and the sonographic estimate of fetal weight (SEFW) yielded a correlation coefficient (r) of 0.40 (P<0.0001). The correlation between the SEFW and SEGA resulted in ar=0.97 (P<0.0001). The customized gravidogram and fetal growth chart followed the general trend seen in their Caucasian equivalents.Conclusion: The comparison of our customized gravidogram and intra‐uterine fetal growth curve with similar charts established in Caucasians does not show any significant difference.
The rotational spectrum and molecular properties of a hydrogen-bonded complex formed between hydrogen cyanide and hydrogen chloride
Authors: Legon A. C. , Campbell E. J. , Flygare W. H. 
Published: February 2003

The rotational spectra of four isotopic species of a weak complex formed between HCN and HCl have been detected and analyzed by using the technique of Fourier-transform microwave spectroscopy conducted in a Fabry–Perot cavity with a pulsed nozzle molecular source. The rotational constants B̃0, centrifugal distortion constants DJ, and nuclear quadrupole coupling constants χaa that result are as follows:
Interpretation of the spectroscopic constants leads to the conclusion that the atoms in the complex are colinear in the order HCN⋅⋅⋅HCl, with the weak binding through a hydrogen bond to the N atom HCN. Some quantitative details of the molecular geometry and intermolecular potential function have also been determined for the complex and are compared with those similarly obtained for other members of the series HCN⋅⋅⋅HX and the series B⋅⋅⋅HCl, where B is one of several different proton acceptors.