bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of MECP2 gene in Rett syndrome variants and autistic girls
Authors: Zappella Michele , Meloni Ilaria , Longo Ilaria , Canitano Roberto , Hayek Giuseppe , Rosaia Lucia , Mari Francesca , Renieri Alessandra
Published: April 2003

Mutations in MECP2 gene account for approximately 80% of cases of Rett syndrome (RTT), an X‐linked severe developmental disorder affecting young girls, as well as for most cases of Preserved Speech Variant (PSV), a mild RTT variant in which autistic behavior is common. The aim of this study is to determine whether MECP2 mutations are responsible for PSV only or may cause other forms of autistic disorders. We screened for mutations by SSCP 19 girls with a clinical diagnosis of autism, two of them fulfilling the PSV criteria. A pathogenic mutation was found only in the latter two cases (R133C and R453X). A long follow‐up of these two girls revealed a unique clinical course. They initially developed the first three stages of RTT, they were severely retarded and had autistic behavior. Over the years their abilities increased progressively and by early adolescence they lost autistic behavior, becoming adequately accustomed to people and reaching an IQ close to 45. These results confirm previous clinical studies suggesting that a wide spectrum of RTT exists including girls with mental abilities considerably higher than in classic RTT. We conclude that MECP2 mutations (missense or late truncating) can be found in girls with an IQ close to 45 and a clinical history of PSV of Rett syndrome. Furthermore, MECP2 mutations are not found in patients in which autism remains stable over the years. © 2003 Wiley‐Liss, Inc.
Evaluation of the genes for the adrenergic receptors α2A and α1C and Gilles de la Tourette Syndrome
Authors: Xu Chun , Ozbay Fatih , Wigg Karen , Shulman Rayzie , Tahir Eda , Yazgan Yanki , Sandor Paul , Barr Cathy L.
Published: April 2003

Gilles de la Tourette Syndrome (GTS) has long been known to be familial, and evidence from twin studies indicates that it has a substantial genetic component. Our genome scan of sibling pair families with GTS found evidence suggestive of linkage to several chromosomal locations. On the basis of these findings, we have begun to study additional markers in these regions, with some of the markers located in candidate genes. Two candidate genes stand out in these regions: the adrenergic receptor α1C(1A) (ADRA1C) located on chromosome 8p and the adrenergic receptor α2A (ADRA2A) located on chromosome 10q. The adrenergic system has been suggested to play a role in GTS based on the reduction of symptoms with the adrenergic receptor agonists, clonidine and guanfacine. We examined the inheritance of polymorphisms in the ADRA2A and ADRA1C genes in 113 nuclear families identified through a GTS proband. We found no significant evidence for linkage using the transmission disequilibrium test for these two genes. Based on our families, we conclude that these genes are not major genetic factors contributing to the susceptibility to GTS. © 2003 Wiley‐Liss, Inc.
Dopamine D2 receptor gene Ser311Cys variant and schizophrenia: association study and meta‐analysis
Authors: Jönsson Erik G , Sillén Anna , Vares Maria , Ekholm Birgit , Terenius Lars , Sedvall Göran C
Published: April 2003

An association has been reported between a dopamine D2 receptor gene (DRD2) Ser311Cys variant and schizophrenia. In a replication attempt, Swedish patients with schizophrenia (n = 173) and control subjects (n = 236) were assessed for the DRD2 Ser311Cys variant. Schizophrenic patients displayed higher Cys311 allele frequencies than control subjects (4.0 vs. 0.8%, χ2 = 9.49, df = 1, P = 0.002; odds ratio (OR) 4.93, 95% confidence interval (95% CI) 1.61–15.12). The association was detected only in men. The results were supported by a meta‐analysis of all published case–control studies comprising a total of 9,152 subjects (χ2 = 11.37, df = 1, P < 0.001; OR 1.43, 95% CI 1.16–1.78). The present results support the involvement of the DRD2 gene in the pathogenesis of schizophrenia. © 2003 Wiley‐Liss, Inc.
Association of the dopamine beta hydroxylase gene with attention deficit hyperactivity disorder: Genetic analysis of the Milwaukee longitudinal study
Authors: Smith Karen Müller , Daly Mark , Fischer Mariellen , Yiannoutsos Constantin T. , Bauer Lorri , Barkley Russell , Navia Bradford A.
Published: April 2003

Attention deficit hyperactivity disorder (ADHD) is a highly heritable and common disorder that partly reflects disturbed dopaminergic function in the brain. Recent genetic studies have shown that candidate genes involved in dopamine signaling and metabolism contribute to ADHD susceptibility. We have initiated genetic studies in a unique cohort of 158 ADHD and 81 control adult subjects who have been followed longitudinally since childhood in the Milwaukee study of ADHD. From this cohort, genetic analysis was performed in 105 Caucasian subjects with ADHD and 68 age and ethnicity‐matched controls for the DRD4 exon 3 VNTR, the SLC6A3 (DAT1) 3′ UTR VNTR, dopamine beta hydroxylase (DBH) TaqI A polymorphism, and the DBH GT microsatellite repeat polymorphism that has been quantitatively associated with serum levels of DBH activity, but not previously studied in ADHD. Results indicate a significant association between the DBH TaqI A1 allele and ADHD (P = 0.018) with a relative risk of 1.33. The DBH GT repeat 4 allele, which is associated with high serum levels of DBH, occurred more frequently in the ADHD group than controls, but the difference did not reach statistical significance. Associations were not found with the SLC6A3 10 repeat or DRD4 7 repeat alleles. These results indicate that the DBH TaqI A allele, or another polymorphism in linkage disequilibrium with this allele, may confer increased susceptibility towards ADHD. © 2003 Wiley‐Liss, Inc.
Family‐based and case–control study of catechol‐O‐methyltransferase in schizophrenia among Palestinian Arabs
Authors: Kremer I. , Pinto M. , Murad I. , Muhaheed M. , Bannoura I. , Muller D.J. , Schulze T.G. , Reshef A. , Blanaru M. , Gathas S. , Goichman R. , Rietschel M. , Dobrusin M. , Bachner‐Melman R. , Nemanov L. , Belmaker R.H. , Maier W. , Ebstein R.P.
Published: April 2003

COMT is a ubiquitous enzyme crucial to catechol metabolism. The molecular basis of COMT thermolability, that leads to three to fourfold differences in enzyme activity, is due to a substitution of valine with methionine in the Val158/108Met polymorphism. Of special interest is the role of this gene in major psychoses especially since a microdeletion (22q11) containing the COMT gene (velo‐cardio‐facial syndrome) also carries with it several types of behavioral disorders, including an increased prevalence of schizophrenia. Almost 20 genetic studies have examined the role of COMT in schizophrenia with ambiguous results. Towards clarifying the role of this polymorphism in conferring risk for psychosis, we examined a large group of culturally and ethnically akin Palestinian Arab schizophrenic triads (N = 276) using both a case–control and family‐based study. In 194 informative triads with at least one heterozygote parent, no preferential transmission of either COMT allele was observed in this sample (TDT statistic chi‐square = 0.14 NS; 131 COMT valine alleles were transmitted and 125 alleles not transmitted). However, using a case–control design a significant increase (Likelihood ratio = 3.935, P = 0.047) in the valine allele was observed in the group of schizophrenic patients (N = 276) compared to an ethnically matched control group (N = 77). The association was stronger in female patients (P = 0.012) similar to other studies showing that some COMT behavioral effects are gender sensitive. In summary, by case–control design but not by a family‐based study, there is a weak effect in female patients of the high activity COMT allele in conferring risk for schizophrenia. © 2003 Wiley‐Liss, Inc.
Wolfram syndrome and suicide: Evidence for a role of WFS1 in suicidal and impulsive behavior
Authors: Sequeira Adolfo , Kim Caroline , Seguin Monique , Lesage Alain , Chawky Nadia , Desautels Alex , Tousignant Michel , Vanier Claude , Lipp Olivier , Benkelfat Chawki , Rouleau Guy , Turecki Gustavo
Published: April 2003

There is evidence suggesting that subjects affected with the Wolfram syndrome (WFS) and normal carriers present an increased risk of psychiatric disorders, particularly depression and suicidal behavior. We investigated a possible role of the gene involved in WFS (WFS1) in the neurobiology of suicide and the potential modulatory effect on traits associated to suicidal behavior. Genetic variation at WFS1 (H611R, R456H, and I333V) was investigated in 111 suicide victims and 129 normal controls. Possible effects on psychopathology and behavioral traits were investigated in a subsample of suicide cases (N = 31) for whom phenotyping was carried out by means of structured psychiatric interviews and questionnaires adapted for psychological autopsies. We found a significantly higher frequency of the 611R/611R genotype in suicide completers as compared to controls (χ2 = 19.21, df=2, P = 0.001). Suicide completers with this genotype had higher scores on measures of impulsivity (t = −3.15, df = 15.3, P = 0.006); novelty seeking (NS) (t = −3.35, df = 13.8, P = 0.005); and conversely, lower scores of persistence (t = 2.4, df = 16.6, P = 0.028). Scores of impulsivity and NS remained higher in subjects with the associated genotype after adjusting for age, gender, and psychopathology. These results suggest a role for WFS1 in the pathophysiology of impulsive suicide, and are consistent with previous clinical reports suggesting an increased risk of suicidal behavior in WFS homozygotes and heterozygotes. However, these findings are preliminary and should be confirmed in independent samples. © 2003 Wiley‐Liss, Inc.
Nanotechnology with Soft Materials
Authors: Hamley I. W.
Published: April 2003

Nature exploits self‐organization of soft materials in many ways, to produce cell membranes, biopolymer fibers and viruses, to name just three. Mankind is now able to design materials at the nanoscale, whether through atom‐by‐atom or molecule‐by‐molecule methods (top‐down) or through self‐organization (bottom‐up). The latter method encompasses soft nanotechnology. Self‐organization of soft materials can be exploited to create a panoply of nanostructures for diverse applications. The richness of structures results from the weak ordering because of noncovalent interactions. Thus, thermal energy is important as it enables transitions between phases with differing degrees of order. The power of self‐organization may be harnessed most usefully in a number of nanotechnology applications, which include the preparation of nanoparticles, the templating of nanostructures, nanomotor design, the exploitation of biomineralization, and the development of functionalized delivery vectors.
Nonparametric Tests for Interval‐Censored Failure Time Data
Authors: Lim Hee‐Jeong , Sun Jianguo
Published: April 2003

This paper discusses two sample nonparametric comparison of survival functions when only interval‐censored failure time data are available. The problem considered often occurs in, for example, biological and medical studies such as medical follow‐up studies and clinical trials. For the problem, we present and study several nonparametric test procedures that include methods based on both absolute and squared survival differences as well as simple survival differences. The presented tests provide alternatives to existing methods, most of which are rank‐based tests and not sensitive to nonproportional or nonmonotone alternatives. Simulation studies are performed to evaluate and compare the proposed methods with existing methods and suggest that the proposed tests work well for nonmonotone alternatives as well as monotone alternatives. An illustrative example is presented.
Tests for Trend in Binary Response
Authors: Salanti Georgia , Ulm Kurt
Published: April 2003

Tests for trend are important in analyzing data where the binary response in ordered categories is of interest. An example is in toxicology where the response in various dose groups is observed. For testing an association between the dose and the response the approach from Cochran and Armitage is widely used. However the result of this test is highly dependent on the scores assigned to the dose groups. Various dose assignments can lead to different outcomes. As an alternative the isotonic regression, a nonparametric method, is proposed. The outcome of this approach is independent of the quantification of the dose. Both methods (Cochran‐Armitage test and isotonic regression) are compared within a simulation study to an isotonic version of the Pearson's Chi‐squared test and the Wilcoxon rank sum test.
Choice of Scores in Trend Tests for Case‐Control Studies of Candidate‐Gene Associations
Authors: Zheng Gang , Freidlin Boris , Li Zhaohai , Gastwirth Joseph L.
Published: April 2003

When applying the Cochran‐Armitage (CA) trend test for an association between a candidate allele and a disease in a case‐control study, a set of scores must be assigned to the genotypes. Sasieni (1997, Biometrics 53, 1253–1261) suggested scores for the recessive, additive, and dominant models but did not examine their statistical properties. Using the criteria of minimizing the required sample size of the CA trend test to achieve prespecified type I and type II errors, we show that the scores given by Sasieni (1997) are optimal for the recessive and dominant models and locally optimal for the additive one. Moreover, the additive scores are shown to be locally optimal for the multiplicative model. The tests are applied to a real dataset.
Estimation of Linkage and Association from Allele Transmission Data
Authors: Malley James D. , Redner Richard A. , Severini Thomas A. , Badner Judith A. , Pajevic Sinisa , Bailey‐Wilson Joan E.
Published: April 2003

The TDT provides a hypothesis test for the presence of linkage or association (linkage disequilibrium). However, since the TDT is a single test statistic, it cannot be used to separate association and linkage. The importance of this difficulty, following a significant TDT result, has been recently emphasized by Whittaker, Denham and Morris (2000), who alert the community to the possibility that a significant TDT may result from loose linkage and strong association, or from tight linkage and weak association.

To attack this problem we start with the parametric model for family‐based allele transmission data of Sham and Curtis (1995) (or Sham (1998)) and find that the parameters in the model are not always identifiable. So we introduce a reparameterization that resolves the identifiability issues and leads to a valid likelihood ratio (LR) test for linkage.

Since the linkage and association parameters are both of interest, we next introduce and apply an integrated likelihood (IL) approach to provide separate point estimates and confidence intervals for these parameters. The estimates are shown to have generally small bias and mean square error, while the confidence intervals have good average length and coverage probabilities. We compare the power of the IL approach for testing linkage and, separately association, with the TDT and LR.
Spatial Point Pattern Analysis by using Voronoi Diagrams and Delaunay Tessellations – A Comparative Study
Authors: Chiu S.N.
Published: April 2003

Given a spatial point pattern, we use various characteristics of its Voronoi diagram and Delaunay tessellation to extract information of the dependence between points. In particular, we use the characteristics to construct statistics for testing complete spatial randomness. It is shown that the minimum angle of a typical Delaunay triangle is sensitive to both regularity and clustering alternatives, whilst the triangle's area or perimeter is more sensitive to clustering than regularity. These statistics are also sensitive to the Baddeley‐Silverman cell process.
Support Vector Machines for Protein Fold Class Prediction
Authors: Markowetz Florian , Edler Lutz , Vingron Martin
Published: April 2003

Knowledge of the three‐dimensional structure of a protein is essential for describing and understanding its function. Today, a large number of known protein sequences faces a small number of identified structures. Thus, the need arises to predict structure from sequence without using time‐consuming experimental identification. In this paper the performance of Support Vector Machines (SVMs) is compared to Neural Networks and to standard statistical classification methods as Discriminant Analysis and Nearest Neighbor Classification. We show that SVMs can beat the competing methods on a dataset of 268 protein sequences to be classified into a set of 42 fold classes. We discuss misclassification with respect to biological function and similarity. In a second step we examine the performance of SVMs if the embedding is varied from frequencies of single amino acids to frequencies of tripletts of amino acids. This work shows that SVMs provide a promising alternative to standard statistical classification and prediction methods in functional genomics.
Nonenzymatic protocol for Pseudomonas aeruginosa DNA preparation and rapid subtyping by mini pulsed‐field gel electrophoresis
Authors: López‐Cánovas Lilia , Sánchez‐Alonso Axel , Higginson David , Ariosa Concepcion , Clark Hilda , Riverón Ana Maria
Published: April 2003

The fastest protocol for Pseudomonas aeruginosa subtyping by contour clamped homogeneous electric field (CHEF) electrophoresis takes around 20 h. It includes enzymatic sample preparation, DNA restriction and fragment separation. Here, P. aeruginosa cells embedded in agarose miniplugs were lysed and deproteinized by incubating the miniplugs for 30 min in a single nonenzymatic solution. DNA molecules were digested for 2 h with 5 U of XbaI, and fragments were separated in 4.96 h by miniCHEF electrophoresis at 10 V/cm. Total time for P. aeruginosa subtyping was 8 h. Control experiments included DNA preparation by enzymatic or nonenzymatic protocols, different times of DNA restriction and comparisons of DNA separations done by miniCHEF or CHEF electrophoresis. Both methods and chambers gave similar results, but the rapid nonenzymatic method and the miniCHEF gave them in less time. Cells grown in broth or on plates were useful for nonenzymatic DNA preparation. Thirteen P. aeruginosa isolates were successfully fingerprinted using the protocol described here.
Poly‐N‐hydroxyethylacrylamide as a novel, adsorbed coating for protein separation by capillary electrophoresis
Authors: Albarghouthi Methal N. , Stein Thomas M. , Barron Annelise E.
Published: April 2003

We present the polymer poly‐N‐hydroxyethylacrylamide (PHEA) (trade name, polyDuramide™) as a novel, hydrophilic, adsorbed capillary coating for electrophoretic protein analysis. Preparation of the PHEA coating requires a simple and fast (30 min) protocol that can be easily automated in capillary electrophoresis instruments. Over the pH range of 3–8.4, the PHEA coating is shown to reduce electroosmotic flow (EOF) by about 2 orders of magnitude compared to the bare silica capillary. In a systematic comparative study, the adsorbed PHEA coating exhibited minimal interactions with both acidic and basic proteins, providing efficient protein separations with excellent reproducibility on par with a covalent polyacrylamide coating. Hydrophobic interactions between proteins and a relatively hydrophobic poly‐N,N‐dimethylacrylamide (PDMA) adsorbed coating, on the other hand, adversely affected separation reproducibility and efficiency. Under both acidic and basic buffer conditions, the adsorbed PHEA coating produced an EOF suppression performance comparable to that of covalent polyacrylamide coating and superior to that of adsorbed PDMA coating. The protein separation performance in PHEA‐coated capillaries was retained for 275 consecutive protein separation runs at pH 8.4, and for more than 800 runs at pH 4.4. The unique and novel combination of hydrophilicity and adsorptive coating ability of PHEA makes it a suitable wall coating for automated microscale analysis of proteins by capillary array systems.
Laser‐induced quenched phosphorescence detection in capillary electrophoresis
Authors: Kuijt Jacobus , Ariese Freek , Brinkman Udo A. T. , Gooijer Cees
Published: April 2003

The feasibility of laser‐based excitation for quenched phosphorescence detection in capillary electrophoresis (CE) was explored for the first time by using a small‐size, quadrupled Nd‐YAG laser emitting 266 nm pulses (duration, 0.4 ns) at a repetition rate of 7.8 kHz. To provide a continuous phosphorescence background, the phosphorophore 1‐bromo‐4‐naphthalene sulfonic acid (BrNS) was added to the separation buffer. Both experiments and theory show that in laser‐induced phosphorescence (LIP) – in contrast with lamp‐excited phosphorescence – one normally deals with such high triplet‐state phosphorophore concentrations that triplet‐triplet annihilation is the major deactivation pathway. This results in a lower quantum yield of the analyte‐induced bimolecular quenching interaction and, thus, the observed quenching signal. The situation can be improved by using a cylindrical lens for excitation in order to reduce the irradiance. In this case limits of detection (LODs) similar to those obtained using lamp excitation (1×10–8 M) were achieved, while the width of the detection window was reduced from about 4 mm to 1 mm. Even under exclusion of triplet‐triplet annihilation, i.e., under conditions of low irradiance, for our setup the quenching yields in LIP were smaller than in lamp‐based phosphorescence detection. This is due to the repetition rate of the laser (7.8 kHz), which is too high in view of the phosphorescence lifetime (ca. 300 μs at low irradiance). Theory shows that this disadvantageous effect will be fully eliminated if the repetition rate is decreased to 1 kHz.
Evaluation of diabetic ketoacidosis‐related ionic metabolites in human blood serum by capillary electrophoresis
Authors: Jager Alessandra V. , Tavares Marina F. M.
Published: April 2003

Three methodologies are presented to contemplate the analysis of sodium, potassium, chloride, bicarbonate, lactate, acetoacetate, and β‐hydroxybutyrate in blood serum samples of diabetic patients using free solution capillary electrophoresis with indirect detection (214 nm for cations and 254 nm for anions). The cations were analyzed in less than 6 min in an electrolyte comprised of 15 mmol·L–1 imidazole, 5 mmol·L–1 lactate and 1 mmol·L–1 18‐crown‐6‐ether, adjusted to pH 4.5. Chloride and bicarbonate were analyzed in 2 min in a 5 mmol·L–1 chromate, 0.1 mmol·L–1 cetyltrimethylammonium bromide (CTAB), pH 9.0 electrolyte solution. Ketoacids and lactate were analyzed in less than 11 min in an electrolyte composed of 15 mmol·L–1 3,5‐dinitrobenzoate, 0.1 mmol·L–1 CTAB, at pH 3.5. All methodologies were validated with respect to linearity, selectivity, sensitivity, precision and accuracy performing adequately for clinical purposes.
Strategies for the determination of cefazolin in plasma and microdialysis samples by short‐end capillary zone electrophoresis
Authors: Mayer Bernhard X. , Petsch Martina , Tschernko Edda M. , Müller Markus
Published: April 2003

Capillary zone electrophoresis was employed to determine cefazolin, a first‐generation cephalosporin antibiotic, in plasma and microdialysis samples from patients. To shorten the analysis, the samples were injected from the short end of the capillary, resulting in a separation time of < 3 min. Due to a high ionic strength of the biological matrices it was necessary to optimize the stacking conditions. For microdialysis samples a 1:10 dilution with water before injection was sufficient to obtain good peak shape. For plasma samples a protein removal step was required to obtain clean electropherograms and a good peak shape. Acetonitrile was used as precipitant resulting in an enhanced sample stacking in comparison to water dilution. The disadvantage of using acetonitrile was severe evaporation loss making quantitation impossible. A self‐sealing film was used to seal each individual sample vial to suppress evaporation during long‐term sequences. The calibration curves for spiked plasma and cefazolin in Ringer's solutions were linear in the range from 2–500 and 2.5–100 μg/mL, respectively. Limits of detection were 1.0 and 2.0 μg/mL in plasma and microdialysis samples, respectively. The assay was successfully applied to plasma and microdialysis samples obtained in vivo from the interstial space fluid of subcutaneous adipose and muscle tissue of patients undergoing cardiac surgery.
Quantitative analysis of aglycone quercetin in mulberry leaves (Morus alba L.) by capillary zone electrophoresis
Authors: Suntornsuk Leena , Kasemsook Saowapak , Wongyai Surapote
Published: April 2003

A capillary zone electrophoresis method was established for analysis of aglycone quercetin in mulberry leaves (Morus alba L.). The influence of, e.g., background electrolyte concentrations and pH, surfactant concentrations, organic solvents, temperature, and voltage on the separation of aglycone quercetin, rutin, quercitrin, kaempferol, catechin, and gallic acid was systematically investigated. The optimum condition providing baseline separation of all compounds within 16.5 min was obtained in 150 mM boric acid (pH 10.0) using a fused‐silica capillary with an effective length of 42.5 cm (50 μm inner diameter), temperature of 32°C, and voltage of 15 kV. Method assessment was performed by standard addition method using rutin as an internal standard. Linearity of the method was excellent (r2 > 0.999) over the concentration tested (40–160 μg/mL). The relative standard deviations (%RSDs) from injection, intraday, and interday precision were less than 2.5%. Recoveries were good (≈︁ 100.0%,%RSD = 0.8%) with a limit of detection (LOD) and limit of quantitation (LOQ) of 0.86 and 3.16 μg/mL (%RSD = 1.8%), respectively. The aglycone quercetin found in the mulberry leaves was 0.452 g/100 g (%RSD = 0.6%) on dry weight.
Low‐voltage driven control in electrophoresis microchips by traveling electric field
Authors: Fu Lung‐Ming , Yang Ruey‐Jen
Published: April 2003

This paper presents the use of a physical model and numerical simulation in the investigation of traveling electric fields on capillary electrophoresis (CE) chips. The principal material transport mechanisms of electrokinetic migration, ionic concentration, fluid flow, and diffusion are all taken into consideration. Traditionally, the high electric field strength required for the separation of biological samples by microfluidic devices has involved the application of high external voltages. In contrast, this study presents a proposal for samples separation by means of a moving electric field within a low voltage‐driven CE chip. Under this proposal, the separation channel is partitioned into a series of smaller separation zones by means of electrode pairs. This paper considers two different electrode configurations, namely arranged along a single side of the separation channel, and arranged on two sides of the separation channel. The quality of the separation achieved with these two configurations is then compared with the traditional straight separation channel approach. The results confirm that the proposed method is successful in maintaining an adequate field strength for separation purposes in a low‐voltage driven CE chip. Furthermore, it is determined that the best separation results are obtained using electrodes arranged along both sides of the separation channel.
Towards a microchip‐based chromatographic platform. Part 2: Sol‐gel phases modified with polyelectrolyte multilayers for capillary electrochromatography
Authors: Breadmore Michael C. , Shrinivasan Sushil , Karlinsey James , Ferrance Jerome P. , Norris Pamela M. , Landers James P.
Published: April 2003

The potential for using polyelectrolyte multilayers (PEMs) to provide chromatographic functionality on continuous silica networks created from sol‐gel chemistry has been evaluated by capillary electrochromatography (CEC). Construction of the PEM was achieved by flushing the column with polyelectrolytes of alternative charge, with variation of the properties of the exposed polyelectrolyte providing a unique means to vary the chromatographic surface. Variation of the exposed polyelectrolyte from poly(diallyldimethylammonium chloride) (PDDAC) to dextran sulfate (DS) allowed the direction of the electroosmotic flow (EOF) to be changed and also provided a means to vary the chromatographic capacity. Variation of negative polymer from DS to poly(styrene sulfonate) (PSS) significantly altered the EOF and the migration of peptides, with both the reversed‐phase and ion‐exchange capacities increasing. An alternative method for changing the column capacity was to change the thickness of the PEM, which was evaluated by anion‐exchange CEC. A 70–80% increase in retention was observed for all anions without any increase in EOF suggesting significant penetration of the analytes through the PEM and interaction with buried charges within the PEM.
Isoelectric focusing in long immobilized pH gradient gels to improve protein separation in proteomic analysis
Authors: Poland Julia , Cahill Michael A. , Sinha Pranav
Published: April 2003

The number of protein spots detected on two‐dimensional polyacrylamide gel electrophoresis (2‐D PAGE) gels increases as the gel size increases. The largest commercially available systems resolve a few thousand spots, being only a fraction of the total proteome. We have developed an extremely long isoelectric focusing (IEF) system aimed at more complete protein profiling. The system is especially well suited to sensitive detection methods, such as radioactive detection. The major constraint preventing progress in this area has been the inability to create an even density gradient during the immobilized pH gradient (IPG) casting process. We demonstrate for the first time that this constraint can be effectively overcome, to enable greatly increased IEF separating power with all the advantages of IPG technology,
Spotting and quantification of phosphoproteins purified by gel electrophoresis and laser ablation‐element mass spectrometry with phosphorus‐31 detection
Authors: Wind Mathias , Feldmann Ingo , Jakubowski Norbert , Lehmann Wolf D.
Published: April 2003

Laser ablation inductively coupled plasma‐mass spectrometry (ICP‐MS) with 31P detection has been used for spotting of phosphoproteins after one‐dimensional polyacrylamide gel electrophoresis (1‐D PAGE) and membrane transfer. By analyzing a mixture of myoglobin, α‐casein and reduced fibrinogen it is demonstrated that phosphoproteins are specifically recognized by this method. A special washing step was found to be necessary to remove phosphate noncovalently bound to proteins. The 31P signal was found to contain quantitative information both with respect to relative and absolute amounts of phosphorus present in phosphoproteins. Normalizing the 31P signal from a single laser ablation trace by the total amount of phosphoprotein applied to the gel, a detection limit of 5 pmol of phosphorus is estimated.
Assessing matrix assisted laser desorption/ ionization‐time of flight‐mass spectrometry as a means of rapid embryo protein identification in rice
Authors: Fukuda Masafumi , Islam Nazrul , Woo Sun‐Hee , Yamagishi Azumi , Takaoka Motoko , Hirano Hisashi
Published: April 2003

Rice embryo proteins were separated by two‐dimensional gel electrophoresis (2‐DE). A total of 105 spots were digested with trypsin and the resultant peptides were analyzed by matrix assisted laser desorption/ionization‐time of flight‐mass spectrometry (MALDI‐TOF‐MS). Raw mass spectra were fully‐automatically processed and searched with selected monoisotopic masses against SWISS‐PROT/TrEMBL and NCBInr databases. High quality mass spectra were obtained from 53 spots, of which 36 spots were identified including 29 not registered in databases. Fifty percent of the rice embryo proteins resolved in 2‐DE could not be identified, indicating more efficient sample preparation techniques need to be developed in the future. At least four to five matching peptides were found to be essential for unambiguous identification of rice embryo proteins; peptide matching of less than four lead to ambiguous results. The suitability of peptide mass fingerprinting method as a means of rapid embryo protein identification in rice was discussed.
Geoarchaeological insights gained from surficial geologic mapping, middle Moche Valley, Peru
Authors: Huckleberry Gary , Billman Brian R.
Published: April 2003

We present the results of detailed surficial geologic mapping for a 10 km2 area of alluvial (quebrada) deposits located in the middle Moche Valley of Peru, where archaeological features and deposits provide cross‐cutting relationships and numerical age control for late Holocene erosion and deposition associated with El Niño. Despite surfaces containing clasts that are heavily pitted and cracked due to salt weathering, archaeological and 14C dates indicate that most quebrada landforms in the study area are late Holocene in age and may reflect enhanced alluviation associated with increased El Niño activity beginning ca. 6000 cal yr B.P. Our study provides criteria for correlative dating of other Holocene landforms in the Moche Valley area but urges caution in long‐distance (>100 km) correlation because of geographic variability in surface weathering. Surficial geologic mapping aided by archaeological age control allows improved understanding of the rates of landscape change important to the development of complex irrigation‐based societies in the Peruvian Desert. © 2003 Wiley Periodicals, Inc.
Paleolithic burnt bone horizons from the Swabian Jura: Distinguishing between in situ fireplaces and dumping areas
Authors: Schiegl Solveig , Goldberg Paul , Pfretzschner Hans‐Ulrich , Conard Nicholas J.
Published: April 2003

Hohle Fels Cave is one of several Upper Paleolithic sites on the eastern extension of the Swabian Alb in southwestern Germany. Several phases of excavations have been conducted since 1870. The archaeological inventories comprise a broad range of artifacts produced from stone, bone, teeth, ivory, and antler. The site has also yielded Paleolithic rock art, sculpture, and engravings. The Pleistocene inventories unearthed so far belong to the Magdalenian, Gravettian, and Aurignacian; Middle Paleolithic horizons may well be uncovered as excavations continue. The chronology of three main occupation phases has been established with numerous 14C measurements. The Magdalenian dates to about 13,000 yr B.P., and the richest Gravettian deposit contains a burnt bone‐layer extending over ca. 12 m2 that dates to about 29,000 yr B.P. The underlying Aurignacian horizons predate 30,000 yr B.P. The Gravettian burnt bone layer (archaeological layer IIcf) is a key horizon because of its distinct composition and color and its large horizontal extension. Layer IIcf has been examined using a combination of analytical techniques including micromorphological analysis of thin sections with polarizing light microscopy and scanning electron microscopy for fabric and identification of mineral and biogenic constituents. The bone mineral composition was analyzed by Fourier transform infrared spectroscopy (FTIR) and electron probe microanalytical techniques. These investigations in tandem with the field observations indicate intense burning of bones as fuel. The micromorphological and contextual archaeological data suggest that layer IIcf is a secondary dump rather than an in situ accumulation. This deposit and other Paleolithic burnt deposits in the Swabian Jura appear to reflect intense periods of winter occupation in these caves. © 2003 Wiley Periodicals, Inc.
Intra‐ and extracellular macromolecular networks: physics and biological function
Authors: Sackmann Erich
Published: April 2003

In order to adapt the physical properties of living materials to their biological function, nature has developed (polyelectrolytic) polymers with outstanding physical behaviour. Nature provides giant macromolecules (such as actin filaments), which can be directly observed and which comprise the whole range of flexibilities from the random coil to the rigid rod. The structure and dynamics of the macromolecules and networks can be manipulated in many ways by making use of the tricks of nature. In the present contribution some of the most pertinent elements of the intracellular and extracellular matrix are introduced. One main purpose of this contribution is to show that many of these polymers are also of great potential interest in polymer science, in order to study fundamental properties of macromolecules and macromolecular networks. Another intention is to bridge the gap between biological material research and the physics and chemistry of polymers and other complex fluids and to plead for a closer cooperation between the two fascinating worlds.
Engineering plastics from lignin, 23. Network formation of lignin‐based epoxy resins
Authors: Hofmann Klaus , Glasser Wolfgang
Published: April 2003

The network‐forming behavior, gelation, and vitrification of lignin‐polyether‐copolymer‐epoxide/amine resins were determined using a recently described dynamic mechanical thermal analysis (DMTA)‐based method. Six resins were studied which differed in lignin content, polyether arm length, and molecular weight. Glass transition temperature (Tg)‐cure time master curves could be constructed for cure temperatures ranging from 90 to 200°C; and semiexperimental vitrification plots were derived for each system based on the knowledge of activation energy and cure time at a reference temperature. The point at which the cure process becomes diffusion‐controlled (i.e., vitrification) happens at lower extents of conversion for lignin‐rich fractions. Near vitrification, the cure events change from n‐th‐ to second‐order kinetics, and this indicates a reduction in polyether‐arm mobility. This suggests that the crosslinking of lignin centers with polyether arms produces a network in which the reactant‐carrying flexible arms do not have sufficient free volume to react. The greatest increase in Tg during crosslinking is about 100°C for all molecular weight fractions, and this suggests that high‐Tg networks can only be achieved with high‐Tg prepolymers.
Conformational stability and force field of polyphosphazenes: MNDO calculations, vibrational spectra and normal coordinate analyses of [NP(R)2]n (R = Cl, OCH2CF3, OC6H5)
Authors: Bougeard Daniel , Brémard Claude , De Jaeger Roger , Lemmouchi Yahia
Published: April 2003

Raman and Fourier‐transform Raman spectra (1500 − 100 cm−1) of (PCl2N)n (PDCP) were recorded in the solid phase and in solution at room temperature. Raman (3 500 − 100 cm−1) and infrared (4 000 − 200 cm−1) spectra of [P(OCH2CF3)2N]n (PDFP) and [P(OC6H5)2N]n (PDPP) were recorded in the solid phase and at different temperatures (in the case of Raman spectroscopy). The conformation of the isolated macromolecule PDCP is assumed to be analogous to the geometry of the Cl2(O)PN(PCl2N)6PCl3 oligomer optimized by the use of MNDO (modified neglect of diatomic overlap) calculations. The optimized cis‐trans conformation is in good agreement with the X‐ray experimental data concerning the polymer. The calculated low energy barriers around the PN bond along the chain axis can explain the flexibility of the phosphazene backbone and the elastomeric properties of the polymers. The MNDO calculation of the harmonic force field of Cl2(O)PN(PCl2N)6PCl3 is in reasonable agreement with the experimental values for (PCl2N)n in solution as well as in the amorphous phase. The normal coordinate analyses of (PCl2N)n were undertaken according to several structural hypotheses using a force field derived from linear short‐chain molecules. The Raman spectra of PDCP in solution or in the amorphous phase are in reasonable agreement with the vibrational frequencies calculated for a planar cis‐trans macromolecule and have a striking resemblance with those of linear short‐chain analogs Cl2(O)PN(PCl2N)n PCl3 (n = 1,2). The Raman and infrared spectra of the substituted polymers PDFP and PDPP are dominated by the characteristic features of the chain substituents.
Etude de la réaction de télomérisation d'un monomère tensioactif cationique
Authors: Boutevin Bernard , Robin Jean‐Jacques , Boyer Bernard , Roque Jean‐Pierre , Senhaji Omar
Published: April 2003

A polymerizable methacrylic surfactant is synthetized from methacryloyl chloride and 11‐bromoundecanol. The obtained cationic monomer is telomerized with a fluorinated thiol, and the transfer constant CT is calculated. This value is in the same range as transfer constants of classical methacrylic monomers. The obtained kp2/kT is low because of the long chain ester. Polymers were prepared in homogeneous solution with an average molecular weight of 25 000.
Synthesis of chiral and racemic functional polymers from glycidol and thioglycidol
Authors: Taton Daniel , Le Borgne Alain , Sepulchre Maurice , Spassky Nicolas
Published: April 2003

Racemic and optically active protected glycidols (as 1‐ethoxyethyl ethers) are readily polymerized with anionic initiators (e.g., CsOH). Polymers with molecular weights up to 30 000 are obtained without cleavage of the protective group. Oligomers (degree of polymerization [DPn] 5 to 10) are prepared using an aluminium complex derived from a Schiff's base. The protected thioglycidol (synthesized from the protected glycidol) leads to very high‐molecular‐weight polymers (150 000–320 000) using anionic or anionic coordinated initiators. Copolymers of protected glycidol with ethylene oxide are obtained with KOH as initiator. Regeneration of hydroxyl groups in polymers is carried out with acidic cleavage. Treatment of protected polyglycidol with formic acid leads first to the formate of polyglycidol. Then, after saponification, pure polyglycidol is obtained. The use of aqueous hydrochloric acid leads directly to the free polymer.
End‐group modification of α‐hydro‐ω‐methoxypoly(oxyethylene), 3. Facile methods for the introduction of a thiol‐selective reactive end‐group
Authors: Herman Sabine , Loccufier Johan , Schacht Etienne
Published: April 2003

Three methods for the introduction of a thiol‐selective reactive end‐group into α‐hydro‐ω‐methoxypoly(oxyethylene) are described and evaluated. In a first method, α‐amino‐ω‐methoxypoly(oxyethylene) was reacted with succinimido 3‐(2‐pyridyldithio)propionate (SPDP). In a second approach, the hydroxyl end‐group of α‐hydro‐ω‐methoxypoly(oxyethylene) was activated with 4‐nitrophenyl chloroformate, and subsequently reacted with 2‐tritylthioethylamine. Conversion of the trityl thioether into an aromatic disulfide with 2‐nitrophenylsulfenyl chloride yielded a polymer with a thiol‐specific reactive disulfide end‐group. However, it was shown that dismutation in buffer medium does occur, what makes this approach less attractive. A third method involved the conversion of the trityl thioether into a sulfenyl thiocarbonate by reaction with an alkoxycarbonylsulfenyl chloride. Both the SPDP‐modified and the alkoxycarbonyl disulfide‐modified poly(oxyethylene) were found to be suitable thiol‐specific reactive polymers for protein modification. This was demonstrated in a model reaction using reduced glutathione as a thiol‐carrying peptide.
Studies on the polymerization of ethylene using a high‐yield MgCl2‐supported titanium catalyst, 3. Chemical composition of the standard system and its alterations
Authors: Fuhrmann Hans , Strübing Brigitte
Published: April 2003

Middle‐range n‐alkyl chlorides are the most suitable components among a variety of tested alkyl halides in the preparation process of the highly active Ti‐Mg catalyst MTKST. A material balance of the initial components RCl, THF and CCl4 revealed the formation of oligomers, chloro‐containing telomers and poly‐THF apart from low‐molecular side products. The former are important modifiers of the suspension catalyst and exert a positive influence on catalyst activity and polymer properties, as was shown in the polymerization of ethylene. Schlenk equilibrium and extent of Wurtz type coupling in the Grignard synthesis step, which have been evaluated by titration of RMg bonds and Cl analysis of both the liquid and solid phase of the catalyst, predetermine the quality of the catalyst being formed.
Side‐chain liquid‐crystalline polymers containing siloxane spacer, 3. Thermal properties of copolymers containing different types of mesogens
Authors: Nagase Yu , Saito Takanori , Abe Hirokazu , Takamura Yuriko
Published: April 2003

Copolymerization of monomers containing the disiloxane unit in the spacer component and linear triple‐core mesogens with comonomers containing linear double‐core mesogens, or laterally attached triple‐core mesogens was carried out radically. The effect of copolymer composition and monomer structure on the mesomorphic properties of the obtained copolymers was investigated in detail. The copolymers with a comonomer content up to 50 mol‐%, exhibit an enantiotropic nematic phase, whereas the parent homopolymers containing triple‐core mesogens exhibit a smectic phase. The copolymer containing more than 50 mol‐% of the comonomer shows no mesophase. The isotropization temperature of the copolymers decreases with increasing comonomer content. However, the glass transition temperature is almost unchanged upon introduction of the comonomer unit. In case of copolymers containing laterally attached mesogens, a smectic phase was observed below the temperature range of the nematic phase. Consequently, the mesophase and the temperature range of the liquid‐crystalline state can be controlled by the introduction of the comonomer unit whose parent homopolymer does not exhibit any mesophase.
Liquid‐crystalline epoxy resins: a glycidyl‐terminated benzaldehyde azine cured in the nematic phase
Authors: Carfagna Cosimo , Amendola Eugenio , Giamberini Marta , Filippov Andrei G.
Published: April 2003

A novel glycidyl‐terminated benzaldehyde azine was synthesized and subsequently cured with an aromatic diamine. The resulting liquid‐crystalline network was characterized by means of optical microscopy, X‐ray analysis and dynamic‐mechanical analysis. The influence of the curing temperature on the nematic textures is pointed out. The curing reaction was followed by means of differential scanning calorimetry and dielectric analysis.
Palladium‐catalyzed synthesis of poly(p‐phenyleneethynylene)s
Authors: Solomin Victor A. , Heitz Walter
Published: April 2003

Poly(p‐phenyleneethynylene)s were obtained by reacting 1,4‐dihaloarenes with 2‐methyl‐3‐butyn‐2‐ol in a two‐step one‐pot process. In the first step a dihaloarene is reacted with two equivalents of 2‐methyl‐3‐butyn‐2‐ol at room temperature in the presence of an aqueous base. For polycondensation a second equivalent of dihaloarene is added and reacted at 100°C. Soluble polymers with M̄w of 1–2 · 104 were obtained. They show blue fluorescence.
Détermination des masses et des distributions moléculaires d'un poly(aryléthercétone‐co‐sulfone) semi‐cristallin (HTX) à l'aide d'une méthode de dérivatisation chimique, 1. Caractérisation moléculaire du HTX en solution dans l'acide sulfurique concentre
Authors: Daoust Daniel , Devaux Jacques , Godard Pierre , Strazielle Claude
Published: April 2003

HTX, a poly(aryletherketone‐co‐sulfone), is characterized in solution in concentrated sulfuric acid. Upon dissolution in concentrated H2SO4, HTX is chemically modified by sulfonation of phenyl rings. The modification of the chemical structure is studied with a model compound by means of IR spectroscopy. The increase of the molar mass corresponding to a complete sulfonation is determined by means of mass spectrometry. Light scattering and 19F NMR measurements are performed in order to obtain the weight‐ (M̄w)s and number‐average (M̄n)s molar masses of sulfonated HTX samples. (M̄w)s values allow the determination of the Mark‐Houwink‐Sakurada relationship for HTX in 99,5% H2SO4 at 25°C.