Treatment of active rheumatoid arthritis with leflunomide compared with placebo and methotrexate. Leflunomide Rheumatoid Arthritis Investigators Group

CONTEXT

Leflunomide is a reversible inhibitor of de novo pyrimidine synthesis shown to be effective in a phase 2 trial in 402 patients with active rheumatoid arthritis (RA).

OBJECTIVE

To compare the efficacy and safety of leflunomide treatment with placebo and methotrexate treatment in patients with active RA.

DESIGN

Randomized, double-blind, placebo, and active-controlled 12-month study.

SETTING

Forty-seven university and private rheumatology practices in the United States and Canada.

PATIENTS

Diagnosis of RA by the American College of Rheumatology (ACR) criteria for duration of 6 months or longer and no previous methotrexate treatment.

INTERVENTION

Leflunomide treatment (20 mg/d), placebo, or methotrexate treatment (7.5-15 mg/wk).

MAIN OUTCOME MEASURES

American College of Rheumatology success rate (completed 52 weeks of treatment and met the ACR > or = 20% response criteria), disease progression as assessed by x-ray films, and improvement in function and health-related quality of life using the intent-to-treat population.

RESULTS

The 482 patients studied were predominantly women (mean age, 54 years; mean disease duration, 6.7 years) for whom a mean of 0.8 disease-modifying antirheumatic drugs had failed. The ACR response and success rates for patients receiving leflunomide treatment (52% and 41%, respectively) and methotrexate treatment (46% and 35%, respectively) were significantly higher than those for patients receiving placebo (26% and 19%, respectively) (P<.001), and they were statistically equivalent, with mean time to initial response at 8.4 weeks for patients receiving leflunomide vs 9.5 weeks for patients receiving methotrexate therapy. X-ray analyses demonstrated less disease progression with leflunomide (P=.001) and methotrexate (P = .02) therapy than with placebo. Leflunomide and methotrexate treatment improved measures of physical function and health-related quality of life significantly more than placebo (P<.001 and P<.05, respectively). Common adverse events for patients receiving leflunomide treatment included gastrointestinal complaints, skin rash, and reversible alopecia. Asymptomatic transaminase elevations resulted in treatment discontinuations for 7.1% of patients receiving leflunomide therapy, 1.7% of patients receiving placebo, and 3.3% of patients receiving methotrexate therapy.

CONCLUSIONS

Clinical responses following administration of leflunomide, a new therapeutic agent for the treatment of RA, were statistically superior to those with placebo and equivalent to those with methotrexate treatment. Both active treatments improved signs and symptoms of active RA, delayed disease progression as demonstrated by x-ray films, and improved function and health-related quality of life.

Antibiotic therapy for Pseudomonas aeruginosa bacteremia: outcome correlations in a prospective study of 200 patients

PURPOSE AND PATIENTS AND METHODS

We performed a prospective clinical study of 200 consecutive patients with Pseudomonas aeruginosa bacteremias to analyze in vitro susceptibility and synergistic testing of antibiotics the patients received and clinical parameters to assess their relationship to survival.

RESULTS

No significant correlation between in vitro susceptibility testing (minimal inhibitory concentrations/minimal bactericidal concentrations) and outcome could be demonstrated. Similarly, improved outcome could not be demonstrated for patients receiving antibiotic combinations that were synergistic in vitro (either time-kill or checker-board) versus those combinations that were not. There was also no correlation between results obtained by time-kill curve and checkerboard synergistic testing, i.e., combinations found to be synergistic by one method were not necessarily synergistic by the other method. Clinical parameters associated with improved survival were a urinary portal of entry and absence of neutropenia. Conversely, survival was significantly decreased when the portal was the respiratory tract. The mortality rate between patients receiving combination therapy (27%) and monotherapy (47%) was significant (p less than 0.02); this significant relationship held true for most subgroups including malignancy, nosocomial infection, and infection site.

CONCLUSION

Increasing effort should be placed on ensuring timely administration of combination therapy to patients with P. aeruginosa bacteremia since the use of combination therapy was even more important in determining outcome than was underlying disease.

The neuronal ceroid lipofuscinoses in human EPMR and mnd mutant mice are associated with mutations in CLN8

The neuronal ceroid lipofuscinoses (NCLs) are a genetically heterogeneous group of progressive neurodegenerative disorders characterized by the accumulation of autofluorescent lipopigment in various tissues. Progressive epilepsy with mental retardation (EPMR, MIM 600143) was recently recognized as a new NCL subtype (CLN8). It is an autosomal recessive disorder characterized by onset of generalized seizures between 5 and 10 years, and subsequent progressive mental retardation. Here we report the positional cloning of a novel gene, CLN8, which is mutated in EPMR. It encodes a putative transmembrane protein. EPMR patients were homozygous for a missense mutation (70C-->G, R24G) that was not found in homozygosity in 433 controls. We also cloned the mouse Cln8 sequence. It displays 82% nucleotide identity with CLN8, conservation of the codon harbouring the human mutation and is localized to the same region as the motor neuron degeneration mouse, mnd, a naturally occurring mouse NCL (ref. 4). In mnd/mnd mice, we identified a homozygous 1-bp insertion (267-268insC, codon 90) predicting a frameshift and a truncated protein. Our data demonstrate that mutations in these orthologous genes underlie NCL phenotypes in human and mouse, and represent the first description of the molecular basis of a naturally occurring animal model for NCL.

Free surfaces cause reductions in the glass transition temperature of thin polystyrene films

The effect of free surfaces on the glass transition temperature (T(g)) of thin polystyrene films was studied. Measurements were performed on films (8 nm<h<290 nm) with one free surface and on films capped with a 5 nm thick metal layer (no free surfaces). Potential problems with evaporative deposition were eliminated by studying samples made of two supported films placed with their free surfaces in contact and annealed. Uncapped films displayed reduced T(g) values for h less, similar 40 nm while all "properly" capped films exhibited a T(g) value the same as that of the bulk polymer (370+/-1 K). When the free surface was restored, the measured T(g) values the same as those of uncapped films of the same thickness. These results show that free surfaces are crucial for observing T(g) reductions in thin polymer films and address the role of the sample preparation history.

Two-year, blinded, randomized, controlled trial of treatment of active rheumatoid arthritis with leflunomide compared with methotrexate. Utilization of Leflunomide in the Treatment of Rheumatoid Arthritis Trial Investigator Group

OBJECTIVE

Three 6-12-month, double-blind, randomized, controlled trials have shown leflunomide (LEF; 20 mg/day, loading dose 100 mg x 3 days) to be effective and safe for the treatment of rheumatoid arthritis (RA). This analysis of the North American trial assessed whether the clinical benefit evident at month 12 was sustained over 24 months of treatment with LEF as compared with the efficacy and safety of methotrexate (MTX), an equivalent disease-modifying antirheumatic drug, at 24 months.

METHODS

The year-2 cohort, comprising patients continuing into the second year of treatment with > or = 1 dose of study medication and > or = 1 followup visit after week 52, consisted of 235 patients (LEF n = 98; placebo n = 36; MTX n = 101). The mean (+/- SD) maintenance dose of LEF was 19.6 +/- 1.99 mg/day in year 2 and that of MTX was 12.6 +/- 4.69 mg/week. Statistical analyses used an intent-to-treat (ITT) approach. Statistical comparisons of the active treatments only were prospectively defined in the protocol.

RESULTS

In total, 85% and 79% of LEF and MTX patients, respectively, who entered year 2 completed 24 months of treatment. From month 12 to month 24, the American College of Rheumatology improvement response rates of > or = 20% (LEF 79% versus MTX 67%; P = 0.049), > or = 50% (LEF 56% versus MTX 43%; P = 0.053), and > or = 70% (LEF 26% versus MTX 20%; P = 0.361) were sustained in both of the active treatment groups. The mean change in total Sharp radiologic damage scores at year 2 compared with year 1 and baseline (LEF 1.6 versus MTX 1.2) showed statistically equivalent sustained retardation of radiographic progression in the active treatment groups. Maximal improvements evident at 6 months in the Health Assessment Questionnaire (HAQ) disability index (HAQ DI) and the physical component score of the Medical Outcomes Survey 36-item short form were sustained over 12 months and 24 months; improvement in the HAQ DI with LEF4(-0.60) was statistically significantly superior to that with MTX (-0.37) at 24 months (P = 0.005). Over 24 months in the ITT cohort, serious treatment-related adverse events were reported in 1.6% of the LEF-treated patients and 3.7% of the MTX-treated patients. Frequently reported adverse events included upper respiratory tract infections, diarrhea, nausea and vomiting, rash, reversible alopecia, and transient liver enzyme elevations.

CONCLUSION

The safety and efficacy of LEF and MTX were maintained over the second year of this 2-year trial. Both active treatments retarded radiographic progression over 24 months. LEF was statistically significantly superior to MTX in improving physical function as measured by the HAQ DI over 24 months of treatment. Results indicate that LEF is a safe and effective initial treatment for active RA, with clinical benefit sustained over 2 years of treatment without evidence of new or increased toxicity.

Fast photochemical oxidation of protein footprints faster than protein unfolding

Fast photochemical oxidation of proteins (FPOP) is a chemical footprinting method whereby exposed amino-acid residues are covalently labeled by oxidation with hydroxyl radicals produced by the photolysis of hydrogen peroxide. Modified residues can be detected by standard trypsin proteolysis followed by LC/MS/MS, providing information about solvent accessibility at the peptide and even the amino-acid level. Like other chemical footprinting techniques, FPOP must ensure only the native conformation is labeled. Although oxidation via hydroxyl radical induces unfolding in proteins on a time scale of milliseconds or longer, FPOP is designed to limit (*)OH exposure to 1 micros or less by employing a pulsed laser for initiation to produce the radicals and a radical-scavenger to limit their lifetimes. We applied FPOP to three oxidation-sensitive proteins and found that the distribution of modification (oxidation) states is Poisson when a scavenger is present, consistent with a single conformation protein modification model. This model breaks down when a scavenger is not used and/or hydrogen peroxide is not removed following photolysis. The outcome verifies that FPOP occurs on a time scale faster than conformational changes in these proteins.

Spontaneous Atlanto-Axial Dislocation in Ankylosing Spondylitis and Rheumatoid Arthritis

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Natural history of rheumatoid cervical luxations

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Analysis of Protein Solvent Accessible Surfaces by Photochemical Oxidation and Mass Spectrometry

Protein surfaces are important in most biological processes, including protein-protein interactions, enzymatic catalysis, and protein-ligand binding. We report a method in which hydroxyl radicals generated by a rapid-UV irradiation of a 15% hydrogen peroxide solution were utilized to oxidize specific amino acid side chains of two model proteins (lysozyme, beta-lactoglobulin A), according to the residues' chemical reactivities and the solvent accessibility of the reactive carbons and sulfurs in the residue. Oxidized peptides generated by tryptic digestion were identified by electrospray-Fourier transform mass spectrometry. The specific sites of the stable modification were then identified by reverse-phase liquid chromatography coupled to quadropole ion trap tandem mass spectrometry. The solvent accessibility of the residue was shown to directly affect the rate of oxidation by this method (with the exception of methionine), supporting its use as a rapid measure of the solvent accessibility of specific residues, and in some cases, individual atoms.

Cytosolic phospholipase A2 is induced in reactive glia following different forms of neurodegeneration

Many recent studies have emphasized the deleterious role of inflammation in CNS injury. Increases in free fatty acids, eicosanoids, and products of lipid peroxidation are known to occur in various conditions of acute and chronic CNS injury, including cerebral ischemia, traumatic brain injury, and Alzheimer's disease. Although an inflammatory response can be induced by many different means, phospholipases, such as cytosolic phospholipase A(2) (cPLA(2)), may play an important role in the production of inflammatory mediators and in the production of other potential second messengers. cPLA(2) hydrolyzes membrane phospholipids and its activity liberates free fatty acids leading directly to the production of eicosanoids. We investigated the cellular localization of cytosolic phospholipase A(2) in the CNS following: (1) focal and global cerebral ischemia, (2) facial nerve axotomy, (3) human cases of Alzheimer's disease, (4) transgenic mice overexpressing mutant superoxide dismutase, a mouse model of amyotrophic lateral sclerosis, and (5) transgenic mice overexpressing mutant amyloid precursor protein, which exhibits age-related amyloid deposition characteristic of Alzheimer's disease. We show that in every condition evaluated, cytosolic phospholipase A(2) is present in reactive glial cells within the precise region of neuron loss. In conditions where neurons did not degenerate or are protected from death, cytosolic phospholipase A(2) is not observed. Both astrocytes and microglial cells are immunoreactive for cytosolic phospholipase A(2) following injury, with astrocytes being the most consistent cell type expressing cytosolic phospholipase A(2). The presence of cytosolic phospholipase A(2) does not merely overlap with reactive astroglia, as reactive astrocytes were observed that did not exhibit cytosolic phospholipase A(2) immunoreactivity. In most conditions evaluated, inflammatory processes have been postulated to play a pivotal role and may even participate in neuronal cell death. These results suggest that cytosolic phospholipase A(2) may prove an attractive therapeutic target for neurodegeneration.

Association study of a dopamine transporter polymorphism and attention deficit hyperactivity disorder in UK and Turkish samples

Molecular genetic studies in attention deficit hyperactivity disorder (ADHD) have focussed on candidate genes within the dopamine system, which is thought to be the main site of action of stimulant drugs, the primary pharmacological treatment of the disorder. Of particular interest are findings with the dopamine transporter gene (DAT1), since stimulant drugs interact directly with the transporter protein. To date, there have been eight published association studies of ADHD with a 480 base-pair allele of a variable number tandem repeat (VNTR) polymorphism in the 3'-untranslated region of the gene, five that support an association and three against. We have analysed the same VNTR marker in a dataset of UK Caucasian children and an independent dataset of Turkish Caucasian children with DSM-IV ADHD, using the transmission disequilibrium test (TDT). Results from the UK (chi(2) = 8.97, P = 0.001, OR = 1.95), but not the Turkish sample (chi(2) = 0.93, P = 0.34) support association and linkage between genetic variation at the DAT1 locus and ADHD. When considered alongside evidence from other published reports, there is only modest evidence for the association, consistent with a very small main effect for the 480-bp allele (chi(2) = 3.45, P = 0.06, OR = 1.15), however we find significant evidence of heterogeneity between the combined dataset (chi(2) = 22.64, df = 8, P = 0.004).

One Health contributions towards more effective and equitable approaches to health in low- and middle-income countries

Emerging zoonoses with pandemic potential are a stated priority for the global health security agenda, but endemic zoonoses also have a major societal impact in low-resource settings. Although many endemic zoonoses can be treated, timely diagnosis and appropriate clinical management of human cases is often challenging. Preventive 'One Health' interventions, e.g. interventions in animal populations that generate human health benefits, may provide a useful approach to overcoming some of these challenges. Effective strategies, such as animal vaccination, already exist for the prevention, control and elimination of many endemic zoonoses, including rabies, and several livestock zoonoses (e.g. brucellosis, leptospirosis, Q fever) that are important causes of human febrile illness and livestock productivity losses in low- and middle-income countries. We make the case that, for these diseases, One Health interventions have the potential to be more effective and generate more equitable benefits for human health and livelihoods, particularly in rural areas, than approaches that rely exclusively on treatment of human cases. We hypothesize that applying One Health interventions to tackle these health challenges will help to build trust, community engagement and cross-sectoral collaboration, which will in turn strengthen the capacity of fragile health systems to respond to the threat of emerging zoonoses and other future health challenges. One Health interventions thus have the potential to align the ongoing needs of disadvantaged communities with the concerns of the broader global community, providing a pragmatic and equitable approach to meeting the global goals for sustainable development and supporting the global health security agenda.This article is part of the themed issue 'One Health for a changing world: zoonoses, ecosystems and human well-being'.

Protein surface mapping by chemical oxidation: structural analysis by mass spectrometry

The solvent-accessible surface area of proteins is important in biological function for many reasons, including protein-protein interactions, protein folding, and catalytic sites. Here we present a chemical technique to oxidize amino acid side chains in a model protein, apomyoglobin, and subsequent elucidation of the effect of solvent accessibility on the sites of oxidation. Under conditions of low protein oxidation (zero to three oxygen atoms added per apomyoglobin molecule), we have positively identified five oxidation sites by liquid chromatography-tandem mass spectrometry and high-resolution Fourier transform mass spectrometry. Our results indicate that all oxidized amino acids, with the exception of methionine, have highly solvent-accessible side chains, but the rate of oxidation may not be dictated solely by solvent accessibility and amino acid identity.

Surface denaturation and amyloid fibril formation of insulin at model lipid-water interfaces

We consider the effects that different lipid surfaces have upon the denaturation and subsequent formation of amyloid fibrils of bovine insulin. The adsorption and unfolding kinetics of insulin being adsorbed onto the different lipid surfaces under denaturing conditions are studied using FTIR ATR spectroscopy and are compared to the bulk solution behavior of the protein. Atomic force microscopy studies are also performed to compare the fibrils growing on the different surfaces. This study shows that both the adsorption and unfolding kinetics of insulin can be described by a sum of exponential processes and that different surfaces behave differently, with respect both to one another and to the bulk protein solution. The proteins adsorbed onto the surfaces are observed to have faster unfolding kinetics than those in the bulk, and the fibril-like structures formed at the surfaces are shown to be different in a number of ways from those found in bulk solution. The beta-sheet content and growth kinetics of the adsorbed proteins also differ from those of the bulk system. An attempt is made to describe the observed behavior in terms of simple physical arguments involving adsorption, unfolding, and aggregation of the proteins.

Association between leukocyte count and the presence and extent of coronary atherosclerosis as determined by coronary arteriography

Angiographic evidence of coronary artery disease (CAD) was correlated with leukocyte count (WBC), red cell count (RBC), cigarette smoking, age, sex, and cholesterol and triglyceride concentrations in 573 patients who underwent coronary arteriography and who did not have evidence of infection or recent myocardial infarction. Smokers had a higher WBC (7,449 +/- 1,964 leukocytes/mm3 vs 6,533 +/- 1,557, p = 0.0001) and RBC (4.921 X 10(6) +/- 0.491 X 10(6) erythrocytes/mm3 vs 4.753 X 10(6) +/- 0.480 X 10(6) p = 0.0001) than nonsmokers. Patients with CAD had a higher WBC (7,280 +/- 1,926 vs 6,664 +/- 1,700, p = 0.0005) and RBC (4.903 X 10(6) +/- 0.488 vs 4.777 X 10(6) +/- 0.485 X 10(6), p = 0.0062) than those with normal coronary arteriograms. A positive correlation between WBC and the severity of CAD (sum of arterial diameter narrowing) was noted (r = 0.16, p = 0.0001). Multiple regression showed an independent contribution of WBC in predicting severity of CAD (F = 9.26, p = 0.0025), after accounting for the effects of age, sex, serum cholesterol and triglyceride levels. When smoking was entered into the equation, the contribution of WBC in predicting the severity of angiographic CAD became weaker (F = 4.46, p = 0.035). Similar relations were seen when only smokers were analyzed and when patients with history of remote myocardial infarction were excluded. In nonsmokers these associations became either insignificant or much weaker. Thus, the relation of WBC, and RBC with CAD is mainly due to the elevation of WBC and RBC and the increase of CAD risk induced by cigarette smoking.

Rheumatoid arthritis joint progression in sustained remission is determined by disease activity levels preceding the period of radiographic assessment

OBJECTIVE

Joint damage is related to disease activity in rheumatoid arthritis (RA), but the degree of its progression and the temporal associations between disease activity and joint damage are unclear. The aim of this study was to evaluate whether there is a latency in the effect of disease activity on radiographic progression in patients with RA.

METHODS

Data were obtained from the PREMIER trial, a 2-year randomized, controlled clinical trial of adalimumab plus methotrexate versus methotrexate alone or adalimumab alone in early RA. Radiographic progression of joint damage was calculated using the modified total Sharp score in a subset of patients whose disease was in remission (Simplified Disease Activity Index<or=3.3) in the second year of the trial. The progression of damage in the second year was compared between groups of patients whose disease was already in remission for an additional period of 3, 6, or 9 months during the first year. Analysis of variance was used to test for a linear trend.

RESULTS

Among 794 patients with early RA, 119 (15%) achieved sustained remission during the second year, with no difference in radiographic progression across the 3 treatment groups. Radiographic progression in the second year was significantly different between patients with 3, 6, or 9 additional months of remission during year 1 (mean change in the modified Sharp score 1.19 in those with 3 additional months of remission versus 0.20 in those with 6 additional months of remission and -0.32 in those with 9 additional months of remission; P<0.05). The results were supported by similar findings in a series of sensitivity analyses.

CONCLUSION

These data indicate that the level of disease activity as well as the duration of remission affect subsequent progression of radiographic damage in RA. This latency between disease activity and its effects on radiographic progression should be considered when evaluating radiographic outcomes in trials of RA.

Psoriatic arthritis imaging: a review of scoring methods

Structural damage assessed on conventional radiographs is an important outcome measure in psoriatic arthritis. This article reviews the available scoring methods. A full description of the methods is given as well as information on various aspects of validity.

Oligomeric structure of the chemokine CCL5/RANTES from NMR, MS, and SAXS data

CCL5 (RANTES) is a proinflammatory chemokine known to activate leukocytes through its receptor, CCR5. Although the monomeric form of CCL5 is sufficient to cause cell migration in vitro, CCL5's propensity for aggregation is essential for migration in vivo, T cell activation and apoptosis, and HIV entry into cells. However, there is currently no structural information on CCL5 oligomers larger than the canonical CC chemokine dimer. In this study the solution structure of a CCL5 oligomer was investigated using an integrated approach, including NMR residual dipolar couplings to determine allowed relative orientations of the component monomers, SAXS to restrict overall shape, and hydroxyl radical footprinting and NMR cross-saturation experiments to identify interface residues. The resulting model of the CCL5 oligomer provides a basis for explaining the disaggregating effect of E66 and E26 mutations and suggests mechanisms by which glycosaminoglycan binding may promote oligomer formation and facilitate cell migration in vivo.

Pulsed electron beam water radiolysis for submicrosecond hydroxyl radical protein footprinting

Hydroxyl radical footprinting is a valuable technique for studying protein structure, but care must be taken to ensure that the protein does not unfold during the labeling process due to oxidative damage. Footprinting methods based on submicrosecond laser photolysis of peroxide that complete the labeling process faster than the protein can unfold have been recently described; however, the mere presence of large amounts of hydrogen peroxide can also cause uncontrolled oxidation and minor conformational changes. We have developed a novel method for submicrosecond hydroxyl radical protein footprinting using a pulsed electron beam from a 2 MeV Van de Graaff electron accelerator to generate a high concentration of hydroxyl radicals by radiolysis of water. The amount of oxidation can be controlled by buffer composition, pulsewidth, dose, and dissolved nitrous oxide gas in the sample. Our results with ubiquitin and beta-lactoglobulin A demonstrate that one submicrosecond electron beam pulse produces extensive protein surface modifications. Highly reactive residues that are buried within the protein structure are not oxidized, indicating that the protein retains its folded structure during the labeling process. Time-resolved spectroscopy indicates that the major part of protein oxidation is complete in a time scale shorter than that of large scale protein motions.

Trial of three-day and ten-day courses of amoxycillin in otitis media

A randomised double-blind controlled trial compared three-day and 10-day courses of amoxycillin (25 mg/kg daily) in children with otitis media. Seventeen doctors from five centres admitted 84 children between the ages of 2 and 10 years. Symptoms and signs were measured on admission to the trial, on day 3, and on day 15. Mother's observations were recorded daily for 10 days. Audiograms were performed at four and 12 weeks after the end of the trial. The treatment groups showed little difference in the speed of resolution of symptoms and signs, the numbers of primary treatment failures, or the frequency of recurrent ear infections. There were no complications in either group. Most children with otitis media can probably be successfully and safely treated with no more than a three-day course of amoxycillin providing their progress is reviewed about the fifth or sixth day after treatment started. This policy could save over 1 million pounds annually in antibiotic costs.

The properties of free polymer surfaces and their influence on the glass transition temperature of thin polystyrene films

We present a detailed study of free polymer surfaces and their effects on the measured glass transition temperature (T(g)) of thin polystyrene (PS) films. Direct measurements of the near-surface properties of PS films are made by monitoring the embedding of 10 and 20 nm diameter gold spheres into the surface of spin-cast PS films. At a temperature T = 378 K( > T(g)), the embedding of the spheres is driven by geometrical considerations arising from the wetting of the gold spheres by the PS. At temperatures below T(g) (363 K < T < 370 K), both sets of spheres embed 3-4 nm into the PS films and stop. These studies suggest that a liquid-like surface layer exists in glassy PS films and also provide an estimate for the lower bound of the thickness of this layer of 3-4 nm. This qualitative idea is supported by a series of calculations based upon a previously developed theoretical model for the indentation of nanoscale spheres into linear viscoelastic materials. Comparing data with simulations shows that this surface layer has properties similar to those of a bulk sample of PS having a temperature of 374 K. Ellipsometric measurements of the T(g) are also performed on thin spin-cast PS films with thicknesses in the range 8 nm < h < 290 nm. Measurements are performed on thin PS films that have been capped by thermally evaporating 5 nm thick metal (Au and Al) capping layers on top of the polymer. The measured T(g) values (as well as polymer metal interface structure) in such samples depend on the metal used as the capping layer, and cast doubt on the general validity of using evaporative deposition to cover the free surface. We also prepared films that were capped by a new non-evaporative procedure. These films were shown to have a T(g) that is the same as that of bulk PS (370+/-1 K) for all film thicknesses measured (> 7 nm). The subsequent removal of the metal layer from these films was shown to restore a thickness-dependent T(g) in these samples that was essentially the same as that observed for uncapped PS films. An estimate of the thickness of the liquid-like surface layer was also extracted from the ellipsometry measurements and was found to be 5+/-1 nm. The combined ellipsometry and embedding studies provide strong evidence for the existence of a liquid-like surface layer in thin glassy PS films. They show that the presence of the free surface is an important parameter in determining the existence of T(g) reductions in thin PS films.

Quantifying protein interface footprinting by hydroxyl radical oxidation and molecular dynamics simulation: application to galectin-1

Biomolecular surface mapping methods offer an important alternative method for characterizing protein-protein and protein-ligand interactions in cases in which it is not possible to determine high-resolution three-dimensional (3D) structures of complexes. Hydroxyl radical footprinting offers a significant advance in footprint resolution compared with traditional chemical derivatization. Here we present results of footprinting performed with hydroxyl radicals generated on the nanosecond time scale by laser-induced photodissociation of hydrogen peroxide. We applied this emerging method to a carbohydrate-binding protein, galectin-1. Since galectin-1 occurs as a homodimer, footprinting was employed to characterize the interface of the monomeric subunits. Efficient analysis of the mass spectrometry data for the oxidized protein was achieved with the recently developed ByOnic (Palo Alto, CA) software that was altered to handle the large number of modifications arising from side-chain oxidation. Quantification of the level of oxidation has been achieved by employing spectral intensities for all of the observed oxidation states on a per-residue basis. The level of accuracy achievable from spectral intensities was determined by examination of mixtures of synthetic peptides related to those present after oxidation and tryptic digestion of galectin-1. A direct relationship between side-chain solvent accessibility and level of oxidation emerged, which enabled the prediction of the level of oxidation given the 3D structure of the protein. The precision of this relationship was enhanced through the use of average solvent accessibilities computed from 10 ns molecular dynamics simulations of the protein.

An oligopeptide transporter gene family in Arabidopsis

We have identified nine oligopeptide transporter (OPT) orthologs (AtOPT1 to AtOPT9) in Arabidopsis. These proteins show significant sequence similarity to OPTs of Candida albicans (CaOpt1p), Schizosaccharomyces pombe (Isp4p), and Saccharomyces cerevisiae (Opt1p and Opt2p). Hydrophilicity plots of the OPTs suggest that they are integral membrane proteins with 12 to 14 transmembrane domains. Sequence comparisons showed that the AtOPTs form a distinct subfamily when compared with the fungal OPTs. Two highly conserved motifs (NPG and KIPPR) were found among all OPT members. The identification of multiple OPTs in Arabidopsis suggests that they may play different functional roles. This idea is supported by the fact that AtOPTs have a distinct, tissue-specific expression pattern. The cDNAs encoding seven of the AtOPTs were cloned into a yeast vector under the control of a constitutive promoter. AtOPT4 expressed in S. cerevisiae mediated the uptake of KLG-[3H]L. Similarly, expression of five of the seven AtOPT proteins expressed in yeast conferred the ability to uptake tetra- and pentapeptides as measured by growth. This study provides new evidence for multiple peptide transporter systems in Arabidopsis, suggesting an important physiological role for small peptides in plants.

Attention deficit hyperactivity disorder (ADHD) and the dopamine D4 receptor gene: evidence of association but no linkage in a UK sample

Recent studies report association and linkage between attention deficit hyperactivity disorder (ADHD) and the 7-repeat allele of a 48 base-pair repeat in the dopamine D4 receptor gene (DRD4). We examined the frequency of this allele in a sample of probands with DSM-IV ADHD using a case-control design, as well as the transmission disequilibrium test (TDT) and haplotype-based haplotype relative risk (HHRR) in the subset of probands with DNA available from both parents. One hundred and thirty-two ADHD probands were compared with 189 controls (chi(2) = 6.17, 1 df, P = 0.01, OR = 1.73, 95% CI = 1.11--2.71). A total of 85 complete trios were available for within-family tests of association and linkage. Fifty-two heterozygous parents carrying one copy of the 7-repeat were informative for the TDT (29 transmitted vs 23 non-transmitted, chi(2) = 0.69). Analysis of the entire sample of 132 probands using TRANSMIT provided no additional evidence for excess transmission of the 7-repeat allele (58 transmitted vs 54 non-transmitted). HHRR gave similar results. We conclude that the case-control findings are likely to be falsely positive, resulting from genetic stratification. However we can not rule out alternative explanations of low statistical power and gene-environment correlation.

Dielectric and ellipsometric studies of the dynamics in thin films of isotactic poly(methylmethacrylate) with one free surface

We have performed dielectric loss measurements at 1 kHz on thin films of isotactic poly(methyl methacrylate). A key distinction of our studies is that the samples measured were supported films with one free surface rather than films that have metallic electrodes covering both surfaces. This unique sample geometry allows us to eliminate any effects due to evaporation of metal onto the top film surface and provides a unique opportunity to make direct comparisons between dielectric loss and glass transition measurements. Film thicknesses in the range from 6 microm to 7 nm were prepared on Al coated substrates. The dielectric loss peak and ellipsometric glass transition temperature of all films were measured. The dielectric loss was found to exhibit no discernible film thickness dependence in either the temperature of the maximum loss value or the shape of the loss curve. In contrast, the measured T(g) values were found to decrease with decreasing film thickness with a maximum shift of 10 K for a 7-nm film. Dielectric measurements were also made on Al coated films and these samples also showed no shift in the temperature of the loss peak. Finally, the T(g) measurements were also made on Si substrates. These values exhibited an increasing T(g) value with film thickness with a maximum increase of approximately 15 K being measured for a 7-nm film.