Subject Of Considerable Research Efforts Research Articles

Structure and Mechanism of a Cold-Adapted Bacterial Lipase.

The structural origin of enzyme cold-adaptation has been the subject of considerable research efforts in recent years. Comparative studies of orthologous mesophilic–psychrophilic enzyme pairs found in nature are an obvious strategy for solving this problem, but they often suffer from relatively low sequence identity of the enzyme pairs. Small bacterial lipases adapted to distinctly different temperatures appear to provide an excellent model system for these types of studies, as they may show a very high degree of sequence conservation. Here, we report the first crystal structures of lipase A from the psychrophilic bacterium Bacillus pumilus, which confirm the high structural similarity to the mesophilic Bacillus subtilis enzyme, as indicated by their 81% sequence identity. We further employ extensive QM/MM calculations to delineate the catalytic reaction path and its energetics. The computational prediction of a rate-limiting deacylation step of the enzymatic ester hydrolysis reaction is verified by stopped-flow experiments, and steady-state kinetics confirms the psychrophilic nature of the B. pumilus enzyme. These results provide a useful benchmark for examining the structural basis of cold-adaptation and should now make it possible to disentangle the effects of the 34 mutations between the two enzymes on catalytic properties and thermal stability.

Click and Bioorthogonal Chemistry: The Future of Active Targeting of Nanoparticles for Nanomedicines?

Over the years, click and bioorthogonal reactions have been the subject of considerable research efforts. These high-performance chemical reactions have been developed to meet requirements not often provided by the chemical reactions commonly used today in the biological environment, such as selectivity, rapid reaction rate, and biocompatibility. Click and bioorthogonal reactions have been attracting increasing attention in the biomedical field for the engineering of nanomedicines. In this review, we study a compilation of articles from 2014 to the present, using the terms "click chemistry and nanoparticles (NPs)" to highlight the application of this type of chemistry for applications involving NPs intended for biomedical applications. This study identifies the main strategies offered by click and bioorthogonal chemistry, with respect to passive and active targeting, for NP functionalization with specific and multiple properties for imaging and cancer therapy. In the final part, a novel and promising approach for "two step" targeting of NPs, called pretargeting (PT), is also discussed; the principle of this strategy as well as all the studies listed from 2014 to the present are presented in more detail.

A Dynamic Energy Budget simulation approach to investigate the eco-physiological factors behind the two-stanza growth of yellowfin tuna (Thunnus albacares)

The growth of yellowfin tuna has been the subject of considerable research efforts since the early 1960s. Most studies support a complex two-stanza growth pattern with a sharp acceleration departing from the von Bertalanffy growth curve used for most fish populations. This growth pattern has been assumed to result from a combination of physiological, ecological and behavioral factors but the role and contribution of each of them have not been addressed yet. We developed a bioenergetic model for yellowfin tuna in the context of Dynamic Energy Budget theory to mechanistically represent the processes governing yellowfin tuna growth. Most parameters of the model were inferred from Pacific bluefin tuna using body-size scaling relationships while some essential parameters were estimated from biological data sets collected in the Indian Ocean. The model proved particularly suitable for reproducing the data collected during the Pacific yellowfin tuna farming experience conducted by the Inter-American Tropical Tuna Commission at the Achotines Laboratory in Panama. In addition, model predictions appeared in agreement with knowledge of the biology and ecology of wild yellowfin tuna. We used our model to explore through simulations two major assumptions that might explain the existence of growth stanzas observed in wild yellowfin tuna: (i) a lower food supply during juvenile stage in relation with high intra- and inter-species competition and (ii) ontogenetic changes in food diet. Our results show that both assumptions are plausible although none of them is self-sufficient to explain the intensity of growth acceleration observed in wild Indian Ocean yellowfin tuna, suggesting that the two factors may act in concert. Our study shows that the yellowfin growth pattern is likely due to behavioral changes triggered by the acquisition of physiological abilities and anatomical traits through ontogeny that result in a major change in intensity of schooling and in a shift in the biotic habitat and trophic ecology of this commercially important tuna species.

Add-drop double bus microresonator array local oscillators for sharp multiple Fano resonance engineering

Asymmetric resonances are currently the subject of considerable research efforts in photonic nanostructures. Here we propose a feasible method to achieve multiple Fano resonances and their control in an optical compound system consisting of an array of on-chip microresonators without mutual coupling and two parallel fiber waveguides side-coupled to the microresonator array by means of a local oscillator. We derive analytical and transparent expressions for the power transmission function summing over the two light transporting paths within the framework of quantum optics. It is clearly shown that introducing the local oscillator as an additional light propagating path plays an important role in the formation of narrow and multiple Fano resonance lineshapes. The power transmission spectrum through the combination of both the microresonator array and the local oscillator is very sensitive to the system parameters, for example, the intrinsic decay rate of the resonator, the phase shift factor of the local oscillator, the transmission coefficient of the fiber beam splitter, and the total number of the microresonators. Through detailed analysis, we identify the optimums for generating Fano resonance lineshapes. Also, we assess the experimental feasibility of the scheme using currently available technology. The proposed method is relatively straightforward as it requires only one local oscillator as one interferometer arm and it is mostly fiber-based. We believe that our work will help to understand and improve multiple Fano resonance engineering.

The potential of ion mobility mass spectrometry for tuning synthetic host guest systems: A case study using novel zinc(II)dipicolylamine anion sensors

Synthetic approaches to produce scaffolds that will act as efficient biosensors have been the subject of considerable research efforts in recent years. The preparation of host complexes which will specifically bind a given guest necessitates structural analysis of the potential complexes formed, as well as an assessment of the strength of the binding interaction. A challenge to the down-stream analytical scientist is to develop a rapid method that can probe the strength of binding, and the architecture of the complex. In this work we apply nano-ESI MS and Drift Tube ion mobility mass spectrometry (DT IM-MS) to examine host guest interactions. We present data on 5 cyclic peptide bis(ZnII-dipicolylamines) which have been systematically designed as potential molecular biosensors for pyrophosphate (PPi). The competition of the macrocycles for PPi compared with other small anions is investigated. Mass spectrometry provides the stoichiometry of the complex, and the proportion of complex preserved into the mass spectrometer correlates with solution phase data. We find the macrocycles have a higher affinity for PPi than for ATP or pyrocatechol violet (PV). The absolute scale of affinity from mass spectrometry is less (4–5 Log Ka) than that found in solution (4–9 Log Ka), but within the series of macrocycles trend in relative affinities are comparable. DT IM-MS shows that the collision cross sections (DTCCSHe) of the macrocycles are unchanged on binding PPi, indicating that the anion is within the designed binding pocket. We also find that binding has tightened the conformation of the macrocycle, as revealed from analysis of the collision cross section distributions (DTCCSDHe), where for 4/5 of the macrocycles there is a significant decrease in FWHM. Molecular mechanics (MMFF94) and semi empirical methods (ONIOM PM6:B3LYP/aug-cc-pvDZ) were used to generate candidate geometries for 4 to support our assertions on the nature of the binding pocket in the uncomplexed host, and to provide a route for improvement in the design.

Alcohol-Selective Oxidation in Water under Mild Conditions via a Novel Approach to Hybrid Composite Photocatalysts.

The oxidation of alcohols to carbonyl compounds in a clean fashion (i.e., with water as a solvent or under solvent‐free conditions, and using O2 or H2O2 as the primary oxidant) is the subject of considerable research efforts. A new approach for the selective oxidation of soluble aromatic alcohols in water under mild conditions via a novel composite photocatalyst has been developed. The catalyst is synthesized by grafting 4‐(4‐(4‐hydroxyphenylimino)cyclohexa‐2,5dienylideneamino)phenol and silver nanoparticles onto the surface of moderately crystalline titanium dioxide. The titanium dioxide‐based composite was first extensively characterized and then employed in the catalytic oxidation of 4‐methoxybenzyl alcohol to 4‐methoxybenzaldehyde under UV irradiation in water at room temperature. The corresponding aldehyde was obtained with unprecedented high selectivity (up to 86 %). The method is general and opens the route to fabrication of photocatalytic composites based on titanium dioxide functionalized with shuttle organic molecules and metal nanoparticles for a variety of oxidative conversions.

A novel approach in ECG beat recognition using adaptive neural fuzzy filter

Accurate and computationally efficient means of electrocardiography (ECG) arrhythmia detec-tion has been the subject of considerable re-search efforts in recent years. Intelligent com-puting tools such as artificial neural network (ANN) and fuzzy logic approaches are demon-strated to be competent when applied individu-ally to a variety of problems. Recently, there has been a growing interest in combining both of these approaches, and as a result, adaptive neural fuzzy filters (ANFF) [1] have been evolved. This study presents a comparative study of the classification accuracy of ECG signals using (MLP) with back propagation training algorithm, and a new adaptive neural fuzzy filter architec-ture (ANFF) for early diagnosis of ECG ar-rhythmia. ANFF is inherently a feed forward multilayered connectionist network which can learn by itself according to numerical training data or expert knowledge represented by fuzzy if-then rules [1]. In this paper we used an adap-tive neural fuzzy filter as an ECG beat classifier. We combined 3 famous wavelet transforms and used them mid 4 the order AR model coefficient as features. Our results suggest that a new proposed classifier (ANFF) with these features can generalize better than ordinary MLP archi-tecture and also learn better and faster. The results of proposed method show high accu-racy in ECG beat classification (97.6%) with 100% specificity and high sensitivity.

A methodology for the development of machining fixtures for components with complicated geometry

At present, fixture design in industry is largely an experienced-based, ad-hoc process. In the case of the design of fixtures for complex components, this approach often results in a need for rework and consequent delays to production. Machining fixture design has been the subject of considerable research efforts; however most research activities have addressed one or a small number of interactions between fixture and other manufacturing system elements. In this paper, a novel fixture design methodology based on concurrent engineering is described. This methodology models physical space, loads, stress, deformation, thermal effects, vibration, etc., determines the loads and deflections arising from the locating, clamping and machining procedures, and estimates the resultant effects on component quality. To assist in the development of the methodology, the high technology industrial partner originally provided the researchers with a range of complex machined components of various sizes, incorporating many different features. The methodology has been tested against a range of successful and unsuccessful fixture designs supplied by the industrial partner.

Spinocerebellar ataxias caused by polyglutamine expansions: A review of therapeutic strategies

Six of the spinocerebellar ataxias (SCAs) are caused by expanded CAG trinucleotide repeats encoding polyglutamine tracts in different genes. Together with three other neurodegenerative diseases they represent the polyglutamine repeat disorders. These disorders share many pathological features beyond a common genetic mechanism. They are the subject of considerable research efforts to elucidate their basic pathophysiologies, with the hope of using this knowledge to develop disease modifying treatments. Here we examine the biology that underpins possible therapeutic strategies for the SCAs caused by CAG repeats and review supportive data from cell and animal models. Therapeutic strategies include silencing gene expression, increasing protein clearance, reducing the toxicity of the protein, influencing downstream pathways activated by the mutant protein and transplantation. We also consider strategies which have been tested in other polyglutamine diseases that may generalize to these SCAs. Finally, we review clinical trials and consider the problems of translating the increasing amount of promising laboratory data into human trials.

Migraine, stroke and patent foramen ovale: a dangerous trio?

The relationship between migraine, stroke and patent foramen ovale (PFO) has been the subject of considerable research efforts. Indeed, a lot of interest has focused on the potential benefits of percutaneous PFO closure. The aim of this article is to review data from the currently available literature. A total of 10 relevant studies were found in the literature, for a total of 1038 patients undergoing percutaneous PFO closure after events of cryptogenic stroke. Thirty-eight percent of these patients suffered from migraine. Combining the results of the available studies, 72% of patients were cured or improved significantly. Analysing the results according to migraine type, 81% of patients with migraine with aura had complete resolution or significantly improved as compared to 72% of patients with migraine without aura. Several limitations and drawbacks exist, however, and they are extensively discussed in this paper.

A user's guide to evidence-based oncology

only. This is a very dangerous practice since abstracts are often not precise accounts of the real contents of a paper. The other situation where Rule no. 1 is violated is when primary references are quoted based on a secondary reference such as another research paper or a review. Again, this is a dangerous practice as documented by Evans et al. [5] in a review of the accuracy of quoting 137 randomly chosen references from The American Journal of Surgery; Surgery Gynecology and Obstetrics; and Surgery. A major error of quotation was assigned if the referenced article failed to substantiate, was unrelated to, or even contradicted the assertion made by the quoting authors. A depressing 27% of the quotations (37 of 137) were classified as major errors. It is probably unrealistic to expect even the keenest reader to check all primary references of a paper. However, in case of key findings quoted in a paper, a closer look at the primary reference is a must for the critical reader. Rule no. 2 is equally important: you should never rely on the authors’ conclusion but try to reach your own based on the data presented in a paper. In the standard lay-out of a scientific paper, the Introduction, Discussion and Conclusion sections are mainly window dressing. Not to say that they cannot be informative if they are well written, but the substance of a paper is in the Methods and Materials and in the Results sections. A rough guide to what to look for in a report of a randomised controlled trial (RCT) is found in Table 1. This is not meant as a checklist that can be ticked while reading the paper as there is no simple yes/no answer to most of these. It is more like a shopping list of ingredients that the critical reader will need in order to assess the strength of evidence presented in a paper. Some of the items in this table will be discussed later. Grading the strength of evidence Clearly, it would be extremely helpful to have a validated instrument for assessing the strength of evidence produced by a given study and this has been the subject of considerable research efforts. A recent systematic review prepared by West and colleagues for the U.S. Department of Health and Human Services found a total of 1602 publications relating to assessment of study quality or strength of evidence [6]. A total of 121 systems were reviewed and these included scales, checklists or other instruments or guidelines for assessment of quality or evidence strength. Twenty of these systems were developed for evaluation of systematic reviews and 49 systems for RCTs. In addition, the report reviewed 40 systems for grading the strength of a body of evidence. Unfortunately, there is no consensus as to the most adequate quality assessment instrument and although there is a considerable overlap between items included in the various scales or checklists, there are also important differences. This was convincingly shown by Juni et al. [7] who applied 25 different scales to assess the quality of 17 trials comparing low molecular weight heparin (LMWH) with standard heparin in the prevention of post-operative thrombosis. For each scale, the possible relative advantage of LMWH was estimated separately in two strata: high-quality and low-quality trials. For six of the scales, high-quality studies showed no significant difference between the two types of heparin whereas low-quality studies showed a significant benefit from LMWH. For seven other scales, the result was the opposite: high-quality studies showed a benefit from LMWH whereas low-quality studies did not. For the remaining 12 scales, the effect estimates were similar in the two quality strata. One of the most frequently cited and used of these quality assessment scales is the simple scale proposed by Jadad et al. [8] which assesses three elements of study design: whether the study is appropriately randomised, whether it is appropriately blinded and whether withdrawals and dropouts are described. The resulting score ranges from 0 to 5 (see Table 2). The scale was developed and applied in the evaluation of the quality of 36 reports on RCTs in pain research. The authors used a panel of assessors and showed that this scale produced consistent results and that the effect estimate from double-blind trials was significantly lower that the estimate from non-blinded trials. Subsequent authors have applied the Jadad scale in diverse fields of medicine. There are, however, two obvious but important caveats here. First

Conducting polymer materials

Conducting polymers represent a very interesting group of polymer materials Investigation of the synthesis, structure and properties of these materials has been the subject of considerable research efforts in the last twenty years. A short presentating of newer results obtained by investigating of the synthesis, structure and properties of two basic groups of conducting polymers: a) conducting polymers the conductivity of which is the result of their molecular structure, and b) conducting polymer composites (EPC), is given in this paper. The applications and future development of this group of polymer materials is also discussed.

Infants diets and insulin-dependent diabetes: evaluating the “cows' milk hypothesis” and a role for anti-bovine serum albumin immunity.

Insulin-Dependent Diabetes (IDD) results from an autoimmune destruction of the insulin secreting pancreatic beta cells. The immunological mechanisms underlying the development of IDD as well as the role of environmental agents (e.g., diet, viruses, stress) in the pathogenesis of the disease are the subject of considerable research efforts. Significant attention has recently been directed to a hypothesis that consumption of cows' milk in infancy may trigger the autoimmune process underlying IDD. Early evidence supporting this “cows' milk hypothesis” included case-control studies surveying infant nutrition practices (i.e., breast feeding versus consumption of infant formula) and the subsequent development of IDD. However, intense media interest surrounding a report indicating anti-bovine serum albumin (BSA) immunity as the cause of IDD has lead to heightened public awareness of the issue, and, together with the epidemiological data, prompted The American Academy of Pediatrics to modify its guidelines for infant feeding practices. However, less public and scientific attention has been given toward the observations that many of these case-control studies were retrospective in design and subject to recall bias, narrow in scope in terms of collecting dietary information, and that similar results have not been duplicated in other more recent (and better designed) investigations. Furthermore, the immunological report implicating anti-BSA immunity with the disease has become controversial due to difficulties in conforming the findings, and experiments in animal models closely resembling human IDD have not uniformly supported a role for anti-BSA immunity in the pathogenesis of IDD. Given the significant morbidity and mortality associated with IDD, an improved understanding of the cause of this disorder as well as identifying possible methods for its prevention are essential. However, without additional supporting information, modification of the cows' milk/BSA composition of diets in order to avoid the disease may be premature. Further studies are needed to clearly establish a role for diet in the pathogenesis of IDD.

Environment and R-ratio effects on fatigue crack propagation transitions in Ti-6A1-4V (ELI)

The multiple-sloped relationship between da/dN and AK in stage II fatigue crack propagation regime in most engineering alloys has been a subject of considerable research efforts. Even though the crack closure is recognized as a crucial factor affecting FCP rates, closure effect on transition behavior is often ignored due to the uncertainties associated with ΔKeff value and the difficulties in measuring closure especially in aqueous environment. The present study therefore focused on the closure-free transition behavior in mill annealed Ti-6A1-4V in moist air and 1% NaCl at a fixed potential of -500 mVSCE as a function ofR ratio. The complex da/dN-ΔK relationship in Ti-6A1-4V remains after closure-correction for eachR ratio and environment, suggesting that closure is not a controlling factor for a transition, while it may complicate transition behavior. After closure-correction, the transition points and slopes are insensitive to R ratio in moist air, suggesting that R ratio effect on transition behavior in moist air is mostly due to crack closure. The 1% NaCl solution further complicates the da/dN-ΔKeff shape in Ti-6A1-4V at R ratios of 0.1 and 0.4 by superimposing cyclic stress corrosion cracking (SCC)-induced transition at intermediate ΔK regime. Varying R ratio in 1% NaCl is complex and appears to modify the cyclic and/or static SCC contribution.