Kinds Of Linkages Research Articles

Pyrene-based covalent organic frameworks (PyCOFs): a review.

Recently, pyrene-based covalent organic frameworks (PyCOFs) have aroused great interest because the large planar structure of the pyrene unit could effectively enhance the interlayer π-π interaction and promote the separation and migration of carriers, significantly improving the crystallinity and photoelectrical properties of PyCOFs. Since the first PyCOF-containing boroxate linkage was reported in 2008 by the Yaghi group, many PyCOFs with different kinds of linkages have been reported, exhibiting great potential applications in different fields such as adsorption/separation, chemical sensing, catalysis, energy storage, etc. However, as far as we know, the reviews related to PyCOFs are rare, although PyCOFs have been widely reported to show promising applications. Thus, it is right time and important for us to systematically summarize the research advance in PyCOFs, including the synthesis with different linkages and applications. Moreover, the prospects and obstacles facing the development of PyCOFs are discussed. We hope that this review will provide new insights into PyCOFs that can be explored for more attractive functions or applications.

Key roles of β-glucosidase BglA for the catabolism of both laminaribiose and cellobiose in the lignocellulolytic bacterium Clostridium thermocellum

The thermophilic bacterium Clostridium thermocellum efficiently degrades polysaccharides into oligosaccharides. The metabolism of β-1,4-linked cello-oligosaccharides is initiated by three enzymes, i.e., the cellodextrin phosphorylase (Cdp), the cellobiose phosphorylase (Cbp), and the β-glucosidase A (BglA), in C. thermocellum. In comparison, how the oligosaccharides containing other kinds of linkage are utilized is rarely understood. In this study, we found that BglA could hydrolyze the β-1,3-disaccharide laminaribiose with much higher activity than that against the β-1,4-disaccharide cellobiose. The structural basis of the substrate specificity was analyzed by crystal structure determination and molecular docking. Genetic deletions of BglA and Cbp, respectively, and enzymatic analysis of cell extracts demonstrated that BglA is the key enzyme responsible for laminaribiose metabolism. Furthermore, the deletion of BglA can suppress the expression of Cbp and the deletion of Cbp can up-regulate the expression of BglA, indicating that BglA and Cbp have cross-regulation and BglA is also critical for cellobiose metabolism. These insights pave the way for both a fundamental understanding of metabolism and regulation in C. thermocellum and emphasize the importance of the degradation and utilization of polysaccharides containing β-1,3-linked glycosidic bonds in lignocellulose biorefinery.

The Advancement of Biodegradable Polyesters as Delivery Systems for Camptothecin and Its Analogues-A Status Report.

Camptothecin (CPT) has demonstrated antitumor activity in lung, ovarian, breast, pancreas, and stomach cancers. However, this drug, like many other potent anticancer agents, is extremely water-insoluble. Furthermore, pharmacology studies have revealed that prolonged schedules must be administered continuously. For these reasons, several of its water-soluble analogues, prodrugs, and macromolecular conjugates have been synthesized, and various formulation approaches have been investigated. Biodegradable polyesters have gained popularity in cancer treatment in recent years. A number of biodegradable polymeric drug delivery systems (DDSs), designed for localized and systemic administration of therapeutic agents, as well as tumor-targeting macromolecules, have entered clinical trials, demonstrating the importance of biodegradable polyesters in cancer therapy. Biodegradable polyester-based DDSs have the potential to deliver the payload to the target while also increasing drug availability at intended site. The systemic toxicity and serious side-effects associated with conventional cancer therapies can be significantly reduced with targeted polymeric systems. This review elaborates on the use of biodegradable polyesters in the delivery of CPT and its analogues. The design of various DDSs based on biodegradable polyesters has been described, with the drug either adsorbed on the polymer's surface or encapsulated within its macrostructure, as well as those in which a hydrolyzed chemical bond is formed between the active substance and the polymer chain. The data related to the type of DDSs, the kind of linkage, and the details of in vitro and in vivo studies are included.

Water-Harvesting Metal-Organic Frameworks with Gigantic Al24 Units and their Deconstruction into Molecular Clusters.

In contrast to the vast Al-oxo molecular cluster chemistry, Al-based building units for metal-organic framework (MOF) construction are limited in structural diversity and complexity. Synthesis of single crystalline MOFs based on this "hard" metal is further complicated by the poor reversibility of the Al-organic coordination linkages. Here, a strategy to employ two kinds of linkages with distinct strength-strong Al-carboxylate linkage and weak Cu-pyrazol N linkage-gives FDM-91 (FDM=Fudan Materials) with gigantic Al24 -based units. After replacing the weak moieties with organic linkers post-synthetically, two new stable MOFs with exceptional water harvesting capacity (up to 0.53 g g-1 ) and outstanding cycling performance are developed. Linkage-selective dissociation of FDM-91 further leads to the isolation of the Al24 molecular clusters. The versatile chemistry performed here to reinforce or deconstruct MOFs provides a new way to make important extended and discrete structures.

Water‐Harvesting Metal–Organic Frameworks with Gigantic Al24Units and their Deconstruction into Molecular Clusters

AbstractIn contrast to the vast Al‐oxo molecular cluster chemistry, Al‐based building units for metal–organic framework (MOF) construction are limited in structural diversity and complexity. Synthesis of single crystalline MOFs based on this “hard” metal is further complicated by the poor reversibility of the Al‐organic coordination linkages. Here, a strategy to employ two kinds of linkages with distinct strength—strong Al‐carboxylate linkage and weak Cu‐pyrazol N linkage—gives FDM‐91 (FDM=Fudan Materials) with gigantic Al24‐based units. After replacing the weak moieties with organic linkers post‐synthetically, two new stable MOFs with exceptional water harvesting capacity (up to 0.53 g g−1) and outstanding cycling performance are developed. Linkage‐selective dissociation of FDM‐91 further leads to the isolation of the Al24molecular clusters. The versatile chemistry performed here to reinforce or deconstruct MOFs provides a new way to make important extended and discrete structures.

The Association between Weather and Emergency Department Visitation for Diabetes in Roanoke, Virginia.

Diabetes mellitus imposes a significant and increasing health burden on the US population. Our objective is to determine if weather is related to daily variations in emergency department (ED) visits for diabetes mellitus in Roanoke, Virginia. A time series of daily ED visits for diabetes mellitus at the Carilion Clinic in southwestern Virginia is associated with daily minimum temperature from 2010-2017. Associations between ED visits (through a 14-day lag period) and temperature are examined using generalized additive models and distributed lag nonlinear models. Heat and cold waves are identified at low and high thresholds, and ED visitation during these events is compared to prior control periods using a time-stratified case crossover approach. ED visits for diabetes exhibit a U-shaped relationship with temperature, with a higher relative risk (RR) during cold events (RR = 1.05) vs. warm events (RR = 1.02). When minimum temperatures are below freezing, ED visitation peaks starting 2days afterward, with RRs approaching 1.04. The RR on warm days (minimum temperature > 10°C) approaches 1.02 but peaks on the day of or the day following the elevated temperatures. Cold waves increase the odds of ED visits by up to 11% (p = 0.01), whereas heat waves exhibit no significant effect (p = 0.07). The increasing health burden linked to diabetes requires new research on environmental factors that might exacerbate related illness. When examined in the context of climate change impacts on local weather variations, these kinds of linkages between environment and disease can aid in facility staffing and public health messaging during extreme weather events.

Challenges in managing semantic annotations in harvested research objects in a national CRIS context

Harvested metadata on research objects can include links between the primary domain objects such as organizational identifiers associated with dataset, persons identified with ORCIDs linked to publications and publications connected through ISSNs to publishing channels. This kind of linkage is the bread-and-butter of the CRIS systems and usually comprehensively maintained. When it comes to the more subjective description of a domain object, such as keywords, themes, or subject headings, the issues related to data management and modeling become prominent with challenges such as flexibility of free text keywords as opposed to authoritative, but rigid classification systems. Many CRIS objects also already contain an extensive description of the content, just meant for human consumption, in the form of an abstract or similar summary text.With the help of automated data mining and annotation tools, these textual representations can be processed into structured data. This paper presents the processing pipelines implemented as part of the research.fi portal for automatic linking of different research inputs based on automatically extracted ontology concepts and discusses the implications of utilizing them as part of the research.fi platform. But more than simply discussing the annotation of research objects and the creation of word clusters for representation of the semantic content of research objects, we also discuss challenges related to maintaining the automatically produced metadata

Stereodynamics of E/Z isomerization in rotaxanes through mechanical shuttling and covalent bond rotation

SummaryThe mechanical bond has opened a new world for structural and dynamic stereochemistry, which is still largely underexplored and whose significance for various applications is becoming increasingly evident. We demonstrate that designed rearrangements involving both covalent and mechanical bonds can be integrated in [2]rotaxanes, leading to interesting consequences in terms of E/Z isomerization mechanisms. Two entirely distinct and concomitant stereomutations, pertaining to the same stereogenic element but involving different kinds of linkages within the molecule, are observed and are thoroughly characterized. The rate of the two processes is affected in opposite ways upon changing solvent polarity; such a phenomenon can be used to selectively modify the rate of each motion and adjust the relative contribution of the two mechanisms to the isomerization. Although the movements are not synchronized, an analysis of the intriguing fundamental implications for transition state theory, reaction pathway bifurcation, and microscopic reversibility was triggered by our experimental observations.

Research on the Technique of Singing Legato in Piano Works Based on Computer Synesthesia Analysis

The word synaesthesia is derived from the ancient Greek word synesthesia. "Synesthesia" is composed of the ancient Greek word "SYN" (meaning together and simultaneously) and “AIST-HEIS” (meaning feeling and perception). That is to say, when we feel a system stimulation, the feeling of one or more other react system will be independent, to produce this kind of phenomenon is due to the system of multiple senses of the body, and this kind of linkage is also known as synesthesia activities, is the human common natural phenomena in the process of mental activity. Computer synesthesia analysis also plays an important role in piano works.

Development of biocompatible natural polymer as promising green emissaries of essential therapeutics-A brief overview

Most of the natural polymers are high molecular weight; water soluble polymers made up of monosaccharide units and joined by different kinds of linkages [1].

Street names in Dakar-Plateau: a colonial and post-colonial perspective

ABSTRACT This article revolves around the naming of streets in Dakar-Plateau. This was borne in mind as analysis considered the system of urban nomenclature applied in the colonial era, when the city was founded and shaped by France’s colonial administration; as well as the (re)naming process ongoing after Senegal’s independence. The approach thus applied quantitative verification methods to a thesis oft-repeated in the subject literature, that a French glossary of toponyms dominates the system by which streets in Dakar are named. Quantitative analysis here shows unequivocally that there is only a slight numerical prevalence of colonial-era names of streets over new names. Beyond that, clear evidence is offered for the idea that, in both colonial days and today, the symbolic urban landscape expressed with the aid of urbanonyms was shaped by authorities in a conscious manner, being pressed into the service of political objectives. To indicate the strength of this kind of linkage, the article engages in the detailed discussion of each change of name that certain streets have been through; the bases for this approach being reference to the historical town/city plans present in the Archives Nationales du Sénégal, as well as fieldwork carried out in the Senegalese capital.

Research on Establishing and Forming "Sports Network" System and Mechanism—Based on the Status of Physical Health and Physical Activity of Middle School Seniors in China

According to the adverse status of physical health and physical activity of middle school seniors, proposing solutions about network system and mechanism of the construction of middle school students by using the methods of literature data, analysis, synthesis and so on. In the longitudinal aspects, form the macroscopic policy makers, middle managers, micro executives and all kinds of linkage among the audience and coordinate system and mechanism. In Lateral aspects, establish and form family, school, social’’ interaction and cooperation mechanism, prompting the coordinated development and deep fusion of school sports, social sports and competitive sports so as to change the bad status of seniors’ physical health and physical activity.

Design and performance evaluation of hinge type pitch control system in small-size wind turbine

The present study is about pitch control system of a small wind turbine using hinge mechanism. Small wind turbines generally apply stall control method or breaking equipment over the rated wind speed by reason of price or efficiency. However we perform pitch control applying the hinge mechanism which is simpler than that of medium and large size wind turbines. The hinge mechanism is a kind of linkage. It is composed of a rotation motion part, a linear motion part and a connection part. Pitch angle is controlled by the rotation parts which are connection to blades. In order to determine relationship between the hinge links and pitch angle, kinematic analysis is performed. Also, we derive design specifications of the actuator which drives the hinge mechanism by the Jacobian analysis. Simulation using MATLAB analyses forces and velocities of the hinge type pitch control system. Finally, as applying it to a 20 kW small wind turbine, the performances are evaluated by wind tunnel test.

Creative Alliances: The Transnational Designs of Indigenous Women’s PoetryBroken Souths: Latina/o Poetic Responses to Neoliberalism and Globalization

Creative Alliances: The Transnational Designs of Indigenous Women’s PoetryBroken Souths: Latina/o Poetic Responses to Neoliberalism and Globalization

Linkages between the ADR market and home country macroeconomic fundamentals: Evidence in the context of the BRICs

This study investigates the long-run and short-run lead–lag linkages between American Depositary Receipt (ADR) prices and home country economic fundamentals in the context of the BRICs (Brazil, Russia, India and China). In order to obtain an indication of the segmentation or integration between the ADR market and its underlying stock market, the same investigation is also undertaken in relation to the latter. We find that in the long run, economic growth positively drives ADR returns in the cases of Brazil and China but negatively in the cases of Russia and India. In the short-run, economic growth and money supply lead ADR prices but ADR prices predict inflation and oil prices with regard to Brazil while in Russia, oil prices predict ADR returns but the ADR market leads monetary policies and real economic activity. As regards India, in the short run, oil prices and economic growth lead ADR prices but ADR prices predict money supply changes. Finally, with respect to China, the ADR index lead economic growth and inflation but economic variables do not predict ADR prices in the short-run. In the long run, with the exception of China, we find the same kind of linkages between these economic fundamentals and the underlying stock market although the linkages are somewhat stronger. The short run dynamics for ADRs with respect to economic fundamentals are, however, different for that of the respective home country stock market. This would imply that the ADR market and its underlying stock market, as far as the BRICs are concerned, are integrated in the long-run but not in the short-run.

Isolation and structural elucidation of a novel homogenous polysaccharide from Tricholoma matsutake

A crude polysaccharide possessing antitumour, radiation-resistant and anti-ageing attributes was extracted from Tricholoma matsutake by water extraction and alcohol precipitation. From this crude polysaccharide, a homogeneous polysaccharide, TMP-5II, was successfully purified by Sephacryl S-300 column chromatography. The average molecular weight (Mw) of TMP-5II was 15.76 kDa. Monosaccharide analysis indicated that the homogeneous polysaccharide contained four different residues: d-glucose, d-galactose, d-mannose and d-fucose. Attenuated total reflectance infrared spectroscopy revealed characteristics typical of carbohydrate polymers and a peak typical of a β-type glycosidic bond. TMP-5II was selected for structural characterisation by nuclear magnetic resonance (NMR) analysis. According to 1H NMR, 13C NMR and two-dimensional-NMR analysis, TMP-5II contains two kinds of linkages, β and α, at a ratio of 4:1. Preliminary results indicated that the polysaccharide had (1-4)-beta-pyran glucose as the main chain, and a branched chain in the O-6 location with fucose (1-2) mannose (1-3)-alpha-pyran galactose.

ChemInform Abstract: From Targeted Aza‐Michael Addition to Linked Azaheterocyclic Scaffolds.

AbstractDifferent kinds of azaheterocyclic scaffolds (hydantoin, 2‐thiohydantoin) are prepared.

From targeted aza-Michael addition to linked azaheterocyclic scaffolds

A straightforward method for the synthesis of spaced, phenyl-linked bis(thiohydantoin) derivatives and (thio)hydantoins spiro-fused to pyrroline ring has been developed. All the synthetic strategies here presented rely on initial aza-Michael addition followed by acylation/regioselective ring-closure step involving DD, primary amine and iso(thio)cyanate in a 3-CR providing 1,3,5-trisubstituted (thio)hydantoins. The choice of opportune acyclic reagents in the sequential 3-CR followed by 1,4-nucleophilic addition/intramolecular ring closing and 1,3-dipolar cycloaddition permits a number of C–N and C–C formation that realizes different kind of linkage between several pharmacophores.

Electrochemical lectin based biosensors as a label-free tool in glycomics.

Glycans and other saccharide moieties attached to proteins and lipids, or present on the surface of a cell, are actively involved in numerous physiological or pathological processes. Their structural flexibility (that is based on the formation of various kinds of linkages between saccharides) is making glycans superb "identity cards". In fact, glycans can form more "words" or "codes" (i.e., unique sequences) from the same number of "letters" (building blocks) than DNA or proteins. Glycans are physicochemically similar and it is not a trivial task to identify their sequence, or - even more challenging - to link a given glycan to a particular physiological or pathological process. Lectins can recognise differences in glycan compositions even in their bound state and therefore are most useful tools in the task to decipher the "glycocode". Thus, lectin-based biosensors working in a label-free mode can effectively complement the current weaponry of analytical tools in glycomics. This review gives an introduction into the area of glycomics and then focuses on the design, analytical performance, and practical utility of lectin-based electrochemical label-free biosensors for the detection of isolated glycoproteins or intact cells.

Crystal structural diversity of sulfur-bridged cysteinato dimolybdenum(V) complexes: The influence of counter metal cations

Eight new crystal structures of sulfur-bridged dinuclear molybdenum(V) complexes with l-cysteine ligands, [Mo2(μ-S)2O2(cys)2]2− (1), were determined by changing the counter cations (K+, Ca2+, Sr2+, Mn2+, Ni2+, Cd2+, and Pb2+, where Mn2+ gave two kinds of crystal structures): K2[Mo2O2S2 (cys)2]·5H2O (1-K), Ca[Mo2O2S2 (cys)2]·8H2O (1-Ca), Sr[Mo2O2S2(cys)2]·6H2O (1-Sr), Mn[Mo2O2S2(cys)2]·12H2O (1-MnA), Mn[Mo2O2S2(cys)2]·7H2O (1-MnB), Ni[Mo2O2S2 (cys)2]·14H2O (1-Ni), Cd[Mo2O2S2(cys)2]·2H2O (1-Cd), and Pb[Mo2O2S2(cys)2]·2H2O (1-Pb). The eight crystal structures and two with other counter cations (Na2[Mo2O2S2(cys)2]·4H2O (1-Na) and Zn[Mo2(μ-S)2O2(cys)2]·2H2O (1-Zn)) so far reported were compared. The structures vary considerably by changing the counter cations, while few remarkable differences were observed with regard to the dimensions in the complex anion 1. There are four kinds of linkages: (1) one-dimensional zigzag chains appear in 1-Na, 1-Zn, 1-Cd, and 1-Pb; (2) a two-dimensional linkage appears in 1-K; (3) the cation and anion are directly linked, but they are separated from other cation–anion groups in 1-MnA; (4) the cation and anion are separated in 1-Ca, 1-Ni, 1-Sr, and 1-MnB. A good relationship exists between the coordination modes of metal cations and solubility of the corresponding metal sulfides. The coordination modes of metals are divided into two groups: Group 1: metal ions (Na+, K+, Sr2+, Ca2+, Mn2+(two kinds of crystals), and Ni2+) whose sulfides have large or medium solubility in water bind to oxygen (the carbonyl oxygen of cysteine, the terminal oxygen of Mo=O, and/or water); Group 2: metal ions (Zn2+, Cd2+, and Pb2+) whose sulfides have small solubility bind to cysteine sulfur. The HSAB principle explains the relationship.