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American Journal of Orthodontics and... May 2015The advances in the field of materials as they relate to orthodontics can be divided into the actual evolution of materials applied to daily practice and the changes in... (Review)
Review
The advances in the field of materials as they relate to orthodontics can be divided into the actual evolution of materials applied to daily practice and the changes in research methods to study the performance and the biologic properties of the materials. Although it is evident that new materials have saturated the market during the past century, the basic concepts of attaching one appliance to the enamel to use as a grip and inserting wires into that to control the spatial orientation of a tooth are identical to the original concepts. In contrast to that, the numbers of treatises about those subjects and the complexity of instrumentation and analytic tools used in published research have advanced tremendously and at a frenetic pace. This highly specialized pattern of research may effectively raise boundaries across research areas, since the complexity of the issues allows researchers to comprehend the content of journal articles in a narrow spectrum of disciplines. The purposes of this article were to review the advances in the research methods for investigating the various properties of orthodontic materials and to assist the reader in navigating this topic. A synopsis of the materials is also provided, listing future applications that already exist at the experimental stage or are yet unavailable but with the relevant technology already presented in broader scientific disciplines.
Topics: Biomechanical Phenomena; Dental Bonding; Dental Materials; Dental Research; Humans; Materials Testing; Orthodontic Appliances
PubMed: 25925652
DOI: 10.1016/j.ajodo.2015.03.007 -
Journal of Bone and Mineral Research :... Oct 1991Calcium is the most closely controlled substance in the blood. The biologic variation of total calcium is approximately 2% and of the biologically active free (ionized,... (Review)
Review
Calcium is the most closely controlled substance in the blood. The biologic variation of total calcium is approximately 2% and of the biologically active free (ionized, ionic) calcium only 1%. Thus, the monitoring of calcium in blood requires analytic procedures of high precision and accuracy. For patients with asymptomatic primary hyperparathyroidism, calcium monitoring involves the measurement of total calcium and free calcium. This review first considers the measurement of total calcium and then free calcium.
Topics: Arsenazo III; Calcium; Coloring Agents; Edetic Acid; Humans; Hyperparathyroidism; Phenolphthaleins; Reference Values; Sensitivity and Specificity; Staining and Labeling
PubMed: 1722382
DOI: 10.1002/jbmr.5650061411 -
BioMed Research International 2013Endocrine-disruptor compounds (EDCs) can mimic natural hormones and produce adverse effects in the endocrine functions by interacting with estrogen receptors. EDCs... (Review)
Review
Endocrine-disruptor compounds (EDCs) can mimic natural hormones and produce adverse effects in the endocrine functions by interacting with estrogen receptors. EDCs include both natural and synthetic chemicals, such as hormones, personal care products, surfactants, and flame retardants, among others. EDCs are characterised by their ubiquitous presence at trace-level concentrations and their wide diversity. Since the discovery of the adverse effects of these pollutants on wildlife and human health, analytical methods have been developed for their qualitative and quantitative determination. In particular, mass-based analytical methods show excellent sensitivity and precision for their quantification. This paper reviews recently published analytical methodologies for the sample preparation and for the determination of these compounds in different environmental and biological matrices by liquid chromatography coupled with mass spectrometry. The various sample preparation techniques are compared and discussed. In addition, recent developments and advances in this field are presented.
Topics: Analytic Sample Preparation Methods; Animals; Chemistry Techniques, Analytical; Endocrine Disruptors; Environmental Monitoring; Environmental Pollutants; Humans
PubMed: 23738329
DOI: 10.1155/2013/674838 -
Molecules (Basel, Switzerland) Feb 2021Fabric phase sorptive extraction (FPSE) is an evolutionary sample preparation approach which was introduced in 2014, meeting all green analytical chemistry (GAC)... (Review)
Review
Fabric phase sorptive extraction (FPSE) is an evolutionary sample preparation approach which was introduced in 2014, meeting all green analytical chemistry (GAC) requirements by implementing a natural or synthetic permeable and flexible fabric substrate to host a chemically coated sol-gel organic-inorganic hybrid sorbent in the form of an ultra-thin coating. This construction results in a versatile, fast, and sensitive micro-extraction device. The user-friendly FPSE membrane allows direct extraction of analytes with no sample modification, thus eliminating/minimizing the sample pre-treatment steps, which are not only time consuming, but are also considered the primary source of major analyte loss. Sol-gel sorbent-coated FPSE membranes possess high chemical, solvent, and thermal stability due to the strong covalent bonding between the fabric substrate and the sol-gel sorbent coating. Subsequent to the extraction on FPSE membrane, a wide range of organic solvents can be used in a small volume to exhaustively back-extract the analytes after FPSE process, leading to a high preconcentration factor. In most cases, no solvent evaporation and sample reconstitution are necessary. In addition to the extensive simplification of the sample preparation workflow, FPSE has also innovatively combined the extraction principle of two major, yet competing sample preparation techniques: solid phase extraction (SPE) with its characteristic exhaustive extraction, and solid phase microextraction (SPME) with its characteristic equilibrium driven extraction mechanism. Furthermore, FPSE has offered the most comprehensive cache of sorbent chemistry by successfully combining almost all of the sorbents traditionally used exclusively in either SPE or in SPME. FPSE is the first sample preparation technique to exploit the substrate surface chemistry that complements the overall selectivity and the extraction efficiency of the device. As such, FPSE indeed represents a paradigm shift approach in analytical/bioanalytical sample preparation. Furthermore, an FPSE membrane can be used as an SPME fiber or as an SPE disk for sample preparation, owing to its special geometric advantage. So far, FPSE has overwhelmingly attracted the interest of the separation scientist community, and many analytical scientists have been developing new methodologies by implementing this cutting-edge technique for the extraction and determination of many analytes at their trace and ultra-trace level concentrations in environmental samples as well as in food, pharmaceutical, and biological samples. FPSE offers a total sample preparation solution by providing neutral, cation exchanger, anion exchanger, mixed mode cation exchanger, mixed mode anion exchanger, zwitterionic, and mixed mode zwitterionic sorbents to deal with any analyte regardless of its polarity, ionic state, or the sample matrix where it resides. Herein we present the theoretical background, synthesis, mechanisms of extraction and desorption, the types of sorbents, and the main applications of FPSE so far according to different sample categories, and to briefly show the progress, advantages, and the main principles of the proposed technique.
Topics: Analytic Sample Preparation Methods; Solid Phase Extraction
PubMed: 33562079
DOI: 10.3390/molecules26040865 -
Journal of Chemical Theory and... Jan 2020For a first-principles understanding of macromolecular processes, a quantitative understanding of the underlying free energy landscape and in particular its entropy...
For a first-principles understanding of macromolecular processes, a quantitative understanding of the underlying free energy landscape and in particular its entropy contribution is crucial. The stability of biomolecules, such as proteins, is governed by the hydrophobic effect, which arises from competing enthalpic and entropic contributions to the free energy of the solvent shell. While the statistical mechanics of liquids, as well as molecular dynamics simulations, have provided much insight, solvation shell entropies remain notoriously difficult to calculate, especially when spatial resolution is required. Here, we present a method that allows for the computation of spatially resolved rotational solvent entropies via a nonparametric -nearest-neighbor density estimator. We validated our method using analytic test distributions and applied it to atomistic simulations of a water box. With an accuracy of better than 9.6%, the obtained spatial resolution should shed new light on the hydrophobic effect and the thermodynamics of solvation in general.
Topics: Entropy; Hydrophobic and Hydrophilic Interactions; Models, Chemical; Molecular Dynamics Simulation; Solvents; Thermodynamics; Water
PubMed: 31822062
DOI: 10.1021/acs.jctc.9b00926 -
The Journal of Biological Chemistry 2021Human D-3-phosphoglycerate dehydrogenase (PHGDH), a key enzyme in de novo serine biosynthesis, is amplified in various cancers and serves as a potential target for...
Human D-3-phosphoglycerate dehydrogenase (PHGDH), a key enzyme in de novo serine biosynthesis, is amplified in various cancers and serves as a potential target for anticancer drug development. To facilitate this process, more information is needed on the basic biochemistry of this enzyme. For example, PHGDH was found to form tetramers in solution and the structure of its catalytic unit (sPHGDH) was solved as a dimer. However, how the oligomeric states affect PHGDH enzyme activity remains elusive. We studied the dependence of PHGDH enzymatic activity on its oligomeric states. We found that sPHGDH forms a mixture of monomers and dimers in solution with a dimer dissociation constant of ∼0.58 μM, with the enzyme activity depending on the dimer content. We computationally identified hotspot residues at the sPHGDH dimer interface. Single-point mutants at these sites disrupt dimer formation and abolish enzyme activity. Molecular dynamics simulations showed that dimer formation facilitates substrate binding and maintains the correct conformation required for enzyme catalysis. We further showed that the full-length PHGDH exists as a dynamic mixture of monomers, dimers, and tetramers in solution with enzyme concentration-dependent activity. Mutations that can completely disrupt the sPHGDH dimer show different abilities to interrupt the full-length PHGDH tetramer. Among them, E108A and I121A can also disrupt the oligomeric structures of the full-length PHGDH and abolish its enzyme activity. Our study indicates that disrupting the oligomeric structure of PHGDH serves as a novel strategy for PHGDH drug design and the hotspot residues identified can guide the design process.
Topics: Biocatalysis; Humans; Molecular Dynamics Simulation; Phosphoglycerate Dehydrogenase; Protein Multimerization; Protein Structure, Quaternary
PubMed: 33753166
DOI: 10.1016/j.jbc.2021.100572 -
The American Journal of Clinical... Jun 2004The chemistry of conjugated fatty acids, specifically octadecadienoic acids (18:2; commonly referred to as conjugated linoleic acid, or CLA), has provided many... (Review)
Review
The chemistry of conjugated fatty acids, specifically octadecadienoic acids (18:2; commonly referred to as conjugated linoleic acid, or CLA), has provided many challenges to lipid analysts because of their unique physical properties and the many possible positional and geometric isomers. After the acid-labile properties of CLAs during analytic procedures were overcome, it became evident that natural products, specifically dairy fats, contain one dominant (c9,t11-CLA), 3 intermediate (t7,c9-, t9,c11-, and t11,c13-CLA), and up to 20 more minor CLA isomers. The best analytic techniques to date include a combination of gas chromatography that uses 100-m highly polar capillary columns, silver ion-HPLC, and a combination of silver ion-thin-layer chromatography and gas chromatography to analyze the CLA and trans 18:1 isomers, because some of them serve as precursors of CLA in biological systems. These analytic techniques have assisted commercial suppliers to prepare pure CLA isomers and have permitted the evaluation of individual CLA isomers for their nutritional and biological activity in animal and human systems. It is increasingly evident that different CLA isomers have distinctly different physiologic and biochemical properties. These techniques are essential to evaluate dairy fats for their CLA content, to design experimental diets to increase the amount of CLA in dairy fats, and to determine the CLA profile in these CLA-enriched dairy fats. These improved techniques are used to evaluate the CLA profile in pork products from pigs fed different commercial CLA mixtures.
Topics: Animals; Cattle; Chromatography, Gas; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Dairy Products; Dietary Fats; Food Analysis; Humans; Isomerism; Linoleic Acids, Conjugated; Milk; Swine
PubMed: 15159247
DOI: 10.1093/ajcn/79.6.1137S -
Frontiers in Cellular and Infection... 2022Malaria is one of the most widespread parasitic diseases, especially in Africa, Southeast Asia and South America. One of the greatest problems for control of the disease...
Malaria is one of the most widespread parasitic diseases, especially in Africa, Southeast Asia and South America. One of the greatest problems for control of the disease is the emergence of drug resistance, which leads to a need for the development of new antimalarial compounds. The biosynthesis of isoprenoids has been investigated as part of a strategy to identify new targets to obtain new antimalarial drugs. Several isoprenoid quinones, including menaquinone-4 (MK-4/vitamin K2), α- and γ-tocopherol and ubiquinone (UQ) homologs UQ-8 and UQ-9, were previously detected in cultures of in asexual stages. Herein, we described for the first time the presence of phylloquinone (PK/vitamin K1) in and discuss the possible origins of this prenylquinone. While our results in metabolic labeling experiments suggest a biosynthesis of PK prenylation phytyl pyrophosphate (phytyl-PP) with phytol being phosphorylated, on the other hand, exogenous PK attenuated atovaquone effects on parasitic growth and respiration, showing that this metabolite can be transported from extracellular environment and that the mitochondrial electron transport system (ETS) of is capable to interact with PK. Although the natural role and origin of PK remains elusive, this work highlights the PK importance in plasmodial metabolism and future studies will be important to elucidate in seeking new targets for antimalarial drugs.
Topics: Antimalarials; Humans; Malaria; Malaria, Falciparum; Plasmodium falciparum; Vitamin K 1
PubMed: 35531326
DOI: 10.3389/fcimb.2022.869085 -
Journal of Chromatography. A Jun 2022In recent years, important efforts have been put into miniaturization, coming on the scene formats such as chips, 3D-printed objects and paper-based devices. These... (Review)
Review
In recent years, important efforts have been put into miniaturization, coming on the scene formats such as chips, 3D-printed objects and paper-based devices. These systems have been applied to biological and chemical processes taking profit of their advantages such as waste reduction, low cost, portability, etc. Despite their benefits, there is a need to continue developing easier-to-use devices with enhanced performance addressed to face the current analytical challenges. In this sense, reticular porous materials such as metal- (MOFs) and covalent- (COFs) organic frameworks with unique features including tailorable porous architectures and tunable chemistry have attracted a lot of attention in various fields. Nevertheless, the combination of these materials with miniaturized and emerging formats has been scarcely investigated. This review is intended to bridge this gap and highlight the recent contributions of these materials in these analytical formats. Thus, this work aims to provide a comprehensive review of the field, highlighting incorporation strategies into the functional supports available to date, and the applications of the resulting systems in both off-site laboratory studies (mostly dedicated to (micro)extraction purposes) and on-site analysis. Finally, a discussion of challenges and future directions in this field is also given.
Topics: Chemistry, Analytic; Metal-Organic Frameworks; Metals; Porosity
PubMed: 35526300
DOI: 10.1016/j.chroma.2022.463092 -
Methods (San Diego, Calif.) Aug 2017The spliceosome is an extraordinarily dynamic molecular machine in which significant changes in composition as well as protein and RNA conformation are required for... (Review)
Review
The spliceosome is an extraordinarily dynamic molecular machine in which significant changes in composition as well as protein and RNA conformation are required for carrying out pre-mRNA splicing. Single-molecule fluorescence resonance energy transfer (smFRET) can be used to elucidate these dynamics both in well-characterized model systems and in entire spliceosomes. These types of single-molecule data provide novel information about spliceosome components and can be used to identify sub-populations of molecules with unique behaviors. When smFRET is combined with single-molecule fluorescence colocalization, conformational dynamics can be further linked to the presence or absence of a given spliceosome component. Here, we provide a description of experimental considerations, approaches, and workflows for smFRET with an emphasis on applications for the splicing machinery.
Topics: Analytic Sample Preparation Methods; Fluorescence Resonance Energy Transfer; Fluorescent Dyes; Microscopy, Fluorescence; Nucleic Acid Conformation; Oligonucleotides; RNA Precursors; RNA Splicing; RNA, Fungal; Saccharomyces cerevisiae; Single Molecule Imaging; Spliceosomes; Staining and Labeling
PubMed: 28529063
DOI: 10.1016/j.ymeth.2017.05.011