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Size-exclusion Chromatography
Size-exclusion chromatography, also known as molecular sieve chromatography, is a chromatography, chromatographic method in which molecules in Solution (chemistry), solution are separated by their Chemical structure, shape, and in some cases molecular weight, size. It is usually applied to large molecules or macromolecular complexes such as proteins and industrial polymers. Typically, when an aqueous solution is used to transport the sample through the column, the technique is known as gel filtration chromatography, versus the name gel permeation chromatography, which is used when an organic solvent is used as a mobile phase. The chromatography column is packed with fine, porous beads which are commonly composed of dextran, agarose, or polyacrylamide polymers. The pore sizes of these beads are used to estimate the dimensions of Macromolecule, macromolecules. SEC is a widely used polymer characterization method because of its ability to provide good molar mass distribution (Mw) resul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromatography
In chemical analysis, chromatography is a laboratory technique for the Separation process, separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system (a column, a capillary tube, a plate, or a sheet) on which a material called the ''stationary phase'' is fixed. Because the different constituents of the mixture tend to have different affinities for the stationary phase and are retained for different lengths of time depending on their interactions with its surface sites, the constituents travel at different apparent velocities in the mobile fluid, causing them to separate. The separation is based on the differential partitioning between the mobile and the stationary phases. Subtle differences in a compound's partition coefficient result in differential retention on the stationary phase and thus affect the separation. Chromatography may be ''preparative'' or ''analytical' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gel Permeation Chromatography
Gel permeation chromatography (GPC) is a type of size-exclusion chromatography (SEC), that separates high molecular weight or colloidal analytes on the basis of size or diameter, typically in organic solvents. The technique is often used for the analysis of polymers. As a technique, SEC was first developed in 1955 by Lathe and Ruthven.Lathe, G.H.; Ruthven, C.R.J. The Separation of Substance and '1956', ''62'', 665–674. The term ''gel permeation chromatography'' can be traced back to J.C. Moore of the Dow Chemical Company who investigated the technique in 1964. The proprietary column technology was licensed to Waters Corporation, who subsequently commercialized this technology in 1964. GPC systems and consumables are now also available from a number of manufacturers. It is often necessary to separate polymers, both to analyze them as well as to purify the desired product. When characterizing polymers, it is important to consider their size distribution and dispersity (''Đ'') as w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dow Chemical Company
The Dow Chemical Company is an American multinational corporation headquartered in Midland, Michigan, United States. The company was among the three largest chemical producers in the world in 2021. It is the operating subsidiary of Dow Inc., a publicly traded holding company incorporated under Delaware law. With a presence in around 160 countries, it employs about 36,000 people worldwide. Dow has been called the "chemical companies' chemical company", as its sales are to other industries rather than directly to end-use consumers. Dow is a member of the American Chemistry Council. In 2015, Dow and fellow chemical company DuPont agreed to a corporate reorganization involving the merger of Dow and DuPont followed by a separation into three different entities. The plan commenced in 2017, when Dow and DuPont merged to form DowDuPont, and was finalized in April 2019, when the materials science division was spun off from DowDuPont and took the name of the Dow Chemical Company. H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nature Methods
''Nature Methods'' is a monthly peer-reviewed scientific journal covering new scientific techniques. It was established in 2004 and is published by Springer Nature under the Nature Portfolio. Like other ''Nature'' journals, there is no external editorial board and editorial decisions are made by an in-house team, although peer review by external experts forms a part of the review process. The editor-in-chief is Allison Doerr. Every year, the journal highlights a field, approach, or technique that has enabled recent major advances in life sciences research as the "Method of the Year". According to the ''Journal Citation Reports'', the journal had a 2021 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a type of journal ranking. Journals with higher impact factor values are considered more prestigious or important within their field. The Impact Factor of a journa ... of 47.990, ranking it first in the category "Biochemical Research ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Per Flodin
Per or PER may refer to: Places * Peru (IOC country code) * Pér, a village in Hungary * Perthshire (Chapman code), historic county in Scotland Science and technology * Physics education research * Packed Encoding Rules, in computing, an ASN.1 wire format * Per (storm), a January 2007 storm in Sweden Mathematics * Rate (mathematics), ratio between quantities in different units * Price–earnings ratio, in finance, a measure of growth in earnings * Player efficiency rating, a measure of basketball player performance * Partial equivalence relation, class of relations that are symmetric and transitive Science * Perseus (constellation) (standard astronomical abbreviation) * Period (gene) or ''per'', that regulates the biological clock and its corresponding protein PER * Protein efficiency ratio, of food * PER or peregrinibacteria, a candidate bacterial phylum Media and entertainment * PeR (band), a Latvian pop band * ''Per'' (film), a 1975 Danish film Transport * Perth Airport ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jerker Porath
Jerker Porath, (23 October 1921 – 21 January 2016) was a Swedish biochemist who invented several separation methods for biomolecules. He was born in Sala. Porath studied at Uppsala University and initially did research in organic chemistry under Arne Fredga, where he got his licentiate degree. After a scholarship to an institute in Heidelberg he got an interest in biochemistry and switched to Arne Tiselius' department. Tiselius recommended Porath to make a research visit to Choh Hao Li and his Hormone Research Laboratory at University of California, Berkeley where Porath stayed 1951–1952. Back in Uppsala he developed methods for zone electrophoresis and ion exchange chromatography for hormone purification. He received his Ph.D. in Uppsala 1957 with the thesis ''Zone electrophoresis in columns and adsorption chromatography on ionic cellulose derivatives as methods for peptide and protein fractionations: application to the study of posterior pituitary hormones''. The separ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Environmental Science & Technology
''Environmental Science & Technology'' is a biweekly peer-reviewed scientific journal published since 1967 by the American Chemical Society. It covers research in environmental science and environmental technology, including environmental policy. ''Environmental Science & Technology'' has a sister journal, '' Environmental Science & Technology Letters'', which publishes short communications. The editor-in-chief of ''Environmental Science & Technology'' is Prof. Julie Zimmerman (Yale University). Previous editors have been: David Sedlak (University of California, Berkeley, 2014 - 2020), James J. Morgan (California Institute of Technology; founding editor, 1967–1975), Russell F. Christman (University of North Carolina, 1975–1987), William H. Glaze (University of North Carolina, 1987–2003) and Jerald L. Schnoor (University of Iowa, 2002–2014). Abstracting and indexing According to the ''Journal Citation Reports'', the journal has a 2022 impact factor of 11.4. The journal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gel Electrophoresis
Gel electrophoresis is an electrophoresis method for separation and analysis of biomacromolecules (DNA, RNA, proteins, etc.) and their fragments, based on their size and charge through a gel. It is used in clinical chemistry to separate proteins by charge or size (IEF agarose, essentially size independent) and in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length, to estimate the size of DNA and RNA fragments, or to separate proteins by charge. Nucleic acid molecules are separated by applying an electric field to move the negatively charged molecules through a gel matrix of agarose, polyacrylamide, or other substances. Shorter molecules move faster and migrate farther than longer ones because shorter molecules migrate more easily through the pores of the gel. This phenomenon is called sieving. Proteins are separated by the charge in agarose because the pores of the gel are too large to sieve proteins. Gel electrophoresi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fractionation
Fractionation is a separation process in which a certain quantity of a mixture (of gasses, solids, liquids, enzymes, or isotopes, or a suspension) is divided during a phase transition, into a number of smaller quantities (fractions) in which the composition varies according to a gradient. Fractions are collected based on differences in a specific property of the individual components. A common trait in fractionations is the need to find an optimum between the amount of fractions collected and the desired purity in each fraction. Fractionation makes it possible to isolate more than two components in a mixture in a single run. This property sets it apart from other separation techniques. Fractionation is widely employed in many branches of science and technology. Mixtures of liquids and gasses are separated by fractional distillation by difference in boiling point. Fractionation of components also takes place in column chromatography by a difference in affinity between statio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molar Mass Distribution
In polymer chemistry, the molar mass distribution (or molecular weight distribution) describes the relationship between the number of moles of each polymer species () and the molar mass () of that species. In linear polymers, the individual polymer chains rarely have exactly the same degree of polymerization and molar mass, and there is always a distribution around an average value. The molar mass distribution of a polymer may be modified by polymer fractionation. Definitions of molar mass average Different average values can be defined, depending on the statistical method applied. In practice, four averages are used, representing the weighted mean taken with the mole fraction, the weight fraction, and two other functions which can be related to measured quantities: *''Number average molar mass'' (), also loosely referred to as ''number average molecular weight'' (NAMW). *''Mass average molar mass'' (), where stands for weight; also commonly referred to as ''weight avera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymer Characterization
Polymer characterization is the analytical branch of polymer science. The discipline is concerned with the characterization of polymeric materials on a variety of levels. The characterization typically has as a goal to improve the performance of the material. As such, many characterization techniques should ideally be linked to the desirable properties of the material such as strength, impermeability, thermal stability, and optical properties. Characterization techniques are typically used to determine molecular mass, molecular structure, molecular morphology, thermal properties, and mechanical properties. Molecular mass The molecular mass of a polymer differs from typical molecules, in that polymerization reactions produce a distribution of molecular weights and shapes. The distribution of molecular masses can be summarized by the number-average molecular weight, weight-average molecular weight, and polydispersity. Some of the most common methods for determining these paramete ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macromolecule
A macromolecule is a "molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass." Polymers are physical examples of macromolecules. Common macromolecules are biopolymers (nucleic acids, proteins, and carbohydrates). and polyolefins (polyethylene) and polyamides (nylon). Synthetic macromolecules Many macromolecules are synthetic polymers (plastics, synthetic fibers, and synthetic rubber. Polyethylene is produced on a particularly large scale such that ethylene is the primary product in the chemical industry. Macromolecules in nature * Proteins are polymers of amino acids joined by peptide bonds. * DNA and RNA are polymers of nucleotides joined by phosphodiester bonds. These nucleotides consist of a phosphate group, a sugar ( ribose in the case of RNA, deoxyribose in the case of DNA), and a nucleotide base (either adenine, guan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
