Proteins are the building blocks of life. The body needs protein to repair and maintain itself. The basic structure of protein is a chain of amino acids. Every cell in the human body contains protein. It is a major part of the skin, muscles, organs, and glands. Protein is also found in all body fluids, except bile and urine. You need protein in your diet to help your body repair cells and make new ones. Protein is also important for growth and development during childhood, adolescence, and pregnancy.
When proteins are digested, amino acids are left. The human body needs a number of amino acids to break down food. Amino acids need to be eaten in large enough amounts for optimal health. Amino acids are found in animal sources such as meats, milk, fish, and eggs, as well as in plant sources such as soy, beans, legumes, nut butters, and some grains (such as wheat germ). You do not need to eat animal products to get all the protein you need in your diet. Essential amino acids cannot be made by the body, and must be supplied by food. They do not need to be eaten at one meal. The balance over the whole day is more important.
Source from: http://www.nlm.nih.gov/medlineplus/ency/article/002467.htm
2013年11月17日星期日
2013年11月10日星期日
Protein Purification Methods Based on Bioproperties (Affinity)
Protein Purification Methods Based on Bioproperties (Affinity) : A
powerful method for separating the desired protein from others is to
use a biospecific method in which the particular biological property of
the protein is exploited. The affinity approach is limited to proteins
that have a specific binding property, except that proteins are
theoretically able to be purified by immunoaffinity chromatography,
which is the most specific of all affinity techniques. Most proteins of
interest do have a specific ligand: enzymes have substrates and
cofactors, and hormone-binding proteins and receptor molecules are
designed to bind specifically and tightly to particular hormones and
other factors. Immobilization of the ligand to which the protein binds
(or of antibody to the protein) enables selective adsorption of the
desired protein in the technique known as affinity chromatography. There
are also nonchromatographic modes of exploiting biospecific
interactions.
Source: protein purification blog
Source: protein purification blog
2013年11月3日星期日
Overview of Protein Purification and Characterization
AIMS AND OBJECTIVES
Protein purification has an over 200-year history: the first attempts at isolating substances from plants having similar properties to “egg albumen,” or egg white, were reported in 1789 by Fourcroy. Many proteins from plants were purified in the nineteenth century, though most would not be considered pure by modern standards. A century later, ovalbumin was the first crystalline protein obtained (by Hofmeister in 1889). The year 1989 may not go down in history as a milestone in protein chemistry, but since then there has been a resurgence of interest in proteins after more than a decade of gene excitement.
The aims of protein purification, up until the 1940s, were simply academic. To then, even the basic facts of protein structure were not fully appreciated, and pure proteins were needed just to study structure and test the rival theories of the pre-DNA days. During the Second World War, an acute need for blood proteins led to development of the Cohn fractionation procedure for purification of albumin and other proteins from serum (Cohn et al., 1946). This was the inception of large-scale protein purifications for commercial purposes; Cohn fractionation continues to be used to this day.
The nature of the proteins studied has also changed substantially. Whereas enzymes were once the most favored subjects, they have now been superceded by nonenzymatic proteins such as growth factors, hormone receptors, viral antigens, and membrane transporters. Many of these occur in minute amounts in the natural source, and their purification can be a major task. Heroic efforts in the past have used kilogram quantities of rather unpleasant starting materials, such as human organs, and ended up with a few micrograms of pure product. It is now more usual, however, to take the genetic approach: clone the gene before the protein has been isolated or even properly identified, and then express it in a suitable host cell culture or organism. The expression level may be orders of magnitude higher than in the original source, which will make purification a relatively simple task. It can be useful to know beforehand some physical properties of the protein, to facilitate the development of a suitable purification protocol from the recombinant source. On the other hand, there are now several ways of preparing fusion proteins, which can be purified by affinity techniques without any knowledge of the properties of the target protein. Moreover, there are ways of modifying the expressed product to simplify purification further.
view more information please click http://www.recombinant-protein.com/overview-of-protein-purification-and-characterization/
Protein purification has an over 200-year history: the first attempts at isolating substances from plants having similar properties to “egg albumen,” or egg white, were reported in 1789 by Fourcroy. Many proteins from plants were purified in the nineteenth century, though most would not be considered pure by modern standards. A century later, ovalbumin was the first crystalline protein obtained (by Hofmeister in 1889). The year 1989 may not go down in history as a milestone in protein chemistry, but since then there has been a resurgence of interest in proteins after more than a decade of gene excitement.
The aims of protein purification, up until the 1940s, were simply academic. To then, even the basic facts of protein structure were not fully appreciated, and pure proteins were needed just to study structure and test the rival theories of the pre-DNA days. During the Second World War, an acute need for blood proteins led to development of the Cohn fractionation procedure for purification of albumin and other proteins from serum (Cohn et al., 1946). This was the inception of large-scale protein purifications for commercial purposes; Cohn fractionation continues to be used to this day.
The nature of the proteins studied has also changed substantially. Whereas enzymes were once the most favored subjects, they have now been superceded by nonenzymatic proteins such as growth factors, hormone receptors, viral antigens, and membrane transporters. Many of these occur in minute amounts in the natural source, and their purification can be a major task. Heroic efforts in the past have used kilogram quantities of rather unpleasant starting materials, such as human organs, and ended up with a few micrograms of pure product. It is now more usual, however, to take the genetic approach: clone the gene before the protein has been isolated or even properly identified, and then express it in a suitable host cell culture or organism. The expression level may be orders of magnitude higher than in the original source, which will make purification a relatively simple task. It can be useful to know beforehand some physical properties of the protein, to facilitate the development of a suitable purification protocol from the recombinant source. On the other hand, there are now several ways of preparing fusion proteins, which can be purified by affinity techniques without any knowledge of the properties of the target protein. Moreover, there are ways of modifying the expressed product to simplify purification further.
view more information please click http://www.recombinant-protein.com/overview-of-protein-purification-and-characterization/
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