Growth substance, first isolation

The advantages of recombinant DNA technology are enormous, as the following example shows. Somatostatin is a hormone that inhibits the secretion of pituitary growth hormone. The researchers who first isolated somatostatin required nearly half a million sheep brairrs to produce 5 mg of the substance. Using a chemically synthesized gene, 9... 

The kidney normally manufactures erythropoietin, the growth factor for the production of red blood cells. In fact, erythropoietin was first isolated from the urine of patients with anemia, a condition characterized by too few red blood cells. Red cells carry oxygen to the body s tissues, and if too little oxygen is delivered to them, certain kidney cells produce erythropoietin. Most of this substance goes into the blood, where it circulates to the bone marrow and other tissues and triggers increased production of red cells from immature cells. Some erythropoietin spills into the urine. The concentration of erythropoietin in the blood is very low. The concentration is even lower in urine, but urine is easy, safe, and cheap to collect, and it does not contain a large number of other proteins. 

The cytokinines (e.g. kinetine. Table 43) are plant growth substances which promote cell division. They are all adenine derivatives, the first of which to be isolated from a natural Source [Zea mays) was zcatin, A -[( )-4-hydroxy-3-methylbut-2-enyl]adenine (4). 

C4H,N02,Mr 101.1 l,mp. 229-231 °C. A non-proteinogenic amino acid first known as a synthetic product and later isolated from pears and apples. ACC is formed from methionine via 5-adenosylmethionine with the help of ACC synthase (EC 4.4.1.14) and cleaved by ACC oxidase to the multifunctional plant growth substance ethylene which plays key roles in various plant physiological processes such as ripening of fruit, aging, germination, and response to stress. 

In most organic chemistry experiments, the desired product is first isolated in an impure form. If this product is a solid, the most common method of purification is crystallization. The general technique involves dissolving the material to be crystallized in a hot solvent (or solvent mixture) and cooling the solution slowly. The dissolved material has a decreased solubility at lower temperatures and will separate from the solution as it is cooled. This phenomenon is called either crystallization, if the crystal growth is relatively slow and selective, or precipitation, if the process is rapid and nonselective. Crystallization is an equilibrium process and produces very pure material. A small seed crystal is formed initially, and it then grows layer by layer in a reversible manner. In a sense, the crystal "selects" the correct molecules from the solution. In precipitation, the crystal lattice is formed so rapidly that impurities are trapped within the lattice. Therefore, any attempt at purification with too rapid a process should be avoided. Because the impurities are usually present in much smaller amounts than the compound being crystallized, most of the impurities will remain in the solvent even when it is cooled. The purified substance can then be separated from the solvent and from the impurities by filtration. 

In 1913, E.V. McCollum isolated a yellow, fat-soluble substance from egg yolks that was critical for animal growth. He called it fat-soluble A, indicating the first isolated of several dietary microconstituents emerging as obligatory for vertebrate life and health. Later, fat-soluble A was renamed vitamin A, derived from the terminology vital amine, coined by Casmir Funk to describe these obligatory micronutrients. 

The first plant bioassay [Avena sativa L (oat) coleoptile test] was employed by F.W. Went in the 1920 s to demonstrate the existence of and to quantitatively assess the first growth-modifying substance [indole-3-acetic acid (IAA)] isolated from plants.122 Plant bioassays have been extremely useful and intimately linked to the discovery and characterization of the major classes of plant hormones. In fact, many of the bioassays used now were developed for PGRs. Bioassays have been used to screen, evaluate phytotoxicity or plant growth promotion, study mode... 

I was working on a peptide growth factor with Dr. Woolley, and we isolated it and 1 sequenced it and synthesized it by standard methods. It was only a simple peptide of 5 amino acids, but it took me 10 or 12 months before 1 could make it and a couple of its analogues. I realized that peptide synthesis was quite hard to do. People who had a lot of experience could have done it faster than that, but it was still slow business, and the yields were not very good. So I had in the back of my mind that there must be a better way to do it. Then one day or one night, I don t know which, I just had this idea couldn t we anchor the peptide onto a solid support If you could put the first amino acid onto a substance that was insoluble in all the solvents you used and then you added the next amino acid and... 

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