Proteins natural sources

Carboline derivatives in various oxidation states have been isolated from a number of natural sources as artifacts. )3-Carboline has been obtained from charred insects, j8-carboline and l-methyl-)3-carboline have been found in cigarette smoke,and the formation of tetrahydro-j8-carboline derivatives has been shown to be responsible for the destruction of tryptophan in acid hydrolyzates of proteins. The golden-yeUow fluorescence observed when enterochromaffin cells are flxed in formaldehyde has been related to their content of... 

Microtubules (MT) are the largest of the cytoskeletal filaments with an outer diameter of about 25 nm, a wall thickness of about 5 nm, and a central lumen measuring about 15 nm. They consist of tubulin and associated proteins. Vertebrate brain tissue is a rich source of extractable tubulin because of the large numbers of microtubules that are present in axons and dendrites. Tubulin obtained from such a natural source is a heterodimer of 100 kD composed of a-tubulin and P-tubulin. Brain a-tubulin is a globular polypeptide that contains 451 amino acid residues, whereas P-tubulin, which is somewhat shorter, is made up of 445 amino acid residues. These two molecular species of tubulin share in common 40% of their amino acid residues. 

SRB contains high-quality protein, oil, dietary fiber, polysaccharides, fat-soluble phytochemicals (plant derived bioactive compounds) and other bran nutrients. Rice bran and germ are the richest natural sources of B complex vitamins as well as E vitamins, polyphenols, several antioxidants and minerals. It is now available in the commercial food ingredient market as a safe and effective functional food and dietary supplement. 

Dairy proteins are rich in nutrients and occupy a unique place of importance in food and human nutrition because of their wide acceptance in the world. Milk proteins are important in the diet because of the many health benefits associated with their consumption. The proteins have long been recognized as natural sources of health enhancing bioactive peptides because of their stmctural and physicochemical components as recently reviewed by Livney (2010). 

The first proteins from transgenic plants to reach commercial status were avidin and P-glucuronidase (GUS) both of which are used as diagnostic agents in molecular biology. An important principle demonstrated by these case studies is that molecular farming in cereals can be an economical alternative even when the natural source of a protein is abundant (i.e. egg whites for avidin, and Escherichia coli for GUS) and where a market is already established. 

Although capable of glycosylating heterologous human proteins, the glycosylation pattern usually varies from the pattern observed on the native glycoprotein (when isolated from its natural source, or when expressed in recombinant animal cell culture systems). 

To date, the lipids so far used have been mainly extracts from natural sources such as EPC and archaeal lipids[17,18] The chemical stability of EPC, however, is not sufficient and the membrane permeability to H1 is sometimes too high for quantitative analyses of membrane protein functions. Though archaeal lipids display many preferable features for... 

Much of the early work which would lead to the identification of proteins as defined chemical entities started from observations on enzymes, either those involved in fermentation or on the characterization of components in gastric secretions which powerfully catalyzed the hydrolysis of different foodstuffs. As well as the digestive enzymes, a number of relatively pure proteins could be isolated from natural sources where they made up the major component (Table 1). Because of the importance and difficulty of isolating pure proteins and demonstrating their homogeneity, functionally active and relatively abundant... 

Once the recombinant expression vectors containing the cDNA inserts are produced, they are used to transform bacteria (or other host cells) and produce cDNA (expression) libraries. Expression libraries may be used to produce recombinant proteins that in some cases have significant advantages over isolating them from natural sources ... 

Consider a molecular structure, which is the most important unifying information model in chemistry. Molecular structures appear in knowledgebases that represent catalogs of commercially available chemicals, pharmacology of named drugs, natural sources of bioactive molecules, protein-ligand interactions, measured molecular bioactivities, metabolic pathways, abstracted research literature, databases of synthetic reactions, and so on. 

Many successful protein products, including antibodies, have been marketed over the years for the treatment of a number of diseases. One of the oldest examples of a protein product is insulin, still one of the most successful drugs after 70-80 years of its discovery. Early insulin preparations, derived from natural sources, are being replaced by recombinant human insulin preparations and new formulations are being marketed that provide a more gradual and continuous release profile and maximise glucose control in diabetic patients. " ... 

Racemizations in the crystalline state have a long history. It is known that L-a-amino acids slowly racemize in the solid state [62]. As this also happens in solid proteins the implications are manifold, not only in pure chemistry but also in biochemistry, nutrition, food technology, and geology. Therefore, techniques have been developed to determine the dl ratio of amino acids down to 0.1% and inversion rate constants have been determined under acid hydrolysis conditions [63]. One could think of very slow deamination and readdition of the amine or an enolization mechanism. However, such reactions can also be induced by photolysis or radiolysis from natural sources [64]. 

Polymers derived from natural sources such as proteins, DNA, and polyhy-droxyalkanoates are optically pure, making the biocatalysts responsible for their synthesis highly appealing for the preparation of chiral synthetic polymers. In recent years, enzymes have been explored successfully as catalysts for the preparation of polymers from natural or synthetic monomers. Moreover, the extraordinary enantioselectivity of lipases is exploited on an industrial scale for kinetic resolutions of secondary alcohols and amines, affording chiral intermediates for the pharmaceutical and agrochemical industry. It is therefore not surprising that more recent research has focused on the use of lipases for synthesis of chiral polymers from racemic monomers. 

There are many instances where a problem in protein chemistry or biology can be studied efficiently and effectively by semisynthesis. For this section, semisynthesis means the combination of a synthetic peptide with a large protein segment derived from natural sources. The combination can be by a covalent peptide bond or, in certain cases, by a specific... 

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