Molecular determination disruption

Proteins that possess a quaternary structure are composed of several separate polypeptide chains held together by noncovalent interactions. When such proteins are examined under dissociating conditions (e.g., 8 M urea to weaken hydrogen bonds and hydrophobic interaction, 1 m/lf mercaptoethanol to disrupt disulfide bonds), the molecular weight of the component polypeptide chains can be determined. By comparison with the native molecular weight, it is often possible to determine how many polypeptide chains are involved in the native structure. 

After hydration, a rise in temperature causes disruption of internal structure, for example crystallites in starch or folded structure in proteins. The extent to which this is achieved is determined primarily by a specific cooperative melting event, whose temperature is dependent upon moisture content and applied pressure. If these critical conditions are reached by any part of the flow stream, then shear can cause further fragmentation of both starch granules and the polymers released from them, whereas for proteins or their dissociated subunits, molecular weights remain largely imchanged. A polymer continuous melt is formed in both cases. 

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