The invention relates to the use of modified starch obtainable by treating amylose containing starch in aqueous medium with an enzyme from the group of the α-1,4-α-1,4-glucosyl transferases (EC 2.4.1.25) or an enzyme the activity of which corresponds to that of enzymes from the group just mentioned, as an agent for forming a thermoreversible gel. The invention also relates to products in the form of a thermoreversible gel having as gel-forming substance a modified starch as defined. The invention further relates to the use of a modified starch as defined in the form of an aqueous solution.
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An analysis was made of the various possible activators of single-chain urokinase-type plasminogen activator (scu-PA) in the dextran sulphate euglobulin fraction (DEF) of human plasma. scu-PA activators were detected in an assay system in which the substrate scu-PA, in physiological concentration (50 pM), was immuno-immobilized. After activation of the immobilized scu-PA for a certain period of time the activity of the generated amount of immuno-immobilized two-chain u-PA was determined with plasminogen and the chromogenic substrate S-2251. The scu-PA activator activity (scuPA-AA) in the DEF of plasmas deficient in factor XII or prekallikrein was about half of that in the DEF of normal plasma. Separation of scuPA-AA in the DEF by gel chromatography showed to major peaks, one eluting with an apparent Mr of 500,000 and the other around Mr 100,000. The former peak, which coincided with the activity peak of the kallikrein-kininogen complex, was absent in the DEF of plasma depleted of prekallikrein and therefore was identified as kallikrein. The latter peak was still present in the depleted plasma and most likely represents plasmin, because its scuPA-AA coincided with the activity peak of plasmin and could be fully inhibited by antibodies raised against human plasminogen. It is concluded that plasmin and the contact-activation factor kallikrein each contribute for about 50% to the scuPA-AA in the DEF. Compared on a molar basis, however, plasmin was found to be almost 1,000 times more effective than kallikrein, and we conclude, therefore, that in vivo plasmin is the primary activator of scu-PA and the role of the contact system is of secondary importance.
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Plastic is one of the biggest contributors to pollution of the planet. Due to the low recyclability of oil-based plastics, most plastic is being disposed into the environment. According to plastic oceans, 10 million tons of plastic are dumped into oceans annually. Currently, researchers are developing recycling methods for oil-based plastics and are looking for biobased alternatives. One of these alternatives are a class of polymers called polyhydroxyalkanoates (PHA’s). PHA’s differ from other biobased polymers, due to the process of fabrication. PHA’s are a natural polymer, acting as an energy and carbon storage for different strains of bacteria. Functioning as an energy storage, nature can break down PHA’s and PHA-based waste. (1) Different companies are working on PHA’s production, but a large deviations in physical properties were observed. This research aims to establish a relationship between the chemical and physical properties of the different PHA’s, using gel permeability chromatography (GPC), nuclear magnetic resonance (NMR) and gas chromatography-mass spectroscopy (GC-MS).
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