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qianminlove银虫 (小有名气)
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[交流]
求助翻译 blood plasma
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The present invention is based on the observation that improved substitutes for blood plasma can be obtained by subjecting collagen degradation products to degradation by mild hydrolysis to products having a molecular weight of 2000 to20,000, and preferably5,000-10,000, cross-linking the hydrolysate so obtained with a proportion of apolyfouctional isocyanate, smaller than that calculated for the total reaction of all the amino and guanidino groups present in the hydrolysate, and preferably amounting to 20-80% of the calculated pnoportion, and adjust ing the solution so obtained to a pH valueob about 7, if it does not have that pH value, and rendering it isotonic by the addition of sodium chloride; or by first cross-linking the collagen degradation products with a proportion of a polyfunctional isocyanate amounting to2080% od that calculated for the total reaction of all the amino and guanidino groups present, then subjecting the cross-linked product to degradation by mild hydrolysis to products having a molecular weight of10,000- 100,000, and preferably to30,000-60,000, and adjusting the solution so obtained to a pH value of about 7, if it does not have that pH value, and rendering it isotonic by the addition of sodiumchloride. The cross-linking effect is the same in both methods. The blocking of the amino or guanidino groups in the final product by the urea bridges introduced with the aid of the isocyanate alters the ratioof freecar'o:yl groups to amino groups in favour of the carboxyl groups, whereby the solubility is increased and the gelling capacity is decreased. The urea bridges newly formed by the cross linkingbe- tween the various molecules are not split under the mild conditions of hydrolysis. Splitting occurs only between the peptide linkages of the protein chains. The optimum proportion of isocyanate for the cross-linking depends on the molecular size of the hydrolysate and on the quality of the starting material used. It may be within the range of 10 to100% of the proportion calculated with reference to NH2 analysis. From a hydrolysate having a molecular weight of5,000 to10,000 especially suitable products are obtained by using30--401%' of the proportion of a polyfunctional isocyanate calculated with reference to the content of amino or guanidino groups depending on the aminoacid compositioniof the gelatine or with reference to the degree of hydrolysis. The cross-linking effect is the same in both methods. The blocking of the amino or guanidino groups in the final product by the urea bridges introduced with the aid of the isocyanate alters the ratioof freecar'o:yl groups to amino groups in favour of the carboxyl groups, whereby the solubility is increased and the gelling capacity is decreased. The urea bridges newly formed by the cross linkingbe- tween the various molecules are not split under the mild conditions of hydrolysis. Splitting occurs only between the peptide linkages of the protein chains. |
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qianminlove
银虫 (小有名气)
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2楼2008-10-17 16:38:26