Desulfation, heparin

Sulfoamino groups may be restored on N-desulfated heparins by treat-... 

The nondestructive introduction of a fluorescent label would provide the molecule with a nonradioactive fluorophore, yet would preserve the option for direct radiolabelling of the fluorescent moiety with 125Iodine. This approach was pioneered by Nagasawa et al. (5) who reacted native or /V-desulfated heparins with a fluorescein isothiocyanate (FITC). The resulting degree of labelling was low... 

After hydrolysis of carboxyl-reduced and partially desulfated heparin with hydrochloric acid, Wolfrom and coworkers117 isolated a disaccharide that was identified118 as 2-amino-2-deoxy-4-0-a-D-glucopyran-osyl-D-glucopyranose ( maltosamine ) hydrochloride, which gave a crystalline N-acetyl derivative (50). This structure was subsequently... 

D-glucopyranoside (LIX and LXI R = CHs). The /3 form, with an equatorial glycosidic group, reacts faster than the a (see page 17). Desulfated heparin, with alternating a-D-glucosamine and n-glucuronic acid units, and chitosan (A -deacetylated chitin) react similarly and... 

Problems of microheterogeneity, to be discussed farther on, complicate the nomenclature of glycosaminoglycans. It is difficult, for example, to establish a clear borderline between N-sulfated heparan sulfates and the most heterogeneous heparin species. As indicated in Table I, the nomenclature of glycosaminoglycans has experienced some changes over the years. (For a discussion, see Ref. 10.) Such atypical heparins as (U-heparin (a whale heparin) and /-heparin (N-desulfated heparin) are now preferably defined in terms of their animal origin, or their chemically modified groups. 

The reaction of nitrous acid on ghicosamine containing p>olysaccharides was first studied on chitosan, which afforded 2,5-anhydro-O-maimose. The same result was obtained in the degradation of the methyl-2-amino-2-deoxy-a- or / -D-glucopyranoside. When applied to iSf-desulfated heparin, the rate of this reaction resembled more that of the a-anomer than that of the fi-anomer, thus establishing on a firmer basis the presence of the a-linkages, suggested by the positive optical rotation . 

Studies of the periodate oxidation of heparin and of its product of degradation have also been used as a basis for proposing various chemical structures. The lack of precision of this method, and the erroneous conclusion derived from similar studies on other glycosaminoglycuronoglycans, render the structural allocation uncertain. The liberation of ammonia by periodate oxidation of an A -desulfated heparin suggests, however, the absence of linkage at position 3 of the glucosamine residue . ... 

The highest reduction of albumin adsorption has been found with 6-0-desulfation of heparin. This result is consistent with those of equilibrium adsorption at longer time. The influence of iduronic acid 2-0-desulfation shows also a similar but reduced reduction of albumin adsorption compared to 6-0-desulfation. The influence of N-desulphated heparin on reduction of albumin adsorption was also pronounced but lower than that at equilibrium and 3-0-desulfated heparin showed the lowest influence. Removal ofNAc-groups and resulphation surprisingly leads to a reduced albumin concentration. The results of albumin adsorption at dynamic conditions, not shown here, show a similar trend. Also the results on fibrinogen adsorption show a similar trend at the equilibrium (not shown). 

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