| | 1 | Author
| DavidJ. Deebleab, Eberhard Bothea, Heinz-Peter Schuchmanna, BarryJ. Parsonsb, GlynO. Phillips ', Clemens Von Sonntaga | Requires cookie* | | | Title
|  | | | | Abstract
| Hydroxyl radicals were generated radiolytically in N 20 -and N 20 / 0 2(4: l)-saturated aqueous solutions o f hyaluronic acid. The hydroxyl radicals react rapidly with hyaluronic acid mainly by abstracting carbon-bound H atom s. A s a consequence o f subsequent free-radical reactions, chain breakage occurs the kinetics o f which has been followed using the pulse radio lysis technique. In the absence o f oxygen, strand breakage was followed by the change in conductivity in duced by the release o f cationic counterions condensed at the surface o f hyaluronic acid which is a polyanion consisting o f subunits o f glucuronic acid alternating with N-acetyl-glucosamine. It appears that strand breakage is not due to one single first-order process, however, the con tributions o f the different com ponents cannot be adequately resolved. At pH 7 the overall half-life is 1.4 ms, in both acid and basic solutions the rate o f free-radical induced strand breakage is accelerated (at pH 4.8, / 1/2 = 0.6 ms; at pH 10, r1/2 = 0.18 ms). In the absence o f oxygen there is no effect o f dose rate on the kinetics o f strand breakage. In the presence o f oxygen in addition to conductom etric detection, strand breakage was also followed by changes in low-angle laser light-scattering. These two techniques are com plem en tary in that in this system the conductom etry requires high doses per pulse while the light-scat tering technique is best operated in the low -dose range. In the presence o f oxygen a pro nounced dose-rate effect is observed, e.g. at pH 9.7 after a dose o f 9.4 Gy the overall half-time is approx. 0.5 s, while after a dose o f 6.6 Gy the half-time is approx. 0.23 s. Both the yield and the rate o f strand breakage increase with increasing pH, e.g. at pH 7 G(strand breaks) = 0.7 x 10"7 mol J" 1 and at pH 10.4, 4.8 x 10"7 mol J"7. The radiolytic yields o f C 0 2, H 20 2, organic hydroperoxides, 0 2'~ and oxygen consum ption have been determined in y-irradiated N 20 / 0 2(4: l)-saturated solutions o f both hyaluronic acid and ß-cyclodextrin. | | | |
Reference
| Z. Naturforsch. 45c, 1031—1043 (1990); received M ay 10 1990 | | | |
Published
| 1990 | | | |
Keywords
| Hyaluronic Acid, Strand Breakage, Pulse R adiolysis, Hydroxyl Radical, Superoxide Radical | | | |
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| default:Reihe_C/45/ZNC-1990-45c-1031.pdf | | | | Identifier
| ZNC-1990-45c-1031 | | | | Volume
| 45 | |
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