REDOX REACTIVITY OF HEMOGLOBINS--SEARCH FOR A SAFER BLOOD SUBSTITUTE

假设血液滞留和毒性问题可以通过以下方法解决 血红蛋白的化学或遗传交联， 设计一种基于血红素蛋白的血液替代品是为了优化氧气 运输和稳定。血红素口袋里和周围的氨基酸 血红蛋白分子在整个进化过程中基本上是保守， 一些人类突变体和动物血红蛋白除外。 我们有 比较了大量的动物血红蛋白， 它们的配体亲和力的差异以及 血红素环境是物种分化的结果。 研究 对动物血红蛋白进行的研究似乎没有提供明确的， 氧化反应之间的可预测的相关性，而不是这些 反应似乎是由特定的化学反应决定的。 血红素蛋白，以提供物种适应不断变化的环境。 定点突变是一种潜在的有效工具， 改造血红蛋白，因为它可以微调蛋白质， 功能和稳定性。 在这一点上，肌红蛋白提供了一个简单的 这些实验的原型，确实有一些肌红蛋白， 已经制备了突变体（在赖斯大学），它们具有不同的 配体结合、自氧化和稳定性。 抹香鲸野生型 肌红蛋白（His 64），单一（V68 F）（苯丙氨酸取代缬氨酸）和 双（L29 F/H64 Q）（苯丙氨酸取代亮氨酸;谷氨酰胺取代亮氨酸） 组氨酸）突变体。 最新结果显示， 这些肌红蛋白之间的明显差异， 形成及其在溶液中的持久性。 差异在于 HOOH处理对血红素和蛋白质的氧化作用 也被观察到。 我们目前正在探索HOOH模式的机制 进入蛋白质。 这最终将有助于设计 一种可以立体化学限制HOOH进入的蛋白质， 减少其氧化作用。

Assuming that blood retention and toxicity problems can be resolved by chemical or genetic cross-linking of hemoglobin, the next step in the design of a heme protein-based blood substitutes is to optimize oxygen transport and stability. Amino acids in and around the heme pocket of the hemoglobin molecule have been largely conserved throughout evolution with the exception of some human mutants and animal hemoglobins. We have compared large number of animal hemoglobins that are known to exhibit differences in their ligand affinity as well as chemical alterations of the heme environment a result of species differentiation. Studies conducted on animal hemoglobins appear to provide no clear and predictable correlation between and oxidation reactions, rather these reactions appear to be determined by the specific chemistry of the heme-protein, to provide a species adaptability to changing environments. Site directed mutagenesis is a potentially effective tool for the engineering hemoglobin because it allows the fine tuning of protein function and stability. At this point, myoglobin has provided a simple prototype for these experiments, and that indeed a number of myoglobin mutants have been prepared (at Rice University) that are have different ligand binding, autoxidation and stability. Sperm whale wild type myoglobin (His 64), single (V68F) (phenylalanine replaces valine) and double (L29F/H64Q) (phenylalanine replaces leucine; glutamine replaces histidine) mutants have been so far studied. Results up-to-date indicate clear differences among these myoglobins in terms of the rates of ferryl formation and its persistence in solutions. Differences in terms of the oxidative effects of HOOH treatment on both the heme and the proteins were also observed. We are currently probing the mechanism of HOOH mode of entry into the proteins. This will ultimately help in the design of a protein that can stereochemically restrict the entry of HOOH and minimize its oxidative effect.