The study displays the immobilization of papain on cysteine functionalized iron oxide nanoparticle coated glass beads. Glass beads were treated with (3-mercaptopropyl) trimethoxysilane and iron oxide nanoparticles capped with cysteine, to create a layer of cysteine on the surface of glass bead. This functionalized glass bead surface was further used to immobilize papain through glutaraldehyde treatment. The average size of cysteine capped iron oxide nanoparticles were found to be 50 nm. The binding of cysteine through the iron oxide nanoparticles was validated by Fourier transform infra-red spectroscopy. The activity of enzyme was found to be stable at variable temperature and pH conditions. The covalently immobilized enzyme on the glass bead sustained high enzyme activity and could be reused for 5 times without losing its activity. The immobilized papain retained 81% of its initial activity after 5 consecutive cycle. The storage stability analysis of the immobilized system revealed that it is stable for 6 months without loss in its activity. An average of 1.8 mg papain was successfully immobilized per gram of glass beads. In this case cysteine emerges as a new and effective medium for immobilizing biomolecules as it provides high efficiency towards immobilization.

中文翻译：

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对可重复使用性的追求：木瓜蛋白酶在半胱氨酸官能化的氧化铁纳米粒子活化的玻璃表面上的简便稳定固定

研究显示木瓜蛋白酶固定在半胱氨酸官能化的氧化铁纳米颗粒涂层玻璃微珠上。用（3-巯基丙基）三甲氧基硅烷和覆有半胱氨酸的氧化铁纳米粒子处理玻璃珠，以在玻璃珠的表面上形成一层半胱氨酸。该功能化的玻璃珠表面还用于通过戊二醛处理固定木瓜蛋白酶。发现半胱氨酸封端的氧化铁纳米颗粒的平均尺寸为50nm。半胱氨酸通过氧化铁纳米粒子的结合已通过傅立叶变换红外光谱法进行了验证。发现酶的活性在可变的温度和pH条件下是稳定的。玻璃珠上的共价固定酶具有很高的酶活性，可以重复使用5次而不会失去其活性。固定的木瓜蛋白酶在连续5个循环后保留了其初始活性的81％。固定化系统的储存稳定性分析表明，该系统可稳定保存6个月，而不会损失其活性。每克玻璃珠平均成功固定了1.8 mg木瓜蛋白酶。在这种情况下，半胱氨酸作为固定化生物分子的一种新的有效介质而出现，因为它提供了固定化的高效率。