Thawari Atul Gajanan, Rao Chebrolu Pulla
Bioinorganic Laboratory, Department of Chemistry, Indian Institute of Technology Bombay , Powai, Mumbai 400 076, India.
ACS Appl Mater Interfaces. 2016 Apr 27;8(16):10392-402. doi: 10.1021/acsami.5b12591. Epub 2016 Apr 18.
A free Cys-SH-containing protein, β-lactoglobulin (β-LG), and another protein not possessing the same, viz., apo-α-lactoglobulin (apo-α-LA), were used in studies to demonstrate the role of this amino acid, along with its secondary structure, in the formation of a protein dimer and a protein-inorganic hybrid nanoflower and in the creation of the peroxidase-like activity of the nanomaterials produced when the proteins were treated with varying Cu(2+) concentration under different pH conditions. An increase in the pH as well as the Cu(2+) mole ratio results in increasing dimer formation in case of β-LG due to the presence of free Cys121-SH, while the dimer is not formed in case of apo-α-LA under the same conditions. The role of Cys in the dimer formation has been demonstrated both by MALDI and sodium dodecyl sulfate-polyacrylamide gel electrophoresis studies. Both of the proteins exhibited changes in their secondary structures to different extents as a function of pH, and the structures were stabilized by Cu(2+) interactions, as studied by CD and fluorescence spectroscopy. The small and spherical nanoparticles formed at pH 7 with lower equivalents of Cu(2+) join together to form larger aggregates at higher equivalents of Cu(2+). For the same concentration at pH 9, both the aggregates and the nanoflowers were noticed. However, at pH 12, the Cu(2+) binding induces the formation of fibers along with the flowers. Both the nanoflowers and nanofibers exhibited peroxidase-like activity in a catalytic manner. Nanoflowers were also shown to detect phenol in the concentration range from 10 to 200 μM. The copper-induced nanobiomaterial obtained in the case of apo-α-LA also exhibited peroxidase-like activity. Thus, this paper deals with the green synthesis of copper-induced protein (β-LG/apo-α-LA)-inorganic hybrid nanomaterials that are important due to their applications as nanobiomaterials.
一种含游离半胱氨酸巯基（Cys-SH）的蛋白质β-乳球蛋白（β-LG）和另一种不含该基团的蛋白质脱辅基α-乳球蛋白（apo-α-LA）被用于研究，以证明这种氨基酸及其二级结构在蛋白质二聚体和蛋白质-无机杂化纳米花形成中的作用，以及在用不同浓度的Cu(2+)在不同pH条件下处理蛋白质时所产生的纳米材料的过氧化物酶样活性的产生过程中的作用。由于存在游离的Cys121-SH，pH值以及Cu(2+)摩尔比的增加会导致β-LG形成二聚体的增加，而在相同条件下apo-α-LA则不会形成二聚体。通过基质辅助激光解吸电离飞行时间质谱（MALDI）和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）研究证明了半胱氨酸在二聚体形成中的作用。两种蛋白质的二级结构都随pH值的变化而不同程度地发生变化，并且如通过圆二色光谱（CD）和荧光光谱所研究的，其结构通过与Cu(2+)的相互作用而稳定。在pH为7时，较低当量的Cu(2+)形成的小的球形纳米颗粒会聚集在一起，在较高当量的Cu(2+)时形成更大的聚集体。对于pH为9时的相同浓度，会同时观察到聚集体和纳米花。然而，在pH为12时，Cu(2+)的结合会诱导形成纤维以及纳米花。纳米花和纳米纤维都以催化方式表现出过氧化物酶样活性。纳米花还被证明能够检测浓度范围为10至200μM的苯酚。在apo-α-LA情况下获得的铜诱导纳米生物材料也表现出过氧化物酶样活性。因此，本文涉及铜诱导的蛋白质（β-LG/apo-α-LA）-无机杂化纳米材料的绿色合成，这些纳米材料因其作为纳米生物材料的应用而具有重要意义。
