Abstract：
A detailed understanding the metals binding with algal organic matter (AOM) is essential to gain a deeper insight into the toxicity and migration of metals in algae cell. However, the molecular complexation mechanism of the metals binding with AOM remains unclear. In this study, cadmium ion (Cd2+) binding properties of AOMs from Scenedesmus obliquus, which included extracellular organic matter (EOM) and intracellular organic matter (IOM), were screened. When Cd2+ < 0.5 mg/L, the accumulation of Cd2+ could reach 40%, while Cd2+ > 0.5 mg/L, the accumulation of Cd2+ was only about 10%. EOM decreased gradually (from 8.51 to 3.98 mg/L), while IOM increased gradually (from 9.62 to 21.00 mg/L). The spectral characteristics revealed that IOM was richer in peptides/proteins and had more hydrophilic than EOM. Both EOM and IOM contained three protein-like components (containing tryptophan and tyrosine) and one humic-like component, and their contents in IOM were higher than that in EOM. The tryptophan protein-like substances changed greatly during Cd2+ binding, and that the tryptophan protein-like substances complexed to Cd2+ before tyrosine protein-like substances in IOM was identified. Moreover, the functional groups of N-H, O-H, and CO in AOM played an important role, and the N-H group was priority to interacts with Cd2+ in the complexing process. More functional groups (such as C-O and C-N) were involved in the metals complexing in EOM than in IOM. It could be concluded that Cd2+ stress promoted the secretion of AOM in Scenedesmus obliquus, and proteins in AOM could complex Cd2+ and alleviate its toxicity to algal cell. These findings provided deep insights into the interaction mechanism of AOM with Cd2+ in aquatic environments.
摘要：
详细了解金属与藻类有机物（AOM）的结合对于更深入地了解藻类细胞中金属的毒性和迁移至关重要。然而,金属与AOM结合的分子络合机制尚不清楚。在这项研究中,斜生栅藻AOM的镉离子（Cd2）结合特性，其中包括细胞外有机质(EOM)和细胞内有机质(IOM)，被筛选。当Cd2+<0.5mg/L时,Cd2+的积累量可以达到40%,当Cd2+>0.5mg/L时，Cd2+的积累量只有10%左右。EOM逐渐下降（从8.51到3.98mg/L），而IOM逐渐增加(从9.62mg/L增加到21.00mg/L)。光谱特征表明，IOM比EOM富含肽/蛋白质，并且具有更高的亲水性。EOM和IOM都含有三种蛋白质样成分（含有色氨酸和酪氨酸）和一种腐殖质样成分，它们在IOM中的含量高于EOM中的含量。色氨酸蛋白样物质在Cd2+结合过程中发生了很大变化,并且在鉴定IOM中的酪氨酸蛋白质样物质之前，色氨酸蛋白质样物质与Cd2复合。此外，N-H的官能团，O-H,CO在AOM中发挥了重要作用，在络合过程中，N-H基团优先与Cd2相互作用。与IOM相比，EOM中的金属络合涉及更多的官能团（例如C-O和C-N）。可以得出结论，Cd2胁迫促进了斜生栅藻中AOM的分泌，AOM中的蛋白质可以复合Cd2并减轻其对藻类细胞的毒性。这些发现为水生环境中AOM与Cd2的相互作用机制提供了深刻的见解。
