Phytochelatins are plants’ small metal-binding peptides which chelate internal heavy metals to form nontoxic complexes. Detecting the complexes in plants would simplify identification of cultivars with both high tolerance and enrichment capabilities for heavy metals which represent phytoextraction performance. Thus, a terahertz spectroscopy combined with density functional theory, chemometrics and circular dichroism was used for characterization of phytochelatin2 (PC₂), Cd-PC₂ mixture standards, and pak choi (Brassica chinensis) leaves as a plant model. Results showed PC₂ chelates Cd²⁺ in a 2:1 ratio to form Cd(PC₂)₂ complex; Cd connected to thoils of PC₂ and changed β-turn and random coil of PC₂ peptide chain to β-Sheet which presented as terahertz vibrations of PC₂ around 1.03 and 1.71 THz being suppressed; the best models for detecting the complex in pak choi were obtained by partial least squares regression modeling combined with successive projections algorithm selection; the models used PC₂ as a natural probe for visualizing and quantifying chelated Cd in pak choi leaf and achieved a limit of detection up to 1.151 ppm. This study suggested that terahertz information of the heavy metal-PCs complexes is qualified for representing a simpler alternative to classical index for evaluating phytoextraction performance of plant; it provided a general protocol for structure analysis and detection of heavy metal-PCs complexes in plant by terahertz absorbance.

植物螯合素是植物的小金属结合肽，可螯合内部重金属形成无毒复合物。检测植物中的复合物将简化对代表植物提取性能的重金属具有高耐受性和富集能力的栽培品种的鉴定。因此，太赫兹光谱结合密度泛函理论、化学计量学和圆二色性被用于表征植物螯合素₂ (PC ₂ )、Cd-PC ₂混合物标准品和作为植物模型的白菜( Brassica chinensis ) 叶子。结果表明PC ₂以2:1的比例螯合Cd ²⁺形成Cd(PC ₂ ) ₂复合物；Cd 连接到 PC 的 thoil₂并将PC ₂肽链的β-转角和无规卷曲改变为β-Sheet，表现为PC ₂在1.03 和1.71 THz 附近的太赫兹振动被抑制；通过偏最小二乘回归建模结合逐次投影算法选择，得到了检测白菜复合体的最佳模型；使用 PC ₂的型号作为用于可视化和量化白菜叶中螯合 Cd 的天然探针，检测限高达 1.151 ppm。该研究表明，重金属-PCs 配合物的太赫兹信息有资格代表评估植物提取性能的经典指标的更简单替代方法；为植物中重金属-PCs配合物的太赫兹吸光度结构分析和检测提供了通用方案。