Thioflavin-T is one of the most important amyloid specific dyes and has been used for more than 50 years; however, the molecular mechanism of staining is still not understood. Chemically synthesized short polyglutamine peptides (Qn, n = 5–10) were subjected to the thioflavin-T (ThT) staining assay. It was found that the minimum Qn peptide that stained positive to ThT was Q6. Two types of ThT-binding sites, a high-affinity site (kd1 = 0.1–0.17 μM) and a low-affinity site (kd2 = 5.7–7.4 μM), were observed in short polyQs (n = 6–9). 13C2H}REDOR NMR experiments were carried out to extract the local structure of ThT binding sites in Q8 peptide aggregates by observing the intermolecular dipolar coupling between [3-Me-d3]ThT and natural abundance Q8 or residue-specific [1,2-13C2] labeled Q8s. 13C2H}REDOR difference spectra of the [3-Me-d3]ThT/natural abundance Q8 (1/9) complex indicated that all of the five carbons of the glutamine residue participated in the formation of ThT-binding sites. 13C2H}DQF–REDOR experiments of [3-Me-d3]ThT/residue-specific [1,2-13C2] labeled Q8 (1/50) complexes demonstrated that the N-terminal glutamine residue had direct contact with the ThT molecule at the high-affinity ThT-binding sites.
硫黄素-T是最重要的淀粉样蛋白特异性
染料之一,已使用超过50年;然而,其染色分子机制仍未被理解。
化学合成的短多聚谷
氨酰胺肽(Qn,n = 5–10)经过
硫黄素-T(ThT)染色测定。发现能被ThT染色的最小Qn肽是Q6。在短多聚Q(n = 6–9)中观察到两种类型的ThT结合位点:高亲和力位点(kd1 = 0.1–0.17 μM)和低亲和力位点(kd2 = 5.7–7.4 μM)。进行13C2H}REDOR NMR实验以通过对[3-Me-d3]ThT和自然丰度Q8或特定位点[1,2-13C2]标记的Q8之间的分子间偶极耦合观察,提取Q8肽聚集体中ThT结合位点的局部结构。[3-Me-d3]ThT/自然丰度Q8(1/9)复合物的13C2H}REDOR差谱表明,谷
氨酰胺残基的五个碳原子均参与了ThT结合位点的形成。[3-Me-d3]ThT/特定位点[1,2-13C2]标记的Q8(1/50)复合物的13C2H}DQF–REDOR实验表明,在高亲和力ThT结合位点上,N末端谷
氨酰胺残基与ThT分子直接接触。