CrAlGe: An itinerant ferromagnet with strong tunability by heat treatment

We present a comprehensive investigation on CrAlGe and realize that it is an itinerant ferromagnet with strong tunability of the Curie temperature $T_{\rm C}$ and the spontaneous moment $\mu_0$ depending on annealing heat treatment. While the value of $T_{\rm C}$ was previously reported to be 80 K with $\mu_0\approx$ 0.41$\mu_{\rm B}$, in this work the two quantities attain values as high as 170 K and 0.66$\mu_{\rm B}$, respectively. Heat treatment does not cause changes of the lattice parameters and symmetry, but results in a slight narrowing of the Bragg peaks. The strong tunability of the itinerant ferromagnetism indicates significantly tunable hybridization between the Cr 3d electrons and the conduction bands, in agreement with the dominant Cr-Al/Ge bonds of this compound. Further tuning along the same line towards even stronger or weaker itinerant ferromagnetism promises an interesting follow-up to clarify the localized-itinerant duality of the 3d electrons in this compound.     

蝎子毒素多肽WaTx的高效化学合成及氧化折叠研究

相比于1-羟基-7-氮杂苯并三氮唑(HOAt)、1-羟基苯并三唑(HOBt)等传统偶联试剂, 新型多肽偶联试剂2-肟氰乙酸乙酯(Oxyma)具有安全、偶联效率高、消旋率低等优势, 在多肽合成特别是微波固相合成中得到广泛应用. 但是, 不同反应温度(例如28、50和75 ℃)对N,N'-二异丙基碳二亚胺(DIC)/Oxyma的偶联效率以及对甲硫氨酸(Met)等易氧化氨基酸的影响尚有待研究. 瞬时受体电位锚蛋白1(TRPA1)通道在感受温度、听觉和炎症痛中发挥重要作用. 蝎子毒素多肽芥末受体毒素(WaTx)是一种新型、非共价结合的TRPA1特异性激动剂. 本研究利用6-氯苯并三氮唑-1,1,3,3-四甲基脲六氟磷酸酯(HCTU)/N,N'-二异丙基乙胺(DIEA)和DIC/Oxyma缩合体系, 首次探索了不同温度下线性WaTx的合成效率以及Met残基的氧化情况. 通过一次氧化折叠和两次氧化折叠策略, 实现了WaTx的体外快速复性折叠, 利用圆二色谱和钙荧光检测等技术评价WaTx的结构和活性. 本研究建立了WaTx的温和、高效合成以及复性折叠方法, 为固相多肽合成特别是手动固相合成WaTx等含有易氧化基团的二硫键构象锁定多肽提供了重要参考.