作者感谢 Scanley 博士为她的技术培训和帮助使用 TEM 在康涅狄格州立大学 (CSCU) 纳米技术中心和 Ishita 博士 Mukerji 在卫斯理大学访问她的 CD分 光 光度计。所报告的工作部分是在美国宇航局康涅狄格州空间赠款联合会的费尔菲尔德大学科学研究所和国家科学基金会 CHE-1624774 的资助下进行的。

1. 12-Dithiolane 改性肽的合成与纯化
<ol><li>dithiolane 前体的合成, 3-(acetylthio)-2-(acetylthiomethyl) 丙酸19。
	<ol>
<li>添加1克 3-溴-2-(溴甲基) 丙酸 (1 equiv) 溶解在极小量的1米氢氧化钠 (约4毫升) 到一个25毫升的圆形底部反应瓶搅拌在55摄氏度。在氮气气氛下, 将反应瓶密封在一个隔膜和地方。</li>
		<li>在4毫升的去离子水和3毫升的2米硫酸 (H2,4) 中, 制备含有1.49 克硫代乙酸钾 (3.2 equiv) 的溶液,在原位制造硫代乙酸酸。</li>
		<li>将硫代乙酸酸溶液拉入塑料一次性10毫升注射器, 并将针头放在注射器上。将混合物滴状到反应瓶中, 用针穿透隔膜。继续反应过夜在55摄氏度。</li>
		<li>用甲醇和二氯甲烷混合物 (1:9) 对硅胶 60 F254板上的薄层层析 (TLC) 进行反应。通过甲酚绿色染色可视化反应过程。该产品有 Rf = 0.57。</li>
		<li>在反应完成并且冷却了到室温之后, 酸化混合物到 pH 值1与 2 M H2那么4。黄色的油从溶液中分离出来。</li>
		<li>用冷氯仿提取产品 (40 毫升 x 3)。将有机层和干燥的硫酸镁结合在一起。在减压下取出氯仿。</li>
		<li>通过核磁共振 (NMR) 光谱学 (如图 1B和C所示) 确认隔离产品1的身份。期望以下结果: 1h 核磁共振, CDCl3, 300 兆赫: d = 10.1 (b, 1 h), 3.2 (m, 4 h), 2.9 (m, 1 h), 2.4 (s, 6 h);13c 核磁共振, CDCl3, 75 兆赫: d = 195.1 (CH3COS-), 177.6 (-c哦), 45.1 (-ch2S), 30.5 (Ch), 29.2 (-上海合作组织Ch3)。 注: 该产品为黄油, 总收率为83%。使用该产品无需进一步净化。</li>
	</ol></li>
	<li>Dithiolane 前驱体的许可证与树脂耦合 注: 下面描述的固相肽合成是根据推荐的制造商的协议在自动肽合成器上进行的。设置和试剂可适用于其他商业仪器或使用专用氨基酸。<ol>
<li>在反应容器中称量0.156 克的溜冰场酰胺 4-methylbenzhydrylamine (MBHA) 树脂 (0.1 毫摩尔) 和位置。在合成开始前, 将树脂在甲基酰胺 (DMF) 中膨胀至少15分钟。</li>
		<li>将每个 fluorenylmethyloxycarbonyl (n-芴甲氧羰基) 受保护氨基酸 (0.4 毫摩尔) 的4当量与0.152 克n、n、n、n '-四甲基O(1Hbenotriazol 1 基) 铀六氟磷酸盐 (0.4 毫摩尔、HBTU) 进行权衡, 以序列中的每个氨基酸。每个墨盒都含有 n-芴甲氧羰基保护的氨基酸和 HBTU。</li>
		<li>在对合成器 (重新灌装试剂、冲洗试剂线和加压的所有试剂瓶) 进行所有预合成检查后, 将氨基酸盒放入 C ' 到 N ' 终点方向的旋转木马中。放置一个空墨盒后, 最终的氨基酸位置为最终 n-末端芴甲氧羰基脱步骤。</li>
		<li>使用标准推荐设置合成肽。<ol>
<li>Deprotect 甲氧羰基基团从树脂与5毫升20% 哌啶在 DMF (5 分钟 x 2)。</li>
			<li>在联轴器步骤前, 用 DMF (6 x 5 毫升) 清洗树脂。</li>
			<li>对于单一的耦合步骤, 在 DMF 中加入4毫升的0.4 米 n-甲基啉) 到 n-芴甲氧羰基保护的氨基酸和 HBTU。在将溶液转移到反应容器之前, 激活三十年代的芴甲氧羰基保护氨基酸溶液。 注: 自动肽合成器混合树脂和解决方案通过冒泡 N2气体每三十年代20分钟, 而耦合反应发生的地方。对于人工肽合成, 在耦合步骤的持续时间内, 将反应容器以低速的速度放置在轨道振动筛上。</li>
			<li>排出溶液, 用 DMF (3 x 5 毫升) 清洗树脂。</li>
			<li>重复步骤1.2.4.1 通过1.2.4.4 的每一个 n-芴甲氧羰基保护氨基酸在 C ' 到 N '-终点方向合成的肽感兴趣。</li>
		</ol>
</li>
		<li>最后的 N 端脱步骤后, 将树脂转移到一次性烧结注射器中。用 DMF (3 x 5 毫升) 和二氯甲烷 (DCM, 3 x 5 毫升) 洗涤树脂。 注: 树脂可贮存后, 在真空干燥的 DCM 洗涤。如果树脂以前储存在联轴器上, 在偶联反应之前确保在 DMF 中膨胀树脂。</li>
		<li>将 dithiolane 前驱体 (1) 加入4当量1、5毫升 DMF、4当量的 HBTU 和10当量的 n、n-diisopropylethylamine (DIPEA), 对树脂肽的 N 端进行耦合。在加入含有烧结注射器的树脂之前, 先激活10分钟的耦合混合物。</li>
		<li>震动2小时的耦合反应。2小时后, 用 DMF (3 x 5 毫升) 清洗树脂, 并在一夜之间反复晃动耦合反应。</li>
		<li>第二联轴器后, 用 DMF (3 x 5 毫升) 和 DCM (3 x 5 毫升) 清洗树脂。 注 : 树脂可储存在真空下直至。</li>
	</ol></li>
	<li>树脂硫代乙酸脱和肽的裂解
	<ol>
<li>从 dithiolane 前驱体 deprotect 硫代乙酸组, 将干树脂转移到10毫升微波反应管中, 加入2毫升的 DMF。允许树脂膨胀, 加入一个小的磁力搅拌条到容器中, 并以低速磁搅拌的速度重新悬浮15分钟。</li>
		<li>加入2毫升的浓缩氢氧化铵, 将反应容器盖上硅胶隔膜, 将反应容器放入微波反应器中, 使用75°c 的微波设置, 搅拌45分钟。</li>
		<li>微波反应完成后, 将树脂转移到干净的一次性烧结注射器中。用 DMF (2 x 5 毫升) 和甲醇 (甲醇, 2 x 5 毫升) 洗涤。</li>
		<li>在甲醇 (1:4) 中加入浓缩氢氧化铵溶液, 总容积为5毫升。留在夜间摇晃, 以增加 dithiolane 环中二硫键的分子内氧化。</li>
		<li>用甲醇 (2 x 5 毫升) 和 DCM (3 x 5 毫升) 清洗树脂。 注: 干燥的树脂可以储存在真空干燥在这一点上。</li>
		<li>在含有注射器的树脂中加入裂解鸡尾酒, 轻轻摇动1.5 小时。所用的裂解鸡尾酒是95% 三氟乙酸酸 (TFA), 2.5% triisopropylsilane (提示), 2.5% 水在总容积5毫升。 注意事项: 仅在化学油烟机下工作。TFA 易挥发和腐蚀性。 注 : 对于多数肽序列和氨基酸边链保护组 , 上述鸡尾酒溶液是足够的 ;然而, 某些氨基酸侧链保护组 (特别是含有胱氨酸、满足、多党和 Arg 的多肽) 或其他树脂化学20可能需要替代的裂解鸡尾酒。</li>
		<li>将粗肽沉淀到25毫升的冷二乙基醚在50毫升圆锥管通过滴状添加从烧结注射器。肽沉淀成白色固体。以 1300 x g 为10分钟的离心法将该肽颗粒醒酒. 小心地将二乙基醚放入一个单独的容器中进行废物收集。</li>
		<li>再将25毫升乙醚加入锥形管, 再用涡流重新悬浮沉淀。重复离心在 1300 x g 10 分钟和醒酒二乙基醚再次。在真空下干燥颗粒。</li>
	</ol></li>
	<li>12-Dithiolane 改性肽的纯化 注: 采用反相高效相色谱法提纯粗肽。用 MALDI 质谱法采集和组合肽峰, 确认质量。<ol>
<li>用 0.1% TFA, 将微量的乙腈中的粗肽颗粒溶解。由于肽的疏水性和聚集倾向, 轻轻地加热样品在40°c, 以帮助溶解度。 注意: 避免更高的温度和超声波的肽, 以防止潜在的二硫化物交换反应21,22,23。</li>
		<li>为高效液相色谱纯化制备1毫升粗肽, 在乙腈中加入 400 ul 的浓缩肽库, 600 ul 为 H2O, 0.1% TFA, 通过22微米注射器过滤器将其过滤成 hplc 瓶。另外还可以添加5% 异丙醇, 以防止肽聚集和沉淀。</li>
		<li>用 C-18 半制备柱, 在15-55% 乙腈的线性梯度20分钟内, 用3毫升/分钟的流速纯化肽. 将紫外线探测器设置为 222 nm (酰胺骨干) 和 330 nm (二硫化物键)。收集并合并感兴趣的峰值 (图 2A)。</li>
		<li>在 reflectron 模式下, 通过 MALDI 质谱仪确认肽类产品质量 (图 2B)。为分析, 混合 0.5 ul 的收集峰值在 MALDI 板与 0.5 ul 25-苯甲酸酸 (DHB) 基质 (10 毫克/毫升 DHB 在50% 乙腈, 0.1% TFA)。 注: MALDI 质谱中常见的加合物包括钠和钾盐加合物 ([m + Na]+和 [m + K]+) 峰。如果盐加成峰抑制主 [米 + H]+峰值的信号, 则建议在分析之前对样品进行脱盐。此外, 在 12-dithiolane 修饰肽中也检测到 [M + O]+的氧化峰。利用 DHB 基质对激光诱导氧化的 MALDI 电离研究表明, 可以对样品浓度、溶剂和激光强度等因素进行修正, 以限制 MALDI 诱导氧化工件24。</li>
		<li>在 MALDI 确认正确质量后, lyophilize 在闪光冷冻后的肽。将冻干肽粉保持在真空下直至组装。</li>
	</ol></li>
</ol>2. 超分子自组装结构的表征
<ol><li>
淀粉样纤维的形成
	<ol>
<li>要准备自组装溶液, 用分析天平称量1毫克的肽粉。溶解成混合物 (pH 7.5) 的20% 乙腈和10毫米 (4-(2-羟乙基)-1-piperazineethanesulfonic 酸 (HEPES) 在1.5 毫升离心管, 最终浓度的1毫克/毫升肽组装混合物。涡流装配解决方案, 并在室温下组装。</li>
	</ol>
</li>
	<li>
淀粉样纤维的光谱表征
	<ol>
<li>通过傅里叶变换红外光谱 (FTIR), 每隔几天跟踪多肽组装过程。以1670厘米-1为中心的宽峰为样本17中未组装肽引起的 IR 特征。多肽组装样品通常需要一到两周的时间才能使宽未组装峰消失并达到成熟。<ol>
<li>干燥整除 8-10 ul 的组装解决方案作为一个薄膜上的 ATR 金刚石晶体。监测1640年至1630厘米-1的大型和宽水位的消失, 作为干膜形式。</li>
			<li>获取红外光谱从 1500-1800 cm-1平均50扫描与 2 cm-1决议。在每次采样扫描之前获取和减去背景扫描。β薄板组件的 IR 签名是介于1625和1635厘米-1 (图 3A)25、26之间的尖峰。</li>
		</ol>
</li>
		<li>用圆形二色谱 (CD) 表征多肽组装成β片丰富的超分子结构。使用 CD spectropolarimeter 与珀尔温度控制系统记录光谱。<ol>
<li>吸管 30 ul 的装配解决方案在0.1 毫米的路径长度 microcuvette。 注: 在仪器中, 需要一个电池架来夹紧和定位短路径长度单元格。</li>
			<li>对于每个频谱, 将 CD 仪器设置为以下参数: 扫描波长为 300 nm 到 180 nm, 扫描速率为 100/分钟, 波段宽度为 1 nm, 25 °c, 平均三扫描。</li>
			<li>收集缓冲区的频谱 (20% acetonitrile/10 mM HEPES, pH 值 7.5), 并减去每个样本扫描作为一个控制。β片的 CD 签名是一个椭圆的最小值, 其中心约为 220 nm (图 3B)27。</li>
		</ol>
</li>
	</ol>
</li>
	<li>
淀粉样纤维显微术
	<ol>
<li>允许三周的多肽样品成熟成β片丰富的超分子结构。 注: 在装配过程的早期阶段, 可以使用透射电镜 (TEM) 对组件进行成像。<ol>
<li>将肽组装溶液的 10 ul 在 TEM 碳网格表面上。 注意: 小心不要接触到网格表面的吸管尖端。在制备过程中, 采用高精度、自闭镊子来控制 TEM 网格。</li>
			<li>等待1-2 分钟, 以允许组件吸附到网格表面上。通过触摸滤纸到网格边缘, 删除多余的样品。</li>
			<li>通过将 100 ul 的去离子水添加到商业上4% 的醋酸盐溶液中, 制备出2% 的醋酸铀染色。吸管 10 ul 2% 的醋酸铀染色到网格表面和孵化2-3 分钟。孵化后, 通过触摸滤纸到网格边缘, 去除多余的污渍。</li>
			<li>将 TEM 网格放在真空干燥过夜。储存在真空下直到成像。</li>
			<li>用 TEM (图 3C) 对准备好的样品进行图像处理。显微镜的典型参数如下: 图像在放大范围从9,300X 到 23,000X, 钨灯丝与加速电压 120 kV。 注: ImageJ 可用于测量获得 TEM 图像的超分子结构的平均纤维宽度28。 警告: 使用前请查阅所有相关的安全数据表 (SDS)。所述 12-dithiolane 修饰自组装肽的合成、纯化和表征中使用的几种化学物质具有腐蚀性或毒性, 只应在化学油烟机下使用。在实验室工作时, 应始终使用适当的个人防护设备 (包括安全眼镜、实验室大衣、全长长裤、闭趾鞋)。</li>
		</ol>
</li>
	</ol>
</li>
</ol>

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C. A., Santiago, G. M., Tezcan, M., Krasnikov, V. V., Otto, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-assembly+can+direct+dynamic+covalent+bond+formation+toward+diversity+or+specificity.">Self-assembly can direct dynamic covalent bond formation toward diversity or specificity.</a> Journal of the American Chemical Society. 139, 6234-6241 (2017).</li><li>McAvery, K. M., Guan, B., Fortier, C. A., Tarr, M. A., Cole, R. 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B., Luyendijk, W., Frangione, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hereditary+cerebral+hemorrhage+with+amyloidosis+in+patients+of+Dutch+origin+is+related+to+Alzheimer+disease.">Hereditary cerebral hemorrhage with amyloidosis in patients of Dutch origin is related to Alzheimer disease.</a> Proceedings of the National Academy of Sciences of the United States of America. 84, 5991-5994 (1987).</li><li>Barth, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+infrared+absorption+of+amino+acid+sidechains.">The infrared absorption of amino acid sidechains.</a> Progress in Biophysics and Molecular Biology. 74, 141-173 (2000).</li><li>Jayaraman, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Slow+amyloid+nucleation+via+&#945;-helix-rich+oligomeric+intermediates+in+short+polyglutamine-containing+Huntingtin+fragments.">Slow amyloid nucleation via &#945;-helix-rich oligomeric intermediates in short polyglutamine-containing Huntingtin fragments.</a> Journal of Molecular Biology. 415, 881-899 (2012).</li></ol>

作者没有什么可透露的。

本文讨论了 n-端 12-dithiolane 修饰自组装肽的合成和纯化的细节, 以及由此产生的超分子结构的特性。本报告所报道的 12-dithiolane 肽的合成具有优点, 包括一步法合成制备 dithiolane 前驱体、3-(acetylthio)-2-(acetylthiomethyl) 丙酸, 以及在树脂上微波脱反应的前体硫代乙酸保护基团, 利用氢氧化铵作为一种较安全的替代物, 脱29的毒性肼, 产生氧化的 12-dithiolane 基团。12-dithiolane 肽 (图 1A) 的整体固相肽合成可以通过改变序列长度和组成, 包括使用 n-芴甲氧羰基保护的非自然氨基酸和 C 端树脂化学来适应许多不同的研究应用。
为了防止不需要的肽副产品, 当氨基酸与亲核侧链或氨基酸与保护组有反应裂解产物, 额外的清道夫应添加到裂解鸡尾酒20。在树脂微波脱步骤前, 可以进行一小部分 (不到10% 的总树脂) 的试裂, 以保证耦合反应的高收率。利用该报告中描述的柱和 HPLC 条件, 硫代乙酸保护 12-dithiolane 前体肽峰值 elutes 5 分钟后游离胺肽。如果有大量的游离胺肽残留, 建议使用 3-(acetylthio)-2-acetylthiomethyl 丙酸的另一个耦合步骤。通过监测 330 nm 的弱二硫键吸收率, 在 HPLC 中检测出内 12-dithiolane 二硫键。用100升100毫米 (2-羧乙基) 膦 (TCEP) 在分离的高效液相色谱中加入多肽样品, 证实了与氧化 12-dithiolane 相对应的高效液相色谱峰。TCEP 还原硫醇含有的肽的保留时间与氧化二硫肽的保持期不同。含硫醇的肽 elutes 的含量比二硫化肽高约1分钟, 使用本报告中描述的列和条件。一个合适的替代 MALDI 矩阵的多肽是α-氰基-4-肉桂酸 (CHCA), 并准备添加1毫升50% 乙腈 0.1% TFA 5 毫克 CHCA。如果盐加合物 (Na+和 K+) 峰值显著抑制 [M + H]+峰值, 则在 MALDI 淡化质量分析之前使用 C18 的拉链尖端可以对样品进行检测。
为这些研究选择的肽序列来源于荷兰突变体的 Aβ肽与阿尔茨海默氏病相关的30, 并曾被证明自组装成淀粉样纤维的平行β片16,17.如代表结果所示,图 3A-dithiolane-KLVFFAQ-NH2肽也组装成淀粉样纤维。红外酰胺 I 拉伸中心在 1627cm-1和 CD 椭圆最小在218毫微米是β板材汇编25,26,27和羰基 CO 舒展在 1676 cm-1 的光谱署名相应的谷氨酰胺侧链相互作用表明, 肽是组织在平行β链16,31,32。
透射电子显微图像, 使用2% 醋酸铀的负染色, 显示延伸和扭曲的超分子纤维, 大约 10 nm 宽度。n-末端乙酰肽的纤维, Ac-KLVFFAQ-NH2, 是光滑和平直的, 以稍微更大的宽度几乎12毫微米16。由于制备 tem 网格和获取图像是一个时间密集型的过程, 最好是在不同的肽浓度一次, 从同一装配样品中制备几个 TEM 网格。为 TEM (1:50 或 1:100) 与原装配溶液样品一起准备稀释样品。高浓度的淀粉样纤维在团簇或斑块上可能附着在网格上, 并且获得单个纤维的图像可能很难。在宽度测量中看到各个光纤的边缘是很重要的, 而纤维螺旋的可视化往往被过度拥挤的样品所遮蔽。
随着越来越多的使用超分子生物材料的应用正在探索中, 有必要将具有正交性的活性官能团整合到自组装的单体中。本报告中描述的方法突出了一种树脂法合成 12-dithiolane 修饰自组装肽和光谱特性的超分子结构。

固相肽合成中的健壮肽键形成化学和控制序列长度和成分的能力使自组装成超分子结构的多肽成为一个研究领域。控制和稳定肽自组装结构的因素, 包括侧链空间和静电相互作用, 氢键和疏水效应1, 作为一套设计规则。随着对这些基本设计规则的研究继续进展, 肽自组装的逻辑下一步包括扩大肽基结构和功能的多样性。自组装多肽是一种多功能生物材料, 通过调整肽序列或装配条件2、3、4, 为许多医学应用而使用, 发展战略为对多肽纳米纤维5、6、7、8、9的组装后的修改仍然是一个相对未开发的领域。
超分子结构表面的动态二硫化物交换和硫醇化学是一个有潜力产生新的和功能性生物材料的领域。12-dithiolane 基团 (通常是硫辛酸 (la) 或 asparagusic 酸 (aa) 的衍生物) 在脂质体系统10、11、嵌段共聚物12、13和组织锚在表面14,15。在这里, 我们报告的合成和表征的自组装肽来源于与阿尔茨海默病相关的 Aβ肽的核核, 在 N 终点被修改 12-dithiolane 功能组16, 17。由此产生的超分子纤维作为实验平台, 研究了淀粉样纤维的超分子表面的二硫交换和硫醇反应性.18。

<table>
	<tbody>
		<tr>
			<td>Rink amide MBHA resin, high load</td>
			<td>Gyros Protein Technologies</td>
			<td>RAM-5-HL</td>
			<td>Avoid contact with skin and eyes; do not inhale</td>
		</tr>
		<tr>
			<td>N,N-Dimethylformamide</td>
			<td>Fisher Scientific</td>
			<td>D119-4</td>
			<td>Flammable liquid and vapor; irritating to eyes and skin; Use personal protective equipment; keep away from open flame</td>
		</tr>
		<tr>
			<td>Fmoc-L-Val-OH</td>
			<td>Gyros Protein Technologies</td>
			<td>FLA-25-V</td>
			<td>Wear personal protective equipment; do not inhale</td>
		</tr>
		<tr>
			<td>Fmoc-L-Leu-OH</td>
			<td>Gyros Protein Technologies</td>
			<td>FLA-25-L</td>
			<td>Wear personal protective equipment; do not inhale</td>
		</tr>
		<tr>
			<td>Fmoc-L-Lys(Boc)-OH</td>
			<td>Gyros Protein Technologies</td>
			<td>FLA-25-KBC</td>
			<td>Wear personal protective equipment; do not inhale</td>
		</tr>
		<tr>
			<td>Fmoc-L-Phe-OH</td>
			<td>Gyros Protein Technologies</td>
			<td>FLA-25-F</td>
			<td>Wear personal protective equipment; do not inhale</td>
		</tr>
		<tr>
			<td>Fmoc-L-Ala-OH</td>
			<td>Gyros Protein Technologies</td>
			<td>FLA-25-A</td>
			<td>Wear personal protective equipment; do not inhale</td>
		</tr>
		<tr>
			<td>Fmoc-L-Gln(Trt)-OH</td>
			<td>Gyros Protein Technologies</td>
			<td>FLA-25-QT</td>
			<td>Wear personal protective equipment; do not inhale</td>
		</tr>
		<tr>
			<td>N,N,N&#8242;,N&#8242;-Tetramethyl-O-(1H-benzotriazol-1-yl)uronium hexafluorophosphate</td>
			<td>Gyros Protein Technologies</td>
			<td>26432</td>
			<td>Causes skin, eye and respiratory irritation; do not inhale; use under hood or in well ventilated area</td>
		</tr>
		<tr>
			<td>0.4 M N-methylmorpholine in DMF</td>
			<td>Gyros Protein Technologies</td>
			<td>PS3-MM-L</td>
			<td>highly flammable; wear personal protective equipment; keep away from heat and keep container tightly closed; do not inhale or swallow; wash skin thoroughly after handling</td>
		</tr>
		<tr>
			<td>20% piperidine in DMF</td>
			<td>Gyros Protein Technologies</td>
			<td>PS3-PPR-L</td>
			<td>Causes severe eye and skin burns; Flammable Liquid and vapor; Do not inhale</td>
		</tr>
		<tr>
			<td>dichloromethane</td>
			<td>Fisher Scientific</td>
			<td>D37-4</td>
			<td>May cause cancer; Do not inhale; Wear personal protective equipment; use under hood only; if contacted rise with water for at least 15 minutes and obtain medical attention</td>
		</tr>
		<tr>
			<td>acetonitrile</td>
			<td>Fisher Scientific</td>
			<td>A998-4</td>
			<td>Flammable; irritating to eyes; Use personal protective equipment; Use only under a fume hood; keep away from open flame or hot surface; if contacted rinse wiith water for at least 15 minutes and obtain medical attention</td>
		</tr>
		<tr>
			<td>trifluoroacetic acid</td>
			<td>Fisher Scientific</td>
			<td>A116-50</td>
			<td>Causes severe burns; do not inhale; harmful to aquatic life; use personal protective equipment; use only under fume hood; if contacted rinse with water for at least 15 minutes and obain immediate medical attention</td>
		</tr>
		<tr>
			<td>4% uranyl acetate</td>
			<td>Electron Microscopy Sciences</td>
			<td>22400-4</td>
			<td>Do not inhale; harmful to aquatic life</td>
		</tr>
		<tr>
			<td>4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid</td>
			<td>Acros Organics</td>
			<td>AC172571000</td>
			<td>Do not inhale; use outdoors or in well-ventilated area</td>
		</tr>
		<tr>
			<td>nitrogen Gas</td>
			<td>TechAir</td>
			<td></td>
			<td>Contents under pressure, may explode if heated</td>
		</tr>
		<tr>
			<td>3-bromo-2-(bromomethyl)propionic acid</td>
			<td>Alfa Aesar</td>
			<td>AAA1963014</td>
			<td>Do not inhale; causes irritation to skin and eyes; corrosive</td>
		</tr>
		<tr>
			<td>sodium hydroxide</td>
			<td>Fisher Scientific</td>
			<td>S318-100</td>
			<td>Use personal protective equipment; use only under fume hood; if contact rinse area for at least 15 minutes and obtain medical attention</td>
		</tr>
		<tr>
			<td>potassium thioacetate</td>
			<td>Acros Organics</td>
			<td>AC221300250</td>
			<td>Causes skin and eye irritation; do not inhale; use personal protective equipment</td>
		</tr>
		<tr>
			<td>sulfuric acid</td>
			<td>Fisher Scientific</td>
			<td>SA213</td>
			<td>Causes burns; keep away from water; keep away from combustible material; do not inhale; use personal protective equipment; if contact rinse area for at least 15 minutes and obtain medical attention</td>
		</tr>
		<tr>
			<td>chloroform-d</td>
			<td>Acros Organics</td>
			<td>AC320690075</td>
			<td>Possible cancer hazard; irritating to skin and eyes; do not inhale; Use personal protective equipment; use only under fume hood; If contact rinse area for at least 15 minutes and obtain medical attention</td>
		</tr>
		<tr>
			<td>chloroform</td>
			<td>Fisher Scientific</td>
			<td>C298-4</td>
			<td>Possible cancer hazard; irritating to skin and eyes; do not inhale; Use personal protective equipment; use only under fume hood; If contact rinse area for at least 15 minutes and obtain medical attention</td>
		</tr>
		<tr>
			<td>N,N-diisopropylethylamine</td>
			<td>Acros Organics</td>
			<td>AC367841000</td>
			<td>Highly flammable; harmful to aquatic life; wear personal protective equipment; do not swallow</td>
		</tr>
		<tr>
			<td>ammonium hydroxide</td>
			<td>Fisher Scientific</td>
			<td>A669S-500</td>
			<td>Corrosive; do not inhale</td>
		</tr>
		<tr>
			<td>methanol</td>
			<td>Fisher Scientific</td>
			<td>A452-4</td>
			<td>Flammable liquid and vapor; use personal protective equipment; do not inhale; If contact rinse area for at least 15 minutes and obtain medical attention</td>
		</tr>
		<tr>
			<td>triisopropylsilane</td>
			<td>Sigma Aldrich</td>
			<td>233781</td>
			<td>Flammable; use personal proctective safety equipment; keep container tightly closed</td>
		</tr>
		<tr>
			<td>diethyl ether</td>
			<td>Fisher Scientific</td>
			<td>E138-1</td>
			<td>Extremely flammable; Irritating to skin and eyes; Use personal protective equipment</td>
		</tr>
		<tr>
			<td>2,5-dihydroxybenzoic acid</td>
			<td>Sigma Aldrich</td>
			<td>39319-10x10MG-F</td>
			<td>do not inhale; irritating to skin and eyes</td>
		</tr>
		<tr>
			<td>alpha-cyano-4-hydroxycinnamic acid</td>
			<td>Alfa Aesar</td>
			<td>AAJ67635EXK</td>
			<td></td>
		</tr>
		<tr>
			<td>c18 zip-tip</td>
			<td>Millipore</td>
			<td>ZTC18S096</td>
			<td></td>
		</tr>
		<tr>
			<td>tris(2-carboxyethyl) phospine hydrochloride</td>
			<td>Thermo Scientific</td>
			<td>PI20490</td>
			<td></td>
		</tr>
		<tr>
			<td>silica gel 60 F254 coated aluminum-backed TLC sheets</td>
			<td>EMD Millipore</td>
			<td>1.05549.0001</td>
			<td></td>
		</tr>
		<tr>
			<td>Thin walled Precision NMR tubes</td>
			<td>Bel-Art</td>
			<td>663000585</td>
			<td>5mm O.D.</td>
		</tr>
		<tr>
			<td>All-plastic Norm-Ject syringes</td>
			<td>Air Tite</td>
			<td>AL10</td>
			<td></td>
		</tr>
		<tr>
			<td>single-use needle</td>
			<td>BD PrecisionGlide</td>
			<td>BD 305185</td>
			<td>used needles get disposed on in sharps waste container</td>
		</tr>
		<tr>
			<td>disposable fritted syringe</td>
			<td>Torviq</td>
			<td>SF1000LL</td>
			<td>10mL fritted syringes were used in the report, but larger syringes are avaibale if needed for larger scale synthesis.</td>
		</tr>
		<tr>
			<td>carbon grid</td>
			<td>Ted Pella, Inc.</td>
			<td>CF200-CU</td>
			<td>Make sure to prepare samples and staining on the carbon grid side, not the shiny copper side of grid</td>
		</tr>
		<tr>
			<td>self-closing tweezers</td>
			<td>Electron Microscopy Sciences</td>
			<td>78318-3X</td>
			<td>very sharp tips, length: 120 mm</td>
		</tr>
		<tr>
			<td>0.1 mm short path length cell</td>
			<td>Starna Cells, Inc.</td>
			<td>20/C-Q-0.1</td>
			<td>Fragile</td>
		</tr>
		<tr>
			<td>10mL Vessel Caps</td>
			<td>CEM</td>
			<td>909210</td>
			<td></td>
		</tr>
		<tr>
			<td>10mL Pressure Vessels</td>
			<td>CEM</td>
			<td>908035</td>
			<td></td>
		</tr>
		<tr>
			<td>Aeris Semi-Prep HPLC column</td>
			<td>Phenomenex</td>
			<td>00F-4632-N0</td>
			<td>150 x 10mm</td>
		</tr>
		<tr>
			<td>cell holder</td>
			<td>Starna Cells, Inc.</td>
			<td>CH-2049</td>
			<td>Needed when using short pathlength cells</td>
		</tr>
		<tr>
			<td>PS3 peptide synthesizer</td>
			<td>Gyros Protein Technologies</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DiscoverSP Microwave Reactor</td>
			<td>CEM</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>centrifuge</td>
			<td>HERMLE</td>
			<td>Z 206 A</td>
			<td>used a fixed 6x50 mL rotor</td>
		</tr>
		<tr>
			<td>HPLC</td>
			<td>Shimadzu</td>
			<td></td>
			<td>UV Detector</td>
		</tr>
		<tr>
			<td>nuclear magnetic resonance spectrometer</td>
			<td>Avance, Bruker</td>
			<td></td>
			<td>300 MHz</td>
		</tr>
		<tr>
			<td>MALDI-TOF mass spectrometer</td>
			<td>Axima Confidence, Shimadzu</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>lyophilizer</td>
			<td>Millrock Technology</td>
			<td>BT85A</td>
			<td></td>
		</tr>
		<tr>
			<td>Fourier-Transform Infrared Spectrometer</td>
			<td>Alpha Tensor, Bruker</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Transmission Electron Microscope</td>
			<td>Tecnai Spirit, FEI</td>
			<td></td>
			<td>Used with Gatan Orius Fiberoptic CCD digital camera. Accessed at CSCU Center for Nanotechnology</td>
		</tr>
		<tr>
			<td>Circular Dichroism Spectropolarimeter</td>
			<td>J-810, JASCO</td>
			<td></td>
			<td>Used with a six-cell Peltier temperature controller. Accessed at Wesleyan University.</td>
		</tr>
	</tbody>
</table>

synthesis and characterization of 1,2-dithiolane modified self-assembling peptides

本报告的重点是合成一个 n-终点 12-dithiolane 修饰自组装肽, 并描述了由此产生的自组装超分子结构。合成路线利用固相肽合成与 dithiolane 前体分子的树脂耦合, 3-(acetylthio)-2-(acetylthiomethyl) 丙酸, 和微波辅助硫代乙酸脱的肽从树脂最终裂解前的 N 终点, 产生 12-dithiolane 修饰肽。用高效液相色谱 (HPLC) 纯化 12-dithiolane 肽, 从 Aβ肽与阿尔茨海默病相关的核核中提取, 该肽显示为自组装成交叉β淀粉样纤维。介绍了用傅里叶变换红外光谱 (IR)、环形二色谱光谱 (CD) 和透射电镜 (TEM) 表征淀粉样纤维的协议。采用 12-dithiolane 基团对特征自组装肽进行 n-末端修饰的方法, 现在可以作为模型系统来开发装配后的修改策略, 并探讨动态共价键化学在超分子肽碳纤维表面。

除了最初一步合成的 dithiolane 前体分子, 其余的 12-dithiolane 改良肽合成发生在坚实的支持 (图 1A)。3-溴-2-溴甲基丙酸转化为 3-(acetylthio)-2-(acetylthiomethyl) 丙酸, dithiolane 前驱体, 由1H 和13C 核磁共振 (图 1B和c) 确认, 然后再耦合到自由肽的 n-末端胺仍然在树脂。用氢氧化铵脱硫代乙酸到硫醇, 在 12-dithiolane 改性肽从树脂中裂解之前, 12-dithiolane 在甲醇中被氧化一夜。采用反相色谱法纯化粗肽 (图 2A), MALDI 质谱法 (图 2B) 证实了产品质量。
纯化的 12-dithiolane 肽自组装成成熟的淀粉样纤维在2-3 周期间。红外光谱 (图 3A) 和 CD 光谱学 (图 3B) 是用来跟踪组装过程和特征的扩展β表构象。光纤由透射电镜成像 (图 3C)。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58135/58135fig1.jpg"> 图1。12-dithiolane 前体分子表征的合成方案.(A)合成方案的最终 12-dithiolane 改良肽, 12-dithiolane-KLVFFAQ-NH2。(B) 1H 核磁共振 3-(acetylthio)-2-(acetylthiomethyl) 丙酸在 CDCl3在300兆赫. (c)13 C 核磁共振 nmr 3-(acetylthio)-2-(acetylthiomethyl) 丙酸在 CDCl3在75兆赫.<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58135/58135fig1large.jpg" target="_blank">请点击这里查看此图的较大版本.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58135/58135fig2.jpg"> 图2。12-dithiolane 改性肽的合成。 (A)高效液相色谱法纯化 12-dithiolane-KLVFFAQ-NH2。(B)采用 DHB 矩阵的 reflectron 模式下, 以高效液相色谱纯化 (17.5 分钟的保留时间) 为主要峰值 MALDI 的质量谱证实了 12-dithiolane KLVFFAQ-NH2的计算质量。还确定了常见的加合物。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58135/58135fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58135/58135fig3.jpg"> 图3。12-dithiolane 修饰肽的超分子特性。(A)红外光谱1毫克/毫升 12-dithiolane KLVFFAQ-NH2纤维组装 10mM HEPES, pH 7.5 在 20% CH3CN。峰值在1627厘米-1是一致的多肽组装在β表构象。(B) CD 1 毫克/毫升 12-dithiolane KLVFFAQ-NH2纤维组装在10毫米 HEPES, pH 7.5 在 20% CH3CN。椭圆最小值在218毫微米是一致的多肽组装在β表构象。(C)透射电镜对 12-dithiolane-KLVFFAQ-NH2淀粉样纤维 (2% 醋酸盐的负染色) 的图像进行了分析。刻度条为 100 nm。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58135/58135fig3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>

Watch this Scientific Journal Video about Synthesis and Characterization of 1,2-Dithiolane Modified Self-Assembling Peptides at JoVE.com

Synthesis and Characterization of 1,2-Dithiolane Modified Self-Assembling Peptides

一种合成 12-dithiolane 修饰肽的协议, 以及肽自组装产生的超分子结构的表征。

12-Dithiolane 改性自组装肽的合成与表征

This report focuses on the synthesis of an N-terminus 1,2-dithiolane modified self-assembling peptide and the characterization of the resulting ...

synthesis-characterization-12-dithiolane-modified-self-assembling

Nanyang Technological University

Research

JoVE Journal

Chemistry

7.1K 次观看.  Fairfield University. 一种合成 12-dithiolane 修饰肽的协议, 以及肽自组装产生的超分子结构的表征。

视频: Synthesis and Characterization of 1,2-Dithiolane Modified Self-Assembling Peptides

Split-and-pool Synthesis and Characterization of Peptide Tertiary Amide Library

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid phase by using combinatorial chemistry. One of the most well studied classes of peptidomimetics is peptoids. Peptoids are easy to synthesize and have been shown to be proteolysis-resistant and cell-permeable. Over the past decade, many useful protein ligands have been identified through screening of peptoid libraries. However, most of the ligands identified from peptoid libraries do not display high affinity, with rare exceptions. This may be due, in part, to the lack of chiral centers and conformational constraints in peptoid molecules. Recently, we described a new synthetic route to access peptide tertiary amides (PTAs). PTAs are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. With side chains on both &#945;-carbon and main chain nitrogen atoms, the conformation of these molecules are greatly constrained by sterical hindrance and allylic 1,3 strain. (Figure 1) Our study suggests that these PTA molecules are highly structured in solution and can be used to identify protein ligands. We believe that these molecules can be a future source of high-affinity protein ligands. Here we describe the synthetic method combining the power of both split-and-pool and sub-monomer strategies to synthesize a sample one-bead one-compound (OBOC) library of PTAs.

Peptide tertiary amides (PTAs) are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. Here we describe a synthetic method which combines&#160;both split-and-pool and sub-monomer strategies to synthesize a one-bead one-compound library of PTAs.

分裂和池合成及肽叔酰胺图书馆表征

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid ...

科研

化学

Nucleoside Triphosphates - From Synthesis to Biochemical Characterization

The traditional strategy for the introduction of chemical functionalities is the use of solid-phase synthesis by appending suitably modified phosphoramidite precursors to the nascent chain. However, the conditions used during the synthesis and the restriction to rather short sequences hamper the applicability of this methodology. On the other hand, modified nucleoside triphosphates are activated building blocks that have been employed for the mild introduction of numerous functional groups into nucleic acids, a strategy that paves the way for the use of modified nucleic acids in a wide-ranging palette of practical applications such as functional tagging and generation of ribozymes and DNAzymes. One of the major challenges resides in the intricacy of the methodology leading to the isolation and characterization of these nucleoside analogues.
	
	In this video article, we present a detailed protocol for the synthesis of these modified analogues using phosphorous(III)-based reagents. In addition, the procedure for their biochemical characterization is divulged, with a special emphasis on primer extension reactions and TdT tailing polymerization. This detailed protocol will be of use for the crafting of modified dNTPs and their further use in chemical biology.

The protocol described herein aims to explain and abridge the numerous obstacles in the way of the intricate route leading to modified nucleoside triphosphates. Consequently, this protocol facilitates both the synthesis of these activated building-blocks and their availability for practical applications.

核苷三磷酸 - 从合成到生化特征

The  traditional strategy for the introduction of chemical functionalities is the  use of solid-phase synthesis by appending suitably modified ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

功能化的合成与表征金属 - 有机骨架

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the hydroxylmethylene phosphine precursor with ammonia in methanol under a nitrogen atmosphere. The N-triphosPh ligand precipitates from the solution after approximately 1 hr of reflux and can be isolated analytically pure via simple cannula filtration procedure under nitrogen. Reaction of the N-triphosPh ligand with [Ru3(CO)12] under reflux affords a deep red solution that show evolution of CO gas on ligand complexation. Orange crystals of the complex [Ru(CO)2{N(CH2PPh2)3}-&#954;3P] (2) were isolated on cooling to RT. The 31P{1H} NMR spectrum showed a characteristic single peak at lower frequency compared to the free ligand. Reaction of a toluene solution of complex 2 with oxygen resulted in the instantaneous precipitation of the carbonate complex [Ru(CO3)(CO){N(CH2PPh2)3}-&#954;3P] (3) as an air stable orange solid. Subsequent hydrogenation of 3 under 15 bar of hydrogen in a high-pressure reactor gave the dihydride complex [RuH2(CO){N(CH2PPh2)3}-&#954;3P] (4), which was fully characterized by X-ray crystallography and NMR spectroscopy. Complexes 3 and 4 are potentially useful catalyst precursors for a range of hydrogenation reactions, including biomass-derived products such as levulinic acid (LA). Complex 4 was found to cleanly react with LA in the presence of the proton source additive NH4PF6 to give [Ru(CO){N(CH2PPh2)3}-&#954;3P{CH3CO(CH2)2CO2H}-&#954;2O](PF6) (6).

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Ruthenium phosphine complexes are widely used for homogeneous catalytic reactions such as hydrogenations. The synthesis of a series of novel tridentate ruthenium complexes bearing the N-triphos ligand N(CH2PPh2)3 is reported. Additionally, the stoichiometric reaction of a dihydride Ru&#8211;N-triphos complex with levulinic acid is described.

一系列钌的合成，表征和反应<em&gt;Ñ</em&gt; -triphos<sup&gt;博士</sup&gt;配合

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the ...

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

合成，表征和混合金/硫化镉和Au / ZnS核/壳纳米颗粒功能化

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

超分子胶体的合成与表征

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Synthesis and Characterization of Fe-doped Aluminosilicate Nanotubes with Enhanced Electron Conductive Properties

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe aims at lowering the band gap of imogolite, an insulator with the chemical formula (OH)3Al2O3SiOH, and at modifying its adsorption properties towards azo-dyes, an important class of organic pollutants of both wastewater and groundwater.
Fe-doped nanotubes are obtained in two ways: by direct synthesis, where FeCl3 is added to an aqueous mixture of the Si and Al precursors, and by post-synthesis loading, where preformed nanotubes are put in contact with a FeCl3&#8226;6H2O aqueous solution. In both synthesis methods, isomorphic substitution of Al3+ by Fe3+ occurs, preserving the nanotube structure. Isomorphic substitution is indeed limited to a mass fraction of ~1.0% Fe, since at a higher Fe content (i.e., a mass fraction of 1.4% Fe), Fe2O3 clusters form, especially when the loading procedure is adopted. The physicochemical properties of the materials are studied by means of X-ray powder diffraction (XRD), N2 sorption isotherms at -196 &#176;C, high resolution transmission electron microscopy (HRTEM), diffuse reflectance (DR) UV-Vis spectroscopy, and &#950;-potential measurements. The most relevant result is the possibility to replace Al3+ ions (located on the outer surface of the nanotubes) by post-synthesis loading on preformed imogolite without perturbing the delicate hydrolysis equilibria occurring during nanotube formation. During the loading procedure, an anionic exchange occurs, where Al3+ ions on the outer surface of the nanotubes are replaced by Fe3+ ions. In Fe-doped aluminosilicate nanotubes, isomorphic substitution of Al3+ by Fe3+ is found to affect the band gap of doped imogolite. Nonetheless, Fe3+ sites on the outer surface of nanotubes are able to coordinate organic moieties, like the azo-dye Acid Orange 7, through a ligand-displacement mechanism occurring in an aqueous solution.

Here, we present a protocol to synthesize and characterize Fe-doped aluminosilicate nanotubes. The materials are obtained by either sol-gel synthesis upon addition of FeCl3&#8226;6H2O to the mixture containing the Si and Al precursors or by post-synthesis ionic exchange of preformed aluminosilicate nanotubes.

以增强电子导电性能的合成与表征Fe掺杂碳纳米管硅铝的

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe ...

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives

A facile method for the preparation of polycarbodiimide-based secondary structures (e.g., nano-rings, &#34;craters,&#34; fibers, looped fibers, fibrous networks, ribbons, worm-like aggregates, toroidal structures, and spherical particles) is described. These aggregates are morphologically influenced by extensive hydrophobic side chain-side chain interactions of the singular polycarbodiimide strands, as inferred by atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques. Polycarbodiimide-g-polystyrene copolymers (PS-PCDs) were prepared by a combination of synthetic methods, including coordination-insertion polymerization, copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) &#34;click&#34; chemistry, and atom transfer radical polymerization (ATRP). PS-PCDs were found to form specific toroidal architectures at low concentrations in CHCl3. To determine the influence of a more polar solvent medium (i.e., THF and THF/EtOH) on polymer aggregation behavior, a number of representative PS-PCD composites have been tested to show discrete concentration-dependent spherical particles. These fundamental studies are of practical interest to the development of experimental procedures for desirable architectures by directed self-assembly in thin film. These architectures may be exploited as drug carriers, whereas other morphological findings represent certain interest in the area of novel functional materials.

Here, we present a protocol to prepare and visualize secondary structures (e.g., fibers, toroidal architectures, and nano-spheres) derived from helical polycarbodiimides. The morphology characterized by both atomic force microscopy (AFM) and scanning electron microscopy (SEM) was shown to depend on molecular structure, concentration, and the solvent of choice.

从螺旋聚碳化二亚胺共聚物及其三唑衍生物获得自组装形貌

A facile method for the preparation of polycarbodiimide-based secondary structures (e.g., nano-rings, &#34;craters,&#34; fibers, looped fibers, fibrous ...

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

化学沉淀法合成铌2O5改性高比表面积镍催化剂

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

Facile Protocol for the Synthesis of Self-assembling Polyamine-based Peptide Amphiphiles (PPAs) and Related Biomaterials

Polyamine-based Peptide Amphiphiles (PPAs) are a new class of self-assembling amphiphilic biomaterials-related to the peptide amphiphiles (PAs). Traditional PAs possess charged amino acids as solubilizing groups (lysine, arginine), which are directly connected to a lipid segment or can contain a linker region made of neutral amino acids. Tuning the peptide sequence of PAs can yield diverse morphologies. Similarly, PPAs possess a hydrophobic segment and neutral amino acids, but also contain polyamine molecules as water solubilizing (hydrophilic) groups. As is the case with PAs, PPAs can also self-assemble into diverse morphologies, including small rods, twisted nano-ribbons, and fused nano-sheets, when dissolved in water. However, the presence of both primary and secondary amines on a single polyamine molecule poses a significant challenge when synthesizing PPAs. In this paper, we show a simple protocol, based on literature precedents, to achieve a facile synthesis of PPAs using solid phase peptide synthesis (SPPS). This protocol can be extended to the synthesis of PAs and other similar systems. We also illustrate the steps that are needed for cleavage from the resin, identification, and purification.

Facile Protocol for the Synthesis of Self-assembling Polyamine-based Peptide Amphiphiles PPAs and Related Biomaterials

The synthesis of polyamine-based peptide amphiphiles (PPAs) is a significant challenge due to the presence of multiple amine nitrogens, which requires judicious use of protecting groups to mask these reactive functionalities. In this paper, we describe a facile method for the preparation of these new class of self-assembling molecules.