目前的工作得到了 BUAP、推广科学和项目编号 Vicerrectoría de Investigación y 研究中心 Posgrado 的支持。REOY-NAT14, 15, 16 克 HEAS-NAT17。RMG 感谢 CONACyT (墨西哥) 奖学金417887。

1. 反应
<ol><li>在通风罩中放置一个打开的圆形100毫升瓶与0.5 摩尔 (29.8 毫升) 的冰川醋酸和添加0.051 摩尔 (5.82 毫升) 35-吡啶和5毫升的 H2O2 (35%)。保持混合反应在恒定的磁性搅拌下, 在内部温度为80°c 为5小时。</li>
	<li>在反应时间以后, 冷却烧瓶到24°c 与冰 (不暴露乙酸气体到冰), 并且插入它到一个高真空蒸馏单位为90-120 分钟去除多余的乙酸。 注意: 不要使用热材料。等待, 直到玻璃器皿达到可控温度。这也将避免蒸汽进入蒸馏装置的顶部。</li>
	<li>添加蒸馏水 (10 毫升) 两次, 以确保去除任何醋酸的痕迹, 并尽可能集中的混合物。</li>
</ol>2. 碱度调整和提取
<ol><li>溶解在双馏分水隔离的粘性和透明的产品, 并使用电位器调整 pH 值为 10, 纯固态 Na2CO3。</li>
	<li>小心地放置在一个250毫升分离漏斗的解决方案, 并提取它5倍250毫升的 CHCl3 , 以提高产量。恢复有机层并将其干燥到固态 Na2, 因此4的最大值为30分钟, 其中将包含产品。如有必要, 请用所需量的 CHCl3重新提取水相。 警告: CHCl3可能导致嗜睡和头晕;小心处理, 并在通风罩内。</li>
	<li>用高真空蒸馏装置去除减压液中的溶剂, 直至形成一种非常吸湿的透明米色结晶粉末 (70%)。</li>
</ol>3. 结晶过程
<ol><li>在50毫升的冷高液相色谱 (HPLC) 二乙基醚中溶解4.3 克的结晶粉末。真空过滤器的解决方案, 以消除任何痕迹的固体起动材料甚至灰尘。将滤液倒入玻璃培养皿中, 使其在实验室冰箱中缓慢蒸发4摄氏度。</li>
	<li>确保两天后, 透明无色晶体得到。然后测量熔点, 它应该在 310-311 K 的范围内。</li>
</ol>4. 35-吡啶n-氧化物脱水的分析
<ol><li>通过迁从烧瓶的墙壁中取出形成的、呈棱镜形状和无色的晶体, 进一步进行 X 射线分析。如果不立即使用, 保持晶体在乙醚, 以避免晶体水化。</li>
	<li>在0.4 毫升 CDCl3中溶解0.010 克的 35-吡啶n-氧化物脱水, 执行核磁共振 H1和 C13分析以证明该过程的有效性。</li>
</ol>

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所有作者声明没有利益冲突。

本文提出的协议是将氧原子与 35-吡啶的氮原子相连接的传统方法, 作为基质的功能化方法。这项技术也很好的建立, 以产生 x 射线合适的脱水晶体 (图 5, 拍摄的照片与一个 DSC-HX300 的网络拍摄索尼相机)。就我们而言, 没有多少报告描述了这种晶体的生产16。许多化合物生长理想晶体的 x 射线分析时, 它们是螯合的各种金属17,18,19,20。一旦结晶粉末形成, 重要的是从他们的母亲的酒, 使用北瓶和傅书礼漏斗提取。使用橡胶软管, 北烧瓶连接到一个真空线, 并在它的顶部, 傅书礼漏斗放置与过滤纸。一旦真空打开, 过滤纸就会用少量的溶剂润湿, 而产品结晶。这防止水晶粉末通过真空作用滴入傅书礼漏斗。在过滤纸固定后, 含有结晶粉末的溶液被震动, 以确保所有的结晶粉末被过滤, 并没有残留在瓶底。溶液很快倒在傅书礼漏斗上。所获得的结晶粉末在滤纸上留下约10分钟, 然后真空关闭, 结晶粉末与纸张分离, 储存在不透明的玻璃瓶中, 标有其编码, 保持在4摄氏度, 直到进一步分析。将过滤后的液体倒入玻璃培养皿中, 使其缓慢蒸发4摄氏度, 以改善 X 射线分析中适当晶体的形成。
重要的是注意到, 该协议使用的溶剂和材料, 容易获得, 一般是在任何研究实验室发现。通过添加 Na2CO3和一致的磁搅拌对最终产品的屈服率来说, pH 值的调整是至关重要的。然而, 重要的是要在所有的过程步骤, 特别是在萃取阶段, 在没有起始材料的痕迹必须存在, 以支付晶体粉末的形成和随后的晶体的额外仔细注意。因此, 这种萃取/净化阶段可以通过核磁共振或红外光谱来监测, 以确保产品的质量。
为了保证该协议的重现性, 核磁共振是一个很好的工具。即使是细微的细节也可以在频谱中看到。在图 1中, 所有信号都显示为嵌入。这些镶嵌清晰地描述了所有信号的分裂, 即多重性。例如, 质子 b (Jdipb ~ 0.75 Hz) 显示四峰值在信号的波峰, 与他们之间的分离 (Δ峰值) 的恶心常数 0.0075 ppm。使用以下等式21可以将 0.0075 ppm 转换为能量
<img alt="Equation 1" src="/files/ftp_upload/57233/57233eq1.jpg">等式1
<img alt="Equation 2" src="/files/ftp_upload/57233/57233eq2.jpg">
由于信号是由甲基基团的三氢核之间的偶极空间相互作用而产生的, 即使它们比4单质子 c 和 a 键更远, 它们也能感知它们的偶极磁动量相互作用22。此外, 在甲基基团中的自由西格玛键合旋转允许超级超精细质子-质子相互作用在信号的多重性中可见。质子 a 和 c 的 septuplets 为6.9 和 7.9 ppm, 分别来源于相同的偶极性质现象。在这些情况下, 质子 a 和 c 可以将甲基基团中的质子区分为相同的旋转动力学。最后, 按照预期, a、b 和 c 的计算出的Jdip的值几乎相同, 即0.75 赫兹。这些相互作用的数量证实了氢核空间安排在整个磁性各向异性。
另一方面, 1的C2v 对称性使等效碳23。13C 频谱 (图 2) 显示了与芳香环相连的甲基基团的典型信号, 碳 d 为 18 ppm。此外, 由于电负元素对碳 a 的影响较小, 在这个区域可以看到 129 ppm 的信号。在高频率信号为更加暴露的炭原子核到磁场在 137 ppm22被提出。
所提出的方法对于合成吡啶 n-氧化物是非常有用的, 在合理的时间内提供良好的产率, 在软反应条件和便宜和容易接近的试剂, 不需要额外的催化剂。这些条件可用于科学和教育界获得广泛的吡啶 n-氧化物作为前体的其他利益分子。适当的方法给学生提供了在教育实验室中获取基本的实验和概念工具的机会, 证明了化合物的成功合成和看到晶体形成的快乐。然而, 重要的是要强调, 像任何化学反应, 有必要采取一切预防措施, 因为通常使用的试剂是危险的。

如今, 全球各地的科学家一直在为芳香族的功能化开发新的合成路线, 这是众所周知的低反应性前添加反应1,2, 3。吡啶, 其中氮原子替代碳原子, 呈现类似的化学反应的模拟环只组成碳原子3, 它通常会经历替代机制, 而不是加法。N-氧化物由在氧原子3上的 nonbonding 电子对的重叠所形成的氮与氧之间存在的供体键的存在而独特。特别地, 吡啶n-氧化物是刘易斯基地, 因为他们的 n-O 基团可能充当电子捐赠者, 并且他们可能结合刘易斯酸形成对应的刘易斯酸基对。这个物产有一个基本的化学后果, 因为它可能增加路易斯酸的 nucleophilicity 对潜在的 electrophiles, 因此允许他们在通常反应不会发生的情况下反应。可能最频繁使用这种化合物是在各种氧化反应, 它们作为氧化剂4。吡啶N-氧化物和它们的许多环功能性衍生物是生物活性和药理作用的经常性分子5, 并建立了一个清晰的空间分布由不同的光谱工具对于其中一些6,7。在研究将不同的基团附着在吡啶环上时, 科学家们测试了各种方法, 以产生一种简单而传统的方法, 因为 isoxazolines 需要催化量的基础, 如 DBU 在沸腾二甲苯形成 6-substituted-2-aminopyridine N-氧化物8,9。在 CH2Cl2/CH3中, 多种吡啶衍生物转化为相应的N-氧化物, 其催化量为四 (26-diclorophenyl) 卟啉和醋酸铵。CN8,10。其他吡啶被氧化到他们的氧化物使用 H2O2在有催化量的 methyltrioxorhenium8,11, 或由加法多余的 dimethyldioxirane 在 CH2Cl2摄氏0摄氏度, 导致相应的N氧化物8,12,13,14。双 (三甲基硅) 过氧化物在 trioxorhenium 的存在中, 在 CH2Cl2中, 已用于合成吡啶N-氧化物8,11。此外, 还报告了用卡萝酸 (peroxomonosulfuric 酸) 合成氨基吡啶N氧化物的情况8。然而, 这里报告的方法, 以及使用落合1报告的方法的一部分, 提供了非常好的结果, 使用更便宜和容易接近的试剂, H 2 O 2 和冰川乙酸.这种做法更适合用于大型制剂, 对叔胺, 它产生良好的产量, 在一个反应, 只需要30% 过氧化氢和冰川乙酸在70-80 摄氏度之间的温度, 并使用净化过程这是可利用的在多数综合实验室例如蒸馏, 不用催化剂或更昂贵的试剂1。文献报道, 其他方法也经常涉及时间框架从10-24 小时和温度在100°c 4,8, 并且清楚地被形成的水晶的屈服为 x 射线分析很少报告。
被动, 各种n-氧化物衍生物用于充分激活吡啶环, 无论是亲核或亲方式。亲核或亲因子受取代基的影响。随着吡啶环为电子提取基团, 主要因子为亲核特征1。自由的N氧化物化合物很少被隔绝作为适当的水晶为 x-射线分析由于移位充电在芳香圆环。然而, 溶剂化因子对于稳定氧的负密度15至关重要。

<table border="0" cellpadding="0" cellspacing="0" style="width:725px;" width="725">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">3,5-lutidine</td>
			<td style="width:228px;">Sigma-Aldrich</td>
			<td style="width:119px;">L4206-500ML</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glacial acetic acid</td>
			<td>Fermont</td>
			<td>3015</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hidrogen peroxide (35%)</td>
			<td>Sigma-Aldrich</td>
			<td>349887-500ML</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Na2CO3 anhydrous</td>
			<td>Productos Qu&#237;micos Monterrey</td>
			<td>1792</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Na2SO4 anhydrous</td>
			<td>Alfa reactivos</td>
			<td>25051-C</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">CHCl3</td>
			<td>Fermont</td>
			<td>6205</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethyl eter</td>
			<td>Mercury Chemist</td>
			<td>QME0309</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Distilled water</td>
			<td>Comercializadora Qu&#237;mica Poblana</td>
			<td>not-existent</td>
			<td></td>
		</tr>
	</tbody>
</table>

syntheses, crystallization, and spectroscopic characterization of 3,5-lutidine n-oxide dehydrate

合成 35-吡啶n-氧化物脱水, 1, 在 2-氨基吡啶-35 二羧酸的合成路线中实现。落合首次在12小时的过程中使用了非取代吡啶的方法, 但没有获得 X 射线合适的晶体。此处介绍的方法中使用的取代环清楚地影响了将水分子加入不对称单元, 在1中赋予不同的亲核强度。X 射线适当的水晶复合物1是可能的由于消极充电的安定在氧气由二个水分子的存在, 在那里氢原子捐赠正电荷入圆环;这种水分子能很好地构建超分子相互作用。水合分子可能为碱性系统, 通过调整 pH 值达到10。重要的是, 双甲基取代环和反应时间为5小时, 使其成为一个更通用的方法和更广泛的化学应用, 未来的环插入。

该协议实质上是落合技术1的扩展.但是, 较低的温度和更少的时间被应用。这个简单的方法可以用来获得一个多才多艺的配体, 这是一个替代的吡啶N氧化物衍生物。要确认1的形成, 请选择核磁共振1H 和13C 分析, 以测试过程的有效性。
化学位移表明了1的形成。信号在 2.28 ppm (每百万) 对应于二个甲基小组的六等效氢在3和5位置, 感觉磁场以较少比例比永久磁性。有两组 septuplets: 一个属于质子在 c 位置在 7.9, 加倍的大小其他信号在6.9 属于质子在位置 a.图 1显示了由氧原子存在引起的化学位移邦德d 到吡啶环的氮原子。氧气原子是电撤回和更加接近的氢原子对氧气原子 (c 和 a) 显示位移到一个更高的频率比那为甲基氢 (b)。
为核磁共振13C 频谱 (图 2) 绘制了相同的过程, 其中, 更接近碳的信号与氧原子 (C 和 a) 之间显示了其ΔC = 1300 Hz 和δa = 200 Hz 信号之间的频率分离。再次, 甲基碳没有显示任何变化。红外光谱也可以用来看到该方法的成功。
ORTEP 图图 4显示了两个水分子围绕不对称分子的存在。这些分子被认为能稳定 N O 键。在类似的情况下, 它被描述为吡啶N氧化物和相关的芳香氧化物。有一个重要的稳定π型 O→N 后捐赠, 反映在计算的债券顺序高于1和一些电子孤对低于 36。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57233/57233fig1.jpg"> 图 1.TMS 引用 CDCl3 500 MHz NMR 1H 频谱 1.三信号的积分和化学位移与三种不同类型的氢原子在 lutine N-氧化物中存在一致。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57233/57233fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57233/57233fig2.jpg"> 图 2.TMS 引用 CDCl3 100 MHz NMR 13C 频谱 1.三信号被观察为五芳香碳和一个为二个甲基小组。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57233/57233fig2large.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/57233/57233fig3.jpg"> 图 3.红外光谱 1.O H 键, 高于 3300 cm-1, 负责超分子结构的形成和晶体的形成。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57233/57233fig3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57233/57233fig4.jpg"> 图 4.ORTEP 图 1, 其中 H2O 的两个分子与吡啶的氧气形成桥梁氢键, 使氢原子向氧原子驱动.这一数字已从美利奴加西亚et . 修改。12<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57233/57233fig4large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/57233/57233fig5.jpg"> 图 5.在二乙基醚 (顶部) 和在露天 (底部), 适当的 X 射线衍射晶体的图片 1.其中一个晶体被证实在 x 射线衍射仪和显示 x 射线衍射路径, 这是中伤和提炼的特殊计算程序在分子和晶体结构24,25, 26,27,28。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57233/57233fig5large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>

Watch this Scientific Journal Video about Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate at JoVE.com

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

在此, 我们报告的合成和结晶的 35-吡啶n-氧化物脱水的一个简单的协议, 不同于经典合成吡啶N氧化物。该协议采用不同的起始材料, 反应时间较少, 产生一种新的溶解超分子结构, 在缓慢蒸发下结晶。

35-吡啶N-氧化物脱水的合成、结晶和光谱表征

The synthesis of 3,5-lutidine N-oxide dehydrate, 1, was achieved in the synthesis route of 2-amino-pyridine-3,5-dicarboxylic acid. Ochiai first used the ...

syntheses-crystallization-spectroscopic-characterization-35-lutidine

Nanyang Technological University

Research

JoVE Journal

Chemistry

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

8.3K 次观看.  Benemérita Universidad Autónoma de Puebla. 在此, 我们报告的合成和结晶的 35-吡啶n-氧化物脱水的一个简单的协议, 不同于经典合成吡啶N氧化物。该协议采用不同的起始材料, 反应时间较少, 产生一种新的溶解超分子结构, 在缓慢蒸发下结晶。

视频: Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

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

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 ...

Diffuse Reflectance Infrared Spectroscopic Identification of Dispersant/Particle Bonding Mechanisms in Functional Inks

In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers. A typical inkjet ink is a colloidal dispersion containing approximately ten components including solvent, the nano to micron scale particles which will comprise the printed layer, polymeric dispersants to stabilize the particles, and polymers to tune layer strength, surface tension and viscosity. To rationally and efficiently formulate such an ink, it is crucial to know how the components interact. Specifically, which polymers bond to the particle surfaces and how are they attached? Answering this question requires an experimental procedure that discriminates between polymer adsorbed on the particles and free polymer. Further, the method must provide details about how the functional groups of the polymer interact with the particle. In this protocol, we show how to employ centrifugation to separate particles with adsorbed polymer from the rest of the ink, prepare the separated samples for spectroscopic measurement, and use Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) for accurate determination of dispersant/particle bonding mechanisms. A significant advantage of this methodology is that it provides high level mechanistic detail using only simple, commonly available laboratory equipment. This makes crucial data available to almost any formulation laboratory. The method is most useful for inks composed of metal, ceramic, and metal oxide particles in the range of 100 nm or greater. Because of the density and particle size of these inks, they are readily separable with centrifugation. Further, the spectroscopic signatures of such particles are easy to distinguish from absorbed polymer. The primary limitation of this technique is that the spectroscopy is performed ex-situ on the separated and dried particles as opposed to the particles in dispersion. However, results from attenuated total reflectance spectra of the wet separated particles provide evidence for the validity of the DRIFTS measurement.

Formulation of stable, functional inks is critical to expanding the applications of additive manufacturing. In turn, knowledge of the mechanisms of dispersant/particle bonding is required for effective ink formulation. Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) is presented as a simple, inexpensive way to gain insight into these mechanisms.

弥漫分散剂/粒子绑定机制反射红外光谱鉴定功能性油墨

In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers.  A typical inkjet ink is a colloidal ...

A Filter-based Surface Enhanced Raman Spectroscopic Assay for Rapid Detection of Chemical Contaminants

We demonstrate a method to fabricate highly sensitive surface-enhanced Raman spectroscopic (SERS) substrates using a filter syringe system that can be applied to the detection of various chemical contaminants. Silver nanoparticles (Ag NPs) are synthesized via reduction of silver nitrate by sodium citrate. Then the NPs are aggregated by sodium chloride to form nanoclusters that could be trapped in the pores of the filter membrane. A syringe is connected to the filter holder, with a filter membrane inside. By loading the nanoclusters into the syringe and passing through the membrane, the liquid goes through the membrane but not the nanoclusters, forming a SERS-active membrane. When testing the analyte, the liquid sample is loaded into the syringe and flowed through the Ag NPs coated membrane. The analyte binds and concentrates on the Ag NPs coated membrane. Then the membrane is detached from the filter holder, air dried and measured by a Raman instrument. Here we present the study of the volume effect of Ag NPs and sample on the detection sensitivity as well as the detection of 10 ppb ferbam and 1 ppm ampicillin using the developed assay.

A procedure for fabrication and performing the filter-based surface enhanced Raman spectroscopic (SERS) assay for the detection of chemical contaminants (i.e., pesticide ferbam and antibiotic ampicillin) is presented.

基于过滤器的表面增强拉曼光谱检测方法的化学污染物快速检测

We demonstrate a method to fabricate highly sensitive surface-enhanced Raman spectroscopic (SERS) substrates using a filter syringe system that can be ...

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 ...

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels

Ion channel gating is a stimulus-driven orchestration of protein motions that leads to transitions between closed, open, and desensitized states. Fundamental to these transitions is the intrinsic flexibility of the protein, which is critically modulated by membrane lipid-composition. To better understand the structural basis of channel function, it is necessary to study protein dynamics in a physiological membrane environment. Electron Paramagnetic Resonance (EPR) spectroscopy is an important tool to characterize conformational transitions between functional states. In comparison to NMR and X-ray crystallography, the information obtained from EPR is intrinsically of lower resolution. However, unlike in other techniques, in EPR there is no upper-limit to the molecular weight of the protein, the sample requirements are significantly lower, and more importantly the protein is not constrained by the crystal lattice forces. Therefore, EPR is uniquely suited for studying large protein complexes and proteins in reconstituted systems. In this article, we will discuss general protocols for site-directed spin labeling and membrane reconstitution using a prokaryotic proton-gated pentameric Ligand-Gated Ion Channel (pLGIC) from Gloeobacter violaceus (GLIC) as an example. A combination of steady-state Continuous Wave (CW) and Pulsed (Double Electron Electron Resonance-DEER) EPR approaches will be described that will enable a complete quantitative characterization of channel dynamics.

This article describes methods for site-directed spin labeling and reconstitution of pentameric ligand-gated channels for Electron Paramagnetic Resonance studies. This protocol can be adapted for any membrane protein. The reconstitution method described here can also be used for patch-clamp measurements of macroscopic and single-channel currents in a defined lipid system.

定点自旋标记和五聚体配体门控离子通道的EPR光谱研究

Ion channel gating is a stimulus-driven orchestration of protein motions that leads to transitions between closed, open, and desensitized states. ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

C 型60/石墨烯混合纳米结构的制备与表征

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

半导体回转金属硫框架结晶的硫醇构建块的合成

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and non-porous supports (polymer, ceramic, metal, carbon, and graphene). We developed a novel crystallization technique, which is termed the ENACT approach: the electrophoretic nuclei assembly for the crystallization of highly intergrown thin films (ENACT). This approach allows for a high density of heterogeneous nucleation of MOFs on a chosen substrate via the electrophoretic deposition (EPD) directly from the precursor sol. The growth of well-packed MOF nuclei leads to a highly intergrown polycrystalline MOF film. We show that this simple approach can be used for the synthesis of thin, intergrown zeolite imidazole framework (ZIF)-7 and ZIF-8 films. The resulting 500 nm-thick ZIF-8 membranes show a considerably high H2 permeance (8.3 x 10-6 mol m-2 s-1 Pa-1) and ideal gas selectivities (7.3 for H2/CO2, 15.5 for H2/N2, 16.2 for H2/CH4, and 2655 for H2/C3H8). An attractive performance for C3H6/C3H8 separation is also achieved (a C3H6 permeance of 9.9 x 10-8 mol m-2 s-1 Pa-1 and a C3H6/C3H8 ideal selectivity of 31.6 at 25 &#176;C). Overall, the ENACT process, owing to its simplicity, can be extended to synthesize intergrown thin films of a wide range of nanoporous crystalline materials.

A simple, reproducible, and versatile approach for the synthesis of intergrown, polycrystalline metal-organic framework membranes on a wide range of unmodified porous and non-porous supports is presented.

超薄高性能金属-有机骨架膜的电泳结晶

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and ...

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of their interactions with cell membranes, lipid bilayers, and viruses. The hydrophilic ligands make these particles colloidally stable in aqueous solutions and the combination with hydrophobic ligands creates an amphiphilic particle that can be loaded with hydrophobic drugs, fuse with the lipid membranes, and resist nonspecific protein adsorption. Many of these properties depend on nanoparticle size and the composition of the ligand shell. It is, therefore, crucial to have a reproducible synthetic method and reliable characterization techniques that allow the determination of nanoparticle properties and the ligand shell composition. Here, a one-phase chemical reduction, followed by a thorough purification to synthesize these nanoparticles with diameters below 5 nm, is presented. The ratio between the two ligands on the surface of the nanoparticle can be tuned through their stoichiometric ratio used during synthesis. We demonstrate how various routine techniques, such as transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectrometry, are combined to comprehensively characterize the physicochemical parameters of the nanoparticles.

Amphiphilic gold nanoparticles can be used in many biological applications. A protocol to synthesize gold nanoparticles coated by a binary mixture of ligands and a detailed characterization of these particles is presented.

两栖金纳米粒子的合成与表征

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of ...