这项工作在财政联合中心储能研究（JCESR），由能源，科学办公室，基础能源科学，美国能源部资助的能源创新中心的支持。作者也承认期刊材料化学A（化学杂志的英国皇家学会）为最初发布此研究（ <a href="http://pubs.rsc.org/en/content/articlehtml/2016/ta/c6ta01177b">http://pubs.rsc.org/en/content/articlehtml/2016/ta/c6ta01177b</a> ）。 PNNL根据合同DE-AC05-76RL01830能源部巴特尔操作多项目国家实验室。

注意:所有的溶液制剂，循环伏安（CV）测试，和流动池的组装和测试在充满氩气的手套箱中进行的与低于1ppm水和O 2的水平。 1. PTIO流动池的电化学评估<ol><li> CV测试 <ol><li>抛光用0.05微米的γ-氧化铝粉末的玻璃碳电极，用去离子水冲洗它，把它放在真空下，在室温下搅拌过夜，并将其转移到手套箱中。 </li><li>溶解硝酸银（8.5毫克）用MeCN（5mL）中在手套式操作箱， 即 ，10毫硝酸银。将溶液添加到银/硝酸银参比电极的玻璃管中。 </li><li>装配玻璃碳工作电极，石墨毡带对电极，并在一个25毫升三颈梨形烧瓶中的银/硝酸银参比电极。 </li><li>溶解PTIO（52毫克）和四丁基hexafluorophosphate（TBAPF 6，0.87克）在MeCN中（1.10克）， 即 ，0.1M PTIO / 1.0M的TBAPF 6。的溶液添加到该烧瓶浸没三个电极的尖端。 </li><li>电极连接到电化学工作站。测量以100mV / s的扫描速率-1.75-0.75Ⅴ的电压范围内的CV曲线。由两个氧化还原对之间的潜在间隙确定PTIO液流电池的理论电池电压。 注意:应该指出的是，银/银离子参考电极的配置是由它的性质的伪参考电极。其结果是，氧化还原峰可能在长期CV测量移位。然而，这种移位通常具有对氧化还原对之间的电压间隙的疏忽的影响，不会影响电池的电压值。 </li></ol></li><li> 流动池装置 <ol><li>切割的石墨毡，以用刀片的1×10 cm 2的区域。同样，切孔九月arator为3×12 平方厘米的面积。 </li><li>干燥，在真空炉中的液流电池部件（细胞区室，管道，5毫升玻璃小瓶中，石墨毡，和多孔隔板）在70℃下过夜，将它们移入手套箱，并冷却到环境温度。 </li><li>组装在一个端板，铜板电流收集器，一个半电池的顺序流动池部件，石墨毡，垫圈，一个多孔隔板，石墨毡，一个半电池，铜板电流收集器，和一个端板。用抗使用扭矩扳手预先设定在125英寸磅两个端板8螺栓紧固组件。电解质流管路连接到流动池。该电池组件示于图1。 </li></ol></li><li> 对称电化学示范 <ol><li>根据第1.2节装配流动池。在glov溶解PTIO（10毫克）和TBAPF 6（3.3 g）在MeCN中4.4克E盒， 即 5.0毫米PTIO / 1.0M的TBAPF 6。加入4毫升的溶液，以每两个玻璃小瓶。泵电解质用蠕动泵以20毫升/分钟的流速流动。 </li><li>流动池的正，负电流收集器连接到电池测试器。充流动池以5 毫安 /平方厘米，直到电压的恒定电流密度达到1.9五停止充电。泵出电解液到玻璃小瓶中。 </li><li>混合用1毫升负电解质的1毫升正电解质在单独的小瓶中。现在有四电解质:原来，在正，负，和混合。 </li><li>测量上述四个电解液的电子自旋共振（ESR）光谱。 25 <ol><li>与管密封，在两端密封少量（〜10微升）的正和负中的PTFE管（1/16"外径和1/32"标识），然后在一个石英血沉管密封它（4-毫米直径）。 </li><li>安装ESR油管配备了SHQE谐振腔微波频率〜9.85 GHz的（X波段）的ESR光谱仪。 </li><li>收集在1.3.3节的四个电解质的ESR谱。 </li></ol></li></ol></li><li> 流通池测试 <ol><li>组装流通池以下1.2节。 </li><li>溶解PTIO（1.05克）和TBAPF 6（3.50 g）在MeCN中（3.60mmol克）在手套箱中， 即 ，0.5M PTIO / 1.0M的TBAPF 6。加入4毫升的溶液到每玻璃小瓶中。以20毫升/分钟流动的电解质。 </li><li>流动池的正和负集电体连接到电化学工作站。测量在100千赫至1赫兹的频率范围内的流动池在开路电位的阻抗。计算由欧姆电阻（高频阻抗）由流电池的活性面积乘以该特定区域电阻率（ASR）。 </li><li>连接的正和负电流山口流动池的电池测试器的讲师。设置为0.8和2.2伏电压截止和20毫安厘米恒流-2在电池操作的软件。反复充电/放电的PTIO流动池。 </li></ol></li></ol> 2.基于FTIR的SOC测定<ol><li> FTIR可行性验证 <ol><li>制备在手套箱以下三种电解质溶液:（一）的MeCN（0.50克）; （二）TBAPF 6（0.23 g）在MeCN中（0.30克）， 即 ，1.0M TBAPF 6; （三）PTIO（75毫克）和TBAPF 6 0.25克用MeCN（0.26克）， 即 ，0.5M PTIO / 1.0M的TBAPF 6。 </li><li>测量FTIR的三个电解质溶液。 <ol><li>添加各溶液到可密封的FTIR细胞与KBr窗和0.2mm的路径长度的小体积（〜0.05毫升）。密封FTIR细胞。 </li><li>把FTIR细胞到存储容器和将其传送出手套箱中。 </li><li>很快亩NT中的FTIR细胞光谱仪和收集红外光谱。 </li></ol></li><li>组装流通池以下1.2节。 </li><li>溶解PTIO（1.05克）和TBAPF 6（3.50 g）在MeCN中（3.60mmol克）在手套箱中， 即 ，0.5M PTIO / 1.0M的TBAPF 6。加入4毫升的溶液到每玻璃小瓶中。以20毫升/分钟流动的电解质。 </li><li>直到电压达到2.2V。停止充电和泵完全充电流通池。 </li><li>测量的FTIR光谱为正和负的电解质，分别以下在第2.1.2节的方法。 </li><li>在的1.0M TBAPF 6在MeCN中与表1中的组合物中的手套箱准备一系列PTIO溶液（0.05-0.5 M）的。 </li><li>测量红外光谱对每个章节2.1.6的解决方案，按照第2.1.2节的程序。 </li></ol></li><li> SOC的红外测量 <ol><li>组装FO流动池llowing 1.2节。 </li><li>溶解PTIO（2.9克）和TBAPF 6（9.6 g）在MeCN中（9.8克）在手套箱中， 即 ，0.5M PTIO / 1.0M的TBAPF 6。添加11毫升的溶液，以每两个玻璃小瓶。以20毫升/分钟流动的电解质。 </li><li>充以10毫安/厘米2的恒定电流流动池以20毫升/分钟的流速。 </li><li>在0，18，36，54和72分钟的充电时间，停止单元电荷和电解液流，取电解质小等份（0.2mL）中，从阳极液和阴极侧的玻璃小瓶，然后恢复细胞。 </li><li>测量红外光谱对上述五个样本等份，按照第2.1.2节的程序。 </li><li>测量ESR谱为上述五个样品等分，按照第1.3.4的步骤。 </li></ol></li></ol>

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The authors have nothing to disclose.

如我们之前显示出，25 FTIR能够非侵入性地检测PTIO液流电池的SOC。作为一种诊断工具，FTIR是因为它拆装方便，响应速度快，成本低，占地面积小，对网上注册成立，没有检测器的饱和，以及相关的结构信息，调查液流电池操作过程中的分子进化的能力，设施的特别有利。 图3E说明了提出的液流电池设备集成在线红外传感器，使得安全运行实时监控SOC。 为了更好地实施电化学评估和基于FTIR的SOC诊断协议，无空气的环境基本上是重要的;否则，在充电状态的氧化还原剂将与O 2或湿气导致材料降解和不准确的SOC测量反应。严格密封的红外细胞必须用于避免与电解质接触空气。此外，由于这项技术仅适用于红外敏感氧化还原材料使用，通过识别良好区分的特征红外光谱峰的可行性验证是一个关键步骤。 考虑到电池膜的选择性有限，氧化还原物质交叉是不可避免的大多数液流电池，这会造成不可逆的容量衰减。在这点上，对称液流电池必须克服该缺点的潜力。在PTIO液流电池，任何交叉物种将被转换为原始PTIO。从理论上说，引起材料交叉容量损失可通过再混合电解质，类似于钒液流电池中回收。 32因此，对称电池设计是有希望发展耐用，可靠的能源存储系统。当前PTIO系统的关键限制是，PTIO - （阳极电解液侧）是不足够稳定的，由于逐渐发生的副反应。这种材料损失解释PTIO流动池衰落所观察到的容量。与所有氧化态高化学稳定性的新双极氧化还原材料的开发是未来的发展方向，以证明这种电池设计的全部潜力。

氧化还原液流电池存储的能量在包含在外部水库和被泵送到内部电极以完成电化学反应液体电解质。储存的能量和动力因此可以分离导致了出色的设计灵活性，可扩展性和模块化。这些优点使液流电池非常适合于集成清洁还间歇性可再生能源的固定能量存储应用，增加格资产利用和效率，和提高能源弹性和安全性。 1，2，3传统的水液流电池从有限的能量密度的困扰，主要是由于狭窄的电压窗口，以避免电解水。 4，5，6，7，8与此相反，非aque基于液流电池的OU电解质因为用于实现高电池电压，高能量密度的潜力被广泛开展。 9，10在这些努力中，各种流量电池化学组成进行了研究，其中包括金属配合物，11，12全有机，13，14的氧化还原活性聚合物，15和锂的混合流动系统。 16，17，18，19 然而，非水液流电池的潜力尚未得到充分展现，由于液流电池相关的条件下，有限的示范的主要技术瓶颈。这个瓶颈是密切多项性能限制性因素有关。第一，大多数电活性材料的小的溶解度的非水流动细胞导致低的能量密度输送。第二，非水液流电池的速率能力主要是由高电解质的粘度和电阻率在相关的氧化还原的浓度限制。第三个因素是缺乏高性能膜。的Nafion和陶瓷膜表现出与非水电解质的低离子传导性。多孔分离器已经证实体面流动池的性能，但是遭受相当大的自放电，因为相对大的孔径。 14，20通常情况下，同时含有阳极电解液和阴极电解液的氧化还原物质的混合反应物电解质（1:1的比例）用于减少氧化还原材料交叉，然而这牺牲了有效的氧化还原浓度，典型地通过一半。 14，21克服上述瓶颈，需要改进母校IALS发现，电池化学设计和流动池结构实现电池相关的循环。 电池状态监测是可靠的操作基本上是很重要的。非正常状态，包括过充电，气体逸出，以及材料的降解可能导致损害电池性能和甚至电池故障。尤其是对于涉及大量电池材料大规模液流电池，这些因素可能会导致严重的安全问题和投资损失。充电状态（SOC），说明电荷或液流电池的放电深度的状态是最重要的电池状态参数中的一个。他们到达危险的水平之前及时SOC的监测可以检测到潜在的风险。然而，该区域似乎是迄今为止下寻址，特别是在非水液流电池。 Spectrophotoscopic方法如紫外可见（UV-VIS）光谱和电解质电导率测量已经在水性流蓄电池装填评价<html> RY的SOC判定。 22，23，24 我们最近引进了基于新的双极的氧化还原物质的新的对称的非水液流电池设计，2-苯基-4,4,5,5- tetramethylimidazoline -1-氧基-3-氧化物（PTIO）。 25此液流电池保持承诺解决非水液流电池前述的挑战。首先，PTIO在乙腈中的电池溶剂（乙腈），该被看好，以使高能量密度的高溶解度（2.6 M）。第二，PTIO呈现被适度分离并因此可以通过本身构成了一个对称电池化学两可逆等的氧化还原对。我们还证明了在FTIR光谱的可分辨的PTIO峰可与未反应的PTIO的流动池中，这导致分光SOC的测定，用ESR结果交叉验证的浓度相关联。姑娘="外部参照"&gt; 26在这里，我们提出了一个协议，以拟定电化学评估和PTIO对称液流电池的基于FTIR的SOC诊断过程。这项工作预计在长期液流电池业务保持了安全性和可靠性，尤其是在现实世界电网应用触发更多的见解。

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>PTIO</td>
			<td>TCI America</td>
			<td>A5440</td>
			<td>&#62;98.0%</td>
		</tr>
		<tr>
			<td>Tetrabutylammonium hexafluorophosphate</td>
			<td>Sigma-Aldrich</td>
			<td>86879</td>
			<td>electrochemical grade, &#8805;99.0%</td>
		</tr>
		<tr>
			<td>MeCN</td>
			<td>BASF</td>
			<td>50325685</td>
			<td>Battery grade</td>
		</tr>
		<tr>
			<td>Silver nitrate</td>
			<td>Sigma-Aldrich</td>
			<td>204390</td>
			<td>99.9999% trace metals basis</td>
		</tr>
		<tr>
			<td>Gamma alumina powder</td>
			<td>CH Instruments</td>
			<td>CHI120</td>
			<td></td>
		</tr>
		<tr>
			<td>Graphite felt</td>
			<td>SGL</td>
			<td>GFD3</td>
			<td>Vacuum-dry at 70&#176;C for 24 h</td>
		</tr>
		<tr>
			<td>Porous separator</td>
			<td>Daramic</td>
			<td>AA800</td>
			<td>Vacuum-dry at 70&#176;C for 24 h</td>
		</tr>
		<tr>
			<td>Battery Tester</td>
			<td>Wuhan LAND electronics Co., Ltd.</td>
			<td>Lanhe</td>
			<td>1A current range</td>
		</tr>
		<tr>
			<td>Electrochemical Workstation</td>
			<td>Solartron Analytical</td>
			<td>ModuLab</td>
			<td></td>
		</tr>
		<tr>
			<td>glove box</td>
			<td>MBRAUN</td>
			<td>Labmaster SP</td>
			<td>oxygen and water levels &#60;1 ppm</td>
		</tr>
		<tr>
			<td>ESR spectrometer</td>
			<td>Bruker&#160;</td>
			<td>Elexsys 580&#160;</td>
			<td>Equipped with an SHQE resonator with microwave frequency ~9.85 GHz (X band) at 2 mW power, with 100 kHz field modulation</td>
		</tr>
	</tbody>
</table>

a protocol for electrochemical evaluations and state of charge diagnostics of a symmetric organic redox flow battery

氧化还原液流电池已被认为是用于改善的可再生能源技术的电网和部署的可靠性的最有希望的静止能量存储解决方案之一。在众多的流动化学电池，非水液流电池具有实现的，因为非水电解质的宽电压窗口的高能量密度的潜力。然而，显著技术障碍存在目前限制非水液流电池以证明其全部潜力，如低氧化还原浓度，低工作电流，欠探索电池状态监视等在试图解决这些限制，我们最近报道了基于高度可溶的，氧化还原活性有机氮氧自由基化合物的非水液流电池，2-苯基-4,4,5,5- tetramethylimidazoline -1-氧基-3-氧化物（PTIO）。这种氧化还原材料表现出双极电化学特性，因此可以作为既anolyte和阴极电解液的氧化还原物质，以形成对称的液流电池化学。此外，我们证明了傅里叶变换红外光谱（FTIR）可以测量PTIO浓度PTIO液流电池循环过程中，并提供充电量（SOC）的电池状态的相当准确的检测，如通过电子自旋共振（ESR）的测量交叉验证。在此，我们提出了PTIO对称液流电池的电化学评估和诊断SOC的视频协议。用的详细描述，我们实验证明的路线来实现这样的目的。该协议的目的是引发关于在非水氧化还原液流电池领域的安全性和可靠性更加的兴趣和见解。

对称PTIO液流电池系统的独特的优点是高度归因于PTIO，有机氮氧自由基化合物的电化学性能。 PTIO可以经历电化学歧化反应以形成PTIO +和PTIO - （ 图2a）。这两个氧化还原对是由〜电压间隙适度分开1.7 V（ 图2b），并且可以同时用作阳极电解液和阴极电解液的氧化还原物质中的对称电池化学。使用PTIO作为氧化还原物质可以消除混合反应电解质需要，并能高效的氧化还原浓度。 PTIO +和PTIO之间的反应-自发重新生成原始PTIO，由PTIO的ESR信号的混合PTIO +和PTIO之后的恢复所证明-以等摩尔Çoncentrations（ 图2c）。在此液流电池，充电PTIO物种（PTIO +或PTIO - ）的交叉不会导致完全不同的化学品和材料损耗，从而导致最小的不可逆的交叉。的PTIO流动池在0.5M的PTIO的氧化还原浓度和具有20毫安/平方厘米的电流输送体面循环效率;的〜90％的平均库仑效率（CE），电压效率（VE）的67％，并得到60％的能量效率（EE）（ 图2d）。低VE是由21.2Ω厘米2被以这样高的电解质浓度与有限的离子导电性密切相关的相对高的细胞的ASR注册。尽管容量衰减，所述PTIO流动池已经证明操作的氧化还原物质的浓度，电流密度，以及电池效率比许多其它的非水区域渔业显著更高，其典型地循环邻近的0.1M浓度，以电流密度少吨汉0.5毫安/厘米2，和/或电子工程师不高于50％。 27，28，29，30 FTIR在1218厘米已经成功地验证其资格作为PTIO液流电池的合适的SOC-诊断工具，因为特性的FTIR峰的-1即推测对应于NO键。 31首先，在支撑的MeCN溶剂和TBAPF 6盐产生可忽略不计的干扰峰在这个位置（ 图3a）。第二，FTIR区分PTIO的三个氧化还原物质中，特别是与在阴极电解液侧该峰为PTIO +的消失（ 图3b）。第三，该峰的强度（T）的显示在PTIO浓度有很强的依赖性（ 图3c和插图）， 即 ，线性-log（T）的与[PTIO]标准关系（式1）根据比尔 - 朗伯定律，得到: <img alt="方程" src="/files/ftp_upload/55171/55171eq1.jpg" /> （1） 从阴极电解液侧（ 图4a）被五个样品等分试样用于测定PTIO流动池的SOC。作为从样品＃0进行到＃4的充电时间，则1218厘米-1峰值的强度连续地由于PTIO的消耗降低（ 图4b）;所以是ESR的信号（ 图4c）。这些样品中的未反应的PTIO的浓度通过的1218厘米-1峰的红外光谱强度按照方程2，然后被用来计算以下等式2 SOC的如在图4d中所示，这样得到的〔PTIO〕及其衍生这些样品的SOC是在与ESR的测量，这似乎是一个很好的交叉验证接近一致。 （2） 部分并在此研究中使用的流通池的组装示于图1。对称PTIO液流电池的电化学性能，其中包括氧化还原反应，CV曲线的对称设计益处血沉验证，和流动细胞周期数据，示于图2。对于用FTIR作为合适的方法来确定PTIO液流电池的SOC的可行性验证示于图3。基于FTIR的SOC的测定，包括流动池的电压曲线，从FTIR和求得的SOC的ESR交叉验证，和建议的在线诊断系统，在图4中示出。 <img alt="图1" src="/files/ftp_upload/55171/55171fig1.jpg" /> 图1:流动池，作为该照片<html> sembly。 <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55171/55171fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图2" src="/files/ftp_upload/55171/55171fig2.jpg" /> 图2:PTIO的电化学性能。 （ 一 ）PTIO的至PTIO +（阴极侧）和PTIO的氧化还原反应- （阳极电解液侧），分别; （ 二 ）PTIO的在玻碳电极几乎完全重叠的CV曲线的500次; （ 三 ）表示PTIO +和PTIO之间的反应ESR谱-再生原始PTIO; （ 四 ）循环容量和0.5M的PTIO流动池的效率。这个数字已经从25参考修改。<html>得到="_空白"&gt;点击此处查看该图的放大版本。 <img alt="图3" src="/files/ftp_upload/55171/55171fig3.jpg" /> 图3:用FTIR确定PTIO液流电池的SOC可行性验证。 （ 一 ）的MeCN，1.0M TBAPF 6在MeCN，和0.5M PTIO的FTIR光谱中的MeCN的1.0M TBAPF6; （ 二 ）PTIO，PTIO +和PTIO的FTIR光谱- （0.5 M在1.0的MeCN中号TBAPF 6）; （ 三 ）标准PTIO解决方案红外光谱在0.05到0.5M用0.05M的间隔。这个数字已经从25参考修改。 <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55171/55171fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> PLOAD / 55171 / 55171fig4.jpg"/&gt; 图4:FTIR基于SOC诊断。 （a）表示五个取样等份0.5M的PTIO流动池的充电电压曲线（＃0，1，2，3，4）在充电期间从细胞撤回; （ 二 ）FTIR和五阴极样品等分（ 三 ）ESR谱; （ 四 ）未反应的PTIO的浓度和流量从FTIR测量和得到的电池的SOC的交叉验证用的ESR测量。 （e）与在线FTIR监测传感器并入流电池装置的示意图。这个数字已经从25参考修改。 <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55171/55171fig4large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody><tr><td> PTIO浓。 （M）的</td><td> 0.05 </td><td> 0.1 &lt;/ TD&gt; <td> 0.15 </td><td> 0.2 </td><td> 0.25 </td><td> 0.3 </td><td> 0.35 </td><td> 0.4 </td><td> 0.45 </td><td> 0.5 </td></tr><tr><td>乙腈</td><td> 0.301克</td><td> 0.295克</td><td> 0.273克</td><td> 0.25克</td><td> 0.291克</td><td> 0.255克</td><td> 0.242克</td><td> 0.232克</td><td> 0.243克</td><td> 0.263克</td></tr><tr><td> TBAPF 6 </td><td> 0.233克</td><td> 0.233克</td><td> 0.223克</td><td> 0.21克</td><td> 0.247克</td><td> 0.222克</td><td> 0.214克</td><td> 0.213克</td><td> 0.225克</td><td> 0.255克</td></tr><tr><td> PTIO </td><td> 0.007克</td><td> 0.014克</td><td> 0.02克</td><td> 0.025克</td><td> 0.037克</td><td> 0.04克</td><td> 0.045克</td><td> 0.051克</td><td> 0.061克</td><td> 0.076克</td></tr></tbody></table> 表1:PTIO标准溶液的成分。

Watch this Scientific Journal Video about A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery at JoVE.com

A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery

我们提出的协议电化学评估对称非水有机氧化还原液流电池和用于诊断其用FTIR充电状态。

- 电化学评估和对称有机氧化还原液流电池的充电诊断状态协议

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid ...

a-protocol-for-electrochemical-evaluations-state-charge-diagnostics

Nanyang Technological University

Research

JoVE Journal

Chemistry

10.4K 次观看.  Joint Center for Energy Storage Research (JCESR). 我们提出的协议电化学评估对称非水有机氧化还原液流电池和用于诊断其用FTIR充电状态。 

视频: A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery

Steady-state, Pre-steady-state, and Single-turnover Kinetic Measurement for DNA Glycosylase Activity

Human 8-oxoguanine DNA glycosylase (OGG1) excises the mutagenic oxidative DNA lesion 8-oxo-7,8-dihydroguanine (8-oxoG) from DNA. Kinetic characterization of OGG1 is undertaken to measure the rates of 8-oxoG excision and product release. When the OGG1 concentration is lower than substrate DNA, time courses of product formation are biphasic; a rapid exponential phase (i.e. burst) of product formation is followed by a linear steady-state phase. The initial burst of product formation corresponds to the concentration of enzyme properly engaged on the substrate, and the burst amplitude depends on the concentration of enzyme. The first-order rate constant of the burst corresponds to the intrinsic rate of 8-oxoG excision and the slower steady-state rate measures the rate of product release (product DNA dissociation rate constant, koff). Here, we describe steady-state, pre-steady-state, and single-turnover approaches to isolate and measure specific steps during OGG1 catalytic cycling. A fluorescent labeled lesion-containing oligonucleotide and purified OGG1 are used to facilitate precise kinetic measurements. Since low enzyme concentrations are used to make steady-state measurements, manual mixing of reagents and quenching of the reaction can be performed to ascertain the steady-state rate (koff). Additionally, extrapolation of the steady-state rate to a point on the ordinate at zero time indicates that a burst of product formation occurred during the first turnover (i.e. y-intercept is positive). The first-order rate constant of the exponential burst phase can be measured using a rapid mixing and quenching technique that examines the amount of product formed at short time intervals (&lt;1 sec) before the steady-state phase and corresponds to the rate of 8-oxoG excision (i.e. chemistry). The chemical step can also be measured using a single-turnover approach where catalytic cycling is prevented by saturating substrate DNA with enzyme (E&gt;S). These approaches can measure elementary rate constants that influence the efficiency of removal of a DNA lesion.

Time courses for the glycosylase activity of 8-oxoguanine DNA glycosylase are biphasic exhibiting a burst of product formation and a linear steady-state phase. Utilizing quench-flow techniques, the burst and the steady-state rates can be measured, which correspond to excision of 8-oxoguanine and release of the glycosylase from the product DNA, respectively.

稳态，稳定前的状态，单营业额动力学测量DNA糖基化酶活性

Human 8-oxoguanine DNA glycosylase (OGG1) excises the mutagenic oxidative DNA lesion 8-oxo-7,8-dihydroguanine (8-oxoG) from DNA. Kinetic characterization ...

科研

化学

Analysis of Volatile and Oxidation Sensitive Compounds Using a Cold Inlet System and Electron Impact Mass Spectrometry

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The analysis of volatile and oxidation sensitive compounds by mass spectrometry is not easily achieved, as all state-of-the-art mass spectrometric methods require at least one sample preparation step, e.g., dissolution and dilution of the analyte (electrospray ionization), co-crystallization of the analyte with a matrix compound (matrix-assisted laser desorption/ionization), or transfer of the prepared samples into the ionization source of the mass spectrometer, to be conducted under atmospheric conditions. Here, the use of a sample inlet system is described which enables the analysis of volatile metal organyls, silanes, and phosphanes using a sector field mass spectrometer equipped with an electron impact ionization source. All sample preparation steps and the sample introduction into the ion source of the mass spectrometer take place either under air-free conditions or under vacuum, enabling the analysis of compounds highly susceptible to oxidation. The presented technique is especially of interest for inorganic chemists, working with metal organyls, silanes, or phosphanes, which have to be handled using inert conditions, such as the Schlenk technique. The principle of operation is presented in this video.

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The presented technique is especially of interest for inorganic chemists, working with metal organyls, silanes, or phosphanes which have to be handled using inert conditions, such as the Schlenk technique.

挥发和氧化敏感的化合物使用冷进气系统和电子轰击质谱分析

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The ...

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 ...

Dynamic Electrochemical Measurement of Chloride Ions

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver chloride electrode is used extensively for potentiometric measurement of chloride ions concentration in electrolyte. In this measurement, long-term and continuous monitoring is limited due to the inherent drift and the requirement of a stable reference electrode. We utilized the chronopotentiometric approach to minimize drift and avoid the use of a conventional reference electrode. A galvanostatic pulse is applied to an Ag/AgCl electrode which initiates a faradic reaction depleting the Cl&#713; ions near the electrode surface. The transition time, which is the time to completely deplete the ions near the electrode surface, is a function of the ion concentration, given by the Nernst equation. The square root of the transition time is in linear relation to the chloride ion concentration. Drift of the response over two weeks is negligible (59 &#181;M/day) when measuring 1 mM [Cl&#713;]using a current pulse of 10 Am-2. This is a dynamic measurement where the moment of transition time determines the response and thus is independent of the absolute potential. Any metal wire can be used as a pseudo-reference electrode, making this approach feasible for long-term measurement inside concrete structures.

Dynamic measurement of chloride ions is presented. Transition time of an Ag/AgCl electrode, during a chronopotentiometric technique, can give the concentration of chloride ions in electrolyte. This method does not require a stable conventional reference electrode.

氯离子的动态电化学测试

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver ...

Glycan Node Analysis: A Bottom-up Approach to Glycomics

Synthesized in a non-template-driven process by enzymes called glycosyltransferases, glycans are key players in various significant intra- and extracellular events. Many pathological conditions, notably cancer, affect gene expression, which can in turn deregulate the relative abundance and activity levels of glycoside hydrolase and glycosyltransferase enzymes. Unique aberrant whole glycans resulting from deregulated glycosyltransferase(s) are often present in trace quantities within complex biofluids, making their detection difficult and sometimes stochastic. However, with proper sample preparation, one of the oldest forms of mass spectrometry (gas chromatography-mass spectrometry, GC-MS) can routinely detect the collection of branch-point and linkage-specific monosaccharides ("glycan nodes") present in complex biofluids. Complementary to traditional top-down glycomics techniques, the approach discussed herein involves the collection and condensation of each constituent glycan node in a sample into a single independent analytical signal, which provides detailed structural and quantitative information about changes to the glycome as a whole and reveals potentially deregulated glycosyltransferases. Improvements to the permethylation and subsequent liquid/liquid extraction stages provided herein enhance reproducibility and overall yield by facilitating minimal exposure of permethylated glycans to alkaline aqueous conditions. Modifications to the acetylation stage further increase the extent of reaction and overall yield. Despite their reproducibility, the overall yields of N-acetylhexosamine (HexNAc) partially permethylated alditol acetates (PMAAs) are shown to be inherently lower than their expected theoretical value relative to hexose PMAAs. Calculating the ratio of the area under the extracted ion chromatogram (XIC) for each individual hexose PMAA (or HexNAc PMAA) to the sum of such XIC areas for all hexoses (or HexNAcs) provides a new normalization method that facilitates relative quantification of individual glycan nodes in a sample. Although presently constrained in terms of its absolute limits of detection, this method expedites the analysis of clinical biofluids and shows considerable promise as a complementary approach to traditional top-down glycomics.

This article presents an enhanced form of a novel bottom-up glycomics technique designed to analyze the pooled compositional profile of glycans in unfractionated biofluids through the chemical breakdown of glycans into their constituent linkage-specific monosaccharides for detection by GC-MS. Potential applications include early detection of cancer and other glycan-affective disorders.

聚糖节点分析:自下而上的方法，以糖原组学

Synthesized in a non-template-driven process by enzymes called glycosyltransferases, glycans are key players in various significant intra- and ...

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single molecule level. An electrostatic self-assembly and covalent fixation (ESA-CF) process is used for the synthesis of the cyclic poly(tetrahydrofuran) (poly(THF)). The diffusive motion of individual cyclic polymer chains in a melt state is visualized using single molecule fluorescence imaging by incorporating a fluorophore unit in the cyclic chains. The diffusive motion of the chains is quantitatively characterized by means of a combination of mean-squared displacement (MSD) analysis and a cumulative distribution function (CDF) analysis. The cyclic polymer exhibits multiple-mode diffusion which is distinct from its linear counterpart. The results demonstrate that the diffusional heterogeneity of polymers that is often hidden behind ensemble averaging can be revealed by the efficient synthesis of the cyclic polymers using the ESA-CF process and the quantitative analysis of the diffusive motion at the single molecule level using the MSD and CDF analyses.

A protocol for the synthesis and characterization of diffusive motion of cyclic polymers at the single molecule level is presented.

环状聚合物的合成及其在熔融状态扩散运动的表征在单分子水平

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single ...

Using Capillary Electrophoresis to Quantify Organic Acids from Plant Tissue: A Test Case Examining Coffea arabica Seeds

Carboxylic acids are organic acids containing one or more terminal carboxyl (COOH) functional groups. Short chain carboxylic acids (SCCAs; carboxylic acids containing three to six carbons), such as malate and citrate, are critical to the proper functioning of many biological systems, where they function in cellular respiration and can serve as indicators of cell health. In foods, organic acid content can have significant impact on taste, with increased SCCA levels resulting in a sour or &#34;acid&#34; taste. Because of this, methods for the rapid analysis of organic acid levels are of particular interest to the food and beverage industries. Unfortunately, however, most methods used for SCCA quantification are dependent on time-consuming protocols requiring the derivatization of samples with hazardous reagents, followed by costly chromatographic and/or mass spectrometric analyses. This method details an alternate method for the detection and quantification of organic acids from plant material and food samples using free zonal capillary electrophoresis (CZE), sometimes simply referred to as capillary electrophoresis (CE). CZE provides a cost-effective method for measuring SCCAs with a low limit of detection (0.005 mg/ml). This article details the extraction and quantification of SCCAs from plant samples. While the method provided focuses on measurement of SCCAs from coffee beans, the method provided can be applied to multiple plant-based food materials.

Using Capillary Electrophoresis to Quantify Organic Acids from Plant Tissue: A Test Case Examining Coffea arabica Seeds

This article presents a method for the detection and quantification of organic acids from plant material using free zonal capillary electrophoresis. An example of the potential application of this method, determining the effects of a secondary fermentation on organic acid levels in coffee seeds, is provided.

利用毛细管电泳从植物组织量化有机酸:一个测试用例检查<em&gt;小粒种咖啡</em&gt;种子

Carboxylic acids are organic acids containing one or more terminal carboxyl (COOH) functional groups. Short chain carboxylic acids (SCCAs; carboxylic ...

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical impedance spectroscopy (EIS) of species that undergo reversible oxidation or reduction in solution was used for determination of rate constants of oxidation or reduction.

电化学阻抗谱作为电化学速率常数估计的一种工具

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, allowing for the synthesis of isotactic poly(&#945;-hydroxy acids) with expected molecular weights (&#62;140 kDa) and narrow molecular weight distributions (Mw/Mn &#60; 1.1). This ring-opening polymerization is mediated by Ni and Zn complexes in the presence of an alcohol initiator and a photoredox Ir catalyst, irradiated by a blue LED (400 - 500 nm). The polymerization is performed at a low temperature (-15 &#176;C) to avoid undesired side reactions. The complete monomer consumption can be achieved within 4 - 8 hours, providing a polymer close to the expected molecular weight with narrow molecular weight distribution. The resulted number-average molecular weight shows a linear correlation with the degree of polymerization up to 1000. The homodecoupling 1H NMR study confirms that the obtained polymer is isotactic without epimerization. This polymerization reported herein offers a strategy for achieving rapid, controlled O-carboxyanhydrides polymerization to prepare stereoregular poly(&#945;-hydroxy acids) and its copolymers bearing various functional side-chain groups.

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

A protocol for the controlled photoredox ring-opening polymerization of O-carboxyanhydrides mediated by Ni/Zn complexes is presented.

镍/锌配合物介导的O-Carboxyanhydrides 的控制 Photoredox 环开聚合

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, ...

Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides

Electrospray ionization (ESI) can transfer an aqueous-phase peptide or peptide complex to the gas-phase while conserving its mass, overall charge, metal-binding interactions, and conformational shape. Coupling ESI with ion mobility-mass spectrometry (IM-MS) provides an instrumental technique that allows for simultaneous measurement of a peptide&#8217;s mass-to-charge (m/z) and collision cross section (CCS) that relate to its stoichiometry, protonation state, and conformational shape. The overall charge of a peptide complex is controlled by the protonation of 1) the peptide&#8217;s acidic and basic sites and 2) the oxidation state of the metal ion(s). Therefore, the overall charge state of a complex is a function of the pH of the solution that affects the peptides metal ion binding affinity. For ESI-IM-MS analyses, peptide and metal ions solutions are prepared from aqueous-only solutions, with the pH adjusted with dilute aqueous acetic acid or ammonium hydroxide. This allows for pH dependence and metal ion selectivity to be determined for a specific peptide. Furthermore, the m/z and CCS of a peptide complex can be used with B3LYP/LanL2DZ molecular modeling to discern binding sites of the metal ion coordination and tertiary structure of the complex. The results show how ESI-IM-MS can characterize the selective chelating performance of a set of alternative methanobactin peptides and compare them to the copper-binding peptide methanobactin.

Ion mobility-mass spectrometry and molecular modeling techniques can characterize the selective metal chelating performance of designed metal-binding peptides and the copper-binding peptide methanobactin. Developing new classes of metal chelating peptides will help lead to therapeutics for diseases associated with metal ion misbalance.