我们感谢在瓦瑟学院本科生暑期研究协会（URSI），露西·梅纳德·三文鱼研究基金，美国航空航天局颁发号NX09AU90A，美国国家科学基金会研究中心卓越科学与技术（NSF-CREST）号裁决的支持0630388和美国国家科学基金会奖号码1058385。

1，C.线虫准备<ol><li>准备的年轻成年C.培养皿如涉及暂停C的以往的实验描述线虫线虫在一个充满液体的比色皿11。 </li><li>在视频分析当天，现场挑选年轻的成年线虫直接使用铂作为选秀第2步中描述的充满去离子，蒸馏水的比色皿。 </li><li>准备死C。线虫用氯仿曝光。继续按照采摘步骤2中所述的现场线虫描述的过程。 </li></ol> 2，光安装的视频分析<ol><li>组装的实验装置如图1创建阴影图像。摄像机可以，只要它是能够捕获屏幕的前视图被放置在离屏幕的任何距离。一个好的地方是旁边对着屏幕的比色皿。 <ol><li>使用至少两个反射镜，以引导所述可调谐氦氖激光输出成一个伽利略扩束器，使得光束被扩展成直径为12毫米。 </li><li>放置一个或两个针孔的光束路径，使得光束穿过针孔而不被阻挡。使用针孔，以保证校准被保持。 </li><li>直接扩束到安装石英比色皿，即10毫米宽10毫米深4厘米高。 </li><li>使用平凸透镜为75毫米的正焦距放大的光束。 </li><li>将投影屏幕从镜头大约120厘米距离大于这将产生阴影图像的更大的放大倍率。然而，图像的质量会降低具有较低的光强度和衍射干涉的增加引人注目。 </li><li>放置一个高速摄像机，它能够至少每秒60帧的，旁边对着屏幕上的比色皿。 </li></ol></li><li>放置在解剖显微镜的光学邻近集向上为快速传递线虫到试管中。 </li><li>暂时固定透明尺，毫米部门到比色皿支架的中心垂直于扩束使光束项目标尺的放大图像到屏幕上。设置长度尺度进行视频分析。 <ol><li>在投影屏幕上，采用了透明尺偏离中心的投影图像，以避免与投影干扰标记刻度的距离。 <a href="Video_1_633nm.MOV" target="_blank">点击此处观看视频。</a> </li><li>记录此图像并测量放大倍率。从设置中删除的统治者。重复对其他波长的折射光的每个波长的透过透镜的角度这个步骤会有所不同，由于色差。 </li></ol></li><li>更换比色皿，并在1毫米蒸馏水轮辋它填充到。 </li><li>开始记录时，使刻度距离被包含在相同的室内光线是上镜头作为投影图像。关灯。 </li><li>使用薄，扁平铂丝接，移动单个年轻的成年C。线虫一次一个地从琼脂板放入反应杯通过触摸拾取到水的表面上。线虫会在水柱中成为可见的，当它进入的光束，由于散射光。 <a href="Video_2_CB678_633nm.mov" target="_blank">点击此处观看视频。</a> </li><li>膜虫的投影图像，因为他们通过扩展的激光束通过。值得注意的是，投影图像被反转，蠕虫会出现在它们的实际运动的相反方向移动是很重要的。被降与重力蠕虫会出现在屏幕上向上移动（ 图2）。 </li></ol> 3，视频数据准备<ol><li>导入的视频到视频分析程序。 </li><li>使用预先确定的放大系数设定刻度。 </li><li>茶CK阴影线虫的头部的至少10个数据点，在整个路径上的线性位移取。 </li><li>发现通过取导数（“Y”，“时间”），在垂直方向上的速度与通过在步骤2.2中确定的放大系数除以该值。 </li></ol> 4，数据分析<ol><li>分析一个C的直线下降线虫 ： <ol><li>检查，以确保在垂直位置与时间的关系曲线图中的数据点通常形成一条直线。一些偏差可由于该线虫的头部运动被忽略。如果数据点通常形成一条直线，则继续到步骤4.1.2，否则后裔是非线性的分析应用在这个协议步骤5.1将继续。 </li><li>通过拟合直线12从分析菜单中的数据建立一个线性回归线。这条线的斜率是那么C的垂直速度。线虫 。的斜率是在位置的变化通过时间的变化在特定的时间间隔划分。确定这种方式的活的和死虫的下降速度（ 图3）。 </li><li>平均从线虫的垂直游动速度。约50蠕虫样本量是足够的。活虫与死虫漂移速度比较游泳速度。 </li></ol></li></ol> 5，分析下的非线性运动线虫 <ol><li>从第3节中，选择一个分析视频文件，其中显示了水柱中的非线性下降（ 图4）。一种非线性的下降可以用一步4.1.1在本协议中确定。 </li><li>从视频分析软件的“分析”菜单中选择“曲线拟合”。选择一个二阶（二次）多项式。拟合曲线。 </li><li>对感兴趣的区域中，通过在每一侧ø滑动托架调整适合在图形上F中的配合图形上，直到曲线非常接近内的配合和/或井内的误差棒的数据点。拟合程序给出了拟合的曲线，它是垂直位置与时间的关系的数学表达式。考虑通过与物理性质相关的节目中给出的拟合曲线的误差。 15％或以下，相对误差通常是可以接受的。 </li><li>添加更多的曲线拟合覆盖数据的其他部分。花键13，用于最佳覆盖的功能：确保该曲线拟合的重叠，并试图使相邻曲线，使得在重叠区域中的道匹配。 </li><li>通过使用在步骤5.1.3中获得的数学表达式同时拟合曲线的导数获得的速度为感兴趣的区域。速度可以随时间变化。注意，该衍生物是一个函数的斜率。衍生工具可以用数学或图形来获得。在这种情况下，实际使用的特定的数学expr的易讯网络。 </li><li>取拟合曲线的二阶导数，得到的加速度。加速度可以随时间变化。 </li><li>蠕虫质量乘以加速度来计算推力，该蠕虫发挥。一个合理的估计质量为3微克假设该蠕虫主要是由水组成。 </li></ol>

<ol>
	<li>Ward, A., Lie, J., Feng, Z., Xu, Z. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light-sensitive+neurons+and+channels+mediate+phototaxis+in+C.+elegans.">Light-sensitive neurons and channels mediate phototaxis in C. elegans.</a> Nature Neurosci. 11, 916-922 (2008).</li><li>Pierce-Shimomura, J. T., Chen, B. L., Mun, J. J., Ho, R., Sarkis, R., McIntire, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+analysis+of+crawling+and+swimming+locomotory+patterns+in+C.+elegans.">Genetic analysis of crawling and swimming locomotory patterns in C. elegans.</a> Proc. Natl. Acad. Sci. USA. , 105-20987 (2008).</li><li>Vidal-Gadea, A. G., Davis, S., Becker, L., Pierce-Shimomura, J. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coordination+of+behavioral+hierarchies+during+environmental+transitions+in+Caenorhabditis+elegans.">Coordination of behavioral hierarchies during environmental transitions in Caenorhabditis elegans.</a> Worm. 1, 5-11 (2012).</li><li>Berri, S., Boyle, J. H., Tassieri, M., Hope, I. A., Cohen, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Forward+locomotion+of+the+nematode+C.+elegans+is+achieved+through+modulation+of+a+single+gait.">Forward locomotion of the nematode C. elegans is achieved through modulation of a single gait.</a> HFSP Journal. 3, 186-193 (2009).</li><li>Keller, H. E., Pawley, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Objective Lenses for Confocal Microscopy. Handbook of Biological Confocal Microscopy. , (2006).</li><li>Conrad, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Depth+of+Field+in+Depth.">Depth of Field in Depth.</a> Large Format Page Retrieved. , (2011).</li><li>Demtr&#246;der, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Laser Spectroscopy Basic Concepts and Instrumentation. , (2003).</li><li>Magnes, J., Raley-Susman, K., Melikechi, N., Sampson, A., Eells, R., Bello, A., Lueckheide, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+Freely+Swimming+C.+elegans+Using+Laser+Diffraction.">Analysis of Freely Swimming C. elegans Using Laser Diffraction.</a> Open J. Biophys. 2 (3), 101-107 (2012).</li><li>Mood, A., Graybill, F., Boes, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Introduction to the Theory of Statistics. , (1974).</li><li>Taylor, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Classical Mechanics. , (2005).</li><li>Magnes, J., Susman, K., Eells, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+Locomotion+Study+of+Freely+Swimming+Micro-organisms+Using+Laser+Diffraction.">Quantitative Locomotion Study of Freely Swimming Micro-organisms Using Laser Diffraction.</a> J. Vis. Exp. (68), (2012).</li><li>Bevington, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Data Reduction and Error Analysis for the Physical Sciences. , (1969).</li><li>Lyche, T., Schumaker, L. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+spline+approximation+methods.">Local spline approximation methods.</a> Journal of Approximation Theory. 15 (4), 294-325 (1975).</li><li>Kim, N., Dempsey, C. M., Kuan, C. -. J., Zoval, J. V., O'Rourke, E., Ruvkun, G., Madou, M. J., Sze, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gravity+Force+Transduced+by+the+MEC-4/MEC-10+DEG/ENaC+Channel+Modulates+DAF-16/FoxO+Activity+in+Caenorhabditis+elegans.">Gravity Force Transduced by the MEC-4/MEC-10 DEG/ENaC Channel Modulates DAF-16/FoxO Activity in Caenorhabditis elegans.</a> Genetics. 177, 835-845 (2007).</li></ol>

作者什么都没有透露。

该SWSI技术提供了解微观生物一样自由生活线虫的运动器官功能的另一种方式。有了这个技术，我们积极运动（游泳）和被动漂移之间有区别，由于对死线虫重力操作。此外，当自由游动的线虫在运动过程中水改变方向，我们能够测量阻力和角的力量，这是经营上的线虫和线虫作用。 线虫所遇到的土壤内的不同的环境条件。有内土壤水分的口袋，以及固体颗粒和不同的形状和纹理的生物材料。此外，线虫内，他们以14回应重力环境中存在。此外，在土壤的表面附近线虫暴露于不同波长的光，变化的温度和湿度，以及生物变量，如细菌，真菌掠夺和其他土壤生物。线虫必须应对所有这些不同的变量，游泳和爬行在不同的媒体，转弯和改变导航策略。所有这些复杂的计算仅由302个神经元，一个子集，其中所涉及的运动，和95的体壁肌肉细胞进行。通过SWSI技术描述的那种测量提供重要的洞察线虫如何做到这一点的导航的复杂性。 在第一部分，我们已经测量野生型C的整体下降速度线虫在633纳米的光。使用这些测量，我们可以估算阻力蠕虫的遭遇。 为加速线虫的案例研究中，势力不断介入，因为有速度的拖曳力变化的变化。有一些报表，我们能够做出关于作用在蠕虫的力量。作为蜗轮减速并试图向swIM向上的阻力的垂直分量降低，直到达到零线虫的轨迹的最低点。在这一点上，该蠕虫必须有一个向上的力来游泳了。 此方法可以以多种方式进行修改。该导航在一种透明的液体的任何微小物质可以使用​​SWSI进行跟踪。研究可以与可访问的数码相机的任何波长进行。数码相机通常会拿起波长范围从紫外到近红外。此外，水平的研究可通过垂直向上引导激光进行。该物种可以​​被放置在水平表面上的透明，如显微镜载玻片。调整扩束器或放大镜扩束后，可以锐化模糊的图像。用户应确实锁紧所有组件表中，以确保一致且易于光束准直。 该方法是通过使用激光wavelengt不限HS和分辨率。在本质上，这方法比现有的显微镜，它是在方向和波长的灵活性的优点，也是缺点，因为安装是简单的。激光的古朴光学和斑点限制了分辨率。一些这些缺点当然是可以在将来通过包括空间滤波器，并直接将图像投影到CCD相机得到改善。 可以很容易地了解到在该协议中最关键的步骤，在第一次进行的实验。而不产生湍流放置线虫中的反应杯是至关重要的。另外，振动可能会干扰设置和改变的蠕虫的行为。一定要限制功率，这是用来遮蔽图像。 2毫瓦的激光束为1毫米的直径应为最大，以避免加热效果。设置应在使用液体比蒸馏水等散射效应进行测试。 目前，大多数米使用白光或彩色过滤器，它们仍然非常广泛的波长范围内的水平面上icroscopes操作。显微镜，真正使用单一波长，并具有灵活性，在观察的情况下， 即水平放置，通常仅限于一个优势或其他。此外，这些类型的显微镜通常是非常昂贵的，仍局限于焦平面我们的方法不同。我们的设置可以很容易地用极低的预算建造。这种方法是随时可以使用的学校，环保公司以及其他实体，与小资金操作。在未来，这种方法可以用在一个非常复杂的设置，研究运动和微观物质的机械感觉实时特效。这种方法使单波长的研究在大范围角度和容易获得的观看深处。

秀丽隐杆线虫是一种自由生活的有益土壤线虫是一个功能强大的模式生物用于研究基因调控，发展和更多的新机制对于理解感官生物学和行为。尽管有只有302个神经元，C。线虫有能力的复杂运动器官的形态，繁殖行为，导航，趋化性和许多其他行为。C。线虫具有机械感受器，化学感受器，甚至侦测光线的蓝色波长（Ward 等 ，2008）1。虽然很多人知道感觉功能的神经回路和C.一般运动器官的形态线虫 ，更少有人知道的回应多个并发的刺激或比可以在显微镜下进行建模更复杂的环境条件。一些研究发现更复杂的运动器官的图案，高塑性2,3,4。我们的方式方法，使NEM研究atodes在溶液中实时在这里我们可以很容易地同时提供多种环境条件。这个问题很难用传统的显微镜为基础的成像技术来解决。我们已经开发了一种成像技术，使我们能够把线虫水柱内检查运动器官的行为，以及确定线虫的能力来改变运动的响应不同的环境条件。 单波长阴影成像（SWSI）列于本文首次以解决传统显微镜的缺点。传统的显微镜限于观察物种在水平焦平面几微米的深度5,6。对于单波长的研究中，最传统的显微镜用彩色滤光片非常广泛，通常为50-100纳米过滤白光。利用激光对SWSI变窄波长选择为小于1纳米，同时保持标志ificant光强7。同样，单一波长已被用于测量C的游泳频率线虫实时8。 对于我们方法的第一个示范，我们监测的水平位置，x和垂直位置，Y，自由游动C的线虫的水柱，在约一厘米的距离。特别是，我们感兴趣的是垂直运动，因为重力也垂直地作用。线性拟合到垂直位置的斜率给出的垂直速度的线虫，V Y，因为它下降的水柱： <img alt="公式" fo:content-width="0.5in" src="/files/ftp_upload/51424/51424eq1.jpg" width="50" /> （1） 的均方根误差（RMSE）9的平方表示拟合的质量和表示的下降速度是否是大致恒定的。垂直速度，然后平均为选管会h种和死虫。利用这些结果，拖动，它的蠕虫经验可估计。 对于我们方法的第二个演示中，我们选择了C。线虫未以恒定的速率下降多数观察到的蠕虫的不同。所选择的蠕虫或者掉头向上游泳或持续下降前徘徊了一会儿。在物理上，这种情况下，研究表明，游泳微生物的推力可以计算出来。牛顿定律支配的一个改变方向的身体加速，这意味着净力， <img alt="式（1）" fo:content-width="0.3in" src="/files/ftp_upload/51424/51424eq.jpg" width="25" /> ，是作用于该机构10： <img alt="式（2）" fo:content-width="0.7in" src="/files/ftp_upload/51424/51424eq2.jpg" width="70" /> （2） 哪里<img alt="p" fo:content-width="0.1in" src="/files/ftp_upload/51424/51424p.jpg" width="10" />是线动量，t是时间。蠕虫的加速度成正比作用于蜗杆的力量，因为该蠕虫的质量保持不变。其结果是，垂直的净力为： <img alt="式（3）" fo:content-width=".8in" src="/files/ftp_upload/51424/51424eq3.jpg" width="70" /> （3） 其中m是蠕虫的质量和y表示垂直加速度。在垂直方向上的净力表示接着蜗杆推力在同一方向上。总推力可以通过采取水平分量在内进行计算。

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			<td height="42" style="height:42px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:143px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:375px;">Comments/Description</td>
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			<td height="21" style="height:21px;width:216px;">Tunable Helium-Neon laser&#160;</td>
			<td>Research Electro-Optics</td>
			<td>30602</td>
			<td>Four wavelengths can be selected between 543 nm and 633 nm.</td>
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			<td height="42" style="height:42px;width:216px;">2 Front Surface Aluminum Mirrors</td>
			<td style="width:143px;">Thorlabs</td>
			<td>PF10-03-F01</td>
			<td></td>
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			<td height="21" style="height:21px;">High Speed Exilim Camera</td>
			<td style="width:143px;">Casio</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Quartz Cuvette</td>
			<td style="width:143px;">Starna Cells</td>
			<td style="width:119px;">21/G/5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">LoggerPro (Software)</td>
			<td style="width:143px;">Vernier</td>
			<td style="width:119px;"></td>
			<td>http://www.vernier.com/products/software/lp/</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Mathematica 8</td>
			<td style="width:143px;">Wolfram</td>
			<td style="width:119px;"></td>
			<td>http://www.wolfram.com/</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">&#160;5x &#8211; 10x variable zoom Galilean beam expander</td>
			<td style="width:143px;">Thorlabs</td>
			<td>BE05-10-A</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Plano-convex lens with a positive focal length of 75 mm</td>
			<td style="width:143px;">Thorlabs</td>
			<td style="width:119px;">LA1257</td>
			<td></td>
		</tr>
	</tbody>
</table>

single wavelength shadow imaging of caenorhabditis elegans locomotion including force estimates

这项研究表明，一种廉价和简单的技术，它允许的物理性能如位置，速度，加速度和参与线虫悬浮在水中的柱响应于单一波长的光的运动器官行为力的测量。我们将演示如何评估使用单波长阴影成像（SWSI）使用两个不同的例子一个微小的有机体的运动。 第一个例子是C的平均下降系统和统计学上可行的研究线虫中的水柱。在这项研究中，我们使用了活着和死去的野生型C。线虫。当我们比较线虫主动运动的速度和方向与引力场中死虫的被动血统，这项研究表明在血统倍没有差别。平均下降​​为1.5毫米/秒±0.1毫米/秒为使用633nm的相干的活的和死虫光。 第二个例子是个人选择C的个案研究线虫在垂直水柱下降改变方向。加速度和力在本实施例进行分析。此案例研究展示了可以使用SWSI同时使用单一波长的环境中，是不是与传统的显微镜评估访问行为进行评估的其他物理特性的范围。使用这种分析，我们估计个别线虫能够与超过28 NN力助推的。 我们的研究结果表明，生活线虫施加28 NN转动或移动对引力场的时候。研究结果进一步表明，线虫被动下降的水柱，但可以积极抵御重力的作用主要是通过转动的方向。

稳步下降第一次调查显示了C的递减率没有区别的差异使用SWSI 633 nm的过程中线虫 。递减率被认为是恒定在1.5毫米/秒±0.1毫米/秒为活和死区C。线虫 。 50蠕虫样本量产生的7％为活的和死虫合理的方差。没有加速度作用在蠕虫以来的下降速度是恒定的，因此，阻力等于重力减去浮力。这意味着该蜗杆的密度比水稍大;然而，对于在它下面的估计仍然是实际的假设，线虫的密度大致是水。 改变方向第二个调查，个案研究，表明线虫能够改变方向，并可以对以上游重力。两条曲线进行拟合到线虫的垂直位移，使这些曲线的二阶导数可以被花键连接到图表加速度随时间变化（ 图5）。 &#160;明智的做法是保持多项式阶数尽可能低，同时保持一个不错的选择。较低的多项式阶表示在加速变化随着时间的推移较少。高阶多项式的计算将是微不足道的，因此，不必要的，如果该多项式的阶数过高。该蠕虫在减速0.110毫米/秒的恒定速率2±0.002毫米/秒2，转身加速以同样的速度0.110毫米/秒2±0.002毫米/秒2，直到不久后 在折返点。该三线虫继续以1.252一个加速递减向上移动- 0.00708吨毫米/秒2，直到加速度下降到零。牢记公式。 3，和3＆＃估计蠕虫质量956;克，蠕虫经历了一个垂直净力0.33 PN，F 尹恩惠 ，直到折返点后不久。 血统：有三种力量作用于蜗杆，直到病虫到达折返点：重力，阻力，浮力和推力（ 图6a）。净力等于所有三个力的矢量和。在这里，我们只考虑垂直分量： F 尹恩惠 = F 镝 + F TY-F G + F B（4） 其中F B是浮力。 F G 是在幅度上相等但在方向上的浮力假设蠕虫的密度是水的对面。式。 4然后可以写成如下方式： F 尹恩惠 = F 镝 + F款（5） F 尹恩惠在下降保持不变。这意味着F 镝 + F款保持不变，直到线虫到达折返点。 F 镝（Dy）是最大的顶部，这是路径的开始，并逐渐降低至零，直到速度为零的折返点，而F款 必须增加，以保持F 尹恩惠不变。 转机：有一个在在折返点的垂直方向上没有阻力，因为垂直速度等于零在这一点上。作用在垂直方向上的唯一的力是重力， - F，G，浮力，F B和垂直蜗杆推力，F 泰 ，如在图6b中描绘。在这点上，C的推力线虫可确定： F款= F 尹恩惠 （6） 在该轨迹的底部的推力则大致等于0.33 PN，这是大约0.001％的蠕虫的重量。考虑到帐户，估计重量，F G一C的线虫是28 NN， 晋：同样，在上升，拖累增加，但被朝下（ 图6c）： F 尹恩惠 =-F 镝 + F款（7） 蠕虫实施的重点现在必须变得更大，等于阻力的总和和重量。该蠕虫病毒正在开始游泳了之后放缓。游泳了在作为蠕虫的后裔相同的速率，该蠕虫将不得不发挥的至少两倍的重量向上的推力。 徘徊一个蠕虫病毒，减缓其下降约3秒的一个例子是在图7。 &#160;有3 次多项式是一个合理的适合于整体路径。在此合适的加速度和速度的误差小于15％。该蠕虫病毒开始于一个显著upwaRD推力，减缓并开始扭转在68秒;然而，向上的加速度连续减小（ 图8） &#160;直到净加速度等于零周围68.5秒。这最终会导致净加速度在向下方向上接着在速度另一个零点（ 图9） &#160;和线虫开始于69秒再次下降。 有趣的是，在这种情况下观察到的最大垂直加速度为2.7毫米/秒2。加速的转折点是0.455毫米/秒2和- 0.455毫米/分别秒2;比在该转身游了线虫的情况下约大4倍。用公式。 6，它可以被估计，向上的推力约为1.32 PN在第一转折点。在第二个转折点，净加速度为负，这样的向上的推力是1.32 PN。 ○：保持-together.within页=“总是”&gt; <img alt="图1" fo:content-width="5in" fo:src="/files/ftp_upload/51424/51424fig1highres.jpg" src="/files/ftp_upload/51424/51424fig1.jpg" /> 图1的实验装置的激光器，光束扩展器，透镜和屏幕所必需的实验装置。转向反射镜和针孔可以省略，但会使光学对准不太稳定。 <img alt="图2" fo:content-width="5in" fo:src="/files/ftp_upload/51424/51424fig2highres.jpg" src="/files/ftp_upload/51424/51424fig2.jpg" /> 图2：单波长阴影图像（SWSI）使用2毫瓦的543纳米激光蠕虫的影子投射到屏幕上。该图像被反转，使得线虫似乎向上倒下。 424/51424fig3highres.jpg“SRC =”/ files/ftp_upload/51424/51424fig3.jpg“/&gt; 一个单一的野生型C的图3。垂直降落线虫的水柱，这线虫却笼罩在633 nm的相干光。线性拟合的斜率表示为1.09毫米/秒±0.01毫米/秒的下降速度。 <a href="https://www.jove.com/files/ftp_upload/51424/51424fig3highres.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图4" fo:content-width="5in" fo:src="/files/ftp_upload/51424/51424fig4highres.jpg" src="/files/ftp_upload/51424/51424fig4.jpg" /> 图4单个向上游动野生型C的位移曲线线虫 ，两个花键配合跟踪线虫的整体路径。拟合的二阶导数揭示的加速度。 0.110毫米：最大加速度容易从第一拟合确定<html> /秒2±0.002毫米/秒2。只有少数误差线显示，使得数据点和拟合保持可见。该线虫却笼罩在633 nm的相干光。 <a href="https://www.jove.com/files/ftp_upload/51424/51424fig4highres.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图5" fo:content-width="5in" fo:src="/files/ftp_upload/51424/51424fig5highres.jpg" src="/files/ftp_upload/51424/51424fig5.jpg" /> 一个单一的野生型C的图5。加速图形线虫 ，这种线虫保持0.110毫米/秒2±0.002毫米/秒2的恒定向上的加速度使其减速，然后向上移动。在折返点后不久，加速平稳下降，净加速度减小到零。<html> G“目标=”_blank“&gt;请点击这里查看该图的放大版本。 <img alt="图6" fo:content-width="5in" fo:src="/files/ftp_upload/51424/51424fig6highres.jpg" src="/files/ftp_upload/51424/51424fig6.jpg" /> 图6。图力为下降，拐点和上升。浮力和重力大小相等，方向相反的方向，使这些力量的影响相互抵消。所以，他们不是在这些图中所示。（一）该蠕虫病毒是降与阻力和推力朝上。（二）该蠕虫病毒是在不拖动轨迹的最低点。推力朝上。（三）该蠕虫与拖动指向下方，而推力朝上上升。 “SRC =”/ files/ftp_upload/51424/51424fig7.jpg“/&gt; 图7。单盘旋线虫位移图。该蠕虫会减慢，并开始扭转约68秒，但开始下降约69秒。 <a href="https://www.jove.com/files/ftp_upload/51424/51424fig7highres.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图8" fo:content-width="5in" fo:src="/files/ftp_upload/51424/51424fig8highres.jpg" src="/files/ftp_upload/51424/51424fig8.jpg" /> 。图8单盘旋线虫的加速曲线图这个蠕虫开始使用2.7毫米/秒2的加速度上升，下降到零，并最终有一个向下的加速度- 2.6毫米/秒2 <a href="https://www.jove.com/files/ftp_upload/51424/51424fig8highres.jpg" target="_blank">，请点击这里查看大图自愿减排量</a>离子这个数字。 <img alt="图9" fo:content-width="5in" fo:src="/files/ftp_upload/51424/51424fig9highres.jpg" src="/files/ftp_upload/51424/51424fig9.jpg" /> 图9。一个盘旋线虫的速度曲线图。该蠕虫来到停在68秒，开始头向上，减缓并达到在69秒之后的下降垂直方向速度为零。 <a href="https://www.jove.com/files/ftp_upload/51424/51424fig9highres.jpg" target="_blank">请点击这里查看更大的版本这个数字。</a> <img alt="表1" fo:content-width="4in" fo:src="/files/ftp_upload/51424/51424table1highres.jpg" src="/files/ftp_upload/51424/51424table1.jpg" width="400" /> 氮气C.表1。平均下降速度线虫 50直播和50人死亡线虫风帆在他们的后裔在得到确认。平均速度为下坡是相同的活和死虫：1.5毫米/秒±0.1毫米/秒。

Watch this Scientific Journal Video about Single Wavelength Shadow Imaging of Caenorhabditis elegans Locomotion Including Force Estimates at JoVE.com

Single Wavelength Shadow Imaging of Caenorhabditis elegans Locomotion Including Force Estimates

这里提出的技术措施的采用单一波长曝光自由游动微观品种的路径。C。线虫是用于演示的阴影成像作为一种廉价的替代昂贵的显微镜。这种技术可以适于容纳各种取向，环境和物种测量方向，速度，加速度和力。

单波长阴影成像<em&gt;秀丽隐杆线虫</em&gt;步态包括武力在内的估算

This study demonstrates an inexpensive and straightforward technique that allows the measurement of physical properties such as position, velocity, ...

single-wavelength-shadow-imaging-caenorhabditis-elegans-locomotion

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Single Wavelength Shadow Imaging of Caenorhabditis elegans Locomotion Including Force Estimates

Unit 1

Newton's Laws of Motion

SCIENTISTS IN ACTION

9.0K 次观看.  Vassar College. 这里提出的技术措施的采用单一波长曝光自由游动微观品种的路径。C。线虫是用于演示的阴影成像作为一种廉价的替代昂贵的显微镜。这种技术可以适于容纳各种取向，环境和物种测量方向，速度，加速度和力。 

视频: Single Wavelength Shadow Imaging of Caenorhabditis elegans Locomotion Including Force Estimates

Compact Quantum Dots for Single-molecule Imaging

Single-molecule imaging is an important tool for understanding the mechanisms of biomolecular function and for visualizing the spatial and temporal heterogeneity of molecular behaviors that underlie cellular biology 1-4. To image an individual molecule of interest, it is typically conjugated to a fluorescent tag (dye, protein, bead, or quantum dot) and observed with epifluorescence or total internal reflection fluorescence (TIRF) microscopy. While dyes and fluorescent proteins have been the mainstay of fluorescence imaging for decades, their fluorescence is unstable under high photon fluxes necessary to observe individual molecules, yielding only a few seconds of observation before complete loss of signal. Latex beads and dye-labeled beads provide improved signal stability but at the expense of drastically larger hydrodynamic size, which can deleteriously alter the diffusion and behavior of the molecule under study.
Quantum dots (QDs) offer a balance between these two problematic regimes. These nanoparticles are composed of semiconductor materials and can be engineered with a hydrodynamically compact size with exceptional resistance to photodegradation 5. Thus in recent years QDs have been instrumental in enabling long-term observation of complex macromolecular behavior on the single molecule level. However these particles have still been found to exhibit impaired diffusion in crowded molecular environments such as the cellular cytoplasm and the neuronal synaptic cleft, where their sizes are still too large 4,6,7.
Recently we have engineered the cores and surface coatings of QDs for minimized hydrodynamic size, while balancing offsets to colloidal stability, photostability, brightness, and nonspecific binding that have hindered the utility of compact QDs in the past 8,9. The goal of this article is to demonstrate the synthesis, modification, and characterization of these optimized nanocrystals, composed of an alloyed HgxCd1-xSe core coated with an insulating CdyZn1-yS shell, further coated with a multidentate polymer ligand modified with short polyethylene glycol (PEG) chains (Figure 1). Compared with conventional CdSe nanocrystals, HgxCd1-xSe alloys offer greater quantum yields of fluorescence, fluorescence at red and near-infrared wavelengths for enhanced signal-to-noise in cells, and excitation at non-cytotoxic visible wavelengths. Multidentate polymer coatings bind to the nanocrystal surface in a closed and flat conformation to minimize hydrodynamic size, and PEG neutralizes the surface charge to minimize nonspecific binding to cells and biomolecules. The end result is a brightly fluorescent nanocrystal with emission between 550-800 nm and a total hydrodynamic size near 12 nm. This is in the same size range as many soluble globular proteins in cells, and substantially smaller than conventional PEGylated QDs (25-35 nm).

We describe the preparation of colloidal quantum dots with minimized hydrodynamic size for single-molecule fluorescence imaging. Compared to conventional quantum dots, these nanoparticles are similar in size to globular proteins and are optimized for single-molecule brightness, stability against photodegradation, and resistance to nonspecific binding to proteins and cells.

紧凑型量子点的单分子成像

Single-molecule imaging is an important tool for  understanding the mechanisms of biomolecular function and for visualizing the  spatial and temporal ...

科研

工程学

Atomic Force Microscopy of Red-Light Photoreceptors Using PeakForce Quantitative Nanomechanical Property Mapping

Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be measured to ~10 pN by a laser and sectored detector, which can be converted to image topography. Amplitude modulation or &#8220;tapping mode&#8221; AFM involves the probe making intermittent contact with the surface while oscillating at its resonant frequency to produce an image. Used in conjunction with a fluid cell, tapping-mode AFM enables the imaging of biological macromolecules such as proteins in physiologically relevant conditions. Tapping-mode AFM requires manual tuning of the probe and frequent adjustments of a multitude of scanning parameters which can be challenging for inexperienced users. To obtain high-quality images, these adjustments are the most time consuming.
PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) produces an image by measuring a force response curve for every point of contact with the sample. With ScanAsyst software, PF-QNM can be automated. This software adjusts the set-point, drive frequency, scan rate, gains, and other important scanning parameters automatically for a given sample. Not only does this process protect both fragile probes and samples, it significantly reduces the time required to obtain high resolution images. PF-QNM is compatible for AFM imaging in fluid; therefore, it has extensive application for imaging biologically relevant materials.
The method presented in this paper describes the application of PF-QNM to obtain images of a bacterial red-light photoreceptor, RpBphP3 (P3), from photosynthetic R. palustris in its light-adapted state. Using this method, individual protein dimers of P3 and aggregates of dimers have been observed on a mica surface in the presence of an imaging buffer. With appropriate adjustments to surface and/or solution concentration, this method may be generally applied to other biologically relevant macromolecules and soft materials.

A method for investigating the structure of a protein photoreceptor using atomic force microscopy (AFM) is described in this paper. PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) reveals intact protein dimers on a mica surface.

冲红灯光感受器原子力显微镜使用PeakForce定量纳米机械性能映射

Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be ...

Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone.

The methodology to perform friction force microscopy experiments for contacting brushes is presented: Two polymer brushes that are grafted from (a) substrates and (b) colloidal probes are slid to show that, by using two contacting immiscible brush systems, friction in sliding contacts is reduced compared to miscible brush systems.

互溶的测量准备和摩擦力显微镜，反对聚合物刷

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low ...

Investigating Single Molecule Adhesion by Atomic Force Spectroscopy

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. At the same time the AFM tip is passivated to prevent unspecific interactions between the tip and the substrate, which is a prerequisite to study single molecules attached to the AFM tip. Analyses to determine the adhesion force, the adhesion length, and the free energy of these molecules on solid surfaces and bio-interfaces are shortly presented and external references for further reading are provided. Example molecules are the poly(amino acid) polytyrosine, the graft polymer PI-g-PS and the phospholipid POPE (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine). These molecules are desorbed from different surfaces like CH3-SAMs, hydrogen terminated diamond and supported lipid bilayers under various solvent conditions. Finally, the advantages of force spectroscopic single molecule experiments are discussed including means to decide if truly a single molecule has been studied in the experiment.

A protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. Procedures and examples to determine the adhesion force and free energy of these molecules on solid supports and bio-interfaces are provided.

调查单分子粘附的原子力谱

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single ...

Measurement of Scattering Nonlinearities from a Single Plasmonic Nanoparticle

Plasmonics, which are based on the collective oscillation of electrons due to light excitation, involve strongly enhanced local electric fields and thus have potential applications in nonlinear optics, which requires extraordinary optical intensity. One of the most studied nonlinearities in plasmonics is nonlinear absorption, including saturation and reverse saturation behaviors. Although scattering and absorption in nanoparticles are closely correlated by the Mie theory, there has been no report of nonlinearities in plasmonic scattering until very recently. 
Last year, not only saturation, but also reverse saturation of scattering in an isolated plasmonic particle was demonstrated for the first time. The results showed that saturable scattering exhibits clear wavelength dependence, which seems to be directly linked to the localized surface plasmon resonance (LSPR). Combined with the intensity-dependent measurements, the results suggest the possibility of a common mechanism underlying the nonlinear behaviors of scattering and absorption. These nonlinearities of scattering from a single gold nanosphere (GNS) are widely applicable, including in super-resolution microscopy and optical switches. 
In this paper, it is described in detail how to measure nonlinearity of scattering in a single GNP and how to employ the super-resolution technique to enhance the optical imaging resolution based on saturable scattering. This discovery features the first super-resolution microscopy based on nonlinear scattering, which is a novel non-bleaching contrast method that can achieve a resolution as low as l/8 and will potentially be useful in biomedicine and material studies.

Saturable and reverse saturable scattering were discovered in isolated plasmonic particles and adopted as a novel non-bleaching contrast method in super-resolution microscopy. Here the experimental procedures of detecting and extracting nonlinear scattering are explained in detail, as well as how to enhance resolution with the aid of saturated excitation microscopy.

从单电浆纳米粒子散射非线性测量

Plasmonics, which are based on the collective oscillation of electrons due to light excitation, involve strongly enhanced local electric fields and thus ...

Use of a Multi-compartment Dynamic Single Enzyme Phantom for Studies of Hyperpolarized Magnetic Resonance Agents

Imaging of hyperpolarized substrates by magnetic resonance shows great clinical promise for assessment of critical biochemical processes in real time. Due to fundamental constraints imposed by the hyperpolarized state, exotic imaging and reconstruction techniques are commonly used. A practical system for characterization of dynamic, multi-spectral imaging methods is critically needed. Such a system must reproducibly recapitulate the relevant chemical dynamics of normal and pathological tissues. The most widely utilized substrate to date is hyperpolarized [1-13C]-pyruvate for assessment of cancer metabolism. We describe an enzyme-based phantom system that mediates the conversion of pyruvate to lactate. The reaction is initiated by injection of the hyperpolarized agent into multiple chambers within the phantom, each of which contains varying concentrations of reagents that control the reaction rate. Multiple compartments are necessary to ensure that imaging sequences faithfully capture the spatial and metabolic heterogeneity of tissue. This system will aid the development and validation of advanced imaging strategies by providing chemical dynamics that are not available from conventional phantoms, as well as control and reproducibility that is not possible in vivo.

A multi-compartment dynamic phantom is used to simulate some biology of interest for metabolic studies using hyperpolarized magnet resonance agents.

一个多腔动态单一酶幻影超极化磁共振剂研究的用途

Imaging of hyperpolarized substrates by magnetic resonance shows great clinical promise for assessment of critical biochemical processes in real time. Due ...

Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid

Atomic force microscopy (AFM) has become a well-established technique for nanoscale imaging of samples in air and in liquid. Recent studies have shown that when operated in amplitude-modulation (tapping) mode, atomic or molecular-level resolution images can be achieved over a wide range of soft and hard samples in liquid. In these situations, small oscillation amplitudes (SAM-AFM) enhance the resolution by exploiting the solvated liquid at the surface of the sample. Although the technique has been successfully applied across fields as diverse as materials science, biology and biophysics and surface chemistry, obtaining high-resolution images in liquid can still remain challenging for novice users. This is partly due to the large number of variables to control and optimize such as the choice of cantilever, the sample preparation, and the correct manipulation of the imaging parameters. Here, we present a protocol for achieving high-resolution images of hard and soft samples in fluid using SAM-AFM on a commercial instrument. Our goal is to provide a step-by-step practical guide to achieving high-resolution images, including the cleaning and preparation of the apparatus and the sample, the choice of cantilever and optimization of the imaging parameters. For each step, we explain the scientific rationale behind our choices to facilitate the adaptation of the methodology to every user's specific system.

We present a method for achieving sub-nanometer resolution images with amplitude-modulation (tapping mode) atomic force microscopy in liquid. The method is demonstrated on commercial atomic force microscopes. We explain the rationale behind our choices of parameters and suggest strategies for resolution optimization.

亚纳米级分辨率成像与调幅原子力显微镜在液体

Atomic force microscopy (AFM) has become a well-established technique for nanoscale imaging of samples in air and in liquid. Recent studies have shown ...

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit manipulation, and integrated single-photon detectors. Here, we present the key aspects of preparing and testing a silicon photonic quantum chip with an integrated photon source and two-photon interferometer. The most important aspect of an integrated quantum circuit is minimizing loss so that all of the generated photons are detected with the highest possible fidelity. Here, we describe how to perform low-loss edge coupling by using an ultra-high numerical aperture fiber to closely match the mode of the silicon waveguides. By using an optimized fusion splicing recipe, the UHNA fiber is seamlessly interfaced with a standard single-mode fiber. This low-loss coupling allows the measurement of high-fidelity photon production in an integrated silicon ring resonator and the subsequent two-photon interference of the produced photons in a closely integrated Mach-Zehnder interferometer. This paper describes the essential procedures for the preparation and characterization of high-performance and scalable silicon quantum photonic circuits.

Silicon photonic chips have the potential to realize complex integrated quantum systems. Presented here is a method for preparing and testing a silicon photonic chip for quantum measurements.

量子干涉效应在硅谐振环光子源测量

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit ...

Fourier-Based Diffraction Analysis of Live Caenorhabditis elegans

This manuscript describes how to classify nematodes using temporal far-field diffraction signatures. A single C. elegans is suspended in a water column inside an optical cuvette. A 632 nm continuous wave HeNe laser is directed through the cuvette using front surface mirrors. A significant distance of at least 20-30 cm traveled after the light passes through the cuvette ensures a useful far-field (Fraunhofer) diffraction pattern. The diffraction pattern changes in real time as the nematode swims within the laser beam. The photodiode is placed off-center in the diffraction pattern. The voltage signal from the photodiode is observed in real time and recorded using a digital oscilloscope. This process is repeated for 139 wild type and 108 &#34;roller&#34; C. elegans. Wild type worms exhibit a rapid oscillation pattern in solution. The &#34;roller&#34; worms have a mutation in a key component of the cuticle that interferes with smooth locomotion. Time intervals that are not free of saturation and inactivity are discarded. It is practical to divide each average by its maximum to compare relative intensities. The signal for each worm is Fourier transformed so that the frequency pattern for each worm emerges. The signal for each type of worm is averaged. The averaged Fourier spectra for the wild type and the &#34;roller&#34; C. elegans are distinctly different and reveal that the dynamic worm shapes of the two different worm strains can be distinguished using Fourier analysis. The Fourier spectra of each worm strain match an approximate model using two different binary worm shapes that correspond to locomotory moments. The envelope of the averaged frequency distribution for actual and modeled worms confirms the model matches the data. This method can serve as a baseline for Fourier analysis for many microscopic species, as every microorganism will have its unique Fourier spectrum.

Fourier-Based Diffraction Analysis of Live Caenorhabditis elegans

This manuscript describes how to distinguish different nematodes using far-field diffraction signatures. We compare the locomotion of 139 wild type and 108 &#34;Roller&#34; C. elegans by averaging frequencies associated with the temporal Fraunhofer diffraction signature at a single location using a continuous wave laser.

活体线虫线虫的傅里叶衍射分析

This manuscript describes how to classify nematodes using temporal far-field diffraction signatures. A single C. elegans is suspended in a water column ...

Force-Clamp Rheometry for Characterizing Protein-based Hydrogels

Here, we describe a force-clamp rheometry method to characterize the biomechanical properties of protein-based hydrogels. This method uses an analog proportional-integral-derivative (PID) system to apply controlled-force protocols on cylindrical protein-based hydrogel samples, which are tethered between a linear voice-coil motor and a force transducer. During operation, the PID system adjusts the extension of the hydrogel sample to follow a predefined force protocol by minimizing the difference between the measured and set-point forces. This unique approach to protein-based hydrogels&#160;enables the tethering of extremely low-volume hydrogel samples (&#60; 5 &#181;L) with different protein concentrations. Under force-ramp protocols, where the applied stress increases and decreases linearly with time, the system enables the study of the elasticity and hysteresis behaviors associated with the (un)folding of proteins and the measurement of standard elastic and viscoelastic parameters. Under constant-force, where the force pulse has a step-like shape, the elastic response, due to the change in force, is decoupled from the viscoelastic response, which comes from protein domain unfolding and refolding. Due to its low-volume sample and versatility in applying various mechanical perturbations, force-clamp rheometry is optimized to investigate the mechanical response of proteins under force using a bulk approach.

A new force-clamp rheometry technique is used to investigate the mechanical properties of low-volume protein-based hydrogel samples tethered between a voice-coil motor and a force sensor. An analog proportional-integral-derivative (PID) system allows for the &#39;clamping&#39; of the force experienced to the desired protocol.

基于蛋白质的水凝胶的力钳 Rheometry

Here, we describe a force-clamp rheometry method to characterize the biomechanical properties of protein-based hydrogels. This method uses an analog ...