Rat CINC-3 (CXCL2) ELISA Kit - FAQs

ProcartaPlex 多重检测基于 Luminex xMAP 技术，提供了一个多功能平台，为用户提供了更大的灵活性和更多的分析物检测选项。无论您是测试单一分析物还是多种分析物，ProcartaPlex 多重分析都使用高效、易于遵循的方案提供准确的分析性能。这些检测中的每一个都经历了我们为 ELISA 进行的相同的开发、验证、制造和质量控制标准化。每批 ProcartaPlex 多重检测和 ELISA 检测都经过适当的样本类型（即物种特异性血清、血浆和细胞培养上清液）的完全验证，并且每批都根据以下性能特征进行评估：
o特异性 - 筛选每个分析物以确保在多重测试中与其他分析物没有明显的交叉反应
o灵敏度 - 对每个分析物的功能灵敏度（与背景的区别）和检测下限 (LLOD) 进行评估
o精密/准确度多重检测具有良好的检测内精密度 (<10% CV)、检测间精密度 (<10% CV) 和批次间一致性 (<20% CV)；这些值与大多数 ELISA 测试相当或更好

ProcartaPlex 多重检测定期针对匹配的 ELISA 进行测试。因此，您可以轻松地从 ProcartaPlex 检测切换到 ELISA，反之亦然，结果可靠。我们的大多数 ProcartaPlex 检测使用与我们传统的基于平板的 ELISA 相同的抗体对，从而导致两种检测之间的高度相关性 (R2 > 0.9)。

ELISA是一种可以在复杂样品中特异性定量单个蛋白质的简单而有效的方法。通过使用高质量的单抗体或双抗体夹心技术实现ELISA的选择性，并通过使用经校准的标准品实现精确定量。ELISAs可以检测低丰度的蛋白质，可以在96孔板中进行，并且仅需60分钟的手动操作时间。此外，ELISA获得的结果通常具有高度可重复性。

虽然ELISA已被作为蛋白质分析的标准方法，但是能够在单个样品中同时测量多种分析物的多重检测方法解决了许多缺陷：

•ELISA检测给定样品时，一次仅测量一种分析物，限制了研究人员日益增加的在研究中测量多种靶标的需求。
•所研究的许多样品可用体积较少可能限制可以进行分析的次数。在提供有限样品体积的小动物研究、儿科测试和微孔板分析中尤其如此。能在单个小体积样品中分析多种分析物可以更有效地使用每种样品。
•当对多次ELISA对分析物的检测结果进行比较时数据解读可能会遇到困难。因为每次检测使用的是不同的分装样本，而且每次检测都可能会有系统误差，这些会导致准确性和精度下降。
•许多分析物需要具有较宽动态范围的检测试剂盒，以避免重复测试或出现超出检测范围的情况。多重检测可以设计为具有针对所有分析物的宽动态范围，或根据各种预期分析物浓度专门定制的范围。

以下是一些可能的原因和解决方案：

标准品或样品移液或后续步骤中出错。始终以相同的顺序将溶液快速分配到孔中。分配时，请勿触摸每个微孔上的移液器吸头。使用经过校准的移液器和与该移液器匹配的吸头。检查移液器吸头是否泄漏。

重复使用吸头进行多种样品或不同试剂的移液。在每一种样品或试剂转移时，使用新的吸头。

孔被移液器吸头或洗涤吸头刮擦。将溶液分配到微孔中和吸出微孔时要小心。

在孵育期间，液体从一个孔转移到另一个孔。调整轨道摇床或检查摇床转速是否正确。小心地撕下粘性封板膜。

分配到微孔中的材料体积不正确。按照方案分配试剂。检查移液器的校准。

用血清、培养基或其他缓冲液稀释标准品。在试剂盒提供的标准品稀释缓冲液中稀释标准品。

样品中存在颗粒或沉淀物。在将溶液用于检测之前，通过离心除去任何颗粒/沉淀物。

微孔脏：微孔内部或底部可见碎屑。 检查微孔并翻转微孔板以除去碎屑。每次洗涤后，用吸水薄纸擦拭板底部。切勿将薄纸插入微孔内。

由于外边缘孔和板中心的孔之间的温度不均匀而产生“边缘效应”。在孵育期间平板密封要严，并且当要在37℃下孵育时，将平板放置在培养箱的中心。

以下是一些可能的原因和解决方案：

标准品原液制备不当。按照小瓶标签上的指示稀释冻干标准品，仅使用标准稀释缓冲液或与您的样品基质最匹配的稀释液。

使用了来自具有不同的分析物或不同批号的不同试剂盒的试剂（冻干标准品、标准稀释液缓冲液等）。切勿使用其他试剂盒中的任何组分。

标准品移液或后续步骤中出错。始终以相同的顺序将溶液快速分配到孔中。分配时，请勿触摸每个微孔上的移液器吸头。使用经过校准的移液器和与该移液器匹配的吸头。

以下是一些可能的原因和解决方案：

检测开始时，试剂不在室温（~25 ± 2°C）条件下。在开始检测之前，使试剂回温至室温。

组分储存不当，例如，未在2-8°C下储存。完全按照方案和标签上的指示储存所有组分。

抗兔IgG HRP或链霉亲和素-HRP工作溶液在用于检测前，已制备超过15分钟。在稀释后15分钟内使用稀释的抗兔IgG HRP或链霉亲和素-HRP。

试剂过期。收到试剂盒后立即查看有效日期，并在有效期前使用该试剂盒。

在不正确的波长上读板。使用TMB底物读取ELISA的正确波长为450nm。

TMB溶液失去活性。确保TMB溶液在分配到板孔中之前是透明的。蓝色和/或存在颗粒物质表明产品被污染。如果发现此问题，请联系技术支持。为避免污染，我们建议将检测所需的量分配到以前未使用过的一次性槽中以便移液。丢弃留在槽中的任何TMB溶液，不要将其放回瓶中。避免TMB溶液接触含有金属离子的物品。 不要用铝箔或铝涂层的Mylar纸封板，因为这可能会在没有HRP的情况下导致显色。

尝试使用ELISA检测未优化过的基质中的分析物。使用其他样品类型时，请联系技术支持。

孔被移液器吸头或洗涤吸头刮擦。将溶液分配到微孔中和吸出微孔时要小心。

显色液或终止液使用不当。仅使用试剂盒中提供的显色液和终止液。

将标准品稀释缓冲液加入到所有孔而不是指定的孔中。遵循方案，仅将标准品稀释液添加到指定的孔和所要求的样品中，或者添加到产生高于最高标准品信号的样品中。 使用含有叠氮化物的缓冲液，而叠氮化物与HRP不相容。避免在检测中使用叠氮化物。

以下是一些可能的原因和解决方案：

抗兔IgG HRP或链霉亲和素-HRP工作溶液的稀释不正确。
-使抗兔IgG HRP或链霉亲和素-HRP（100X）的溶液回温至室温，缓慢吸取，并用实验室薄纸（例如，Kimwipe薄纸）擦拭吸头以除去过量的溶液。仅在所提供的HRP稀释液中进行稀释。

孵化时间过长。遵循方案中规定的孵育时间。

在37°C下孵育。在方案中有说明时，在室温（~25±2°C）下进行孵育。

以下是一些可能的原因和解决方案：

洗涤不充分和/或洗涤后排液不充分。如果含抗兔IgG HRP或链霉亲和素-HRP的残留溶液留在孔中，可能使背景升高。
-根据方案洗涤。验证自动洗板机的功能。在每个洗涤步骤结束时，将培养板倒置于工作台面上的吸水薄纸上，使液体完全排出，必要时用力拍打以除去残留的液体。

显色剂在使用前暴露于光线下，导致呈现出蓝色。
-将显色剂保存在其小瓶中，直到您准备好将其分配到板中，然后将其倒入容器中以防止设备污染小瓶。请勿用箔封微孔板。

孵育时间过长或孵育温度过高。
-减少孵育时间和/或降低孵育温度。

移液器、配液容器或带有抗兔IgG HRP或链霉亲和素-HRP的底物溶液的污染。
请勿使用在加入前就呈现蓝色的显色剂。换一瓶新的显色剂。

空白对照设置不正确。 在指定空白孔时遵循方案。空白孔仅含显色剂和终止液。从所有其他孔中减去空白孔结果。 对标准品原液的稀释不正确，或用血清、培养上清液或其他液体稀释了标准品。 遵循有关标准品稀释的方案说明。仅使用试剂盒提供的标准品稀释缓冲液来稀释标准品。

我们的客户使用种类多样的读板仪。其中一些不能读取高于2 AUFS（满量程的吸光度单位）的吸光度，而其他一些不能读取超过3 AUFS。如果您在室温下孵育30分钟后无法读取1或2 A450值，则可以缩短孵育时间。例如，一些客户发现20分钟是理想的孵育时间，因为他们实验室的环境温度高于~72°F（22°C）。在这种情况下，较高的温度会提高HRP驱动的ELISA反应速度。相反，如果您获得的A450值不够高，则可以相应地增加孵育时间。

ELISA标准曲线不理想有2个主要原因。首先，可能没有遵循推荐的试剂盒标准品的溶解方法。应使用试剂盒中提供的标准稀释剂，根据标签上的指示复溶标准品。请勿使用其他稀释液。然后旋转小瓶或轻轻混匀，然后在室温下静置10分钟以确保完全溶解。这一浓缩的标准品溶液应在复溶后1小时内使用。此外，根据产品手册中提供的说明，在标准品稀释液中制备稀释液之前，应再次轻轻混匀。除非产品手册中另有说明，否则剩余标准品通常可以分装后冷冻储存。

标准曲线不理想的第二个常见原因是HRP偶联物未被正确稀释。100X HRP偶联物溶液含有50％甘油，因此非常粘稠并且难以准确地移液。以下是我们建议解决此问题的方法：首先，让HRP偶联物小瓶达到室温。然后，用干净的移液器吸头轻轻搅拌，以确保均匀。仅使用试剂盒中提供的独立的HRP偶联稀释液对其进行稀释，并按照手册中提供的稀释说明进行操作。

稀释HRP偶联物的关键是确保正确移液。您应该测试您的移液器是否准确地吸出并分配所需的偶联物 - 甘油混合物的体积。如果可能，应该校准此移液器，确保其准确可靠。当吸入粘稠的偶联物溶液时，可能需要5-10秒才能使所需的量进入移液器吸头。在将偶联物转移到合适的HRP稀释液之前，用实验室薄纸（例如，Kimwipes薄纸）擦拭移液器吸头，确保其外部干燥，注意吸头内的内容物不能被薄纸吸收。将偶联物吸移到稀释液中，然后通过上下吹打几次来冲洗吸头。需将最后一滴偶联物移出吸头，这一点尤为重要。接下来，密封容器，并通过轻轻摇晃或上下翻转将其完全混匀。这一步至关重要，因为甘油会将偶联物快速带到试管底部。如果稀释的偶联物未充分混匀，则HRP偶联物的浓度将不是所要求的浓度。

将HRP偶联物稀释并轻轻但完全混匀后，在15分钟内使用。请记住，HRP偶联物稀释液是HRP偶联物唯一可接受的稀释液。不能保存稀释的HRP偶联物，因为HRP活性不稳定，因此不应储存和重复使用。

我们的抗体配对试剂盒包括配对的、预滴定和完全优化的包被和检测抗体，3瓶重组蛋白标准品，链霉亲和素-HRP偶联浓缩物和批次特定的技术数据表。但不含缓冲液。运行抗体对ELISA所需的缓冲液试剂盒必须单独购买（货号CNB0011）。请注意，货号CNB0011中提供的5X检测缓冲液用于封闭您的ELISA微孔板，并作为标准品和样品的稀释液。

不可以。与这些试剂盒中提供的完全相同的链霉亲和素-HRP偶联物不作为单独产品提供。然而，它来自我们确实可以销售的ELISA级链霉亲和素-HRP（货号SNN2004）。请记住，每批ELISA或抗体对试剂盒中提供的链霉亲和素-HRP也因批次而有所不同。所以，如果你使用货号SNN2004或其他来源的链霉亲和素-HRP，您必须确定哪种稀释度的SNN2004最适合您。

是的，可以使用。传统1X RIPA缓冲液的组分与我们的细胞提取缓冲液（货号FNN0011）非常相似。货号FNN0011经常用于制备裂解物，以与我们的ELISA和Luminex试剂盒一起进行测试。我们还使用NP-40细胞提取缓冲液（货号FNN0021）。我们建议将货号FNN0011制成的裂解物稀释至少10倍，以便在将样品加入ELISA或Luminex检测之前将SDS浓度降低至≤0.01％（v / v）。

我们的磷酸特异性ELISA试剂盒具有几个优点，包括易用性和较高的灵敏度。磷酸特异性ELISA试剂盒的灵敏度通常比蛋白质免疫印迹高2-10倍，因此它们特别适用于检测“低表达”蛋白质或小样品量。此外，通过使用试剂盒中提供的重组标准品，磷酸特异性ELISA可在无需进行光密度测定的情况下提供量化的结果。

为了评价磷酸化水平，我们报告了蛋白质磷酸化的比较水平，以“磷蛋白单位/pg或ng总蛋白”为单位。总ELISA试剂盒量化每个样品的蛋白质质量，磷酸特异性ELISA试剂盒以单位量化该蛋白质的磷酸化水平。然后即可确定各种样品的磷酸化水平（例如，以“单位/ pg”为单位）是相似还是不同。

示例：测试两个样品的总CREB和CREB [pS133]

样品1的结果：总ELISA检测（KHO0231）显示样品中的CREB为100pg / mL。磷酸特异性ELISA（KHO0241）显示CREB [pS133]为50单位/ mL。在此样品中，CREB在丝氨酸133处被磷酸化至（50单位/ mL）/（100pg / mL）= 0.5单位/ pg总CREB的水平。

样品2的结果：总ELISA检测显示样品中的CREB为95 pg / mL。磷酸特异性ELISA显示CREB [pS133]为5单位/ mL。在此样品中，CREB在丝氨酸133处被磷酸化至（5单位/ mL）/（95 pg / mL）= 0.053单位/ pg总CREB的水平。当您将样品1与样品2进行比较时，您会看到CREB1在丝氨酸133处的磷酸化水平差异为10倍，即使总CREB蛋白几乎没有变化。

我们的总ELISA的结果以pg / mL表示，或者有时以ng / mL表示。该测量通常以质量单位给出，因为绘制标准曲线时使用的是已知质量的标准品。磷酸特异性ELISA的结果以“单位”表示，我们没有将其与特定的蛋白质质量相关联。我们使用单位，是因为在磷蛋白标准品的特定制剂中，难以精确地知道特定磷酸化反应的效率，因此难以精确地知道磷酸化蛋白与未磷酸化蛋白的比例。磷酸化单位对于每种磷酸特异性ELISA都是不同的，并且在每个试剂盒随附的产品手册中有描述。

  例如，典型的单位描述是“1单位=源自300pg自动磷酸化FAK蛋白的FAK [pY397]的量”。由于不能保证我们的标准制剂中的FAK是100％磷酸化的，因此我们不会声明这相当于300 pg的磷酸化FAK。相反，我们验证了大批磷酸化蛋白质，并用它来开发我们原始检测的单位定义和标准曲线。我们的蛋白质标准品的后续制剂被归一化为蛋白质的原始批次，以确保我们的单位定义在批次之间保持不变。

两种类型的ELISA试剂盒均可在塑料96孔板的孔内捕获总蛋白，无论其磷酸化状态如何。这通过用“泛抗体”包被孔来完成，这种“泛抗体”不区分蛋白质的磷酸化形式和非磷酸化形式，并且不阻断待研究的磷酸化位点。此外，磷酸特异性ELISA试剂盒可对在一种或多种特异性氨基酸上磷酸化的相同蛋白质进行定量。这一检测不使用第二泛抗体，而是使用特异性识别蛋白质被特异性磷酸化时才存在的表位的抗体（即，抗体具磷酸特异性）。

我们建议使用相同的样品同时运行总ELISA和磷酸特异性ELISA。如果无法做到这一点，请务必尽快用两个试剂盒测试相同的样品。 

每个抗体对试剂盒包含捕获（包被）抗体、生物素化检测抗体、重组标准品和链霉亲和素-HRP。其他试剂列于试剂盒中的抗体对手册中，也可单独购买（抗体对缓冲液试剂盒，货号CNB0011；5X检测缓冲液，货号DS98200等）。该手册还提供了一个特定的程序，并说明了遵循特定程序时可以获得的标准曲线的示例。

程序概述总结如下：

1）使用稀释的捕获（包被）抗体将微孔板在2-8℃下包被过夜；冲洗微孔板。
2）在包被的微孔板中孵育标准品或样品；冲洗微孔板。
3）在板中孵育稀释的生物素化检测抗体；冲洗微孔板。
4）将链霉亲和素-HRP在微孔板中孵育15-45分钟；冲洗微孔板。
5）使用TMB底物将微孔板孵育10-60分钟，然后用终止液终止反应。
6）在450nm处读取微孔板。

我们建议测定各种应用的最优缓冲液配方、浓度和孵育时间。

所有ELISA试剂盒均以夹心ELISA形式提供，其中捕获抗体已经包被在96孔板上。典型的检测使用生物素化的检测抗体，接着使用链霉亲和素-HRP和HRP底物。大多数试剂盒以单个96孔板的形式提供，有些试剂盒提供2个或5个96孔板。试剂盒通常包含：

•包被捕获抗体的96孔联排板
•蛋白质标准品
•洗涤缓冲液，10x
•ELISA 缓冲液/稀释液，10x
•检测抗体（大多数试剂盒中，生物素化）
•HRP试剂（HRP偶联的二抗或链霉亲和素）（100x）
•底物（通常为TMB）
•终止液
•粘性封板膜

运行内部对照以及空白对照和标准曲线是监测任何ELISA试剂盒性能的绝佳方法。内部对照是用试剂盒测量的含有已知量的分析物的样品。内部对照的一个关键属性，以及它们与标准曲线样品的区别在于，它们会尽可能地复制您实际样品的组分。这一点很重要，因为您的样品可能含有影响分析物检测的成分，而这种影响方式与试剂盒中提供的标准稀释液的影响方式不同。换句话说，内部对照可以让您确定在标准稀释液（标准曲线）和样品基质（内部对照）中检测等量的分析物是否会给出相同的结果。同样重要的是要记住，内部对照可以让您对结果的准确度充满信心。内部对照有助于确保不同检测在每次运行时都能始终如一。

内部对照的来源之一是含有已知量的待测分析物的自然存在的样品（如血清或血浆）。这种阳性对照样品可以原样运行，或者也可以稀释至各种浓度，最好用自然存在的相同类型的阴性样品稀释。如果可以的话，最好运行至少2个内部对照。其中一个分析物的浓度通常在标准曲线的最低点和曲线的中点之间，而另一个的浓度在中点和最高点之间。有些研究人员还会运行一个浓度接近曲线中点的内部对照。

如果您无法获得自然存在的对照品，您可以自己制备。假设您要使用ELISA试剂盒（货号KHC0061）测量人血清样品中的白细胞介素-6（IL-6）。首先，您需要一些合并的正常人类血清作为内部对照的样品基质。该血清的IL-6含量最好是微乎其微（但是已知存在），或者低到无法测量。接下来，您应该使用试剂盒中提供的人类IL-6标准，将已知量的人类IL-6添加到该血清中以建立内部对照。按照产品手册中的说明制备标准曲线后，将一些剩余的浓缩IL-6标准品添加到血清基质中。如上所述，如果您的ELISA微孔板中有足够的孔，您可以制备具有高和低IL-6水平或高、中和低水平的对照。

即使您的样品类型不是血清并且您也不是测量IL-6，也可按照上述通用程序使用您的目标蛋白质和样品基质制备内部对照。 点击此处（https://tools.thermofisher.com/content/sfs/brochures/TR0058-Spike-and-Recovery.pdf）查找加标回收率和稀释度线性分析的有价值的资源。如果您需要更多帮助，请联系技术支持LifeScience-CNTS@thermofisher.com。

我们的ELISA试剂盒可分为多个不同的组（参见蛋白质分析手册（https://www.thermofisher.com/us/en/home/global/forms/protein-handbook-registration.html）第35页的表2），考虑的许多因素包括：靶标蛋白质分类、灵敏度、读出方法或检测靶标蛋白的特异性磷酸化状态的能力。

•标准的比色法ELISA试剂盒使用标准比色读出，具有出色的灵敏度和检测范围。典型灵敏度<10 pg / mL，标准曲线范围约为10-250 pg / mL，但有些试剂盒的范围更广。
•超灵敏ELISA试剂盒使用标准比色读出，但能够检测和分析低至0.5 pg/mL的蛋白质。基于0.5-20 pg/mL的测量范围，这些试剂盒特别适用于高度稀释的样品。
•Chemi ELISA试剂盒使用化学发光检测技术获得高灵敏度（<1 pg/mL），并且灵活性高，测量范围可达0.5至2000 pg / mL。
•磷酸化ELISA试剂盒能够特异性检测关键信号蛋白的磷酸化，且特异性极高，其通常用于补充免疫印迹的结果并提供量化数据。

我们提供完整的ELISA试剂盒、试剂组和抗体对。ELISA试剂盒是完整的即用型试剂盒，包含预包被的检测板、所有缓冲液、捕获和检测抗体。大多数试剂盒以单块板子的格式提供，但有些试剂盒提供2或5块板子。试剂组适用于需要核心试剂盒组件但更喜欢自己制备缓冲液并自己包被板子的研究人员。抗体对是配对的检测和捕获抗体，适用于需要处理大量样品的研究人员。

After much effort, the search for an IL-8 homologue in rats and mice has been unsuccessful. This has led many researchers to conclude that the role of IL-8 in rats and mice is assumed by other chemokines (Broaddus, VA and Hebert, CA, 1996). However, it has been demonstrated that when an anti-human IL-8 antibody was given intratracheally to rats, the measure of lung inflammation and injury were significantly attenuated (Mulligan, MS et al, 1993). In addition, the authors obtained positive immunostaining with the anti-IL-8 antibody on rat pulmonary artery endothelial cells stimulated by TNF-alpha and in the rat lung after immune complex deposition. The authors were unable to determine what cytokine was being neutralized by the antibody. CINC-1 (a rat CXC chemokine and homologue of human MGSA/GRO) was ruled out since the antibody utilized was shown not to cross-react with that chemokine. These data suggest that a rat IL-8-like molecule which is distinct from CINC-1 exists and plays an important role in neutrophil recruitment.

In addition to CINC-1, three other rat CXC chemokines have been identified: CINC-2 alpha, CINC-2 beta, and CINC-3 (GRO beta/MIP-2) (Richmond, A and Shattuck, RL, 1996; Nakagawa, H et al., 1994). To date, the IL-8 homologue has not been identified, but recent data from Lee, J et al. suggest that it may be MIP-2 in rats. The homolog in mice may be KC. We offer an ELISA kit for the detection of rat MIP-2: catalog number ERCXCL2.

References:
1. Broaddus, V.A. and C.A. Hebert (1996) The Role of IL-8 in Inflammatory Diseases, in Chemoattractant Ligands and Their Receptors. Horuk, R., Ed., CRC Press, New York, pp.16-18.
2. Mulligan, M.S., M.L. Jones, M.A. Bolanowski, M.P. Baganoff, C.L. Deppeler, D.M.Meyers, U.S. Ryan, and P.A. Ward (1993) Inhibition of lung inflammatory reactions in rat by antihuman IL-8 antibody. J. Immunol. 150:5585-5595.
3. Richmond, A. and R.L. Shattuck (1996) Melanoma growth stimulatory activity: Physiology, biology, structure/function, and role in disease, in Chemoattractant Ligands and Their Receptors. Horuk, R., Ed., CRC Press, New York, pp. 89-90.
4. Nakagawa, H., N. Komorita, F. Shibata, A. Ikesue, K. Konishi, M. Fujioka, and H. Kato (1994) Identification of cytokine-induced neutrophil chemoattractants (CINC), rat GRO/CINC-2 alpha and CINC-2 beta, produced by granulation tissue in culture: purification, complete amino acid sequences and characterization. Biochem. J. 301:545-550.
5. Lee, J., G. Cacalano, T. Camerato, K. Toy, M.W. Moore, and W.I. Wood (1995) Chemokine binding and activities mediated by the mouse IL-8 receptor. J. Immunol.155:2158-2164.

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ProcartaPlex multiplex assays, which are based on Luminex xMAP technology, provide a versatile platform that gives users more flexibility and a greater array of options for analyte detection. Whether you are testing for single or multiple analytes, ProcartaPlex multiplex assays deliver accurate analytical performance using efficient, easy-to-follow protocols. Each of these assays has undergone the same development, validation, manufacturing, and quality control standardization we conduct for our ELISAs. Each lot of ProcartaPlex multiplex assays as well as ELISA assays is fully qualified with the appropriate sample type (i.e., species-specific serum, plasma, and cell culture supernatants), and each lot is evaluated based on the following performance characteristics:

Specificity-each analyte is screened to make sure there is no significant cross-reactivity with other analytes in the multiplex test
Sensitivity-each analyte is evaluated for both functional sensitivity (differentiation from background) and lower limit of detection (LLOD)
Precision/accuracy-multiplex assays have good intra-assay precision (<10% CV), inter-assay precision (<10% CV), and lot-to-lot consistency (<20% CV); these values are comparable to or better than most ELISA tests
ProcartaPlex multiplex assays are regularly tested against the matching ELISAs. Therefore, you can switch easily from ProcartaPlex assays to ELISA and vice versa with reliable results. Most of our ProcartaPlex assays use the same antibody pairs as our traditional plate-based ELISAs, resulting in high correlation (R2 > 0.9) between the two assays.

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ELISA is a simple and powerful way to quantify individual proteins specifically in complex samples. The selectivity of ELISA is achieved through the use of qualified single- or double-antibody sandwich technology, and accurate quantitation is achieved through the use of calibrated standards. ELISAs can detect low-level proteins and can be performed in a 96-well format with only 60 minutes of hands-on time. In addition, the results obtained with ELISAs are generally very reproducible. While ELISA has been established as a standard method of protein analysis, multiplexing methods that enable the measurement of multiple analytes simultaneously in a single sample address a number of specific limitations:

ELISA allows for the measurement of only one analyte at a time in a given sample, limiting investigators' increasing need to measure multiple targets in their research studies.
The low available volume of many samples being studied may limit the number of times analyses can be conducted. This is especially true in small animal research, in pediatric testing, and in microplate assays providing limited sample volumes. The ability to assay multiple analytes in a single small-volume sample enables more effective use of each sample.
Difficulties in data interpretation can arise when comparing analyte levels measured by multiple ELISAs, each assay having been performed with different sample aliquots and each susceptible to systematic errors leading to decreased precision and accuracy.
Many analytes require assays with broad dynamic ranges to avoid repeat testing or out-of-range values. Multiplex assays can be designed to have large dynamic ranges for all of the analytes, or ranges tailored to various expected analyte concentrations.

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Here are possible causes and solutions:

Errors in pipetting the standards or samples or in subsequent steps. Always dispense into wells quickly and in the same order. Do not touch the pipette tip on the individual microwells when dispensing. Use calibrated pipettes and the appropriate tips for that device. Check for any leaks in the pipette tip.
Repetitive use of tips for several samples or different reagents. Use fresh tips for each sample or reagent transfer.
Wells have been scratched with the pipette tip or washing tips. Use caution when dispensing into and aspirating out of microwells.
Liquid transferred from well to well during incubations. Adjust the orbital shaker or check for correct rotator rpm. Peel the adhesive plate cover off carefully.
Incorrect volumes of materials dispensed into the microwells. Follow the protocol for dispensing volumes of reagents. Check calibration of the pipettes.
Standard diluted with the serum, culture medium, or other buffer. Dilute the standard with the standard diluent buffer provided in the kit.
Particulates or precipitates present in the samples. Remove any particulates/precipitates by centrifugation prior to dispensing into the assay.
Dirty microwells: visible debris within or on bottom of microwells. Inspect the microwells and invert the plate to remove debris. Wipe the bottom of the plate with an absorbent tissue after each wash step. Never insert tissue into the microwells.
“Edge effect” due to uneven temperature between the outer-edge wells and the wells in the center of the plate. Seal the plate completely with a cover during incubations, and place the plate in the center of the incubator when 37 degrees C incubation is indicated.

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Here are possible causes and solutions:

Improper preparation of standard stock solution.Dilute the lyophilized standard as directed on the vial label, only with the standard diluent buffer or a diluent that most closely matches the matrix of your sample.
Reagents (lyophilized standard, standard diluent buffer, etc.) from different kits, with either different analytes or different lot numbers, were substituted. Never substitute any components from another kit.
Errors in pipetting the standard or in subsequent steps. Always dispense into wells quickly and in the same order. Do not touch the pipette tips on the individual microwells when dispensing. Use calibrated pipettes and the appropriate tips for that device.

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Here are possible causes and solutions:

Reagents not at room temperature (approximately 25 plus or minus 2 degrees C) at start of assay. Allow all reagents to warm to room temperature prior to commencing the assay.
Incorrect storage of components, e.g., not stored at 2-8 degrees C. Store all components exactly as directed in the protocol and on labels.
Anti-rabbit IgG HRP or streptavidin-HRP working solution made more than 15 minutes before use in assay. Use the diluted anti-rabbit IgG HRP or streptavidin-HRP within 15 minutes of dilution.
Expired reagents.Check expiration dates upon receipt of kit and use the kit prior to expiration.
Plate read at incorrect wavelength. The correct wavelength to read ELISAs using the TMB substrate is 450 nm.
TMB solution lost activity. Ensure that the TMB solution is clear before it is dispensed into the plate wells. A blue color and/or the presence of particulate matter indicate that the product is contaminated. Please contact Technical Support if this problem is noted. To avoid contamination, we recommend that the quantity required for an assay be dispensed into a previously unused disposable trough for pipetting. Discard any TMB solution left in the trough and do not put it back in the bottle. Avoid contact between the TMB solution and items containing metal ions. Do not cover your plates with aluminum foil or aluminum-coated Mylar sheets because this can cause color development in the absence of HRP.
Attempt to measure analyte in a matrix for which the ELISA assay is not optimized. Contact Technical Support when using alternative sample types.
Wells have been scratched with pipette tip or washing tips. Use caution when dispensing into and aspirating out of microwells.
Incorrect chromogen or stop solution used. Use only the chromogen and stop solution supplied with the kit.
Standard diluent buffer added to all wells rather than the designated wells. Follow the protocol and only add the standard diluent to the designated wells and to the samples where it is required, or to samples producing signals greater than that of the highest standard.
Use of buffer containing azide, which is not compatible with HRP. Avoid the use of azide in the assay.

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Here are possible causes and solutions:

Incorrect dilution of the anti-rabbit IgG HRP or streptavidin-HRP working solution.
Warm the solution of anti-rabbit IgG HRP or streptavidin-HRP (100X) to room temperature, draw it up slowly, and wipe the tip with a laboratory tissue (e.g., Kimwipe tissue) to remove the excess. Dilute only in the HRP diluent provided.
Incubation times extended. Follow incubation times outlined in the protocol.
Incubations performed at 37 degrees C. Perform incubations at room temperature (approximately 25 plus or minus 2 degrees C) when instructed in the protocol.

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Here are possible causes and solutions:

Insufficient washing and/or draining of wells after washing. Residual solution containing anti-rabbit IgG HRP or streptavidin-HRP can elevate the background if left in the well.
Wash according to the protocol. Verify the function of the automated plate washer. At the end of each washing step, invert the plate on absorbent tissue on the countertop and allow it to completely drain, tapping forcefully if necessary to remove residual fluid.
Chromogen exposed to light prior to use, resulting in a blue color.
Keep chromogen in its vial until you are ready to dispense it into the plate, and then pour it into a reservoir to prevent contamination of the vial with equipment. Do not cover the plate with foil.
Incubation time is too long or incubation temperature is too high.
Reduce incubation time and/or temperature.
Contamination of pipette, dispensing reservoir, or substrate solution with anti-rabbit IgG HRP or streptavidin-HRP.
Do not use chromogen that appears blue prior to dispensing onto the plate. Obtain a new vial of chromogen.
Blanks that have been set up improperly.
Follow the protocol when designating blank wells. Blank wells contain only chromogen and stop solution. Subtract blank well results from all other wells.
Incorrect dilution of standard stock solution or standards diluted in serum, culture supernatant, or other.
Follow the protocol instructions regarding dilution of the standard. Dilute standards only in the Standard Diluent Buffer provided in the kit.

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Our customers use a wide variety of plate readers. Some of these can't read absorbances higher than 2 AUFS (Absorbance Units Full Scale), while others can't go beyond 3 AUFS, for example. If you read your ELISA plates after 30 minutes of incubation at room temperature and 1 or 2 A450 values are off-scale, you can shorten the incubation time. For example, some customers find that 20 minutes is the ideal incubation time because the ambient temperature in their lab is higher than approximately 2 degrees F (22 degrees C). In this case, higher temperatures increase the rate of the HRP-driven ELISA. Conversely, if the A450 values you get are not high enough, you can increase the incubation time accordingly.

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There are 2 main causes of poor ELISA standard curves. First, the recommended method for solubilizing the kit standard may not have been followed. The standard should be reconstituted according to the directions indicated on the label, using the standard diluent provided in the kit. No other diluent should be used. The vial should then be swirled or mixed gently and then allowed to sit for 10 minutes at room temperature to ensure complete solubilization. This concentrated standard solution should be used within 1 hour of reconstitution. Also, it should be mixed gently again before preparing the dilutions in standard diluent according to the instructions provided in the product manual. Leftover standard can usually be stored frozen in small aliquots, unless specified otherwise in the product manual.

The second common reason for poor standard curves is that the HRP conjugate was not diluted correctly. The 100X HRP conjugate solution contains 50% glycerol, which makes it very viscous and difficult to pipet accurately. Here is what we suggest to solve this problem: First, let the vial of HRP conjugate come to room temperature. Then, stir it gently with a clean pipet tip to make sure that it is homogeneous. Use only the separate HRP conjugate diluent provided in the kit to dilute it, and follow the dilution instructions provided in the manual.

The key to diluting the HRP conjugate is to make sure that it is pipetted correctly. You should test that your pipettor accurately aspirates and dispenses the volume of the conjugate-glycerol mixture that is required. If possible, this pipettor should be calibrated so it is accurate and reliable. When you aspirate the viscous conjugate solution, it may take 5-10 seconds for the desired amount to enter the pipet tip. Before transferring the conjugate to the appropriate HRP diluent, make sure that the outside of the pipet tip is dry by wiping it with a lab tissue (e.g., Kimwipes tissue), taking care to ensure that the contents inside the tip do not get absorbed by the tissue. Pipet the conjugate into the diluent, and then rinse out the tip by pipetting up and down several times. It is important to get every last bit of conjugate out of the tip. Next, seal the container and mix it gently but thoroughly by rocking it or turning it upside down. This is crucial because the glycerol carries the conjugate quickly down to the bottom of the tube. If the diluted conjugate is not mixed adequately, the concentration of the HRP conjugate will not be what is required.

Once the HRP conjugate is diluted and mixed gently but well, use it within 15 minutes. Remember that the HRP conjugate diluent is the only acceptable diluent for the HRP conjugate. The diluted HRP conjugate should not be saved because the HRP activity is labile, and it should never be stored and reused.

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Our Antibody Pair kits include matched, pre-titered and fully optimized coating and detection antibodies, 3 vials of recombinant protein standard, the streptavidin-HRP conjugate concentrate, and a lot-specific technical data sheet. The buffers are not included. The Buffer Kit needed to run the Antibody Pair ELISA must be purchased separately (Cat. No. CNB0011). Note that the 5X Assay Buffer supplied in Cat. No. CNB0011 is used to block your ELISA plates and as a diluent for the standards and samples.

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No. The exact same streptavidin-HRP conjugate supplied in these kits is not available as a stand-alone product. However, it is derived from our ELISA-grade streptavidin-HRP (Cat. No. SNN2004), which we do sell. Remember that the streptavidin-HRP provided in each lot of ELISA or Antibody Pair kits is also lot-specific. So, if you use Cat. No. SNN2004 or another source of streptavidin-HRP, you will have to determine which dilution of SNN2004 works best for you.

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Yes, you can. The composition of the traditional 1X RIPA buffer is very similar to that of our Cell Extraction Buffer (Cat. No. FNN0011). Cat. No. FNN0011 is frequently used to prepare lysates for testing with our ELISA and Luminex kits. Our NP-40-based Cell Extraction Buffer (Cat. No. FNN0021) is also used. We recommend diluting lysates made with Cat. No. FNN0011 at least 10-fold in order to lower the SDS concentration to less than or equal to 0.01% (v/v) before adding the samples to the ELISA or Luminex assay.

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Our phosphospecific ELISA kits have several advantages, including ease of use and increased sensitivity. Phosphospecific ELISA kits are typically 2-10 times more sensitive than western blots, so they are particularly useful for the detection of “low-expressing” proteins or for small sample sizes. In addition, with the use of the recombinant standards provided in the kit, phosphospecific ELISAs provide quantitative results without having to perform densitometry.

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In order to evaluate phosphorylation levels, we report comparative levels of protein phosphorylation in units of phosphoprotein per pg or ng of total protein. The total ELISA kit quantifies the mass of protein per sample, and the phosphospecific ELISA kit quantifies the phosphorylation level of that protein in units. One can then determine if phosphorylation levels (in units/pg, for instance) of various samples are similar or different.

Example: Two samples are tested for total CREB and CREB [pS133]
Sample 1 results: The total assay (KHO0231) shows 100 pg/mL of CREB in the sample. The phosphospecific ELISA (KHO0241) shows 50 units/mL of CREB [pS133]. In this sample, CREB is phosphorylated at serine 133 to the level of (50 units/mL)/(100 pg/mL) = 0.5 units/pg of total CREB.
Sample 2 results: The total assay shows 95 pg/mL of CREB in the sample. The phosphospecific ELISA results show 5 units/mL of CREB [pS133]. In this sample, CREB is phosphorylated at serine 133 to the level of (5 units/mL)/(95 pg/mL) = 0.053 units/pg of total CREB. When you compare sample 1 with sample 2, you see a 10-fold difference in the level of phosphorylation of CREB at serine 133, even though the amount of total CREB protein is nearly unchanged.

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The results of our total ELISAs are given in pg/mL of sample, or sometimes ng/mL. This measurement is always given in mass units because standards of known mass are used to prepare the standard curve. The results of the phosphospecific ELISAs are given in “units”, which we do not relate to a particular mass of protein. We use units because it is difficult to precisely know the efficiency of a particular phosphorylation reaction, and therefore the ratio of phosphorylated to unphosphorylated protein, in a particular preparation of phosphoprotein standard. Phosphorylation units will be unique to each phosphospecific ELISA and are described within the product manual that accompanies each kit.

For example, a typical unit description would be “1 unit = the amount of FAK [pY397] derived from 300 pg of auto-phosphorylated FAK protein”. Since there is no guarantee that the FAK in our standard preparation is 100% phosphorylated, we refrain from making the statement that this corresponds to 300 pg of phosphorylated FAK. Instead, we validate a large batch of phosphorylated protein and use this to develop our unit definition and standard curve for our original assay. Subsequent preparations of our protein standards are normalized to the original batch of protein to ensure that our unit definitions remain constant from lot to lot.

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Both types of ELISA kits capture total protein, regardless of its phosphorylation state, within the wells of a plastic 96-well plate. This is done by coating the wells with a “pan-antibody” that does not distinguish between the phosphorylated and non-phosphorylated forms of a protein and does not block the phosphorylation site to be studied. In addition, a phosphospecific ELISA kit quantifies the amount of that same protein that is phosphorylated on one or more specific amino acids. Instead of a second pan-antibody for detection, this assay uses an antibody that specifically recognizes an epitope that is only present on a protein when it is phosphorylated specifically (i.e., it is phosphospecific).

We recommend running the total and phosphospecific ELISAs simultaneously with the same samples. If this is not possible, make sure to test the same samples with both kits as soon as possible.

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Each Antibody Pair kit contains capture (coating) antibody, biotinylated detection antibody, recombinant standard, and streptavidin-HRP. Other reagents required are listed in the Antibody Pair manual included with the kit, and can also be purchased separately (Antibody Pair Buffer Kit, Cat. No. CNB0011; 5X Assay Buffer, Cat. No. DS98200; etc.). The manual also provides a specific procedure and illustrates an example of a standard curve that can be obtained when the specific procedure is followed.

A general procedure is summarized here:
1) Coat the microplate with diluted capture (coating) antibody overnight at 2-8 degrees C; wash the plate.
2) Incubate the standards or samples in the coated microplate; wash the plate.
3) Incubate diluted biotinlyated detection antibody in the plate; wash the plate.
4) Incubate streptavidin-HRP in the plate for 15-45 min; wash the plate.
5) Incubate the plate with TMB substrate for 10-60 min, and then stop the reaction with Stop solution.
6) Read the microplate at 450 nm.
We recommend determining optimal buffer formulations, concentrations, and incubation times for individual applications.

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All ELISA kits are provided in the sandwich ELISA format with capture antibody already coated onto a 96 well plate. Typical detection uses a biotinylated detection antibody followed by Streptavidin-HRP and HRP substrate. Most kits are available as single 96-well plate kits, some are available as 2- and 5-plate kits. Kits typically contain:

96 Well Strip Plate coated with capture antibody
Standard protein
Wash buffer, 10x
ELISA buffer/Diluent, 10x
Detection antibody (in most kits, biotinylated)
HRP Reagent (either secondary antibody or streptavidin conjugated to HRP)(100x)
Substrate (usually TMB)
Stop solution
Adhesive plate covers

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Running internal controls along with the blanks and the standard curve is an excellent way to monitor the performance of any ELISA kit. Internal controls are samples containing known amounts of the analyte being measured with the kit. A key attribute of internal controls, and what differentiates them from the samples of the standard curve, is that they duplicate the composition of your actual samples as closely as possible. This is important because your samples may contain components that affect detection of the analyte differently than does the Standard Diluent provided in the kit. In other words, internal controls allow you to determine if assaying the same amount of analyte in the Standard Diluent (the standard curve) and in the sample matrix (internal controls) gives the same results. It's also important to remember that internal controls give you confidence in the accuracy of your results. Internal controls help ensure that the assay is performing consistently from assay to assay, every time you run it.

One source of internal controls is naturally occurring samples (such as serum or plasma) containing known amounts of the analyte you want to measure. Such positive control samples can be run as-is, or they can be diluted to various known concentrations, preferably with a naturally occurring negative sample of the same type. It's a good idea to run at least 2 internal controls, if you can. One usually has an analyte concentration between the lowest point on the standard curve and the curve's midpoint, while the other has a concentration between the midpoint and the highest concentration. Some researchers also run an internal control that falls close to the midpoint of the curve.

If you don't have access to naturally occurring controls, you can prepare them yourself. Let's say that you will be measuring interleukin-6 (IL-6) in human serum samples with an ELISA kit, Cat. No. KHC0061. First you will need to obtain some pooled normal human sera, which will be used as the sample matrix for your internal controls. Preferably, the IL-6 content of this serum should be negligible (but known) or too low to measure. Next you should add known amounts of human IL-6 to this serum to create the internal controls, using the human IL-6 standard provided in the kit. After you prepare the standard curve as described in the product manual, add some of the leftover concentrated IL-6 standard to the serum matrix. As described above, you can prepare controls with high and low IL-6 levels, or high, medium, and low, if you have enough wells in your ELISA plate.

Even if your sample type is not serum and you're not measuring IL-6, follow the general procedure outlined above to prepare your internal controls with your protein and sample matrix of interest. A valuable resource describing Spike and Recovery and Linearity of Dilution assays can be found here (http://tools.thermofisher.com/content/sfs/brochures/TR0058-Spike-and-Recovery.pdf). If you need more help, please contact Technical Support at techsupport@thermofisher.com.

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Our ELISA kits can be categorized into several different groups (see Table 2, Page 35 of the Protein Analysis Handbook - http://www.thermofisher.com/us/en/home/global/forms/protein-handbook-registration.html), based on a number of factors: target protein class, sensitivity, readout method, or ability to detect specific phosphorylation states of the target protein.

Standard colorimetric ELISA kits use a standard colorimetric readout and allow excellent sensitivity and detection range. Typical sensitivity is less than 10 pg/mL and standard curve range is around 10-250 pg/mL, although there are some kits with wider ranges.
Ultrasensitive ELISA kits use a standard colorimetric readout but enable detection and analysis of proteins to levels as low as 0.5 pg/mL. With measurement range of 0.5-20 pg/mL, these kits are especially useful with highly diluted samples.
Chemi ELISA kits use chemiluminescence detection for high sensitivity (less than 1 pg/mL) and are highly flexible with a wide measurement range from 0.5 to 2000 pg/mL.
Phospho ELISA kits enable the specific detection of phosphorylation of key signaling proteins with high specificity, and are often used to supplement western blot results and provide quantitative data.

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We offer full ELISA kits, Reagent Sets and Antibody Pairs. ELISA kits are complete, ready-to-use kits with pre-coated plates, all buffers, capture, and detection antibodies included. Most kits are single plate format, but some are available in 2- or 5-plate formats. Reagent Sets are for researchers who need the core kit components but prefer to make their own buffers and coat their own plates. Antibody Pairs are matched pairs of detection and capture antibodies for researchers who need to process large numbers of samples.

Find additional tips, troubleshooting help, and resources within our Antibodies and Immunoassays Support Center.