Dynabeads™ FlowComp™ Flexi Kit - FAQs

View additional product information for Dynabeads™ FlowComp™ Flexi Kit - FAQs (11061D)

75 product FAQs found

我的Dynabeads磁珠不能很好地吸附到磁力架上，对此你们有什么建议吗？

请查看以下可能原因：

•溶液太粘稠。
•蛋白质间相互作用导致磁珠聚集。

尝试以下建议：
•延长分离时间（将管子留在磁力架上2-5分钟）。
•向裂解液中加入DNase I（约0.01 mg/mL）。
•将结合和/或清洗缓冲液中的Tween20浓度增加至约0.05%。
•向结合和/或清洗缓冲液中加入最多至20 mM 的β-巯基乙醇。

我想要分离较长的双链DNA片段，你们有什么产品可以推荐？

对于小于1 kb的生物素标记DNA，我们推荐使用Dynabeads M270链霉亲和素磁珠和MyOne C1磁珠。对于大于1kb的双链DNA分子，我们推荐Dynabeads KilobaseBINDER试剂盒。KilobaseBINDER试剂包括M-280链霉亲和素偶联的Dynabeads磁珠和一种含有专利的固定活化剂的结合液，可结合较长的生物素化DNA分子以进行分离。请点击以下链接(https://www.thermofisher.com/us/en/home/life-science/dna-rna-purification-analysis/napamisc/capture-of-biotinylated-targets/immobilisation-of-long-biotinylated-dna-fragments.html)，查看关于长的生物素化DNA片段分离的更多信息。

我能否使用Dynabeads磁珠分离单链DNA模板？

可以，Dynabeads磁珠可用于分离单链DNA。链霉亲和素Dynabeads磁珠能够以生物素化的DNA片段为靶标，通过使双链DNA变性，从而去除非生物素化链。链霉亲和素偶联的Dynabeads磁珠不会抑制任何酶活性。因此，可以在固相上直接对磁珠结合的DNA进行下一步处理。请点击以下链接(https://www.thermofisher.com/us/en/home/life-science/dna-rna-purification-analysis/napamisc/capture-of-biotinylated-targets/preparing-single-stranded-dna-templates.html)，查看关于单链DNA捕获的更多信息。

什么是磁化率？

磁化率能够衡量磁珠向磁力架迁移的速度，其大小取决于铁含量和氧化铁的特性。Dynabeads磁珠的磁化率是指质量磁化率，单位可以是cgs单位/g或m^3/kg（国际单位制）。对于亚铁磁性和铁磁性物质，质量磁化率取决于磁场强度（H），这些物质的磁化强度与H不是线性关系，而是随着场强增加而趋于饱和。因此， Dynabeads磁珠的质量磁化率是在固定条件下由标准操作程序而测定的。我们产品目录中给出的质量磁化率是国际单位制。磁化率由从高斯（cgs、emu）单位向国际单位的转换，是通过“高斯系数（emu/g或cgs/g）x 4π x 10^-3”而实现的。所得单位也被称为合理化质量磁化率，与（国际单位制）无量纲磁化率单位有所区别。通常，质量磁化率可用来衡量在非均匀磁场中影响物体的力（Fz）。测定Dynabeads磁珠的质量磁化率时，首先对样本称重，然后将样本放置于已知强度的磁场中。随后，再次称重得到样本重量（F1），并与关闭磁场时样本的重量（F0）进行对比。使用下述公式计算磁化率：K x 10^–3 = [(F1-F0) x m x 0.335 x 10^6]，K表示质量为m的样本的质量磁化率。最后，将磁化率转换为国际单位制。

我如何确定Dynabeads磁珠的偶联效率？

有多种不同的方法可以检测配体与磁珠结合，包括光密度（OD）检测、荧光标记和放射性标记。

对于OD检测，应在配体固定到磁珠上之前检测配体的OD值，并将其与包被后上清液中剩余的配体浓度进行比较。这样可以粗略检测有多少蛋白与磁珠结合。 实验方案： 1.将分光光度计设置到正确的波长。使用偶联缓冲液作为空白组。 2.检测偶联前溶液的吸光值。根据配体的加入量，可能需要进一步稀释以读取吸光值。 3.检测偶联后溶液的吸光值。也可能需要进一步稀释以读取吸光值。 4.计算偶联效率，以“蛋白质摄取量%”表示，如下所示：[(偶联前溶液的吸光值x D) – (偶联后溶液的吸光值x D)] x 100/(偶联前溶液的吸光值 x D)，D = 稀释倍数。 对于荧光标记，我们建议对配体结合量进行反向定量，即检测偶联上清液中剩余的配体量（与原始样本对比），而不是直接检测磁珠上的配体量。将标记的配体加入到磁珠中，并检测上清液中剩余多少配体（而不是结合到磁珠上的配体）。通过与开始时加入的总配体量相比，可以计算出结合到磁珠上的配体量。由于Dynabeads磁珠具有自发荧光，因此，我们不推荐直接检测与磁珠结合的配体的荧光，而是推荐这种间接方法。标记物可以是FITC/PE等。有些研究人员也成功使用了直接检测方法（采用流式细胞仪）。 在3种方法中，放射标记的灵敏度最高，但难度最大。该方法涉及到对配体的一部分进行放射性标记。在偶联前，使用示踪剂量的放射性标记的I-125，将其以一定比例与“冷”配体混合。使用闪烁（γ）计数器对磁珠进行检测，并将磁珠的cpm值与标准品对比，得到磁珠上配体的绝对量。 实验方案： 1.取出适量磁珠，并使用1 mL结合缓冲液清洗。 2.吸取适量人IgG，置于一个单独的管子中。 3.将人IgG与I-125标记的人IgG（30,000–100,000 cpm）混合。 4.使用结合缓冲液将人IgG与I-125标记的人IgG混合物稀释至100mL。 5.室温下孵育30分钟，使用闪烁计数器检测cpm值。 6.清洗磁珠（和包被层）4次，再次检测cpm值。 使用下述方程计算结合率%：（清洗后cpm值/清洗前cpm值）x100%。

Dynabeads磁珠有哪些尺寸？

Dynabeads磁珠有3种尺寸：4.5 µm （M-450）、2.8 µm （M-270/M-280）和1 µm （MyOne beads）。其中最大尺寸的磁珠非常适合细胞等较大的目标，2.8 µm磁珠推荐用于蛋白质组学和分子研究，而最小的1 µm磁珠则适用于自动化处理。

Dynabeads磁珠可使用超声处理么？

一般来说，在加入配体包被磁珠时，短时间超声是减少磁珠聚集、确保磁珠获得最佳均一性的好方法。一旦目标分子结合到磁珠，就要加倍小心了，以防结合被破坏。链霉亲和素磁珠本身能够承受超声。超声5分钟是可以的，更长时间超声的影响还未被测试。关于链霉亲和素-生物素的相互作用可否被超声破坏目前也尚无相关信息。

Dynabeads磁珠能否灭菌？

只有未包被的环氧基或甲苯磺酰基活化的磁珠可根据需要使用70%乙醇进行清洗除菌。包被的磁珠不可灭菌。

什么是Dynabeads磁珠？

Dynabeads磁珠是一种大小均一、无孔、超顺磁的、单分散的、高度交联的聚苯乙烯微球，整个磁珠由均匀分散的磁性材料构成。该磁性材料由磁赤铁矿(γ-Fe2O3)和磁铁矿(Fe3O4)的混合物组成。在Dynabeads磁珠M-280和M-450中，铁(Fe)分别占磁珠重量的12%和20%。Dynabeads磁珠表面覆盖有一层薄的聚苯乙烯外壳，将磁性材料包裹在内，可防止磁珠泄漏或在内部捕获配体。此外，该外壳也可避免目标分子直接接触铁，同时为每次实验提供特定的表面来吸附或偶联各种分子。
磁珠尺寸和形状均一，确保物理和化学性质稳定一致，进而提高实验结果的质量和可重复性。
Dynabeads磁珠分为3种不同尺寸：4.5 μm （M-450磁珠），2.8 μm （M-270/M-280磁珠）和1 μm （MyOne磁珠）。

如果带着Dynabeads磁珠共培养的话，磁珠会发生细胞内化么？

在培养中细胞是否会内吞Dynabeads磁珠要视具体细胞类型而定。由于磁珠尺寸的关系（通常直径为4.5 μM），Dynabeads磁珠将不会通过内吞途径（例如通过网格蛋白有被小窝）发生细胞内化。网格蛋白有被小窝在尺寸上一般不会大于500 nm，这对于磁珠的内吞来说太小了。不过，如果细胞具有吞噬活性（如单核细胞/巨噬细胞），Dynabeads磁珠还是可能在这些特定类型的细胞中被吞噬进入吞噬溶酶体的。所以您问题的答案可能为是或否——视具体的细胞类型而定。

在没有磁珠解离试剂的条件下，有办法将磁珠从分离出的细胞上去除么？

我们提供了多种不含释放机制的Dynabeads磁珠，这些产品可用于细胞阳性分离（捕获靶标细胞）或去除操作（将靶标细胞从样本中去除）：

•适用于细胞去除操作的Dynabeads磁珠：通过Dynabeads磁珠进行的细胞清除是一种十分快速、高效和方便的技术。选用预先包被的Dynabeads磁珠，或使用您的自备靶标抗体来包被我们的二抗包被磁珠，将其加入样本（如全血、PBMC、白细胞层，组织消化产物），混匀并孵育20分钟，再置于磁力架2分钟，您就完成了细胞去除操作。
•适用于阳性分离操作的Dynabeads磁珠，可匹配分子水平的下游分析应用：不含磁珠释放机制的靶细胞阳性分离可用于DNA、RNA或蛋白分析等分子水平的下游研究。在这些应用中，当磁珠连着细胞时，可对分离的细胞进行裂解，当细胞裂解后，磁珠可被移除。如果体系中存在磁珠不是问题，您也可在磁珠存在的条件下培养细胞。在大多数情况下，2-3天后表面的抗原会发生内化，磁珠也会随之脱落——因为这些磁珠相对体积过大，而无法通过细胞内吞途径来实现内化。

为何靶细胞会内吞Dynabeads磁珠？

在通常情况下，Dynabeads磁珠的尺寸很大，不会发生细胞内吞的现象。网格蛋白有被小窝通常不会大于500 nm，这对Dynabeads磁珠的内吞作用来说太小了。不过，对于像单核细胞/巨噬细胞等具有吞噬活性的靶细胞而言，Dynabeads磁珠还可能由吞噬作用介导进入细胞内部。

当抗体浓度较低时，我应如何对我的抗体进行生物素化操作？

在抗体浓度较低的情况下，生物素化效率会降低(操作手册中给出的最低浓度为0.5 mg / mL)。在公司内部，我们并没有使用低于0.5mg/mL的抗体，而是增加了DSB-X生物素的含量（从《DSB-X生物素蛋白标记试剂盒手册》(货号D-20655）中的表1可见在偶联反应中把DSB-X生物素含量从2 μL提高到4 μL可以提高反应效率)。< br / > < br / > 根据操作步骤生物素化0.5毫克/毫升的抗体：< br / > 0.5毫克/毫升x 0.2毫升 = 0.1毫克抗体< br / >生物素化的抗体的产量：在0.2毫升中的产量(0.1毫克抗体x 0.85%)= 0.4毫克/毫升< br / >在25μL中的生物素化的抗体量：0.4毫克/毫升x 25μL = 10μg，在推荐范围(每 5 x 10 e7细胞推荐5-50μg)。< br / > < br / > 生物素化0.2毫克/毫升的抗体：0.2毫克/毫升x 0.2毫升 = 0.04毫克抗体< br / >生物素化抗体的产量：在0.2毫升中的产量(0.04毫克抗体x 0.85%)= 0.17毫克/毫升< br / >在25μL中的生物素化的抗体量：0.17毫克/毫升x 25μL = 4μg，稍低于推荐范围。注意：可简单通过离心浓缩器（Centricon滤柱）对抗体进行浓缩，而不影响抗体的生物学活性。

我自备了DSB-X生物素标记抗体。我能使用Dynabeads生物素结合剂（Biotin Binder）磁珠或其他链霉亲和素包被的Dynabeads磁珠来分离细胞，并通过游离生物素来释放磁珠么？

不能，生物素结合剂和链霉亲和素Dynabeads磁珠均包被了野生型的链霉亲和素，后者与DSB-X生物素之间的结合过于紧密，无法通过普通型生物素高效解离下来。

我需要使用自备的生物素化抗体；我能在Dynabeads FlowComp Flexi试剂盒中使用这些抗体么？

不可以，使用我们在Dynabeads FlowComp Flexi试剂盒中所提供的生物素化模块非常重要，因为解离试剂（Release Buffer）只会竞争DSB-X生物素，而不会竞争普通型生物素。您可能会通过自备的生物素化抗体获得良好的分离效果，但您无法完成释放操作，除非使用我们在试剂盒中提供的DSB-X生物素化抗体。

在使用Dynabeads FlowComp试剂盒的过程中，我们能使用比一次测试的指定用量更少的细胞样本么？

大多数人源FlowComp试剂盒实验方案需要为一次测试准备5 x 10E7个（或以上的）细胞。您可尝试使用更少量的细胞样本，但我们不推荐您按比例减少Dynabeads磁珠或缓冲液的体积；请将这些试剂的用量维持在5 x 10E7个细胞时的推荐用量。这一用法也同样适用于释放步骤，解离缓冲液的体积须大于500 μL，所以请确保不要将试剂用量缩减至推荐值以下。

使用Dynabeads FlowComp细胞分离试剂盒之后，我应如何检测细胞纯度？

我们推荐用户使用FACS技术来检测细胞纯度。不过，由于靶标抗体仍粘附在细胞表面，我们推荐您使用另一种能够结合同一膜表面标志物上不同抗原表位的抗体。在产品附页中，我们会为FACS实验推荐最佳的适用抗体。

使用Dynabeads FlowComp阳性分离试剂盒的过程中，如何对细胞进行释放操作？

Dynabeads FlowComp试剂盒基于经修饰的生物素-链霉亲和素分离与释放技术。捕获抗体由DSB-X生物素进行标记，而Dynabeads FlowComp试剂盒中的Dynabeads磁珠则由修饰过的链霉亲和素进行包被。靶标抗体上的DSB-X生物素相比普通生物素而言，与链霉亲和素的亲和力更低。因此在阳性分离之后，用户可通过加入含有过量普通型生物素的解离缓冲液来释放细胞，这些普通型的生物素会从DSB-X生物素标记的靶标抗体上将Dynabeads磁珠偶联的修饰链霉亲和素竞争性结合下来。其结果是，用户能够获得不含磁珠，但含有抗体的分离细胞（DSB-X生物素化的靶标抗体仍粘附在细胞表面）。

我应如何在细胞分离之后去除Dynabeads磁珠？这些磁珠解离试剂盒之间的主要区别是什么？

有三种方法可去除所分离细胞上结合的Dynabeads磁珠。

•DETACHaBEAD 试剂盒（阳性分离）——解离试剂为抗Fab的多抗试剂，将磁珠结合的抗体从细胞上竞争性结合下来，从而帮助用户获得不含抗体和磁珠的细胞。提供适用于人CD4+和CD8+ T细胞，CD19+ B细胞和CD34+造血干细胞的试剂盒。
•CELLection试剂盒——解离试剂是一种DNA酶，能够消化抗体与磁珠之间的DNA接头，从而帮助用户最终获得不含磁珠的细胞。提供适用于人体EpCAM（Ber-EP4）上皮细胞和链霉亲和素（能够结合任一种生物素标记的抗体）的试剂盒。
•FlowComp试剂盒——解离试剂为生物素，能够竞争性结合与磁珠相偶联的des-生物素化抗体。提供适用于人类和小鼠总T细胞，CD4+和CD8+的T细胞亚群，以及人单核细胞的试剂盒。

我应如何复苏冻存的细胞？

在37°C水浴中对细胞冻存管中的细胞进行解冻，直至剩余一个小冰晶时取出。解冻后立即将细胞轻柔地转入10-15 mL的新离心管中，向细胞中逐滴加入10 mL 20% FCS/人血清，并温和的吹打。避免气泡产生并尽快完成操作。以200 x g离心细胞8分钟。弃去上清。在适当的缓冲液/培养基中重悬细胞。

我应如何进行细胞冻存？

通常情况下，冻存培养基（10% DMSO和90% FCS）或Gibco Recovery细胞冻存培养基（货号12648-010）的使用效果都很好。冻存过程中总有一些细胞会发生死亡。此外，冻存和复苏过程可能会造成某些细胞的裂解。请按以下步骤使用Gibco Recovery培养基冻存哺乳动物细胞：

1.化冻Recovery细胞冻存培养基，彻底混匀后在2–8°C放置，直至使用。
2.对于悬浮细胞从步骤3开始操作。对于贴壁细胞而言，用户应使用Gibco TrypLE试剂等适当的解离试剂，将细胞从其生长基质上轻柔地解离下来。使用该细胞的完全培养基重悬细胞。
3.将细胞悬液移至15-mL的无菌离心管中。
4.使用Invitrogen Countess自动细胞计数仪（也可使用类似的自动或手动方法）确定活细胞的密度和百分比，并计算所需Recovery细胞冻存培养基的体积，使最终细胞密度达到1 × 10E6至1 × 10E7个细胞/mL。
5.100-200 × g离心细胞悬液5-10分钟。在无菌条件下倒出上清液，但不要扰动细胞沉淀。注意：离心速度和时间可基于具体细胞类型来进行调整。
6.使用（2–8°C）冷却的Recovery细胞冻存培养基，以基于具体的细胞类型而推荐的活细胞密度（通常为1 × 10E6个细胞/mL或更高）重悬细胞沉淀。
7.按照生产商的技术说明（即在2 mL冻存管中加入1.5 mL悬液）将细胞悬液分装于冻存管中（应不时地轻柔混匀，以维持细胞悬液均匀）。
8.使用自动或手动控制变温速率的冷冻装置，按照标准步骤执行细胞冻存操作（约每分钟降低1°C左右）。
9.将冻存细胞移入液氮（气相）中，推荐保存于–200°C至–125°C。

骨髓可作为使用Dynabeads磁珠进行细胞分离的起始样本么？

加入Dynabeads磁珠之前需对骨髓进行洗涤和稀释，以降低样本粘性。在制备骨髓细胞的过程中，推荐在使用Dynabeads磁珠分离细胞之前，对样本进行洗涤和DNA酶处理：

1.将2 mL（10E7-10E8个细胞）骨髓样本与2 ml PBS w/ 0.1% BSA + 0.6%柠檬酸钠溶液进行混合。
2.在18-25°C条件下以600 g离心8分钟。
3.弃去上清，再使用5 mL 含0.1% BSA + 1mM CaCl2 + 0.5 mM MgCl2的PBS进行重悬。
4.加入600个Kunitz单位的DNase I（120个Kunitz单位DNase I/毫升）。
5.在18-25°C条件下孵育细胞30分钟，期间不断地进行轻柔的倾斜和旋转。
6.在18-25°C条件下以600 g对细胞悬液离心8分钟。
7.弃去上清，在5 mL含0.1% BSA的 PBS 中重悬细胞。
8.在18-25°C条件下以600 g对细胞悬液离心8分钟。
9.弃去上清，使用RPMI 1640 / 1% FCS将细胞重悬至1 x 10E8个细胞/毫升的浓度。

在使用Dynabeads磁珠进行细胞分离之前，我应如何对组织进行消化以获得单细胞悬液？

使用酶解消化和机械破碎等标准组织处理方法来制备单细胞悬液。通过细胞筛或30 µm滤网对消化后的细胞悬液进行过滤，以减少大块的聚集物。组织破碎通常会导致部分细胞死亡并释放出DNA。游离DNA会降低细胞捕获效率，回收率和纯度。DNase I处理的方法是：在18–25°C条件下将细胞悬液与含0.1% BSA + 1 mM CaCl2 + 0.5 mM MgCl2的PBS溶液以及120 Kunitz单位DNase I/mL共同孵育30分钟（对于CELLection产品，需要在加入磁珠前对细胞进行洗涤以去除DNA酶）。

我应如何制备单核细胞（MNC）？MNC中有哪些细胞亚类？各占多少比例？

MNC也称为外周血单核细胞（PBMC），是从全血、白细胞层、骨髓或脐带血中通过密度梯度离心分离出来的。下面介绍了用于阳性分离或去除法实验方案的标准MNC制备实验方案：

1.收集含抗凝剂（EDTA，ACD，肝素）的血样。分别按照外周血1+1，白细胞层1+2，骨髓1+1和脐带血1+3的比例，使用PBS （含0.1% BSA+ 0.6%柠檬酸钠或2 mM EDT）进行稀释。
2.取一个50 mL离心管，将35 mL稀释后的样本加在15 mL梯度介质（如Ficoll或Lymphoprep溶液）上层。
3.在18–20°C条件下以400 x g离心30-40分钟。如果血液保存时间超过两小时，则再增加10分钟离心时间。
4.收集中间层中的MNC，并将这些细胞移至50 mL离心管中。
5.使用含0.1% BSA的PBS 洗涤MNC三次，其间通过2–8°C300 x g离心8分钟的操作来沉淀细胞。
6.使用含0.1% BSA的PBS溶液将细胞重悬至1 x 10E7个细胞/毫升，并冷却至2–8°C。

请注意：MNC中包含T细胞（50%），B细胞（5-10%），NK细胞（5-10%）和单核细胞（30%），极少量的血小板且不含粒细胞。

如后续需要使用非接触式/阴性分离试剂盒，则推荐使用下列方案来制备低血小板含量和最高纯度的MNC：

可使用全血/白细胞层和骨髓样本作为起始样本。
1.在18–25°C条件下使用PBS （含0.1% BSA+ 0.6%柠檬酸钠或2 mM EDTA），将10-18 mL血液/白细胞层样品稀释至35 mL。
2.将稀释后的血液/白细胞层样本加至15 mL梯度介质（如Lymphoprep或Ficoll溶液）上方。
3.在20°C条件下以160 x g离心20分钟。离心结束后逐渐减速而不要骤然停止。
4.去除20 mL上清液，以减少血小板组份。
5.在20°C条件下以350 x g离心20分钟。离心结束后逐渐减速而不要骤然停止。
6.从血浆/Lymphoprep溶液的中间层收集MNC，并将这些细胞移至50 mL离心管中。
7.使用含0.1% BSA的PBS洗涤MNC一次，通过2–8°C下400 x g离心8分钟来沉淀细胞。
8.使用含0.1% BSA的PBS洗涤MNC两次，通过2–8°C下225 x g的离心8分钟来沉淀细胞。使用含0.1% BSA的PBS，以1 x 10E8个MNC/毫升的密度重悬MNC。

何为白细胞层？

白细胞层，即白细胞浓缩层，是对抗凝血样进行离心（不使用例如Ficoll溶液等密度梯度试剂）后获得的中间层组份，位于血浆下方，红细胞上方。白细胞层同时含有白细胞和血小板，因此可作为这些细胞材料的来源。

正常成年人血样本中主要细胞群的浓度是多少？

通常情况下，1毫升成年人血中包含：
~5 x 10E9 个红细胞
~7 x 10E6 个白细胞
~3 x 10E8 个血小板

在7 x 10E6个白细胞组份中，包含：
4 x 10E5个单核细胞
1 x 10E5个NK细胞

淋巴细胞：
2 x 10E5个B细胞
1 x 10E6个T细胞（约70%为CD4+ T细胞，30%为CD8+ T细胞）

粒细胞：
5 x 10E6个嗜中性白细胞
2 x 10E5个嗜酸性细胞
4 x 10E4个嗜碱性细胞

我应选择使用何种尺寸的Dynabeads磁珠？

这要视您的具体应用而定。一般来说，4.5微米的磁珠最适合细胞分离和激活/扩增。这些较大的磁珠具有更高的磁流动性，而且尺寸上与哺乳动物细胞近似，因而不大可能被细胞吞噬。较小的1微米磁珠和2.8微米磁珠通常用于分离核酸或蛋白，或用于免疫沉淀实验。阴性分离细胞试剂盒中通常使用1微米的磁珠，因为它们具有更高的每毫升结合能力和更快的结合动力学。在阴性分选过程中，细胞对磁珠的吞噬不会成为问题，因为用户只需对剩余的细胞群体进行观察。用二抗，蛋白A或蛋白G，或链霉亲和素包被的2.8微米Dynabeads磁珠，配合使用自选的一抗，靶向结合特异性的细胞表面抗原，也可应用于阳性细胞筛选。

Dynabeads磁珠的尺寸是多大？

我们提供三种不同大小的Dynabeads磁珠：1微米的磁珠（在产品名称中搜索Invitrogen MyOne磁珠），2.8微米的磁珠和4.5微米的磁珠。通常情况下，每毫升磁珠的结合能力和结合动力学参数随着磁珠尺寸的减小而增大。

Dynabeads磁珠有哪些特性和优势？

Dynabeads 磁珠具有超强的顺磁性，这意味着它们只在磁力架作用的条件下表现出磁性。一旦移除磁力架，磁珠就可像液体一样操作，也可方便地分装于样品管中。在细胞分离的相关应用中，这些特性具有显著的优势——能够实现轻柔的操作，以减少细胞承受的压力。第二，这些磁珠的形状和大小均一，并具有快速的液相反应动力学性质。磁珠光滑的表面能够有助于减少非特异性结合。这些性质能够降低体系的变异度，从而帮助您在纯化和分析过程中获得更为可靠和重复性良好的实验结果——无论您需要观察细胞还是其他靶分子（RNA/DNA/蛋白质/蛋白复合物/细胞器/外泌小体等等。）

当找不到适合我的细胞类型的阳性分离试剂盒时，我该怎么办？

最佳的选择是将Dynabeads FlowComp Flexi试剂盒与一款用于细胞分离的合适靶标抗体联用。Flexi试剂盒含有进行分离和释放操作所需的部分试剂，包括用于对您的抗体进行生物素化操作的DSB-X生物素化试剂盒，经修饰的链霉亲和素包被的FLowComp Dynabeads 磁珠和FlowComp 释放缓冲液。

My Dynabeads magnetic beads are not pelleting well with the magnet. Do you have any suggestions for me?

Please review the following possibilities for why your Dynabeads magnetic beads are not pelleting:

- The solution is too viscous.
- The beads have formed aggregates because of protein-protein interaction.

Try these suggestions: - Increase separation time (leave tub on magnet for 2-5 minutes)
- Add DNase I to the lysate (~0.01 mg/mL)
- Increase the Tween 20 concentration to ~0.05% of the binding and/or washing buffer.
- Add up to 20 mM beta-merecaptoethanol to the binding and/or wash buffers.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center.

I have a long double-stranded DNA fragment I would like to isolate. What product do you recommend?

For biotin-labeled DNA that is less than 1 kb, we recommend you use Dynabeads M270 Streptavidin (Cat. No. 65305) and MyOne C1 magnetic beads (Cat. No. 65001). We recommend our Dynabeads KilobaseBINDER Kit (Cat. No. 60101), which is designed to immobilize long (>1 kb) double-stranded DNA molecules. The KilobaseBINDER reagent consists of M-280 Streptavidin-coupled Dynabeads magnetic beads along with a patented immobilization activator in the binding solution to bind to long, biotinylated DNA molecules for isolation. Please see the following link (https://www.thermofisher.com/us/en/home/life-science/dna-rna-purification-analysis/napamisc/capture-of-biotinylated-targets/immobilisation-of-long-biotinylated-dna-fragments.html) for more information in regards to long biotinylated DNA fragment isolation.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center.

Can I use Dynabeads magnetic beads to isolate single-stranded DNA templates?

Yes, Dynabeads magnetic beads can be used to isolate single-stranded DNA. Streptavidin Dynabeads magnetic beads can be used to target biotinylated DNA fragments, followed by denaturation of the double-stranded DNA and removal of the non-biotinylated strand. The streptavidin-coupled Dynabeads magnetic beads will not inhibit any enzymatic activity. This enables further handling and manipulation of the bead-bound DNA directly on the solid phase. Please see the following link (https://www.thermofisher.com/us/en/home/life-science/dna-rna-purification-analysis/napamisc/capture-of-biotinylated-targets/preparing-single-stranded-dna-templates.html) for more information in regards to single-stranded DNA capture.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center.

What is the magnetic susceptibility for Dynabeads magnetic beads?

Magnetic susceptibility is a measure of how quickly the beads will migrate to the magnet. This will depend on the iron content and the character of the iron oxide. The magnetic susceptibility given for the Dynabeads magnetic beads is the mass susceptibility, given either as cgs units/g or m^3/kg (the latter being an SI unit). For ferri- and ferromagnetic substances, the magnetic mass susceptibility is dependent upon the magnetic field strength (H), as the magnetization of such substances is not a linear function of H but approaches a saturation value with increasing field. For that reason, the magnetic mass susceptibility of the Dynabeads magnetic beads is determined by a standardized procedure under fixed conditions. The magnetic mass susceptibility given in our catalog is thus the SI unit. Conversion from Gaussian (cgs, emu) units into SI units for magnetic mass susceptibility is achieved by multiplying the Gaussian factor (emu/g or cgs/g) by 4 pi x 10^-3. The resulting unit is also called the rationalized magnetic mass susceptibility, which should be distinguished from the (SI) dimensionless magnetic susceptibility unit. In general, magnetic mass susceptibility is a measure of the force (Fz) influencing an object positioned in a nonhomogenous magnetic field. The magnetic mass susceptibility of the Dynabeads magnetic beads is measured by weighing a sample, and then subjecting the sample to a magnetic field of known strength. The weight (F1) is then measured, and compared to the weight of the sample when the magnetic field is turned off (F0). The susceptibility is then calculated as K x 10^-3 = [(F1-F0) x m x 0.335 x 10^6], where K is the mass susceptibility of the sample of mass m. The susceptibility is then converted to SI units.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center.

How can I determine coupling efficiency of Dynabeads magnetic beads?

There are different methods to check binding of ligands to the beads, including optical density (OD) measurement, fluorescent labeling, and radioactive labeling.

For OD measurement, you would measure the OD of the ligand before immobilization to the beads and compare it with the ligand concentration that is left in the supernatant after coating. This gives a crude measurement of how much protein has bound to the beads.

Protocol:

1.Set spectrophotometer to the right wavelength. As a blank, use the Coupling Buffer.
2.Measure the absorbance of the Pre-Coupling Solution. A further dilution may be necessary to read the absorbance, depending upon the amount of ligand added.
3.Measure the absorbance of the Post-Coupling Solution. A dilution may be necessary to read the absorbance.
4.Calculate the coupling efficiency, expressed as the % protein uptake, as follows. [(Pre-Coupling Solution x D) - (Post-Coupling Solution x D)] x 100/(Pre-Coupling Solution x D) where D = dilution factor.

For fluorescent labeling, we suggest negatively quantifying the amount of ligand bound by measuring ligand remaining in the coupling supernatant (compared to the original sample), rather than directly measuring the ligands on the beads. Add labeled ligand to the beads, and measure how much ligand is left in the supernatant (not bound to the beads). By comparing this with the total amount added in the first place, you can then calculate how much of the ligand that has been bound to the beads. Keep in mind that the Dynabeads magnetic beads are also autofluorescent, which is why direct measuring of fluorescence of the bead-bound ligands is not recommended, but rather this indirect approach. The label could be, for example, FITC/PE. Some researchers perform a direct approach with success (using a flow cytometer).

Radioactive labeling is the most sensitive method of the three, but it is also the most difficult one. It involves radioactively labeling a portion of the ligand. We use radiolabeled I-125 in tracer amounts and mix it with "cold" ligands in a known ratio before coupling. The absolute quantities for the ligand on the beads should be obtained by measuring the beads in a scintillation (gamma) counter and comparing the cpm with a standard.

Protocol:

1.Take out an appropriate amount of beads and wash the beads in 1 mL of binding buffer.
2.Pipette out desired amount of human IgG in a separate tube.
3.Mix the human IgG with I-125-labeled human IgG (30,000 - 100,000 cpm).
4.Dilute the mixture of human IgG and I-125-labeled human IgG to 100 mL in binding buffer.
5.Incubate for 30 minutes at room temperature and measure the cpm in a scintillation counter.
6.Wash the beads (with coating) four times, and measure cpm again.
The % binding is calculated by using the equation : (cpm after washing/cpm before washing)x100%.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center.

What sizes do you offer for the Dynabeads magnetic beads?

Dynabeads magnetic beads come in three sizes: 4.5 µm (M-450), 2.8 µm (M-270/M-280), and 1 µm (MyOne beads). The largest of the Dynabeads magnetic beads is ideal for big targets like cells. The 2.8 µm beads are recommended for proteomics and molecular applications. The smallest of the beads, 1 µm, are ideal for automated handling.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center.

Can Dynabeads magnetic beads be sonicated?

In general, short sonication is a good way to reduce aggregation of the beads and ensure optimal homogenous conditions at the time of ligand addition when coating the beads. When target is bound to the beads, more care is needed, as the binding might break. The streptavidin beads themselves should tolerate sonication. We have not tested sonication for long periods, but 5 minutes is fine. We do not have information about the streptavidin-biotin interaction being broken by such treatment.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center.

Can Dynabeads magnetic beads be sterilized?

If desired, the uncoated epoxy or tosylactivated beads can be sterilized by washing with 70% ethanol. Coated beads cannot be sterilized.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center.

What are Dynabeads magnetic beads?

Dynabeads magnetic beads are uniform, non-porous, superparamagnetic, monodispersed and highly cross-linked polystyrene microspheres consisting of an even dispersion of magnetic material throughout the bead. The magnetic material within the Dynabeads magnetic beads consists of a mixture of maghemite (gamma-Fe2O3) and magnetite (Fe3O4). The iron content (Fe) of the beads is 12% by weight in Dynabeads magnetic beads M-280 and 20% by weight in Dynabeads magnetic beads M-450. The Dynabeads magnetic beads are coated with a thin polystyrene shell which encases the magnetic material, and prevents any leakage from the beads or trapping of ligands in the bead interior. The shell also protects the target from exposure to iron while providing a defined surface area for the adsorption or coupling of various molecules.

Uniformity of bead size and shape provides consistent physical and chemical properties. These uniform physical characteristics lead to high-quality, reproducible results.

The Dynabeads magnetic beads are available in three different sizes: 4.5 µm (M-450 beads), 2.8 µm (M-270/M-280 beads) and 1 µm (MyOne beads).

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center as well as our Protein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

When isolating cells with Dynabeads magnetic beads, what is more important: bead-to-target cell ratio or the concentration of beads in the bead/cell mixture?

Both bead-to-target cell ratio and the concentration of beads in the bead/cell mixture are important and should be considered. For example, when using the Dynabeads magnetic beads M-450 CD4 positive isolation or depletion kit, a 4:1 bead-to-target cell ratio should be maintained. To capture 95% of target cells for molecular applications, the bead concentration must always be 1 x 10e7 beads per milliliter of sample. To deplete 99% CD4 cells from the starting sample, the bead concentration must always be 2 x 10e7 beads per milliliter of sample. Please consult the package insert for recommended bead concentrations of each product.

Find additional tips, troubleshooting help, and resources within our Protein Assays and Analysis Support Center.

What is the definition of superparamagnetic, and what does this mean for my cell isolation application with Dynabeads magnetic beads?

Superparamagnetic means that the Dynabeads magnetic beads exhibit magnetic properties when placed within a magnetic field, but have no residual magnetism when removed from the magnetic field.

This means that your targeted cells, proteins, or nucleic acids are only subjected to magnetic forces during the time the beads are on the magnet. The beads do not aggregate, but remain evenly dispersed in suspension.

Find additional tips, troubleshooting help, and resources within our Dynabeads Cell Isolation and Expansion Support Center.

Are the antibodies on your Dynabeads magnetic beads for cell isolation/activation/expansion covalently bound to the beads?

Yes. The antibodies are covalently bound and should be very stable in your applications.

Find additional tips, troubleshooting help, and resources within our Protein Assays and Analysis Support Center.

What is the average shelf life of Dynabeads magnetic beads?

Depending on the antibody coated on the Dynabeads magnetic beads, the shelf life can vary from 24-36 months.
Some kits may have 18 months shelf life depending on other components supplied in the kit. The kits are guaranteed for 6 months from when you receive them.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center as well as our Protein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

What do the designations M-280, M-270, and MyOne mean on Dynabeads magnetic beads?

The M stands for magnetic. M-280 refers to hydrophobic 2.8 micron beads, while M-270 refers to hydrophilic 2.8 micron beads. MyOne refers to 1 micron beads.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center as well as our Protein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

What is the detection limit when using Dynabeads magnetic beads for immunoprecipitation (IP)?

Answering this question is not straightforward. It will depend on the detection method. When using HRP (horseradish peroxidase)-based detection system or radioactivity in combination with a good antibody, very little target is required. More target is required when using an AP (alkaline phosphatase)-based detection system. When a sensitive detection system is used, detection will most likely be in the nanogram range. In some cases, pictograms of target can be detected.

Find additional tips, troubleshooting help, and resources within our Protein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

What is the elution volume when using Dynabeads magnetic beads for immunoprecipitation (IP)?

Within practical limits, the elution volume can be scaled up or down to suit your experiment. However, volumes less than 10 µL become more difficult to work with. In addition, the amount of target is important. If you have a lot of beads with a lot of bound target in a small elution volume, your elution may not be very efficient. Typically, 15-100 µL of beads may be eluted in 30 µL. For efficient recovery of the antigen and/or binding partners, the elution volume should at minimum equal the volume of the beads.

Find additional tips, troubleshooting help, and resources within our Protein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

How can I quantify the amount of antibody bound to Dynabeads magnetic beads?

There are several methods to quantify the amount of antibody bound to the beads. The crudest method is to measure the concentration of antibody in the coupling reaction before and after antibody attachment. Either fluorescence measurements or absorbance at 280 nm can be used. Alternatively, you could measure the amount of antibody bound to the beads by fluorescence, chemiluminescence, or radiolabeling detection methods.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center as well as our Protein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

How long should I incubate my antibody with the lysates?

Incubation time will depend on the immunogenicity of the primary antibody and its binding affinity with the specific antigens. For a good primary antibody, 30-40 minutes incubation should work well. If you are working with a poor antibody or a very low-abundance protein, you could try to increase binding by incubating overnight. However, this also increases the chance of background protein binding.

Find additional tips, troubleshooting help, and resources within our Protein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

When should I covalently bind the antibody to the Dynabeads surface?

If the target protein has the same molecular weight as the heavy or light chain antibody, we would recommend covalently binding the antibody to the bead surface. This can be done by either crosslinking the antibody to the Dynabeads Protein A or G magnetic beads, or secondary coated beads, or by using one of the surface-activated Dynabeads magnetic beads.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center as well as our Protein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

What are the general advantages of using Dynabeads magnetic beads for protein isolation?

Using Dynabeads magnetic beads for protein isolation provides several advantages:

-Rapid binding kinetics: since the number of beads per volume for Dynabeads is approximately 1,000 times higher than for the same volume of a Sepharose slurry, the probability for Dynabeads magnetic beads to hit the target is far greater.

-Incubation time: due to the rapid binding kinetics, the protocol is usually very short.
-Low background: due to the rapid binding kinetics and the short incubation time, the background is also very low.
-Trapping of impurities: the beads offer no internal volume for binding or trapping of impurities.
-Low antibody consumption: this is because Dynabeads magnetic beads are nonporous, uniform superparamagnetic, monodispersed, highly crosslinked polystyrene microspheres consisting of an even dispersion of magnetic material throughout the bead. The beads are coated with a thin layer of a highly crosslinked polystyrene shell that encases the magnetic material and prevents any leakage from the beads or trapping of ligands in the bead interior. The outer layer also provides a defined surface area for the adsorption or coupling of various molecules such as antibodies. Uniformity of bead size and shape provide consistent physical and chemical properties. These uniform physical characteristics lead to high-quality, reproducible results.
-Reproducibility: due to easier practical handling, such as pipetting. No centrifugation steps or preclearing are required.

Find additional tips, troubleshooting help, and resources within ourProtein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

Are Dynabeads magnetic beads compatible with dithionite, DTT, and EDTA?

No. Not only is dithionite a reducing agent, but the strong affinity of the dithionite ion for bivalent and trivalent metal cations (M2+, M3+) allows it to enhance the solubility of iron, making it a chelating agent. As a result, the iron in the Dynabeads magnetic beads is reduced and pulled out when they are exposed to dithionite. The same is observed if Dynabeads magnetic beads are exposed to DTT and EDTA. With EDTA, we highly recommend checking the minimal amount of EDTA that your specific molecules would tolerate for binding to the Dynabeads, and if it will affect your specific application. For some applications, low concentrations of EDTA can be tolerated by Dynabeads. On the other hand, using 10 mM EDTA with heating affects the binding of biotin molecules to Dynabeads streptavidin.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center as well as our Protein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

Are Dynabeads magnetic beads compatible with Urea?

Yes, they are compatible with 6-8 M Urea when used during post-coupling steps.

Find additional tips, troubleshooting help, and resources within our Protein Assays and Analysis Support Center.

Are Dynabeads magnetic beads compatible with centrifugation?

Dynabeads magnetic beads, being magnetic in nature are really not designed to be centrifuged. That being said, the beads themselves are compact, as the pores in the polymer matrix are filled with magnetic material and coated with a final outer polymer shell that will further add to the rigidity of the beads. Hence, pressure should theoretically not be a problem for the beads themselves, but the force exerted by the beads on surrounding cells in the pellet may be detrimental to the cells.

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center as well as our Protein Immunoprecipitation (IP), Co-Immunoprecipitation (Co-IP), and Pulldown Support Center.

What are the benefits of using magnetic beads in immunoprecipitation (IP) experiments?

Magnetic beads, unlike agarose beads, are solid and spherical, and antibody binding is limited to the surface of each bead. While magnetic beads do not have the advantage of a porous center to increase the binding capacity, they are significantly smaller than agarose beads (1 to 4 µm), which collectively gives them adequate surface area-to-volume ratios for optimum antibody binding.

High-power magnets are used to localize magnetic beads to the side of the incubation tube and out of the way to enable cell lysate aspiration without the risk of also aspirating immune complexes bound to the beads. Magnetic separation avoids centrifugation, which can break weak antibody-antigen binding and cause loss of target protein.

However, an issue with the use of magnetic beads is that bead size variations may prevent all beads from localizing to the magnet. Additionally, while immunoprecipitation using agarose beads only requires standard laboratory equipment, the use of magnetic beads for immunoprecipitation applications requires high-power magnetic equipment that can be cost-prohibitive. Read more about our Magnetic Immunoprecipitation Products (https://www.thermofisher.com/us/en/home/life-science/protein-biology/protein-assays-analysis/immunoprecipitation.html#products).

Find additional tips, troubleshooting help, and resources within our Protein Assays and Analysis Support Center.

Will Dynabeads magnetic beads be internalized if cultured with the beads on?

Whether cells will internalize the Dynabeads magnetic beads during culture will depend on the cell type. Due to the bead size (usually 4.5µm in diameter) Dynabeads magnetic beads will not be internalized into the endocytic pathway e.g., via clathrin coated pits. The clathrin coated pits are typically not more than 500 nm in size, which is far too small for endocytosis of the beads. However, if cells with phagocytic activities (e.g., monocytes/macrophages) are present, the Dynabeads magnetic beads will be phagocytosed into the phagolysosomes by these specialized cells. So it would really depend on the cell type.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

Is there a method to remove the Dynabeads magnetic beads from isolated cells if the bead releasing reagent is not available?

We offer several Dynabeads magnetic beads that can be used for either positive isolation (keep the target cells) or for depletion (remove the target cell from a sample) that does not include any release mechanism:

- Dynabeads magnetic beads for depletion: Using Dynabeads magnetic beads for depletion is a very fast, efficient and easy method. Use pre-coated Dynabeads magnetic beads or coat your own target antibody onto our secondary coated beads, add to any sample (e.g., whole blood, PBMC, buffy coat, tissue digests), incubate for 20 minutes with mixing, apply to a magnet for 2 minutes, and you have your cells depleted.

- Dynabeads magnetic beads for positive isolation for molecular downstream assays: Positive isolation of target cells without bead release can be used when the aim is downstream molecular studies such as DNA, RNA, or protein analysis. In these applications, the isolated cells can be lysed while the beads are attached to the cells, and the beads can be removed after cell lysis. If the bead presence is not a problem, you can also culture the cells with the beads on. In most cases the surface antigen will be internalized after 2-3 days, and then the beads will fall off since the beads are too big to be internalized by the endocytosis pathway.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

Will Dynabeads magnetic beads be internalized by the target cells?

In general, the size of the Dynabeads magnetic beads is so large that they will not be internalized. The clathrin-coated pits are typically not more than 500 nm in size, which will be too small for Dynabeads magnetic beads to be internalized by endocytosis. However, if the target cells have phagocytic activities such as monocytes/macrophages, the Dynabeads magnetic beads could be internalized by phagocytosis.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

How can I biotinylate my antibodies if the antibody concentration is low?

Given that the concentration of your antibodies is low, the biotinylation efficiency will be reduced (the lowest concentration given in the protocol is 0.5 mg per mL). In-house, we have not used less than 0.5 µg per mL of antibody, but increasing the amount of DSB-X biotin (Table 1 in manual for DSB-X Biotin Protein Labeling Kit (Cat. No. D-20655) from 2µL to 4µL in the coupling reaction might increase the efficiency).

Biotinylation of 0.5 mg per mL antibody according to the protocol:
0.5 mg per mL x 0.2 mL = 0.1 mg antibody
Yield of biotinylated antibody: (0.1 mg antibody x 0.85%) in 0.2 mL = 0.4 mg per mL
Amount of biotinylated antibody in 25 µL: 0.4 mg per mL x 25 µL = 10 µg antibody in 25 µL, which is in the recommended range (5-50 µg for 5 x 10e7 cells).

Biotinylation of 0.2 mg per mL: 0.2 mg per mL x 0.2 mL = 0.04 mg antibody
Yield of biotinylated antibody: (0.04 mg antibody x 0.85%) in 0.2 mL = 0.17 mg per mL
Amount of biotinylated antibody in 25 µL: 0.17 mg per mL x 25 µL = 4 µg antibody in 25 µL, which is slightly outside the recommended range.

Note: Antibody may be easily concentrated without affecting the biological activity by using centrifuge concentrators (i.e., Centricon filter columns).

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

I have my own antibody that is labeled with DSB-X biotin. Can I use either the Dynabeads Biotin Binder beads or any other streptavidin-coated Dynabeads magnetic beads to isolate cells and release the beads with free biotin?

No, both Biotin Binder and streptavidin Dynabeads magnetic beads are coated with wild type streptavidin, which binds DSB-X biotin too tightly to be efficiently released by free normal biotin.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

I have my own biotinylated antibody; can I use it in the Dynabeads FlowComp Flexi kit?

No, it is very important to use the supplied biotinylation module provided in the Dynabeads FlowComp Flexi kit since the Release Buffer only will out-compete the binding with DSB-X biotin and not ordinary biotin. You will probably get good isolation using your own biotinylated antibody, but you won't get any release unless you use the DSB-X biotinylated antibodies supplied in the kit.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

Is it possible to work with fewer cells than is specified for one test with Dynabeads FlowComp kits?

Most human FlowComp kit protocols are for 5 x 10E7 total cells or more per test. You can work with fewer cells, but we don't recommend that you scale down the volume of Dynabeads magnetic beads or the buffers; stick to the volumes recommended for 5 x 10E7 cells. This is also true for the release step, where the volume of release buffer must be at least 500 µL, so make sure not to scale down more than recommended.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

How do I check the cell purity after using Dynabeads FlowComp cell isolation kits?

We recommend using FACS to check the cell purity. But, since the target antibody is still attached to the cell surface, we recommend that you use an antibody that binds at a different epitope of the same surface marker. In the product insert, we give recommendations for the best suitable antibodies for use in FACS.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

How are the cells released when using the Dynabeads FlowComp positive isolation kits?

Dynabeads FlowComp kits are based on modified biotin-streptavidin isolation and release technology. The capture antibodies are labeled with DSB-X biotin, while the Dynabeads magnetic beads in the Dynabeads FlowComp kits are coated with modified streptavidin. The DSB-X biotin on the target antibody has a lower affinity to the streptavidin than normal biotin. Thus, following the positive isolation, the cells are released by adding the release buffer containing excess of normal biotin that out-competes the binding between the modified streptavidin on the Dynabeads magnetic beads and the DSB-X biotin-labeled target antibody. As a result, the isolated cells are bead-free but not antibody-free (the DSB-X biotinylated target antibody is still attached to the cell surface).

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

How can I remove the Dynabeads magnetic beads from the cells isolated, and what are the major differences between the bead releasing kits?

There are three methods to remove the Dynabeads magnetic beads from the isolated cells:

1. DETACHaBEAD Kits (positive isolation) - where the release agent is a polyclonal anti-Fab reagent outcompeting the binding of the bead-bound antibody on the cell, giving both antibody- and bead-free cells. Kits are available for Human CD4+ and CD8+ T cells, CD19+ B cells, and CD34+ hematopoietic stem cells.
2. CELLection Kits - where the release agent is a DNase enzyme, digesting the DNA-linker between the antibody and the bead, ultimately leading to bead-free cells. Kits are available for human EpCAM (Ber-EP4) epithelial cells and streptavidin (binding any biotinylated antibodies).
3. FlowComp Kits - where the release reagent is biotin that is out-competing the des-biotinylated antibody coupled onto the beads. Available for human and mouse whole T cells, the T cells subsets CD4+ and CD8+, and human monocytes.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

How do I thaw frozen cells?

Thaw cells in their cryovial in a 37 degrees C water bath until a small ice-clump is left. Transfer the cells gently to a fresh 10-15 mL tube immediately after the cells are thawed and add 10 mL 20% FCS/human serum in droplets to the cells while gentle pipetting. Avoid air bubbles. Work fast. Centrifuge the cells 200 X g, 8 minutes. Discard the supernatant. Resuspend in the appropriate buffer/media.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

How do I freeze cells?

In general, freezing medium (10% DMSO and 90% FCS) or Gibco Recovery Cell Culture Freezing Medium (Cat. No. 12648-010) work well. Some cells will always die during the freezing process. In addition, freezing and thawing will cause some cells to lyse. The protocol to freeze mammalian cells using Gibco Recovery medium is as follows:

1. Thaw Recovery Cell Culture Freezing Medium, mix well, and keep at 2-8 degrees C until use.
2. For suspension cells proceed to step 3. For adherent cells, gently detach cells from the substrate on which they are growing using a suitable dissociation reagent such as Gibco TrypLE reagent. Resuspend cells in the complete medium required for that cell type.
3. Transfer cell suspension to a sterile 15 mL centrifuge tube.
4. Determine the viable cell density and percent viability using a Countess Automated Cell Counter (similar automated or manual methods may be used) and calculate the required volume of Recovery Cell Culture Freezing Medium to give a final cell density of 1 X 10E6 to 1 X 10E7 cells/mL.
5. Centrifuge cell suspension at 100-200 x g for 5-10 minutes. Aseptically decant supernatant without disturbing the cell pellet. Note: Centrifugation speed and duration may vary depending on cell type.
6. Resuspend the cell pellet in (2- 8 degrees C) chilled Recovery Cell Culture Freezing Medium at recommended viable cell density for specific cell type (typically 1 X 10E6 cells/mL or greater).
7. Dispense aliquots of cell suspension (mix frequently to maintain a homogeneous cell suspension) into cryovials according to the manufacturer's specifications (i.e., 1.5 mL in a 2 mL cryovial).
8. Achieve cryopreservation in an automated or manual controlled rate freezing apparatus following standard procedures (approximately 1 degree C decrease per minute).
9. Transfer frozen cells to liquid nitrogen, (vapor phase); storage at -200 degrees C to -125 degrees C is recommended.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

Can bone marrow be used as starting material for cell isolation using Dynabeads magnetic beads ?

Bone marrow needs to be washed and diluted prior to addition of Dynabeads magnetic beads to make the sample less viscous. Washing and DNase treatment is recommended for preparing bone marrow cells prior to cell isolation using Dynabeads magnetic beads:

- Mix 2 mL (10E7-10E8 cells) bone marrow with 2 ml PBS w/ 0.1% BSA + 0.6% Na-citrate.
- Centrifuge at 600 g for 8 min at 18-25 degrees C.
- Discard the supernatant and resuspend to 5 mL with PBS w/ 0.1% BSA + 1mM CaCl2 + 0.5 mM MgCl2.
- Add 600 Kunitz units DNase I (120 Kunitz units DNase I per milliliter).
- Incubate cells for 30 minutes at 18-25 degrees C with both gentle tilting and rotation.
- Centrifuge cell suspension for 8 minutes, 600 x g, at 18-25 degrees C.
- Discard supernatant and resuspend cell pellet in 5 mL PBS w/ 0.1% BSA.
- Centrifuge cell suspension for 8 minutes, 600 x g, at 18-25 degrees C.
- Discard supernatant and resuspend at 1 x 10E8 cells per milliliter in RPMI 1640 / 1% FCS

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

How do I carry out tissue digests to obtain a single-cell suspension before using Dynabeads magnetic beads for cell isolation?

Follow standard tissue preparations using enzymes and mechanical disruption to get a single-cell suspension. Eliminate large aggregates by sieving the digested cell suspension through a cell strainer or filter through a 30 µm filter. Disruption of tissue normally results in some cell death and release of DNA. Free DNA will impair cell capture, recovery, and purity. DNase I treatment is performed by incubating the cell suspension in PBS with 0.1% BSA + 1 mM CaCl2 + 0.5 mM MgCl2 and 120 Kunitz units DNase I per ml at 18-25 degrees C for 30 min. (For CELLection products, wash cells to remove DNase before adding the beads.)

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

How do I prepare mononuclear cells (MNC), and what kind of cells are present in MNC and in what proportion?

Mononuclear cells (MNC), also known as peripheral blood mononuclear cells (PBMC), are prepared from whole blood, buffy coat, bone marrow, or umbilical cord blood by density gradient separation. The following protocol can be used for standard MNC preparation for positive isolation or depletion protocols:

1. Collect blood sample with anticoagulant present (EDTA, ACD, heparin). Dilute peripheral blood 1 + 1, buffy coat 1 + 2, bone marrow 1 + 1 and umbilical cord blood 1 + 3 in PBS w/ 0.1% BSA + 0.6% Na-citrate or 2 mM EDTA.
2. Layer up to 35 mL of the diluted sample over 15 mL gradient medium (such as Ficoll or Lymphoprep solution) in a 50 mL tube.
3. Centrifuge for 400 x g for 30-40 minutes at 18-20 degrees C. If blood has been stored for more than 2 hours, increase centrifugation time by 10 min.
4. Collect MNC from the interface and transfer cells to a 50 mL tube.
5. Wash MNC three times with PBS w/0.1% BSA by centrifugation at 300 x g for 8 min at 2-8 degrees C.
6. Resuspend the cells to 1 x 10E7 cells per milliliter in PBS with 0.1% BSA and cool to 2-8 degrees C.
Note: MNC contain T cells (50%), B cells (5-10%), NK cells (5-10%), and monocytes (30%) without granulocytes and very few platelets.

For use with Untouched/negative isolation kits, the following protocol is recommended to obtain MNC prep with low platelet numbers and the highest possible purity:

Whole blood/buffy coat and bone marrow can be used as a starting material.

1. Dilute 10-18 mL blood/buffy coat with PBS w/ 0.1% BSA + 0.6% Na-citrate or 2 mM EDTA to a total volume of 35 ml at 18-25 degrees C.
2. Add the diluted blood/buffy coat on top of 15 mL of gradient medium (such as Lymphoprep or Ficoll solution).
3 .Centrifuge at 160 x g for 20 min at 20 degrees C. Allow to decelerate without braking.
4. Remove 20 mL of supernatant to eliminate platelets.
5. Centrifuge at 350 x g for 20 min at 20 degrees C. Allow to decelerate without braking.
6 .Recover MNC from the plasma/Lymphoprep solution interface and transfer the cells to a 50 mL tube.
7. Wash MNC once with PBS w/ 0.1% BSA by centrifugation at 400 x g for 8 min at 2-8 degrees C.
8. Wash MNC twice with PBS w/ 0.1% BSA by centrifugation at 225 x g for 8 min at 2-8 degrees C and resuspend the MNC at 1 x 10E8 MNC per milliliter in PBS w/ 0.1% BSA.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

What is a buffy coat?

Buffy coat, also known as leukocyte concentrate, is the middle fraction of an anti-coagulated blood sample that sits under the plasma and on the top of red blood cells after centrifugation of the sample without using a density gradient reagent such as Ficoll solution. Buffy coat contains both leukocytes and platelets and can be used as a source of this cellular material.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

What is the concentration of major cell populations in normal adult human blood?

Typically, one milliliter of adult human blood contains:
~5 x 10E9 red blood cells
~7 x 10E6 leukocytes
~3 x 10E8 platelets

In the 7 x 10E6 leukocyte fraction, there are:
4 x 10E5 monocytes
1 x 10E5 NK cells

Lymphocytes:
2 x 10E5 B cells
1 x 10E6 T cells (approx. 70% are CD4+ T cells and 30% are CD8+ T cells)

Granulocytes:
5 x 10E6 neutrophils
2 x 10E5 eosinophils
4 x 10E4 basophils


Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

What Dynabeads magnetic bead size should I select for my application?

This will depend on your application. As a guideline, the 4.5 micron beads are best used for cell isolation and activation/expansion. These larger beads have a higher magnetic mobility, they are roughly the same size as mammalian cells, and are less likely to be taken up by the cells. The smaller 1 micron beads and 2.8 micron beads are often used when isolating nucleic acids or proteins, or for immunoprecipitation. In negative cell isolation kits, one micron beads are often used because of their higher binding capacity per milliliter of beads and faster binding kinetics. With negative selection, cells taking up any beads will not be a problem as you want to look at the remaining cell population anyway. The 2.8 micron Dynabeads magnetic beads, coated with secondary antibodies, protein A or protein G, or streptavidin are also used for positive cell isolation with primary antibodies of your own choice, targeting specific cell-surface antigens.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

How large are the Dynabeads magnetic beads?

Three different sizes of Dynabeads magnetic beads are available: One micron beads (look for MyOne magnetic beads in the product name), 2.8 micron beads, and 4.5 micron beads. In general, the binding capacity per milliliter of beads and binding kinetics increases as the bead size reduces.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

What are the characteristics and advantages of Dynabeads magnetic beads?

Dynabeads magnetic beads are super-paramagnetic, meaning they only display magnetic characteristics when a magnet is present. As soon as the magnet is removed, the beads handle like a liquid and are easily dispersed in the sample tube. For cell isolation purposes, this has clear advantages as it allows for gentle handing and reduced stress to the cells. Secondly, the beads all have the same size and shape, with rapid liquid-phase reaction kinetics. The smooth surface of the beads results in less non-specific binding. These properties tend to reduce variability and allow you to get more reliable and reproducible results for your purifications and your analyses whether you are looking at cells or any other target molecule (RNA/DNA/proteins/protein complexes/organelles/exosomes etc.)

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.

What should I do if I cannot find a Dynabeads positive isolation kit available for my cell type?

The best choice is to use the Dynabeads FlowComp Flexi Kit (Cat. No. 11061D) in combination with a suitable target antibody for cell isolation. The Flexi kit contains both a DSB-X biotinylation kit for biotinylation of your antibody, the modified streptavidin-coated FlowComp Dynabeads magnetic beads, and the FlowComp Release Buffer required for performing isolation and release.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.