S. aureus Topoisomerase IV
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S. aureus Topoisomerase IV
Topo IV (from Staphylococcus aureus) is prepared by overexpressing the subunits in E. coliand purifying them by methods developed in-house.
The subunits are purified to >95% purity as judged by SDS-PAGE. The topo IV is supplied as a heterotetramer complex in Dilution buffer.
It is recommended that the enzyme is aliquoted to avoid repeated freeze-thaw cycles. Store at -80ºC.
All enzyme is supplied with 5X concentrated Assay Buffer and Dilution buffers which are also available separately.
See technical documents below for more detailed information and lot specific activities.
Technical Documents
S. aureus Topoisomerase IV Relaxation Assay Kits
These contain S. aureus topo IV and the supercoiled DNA substrate in addition to the Assay and Dilution buffers for relaxation reactions. 1 U of topo IV will relax 0.5 µg supercoiled pBR322 DNA in 30 minutes at 37°C.
Technical Documents
S. aureus Topoisomerase IV Decatenation Assay Kits
These contain S. aureus topo IV and the catenated kDNA substrate in addition to the Assay and Dilution buffers for decatenation reactions. 1 U of topo IV will decatenate 200 ng of kDNA when incubated in 1X Assay buffer in a total reaction volume of 30 µl at 37°C for 30 minutes.
Technical Documents
S. aureus Topoisomerase IV Cleavage Assay Kits
These kits are designed specifically for cleavage reactions. They contain S. aureus topo IV enzyme, supercoiled pBR322 DNA substrate and the Assay and Dilution buffers required for DNA cleavage reactions in addition to linearised pBR322 marker.
Cleavage specific enzyme available separately on request.
Technical Documents
S. aureus Topoisomerase IV Assay Kit for Cell Extracts
These kits are designed for assaying cell extracts and partially purified fractions containing over-expressed S. aureus topo IV and contain supercoiled DNA substrate, Assay buffer, Dilution buffer, control relaxed DNA and stop buffer/loading dye.
Technical Documents
S. aureus Topoisomerase IV ATPase kit
These kits can be used to test the effects of potential ATPase inhibitors. For example, the coumarin drugs such as novobiocin inhibit the action of topoisomerase IV by competitively inhibiting the hydrolysis of ATP thus preventing supercoiling.
These assays are microtitre plate-based and thus large numbers of compounds can be screened in a relatively short period of time. They also continuous assays which can provide more information than an end point assay.
Technical Documents
High / Medium-Throughput Assay Kit - S. aureus Topoisomerase IV
The kit is supplied with sufficient S. aureus topo IV enzyme, plasmid DNA substrate, buffers and other assay components* for 100 assays. The enzyme is supplied at a concentration of 10 U/μl in Dilution Buffer. The kit is also supplied with sufficient wash buffers for one 96-well plate. These buffers are supplied as 20X concentrates and must be diluted with ultra pure water prior to use.
More information about this assay can be found on the "Services" page under "High/Medium Throughput Assay".
Kit issued with limited licence for individual use only.
Patent held by Inspiralis Ltd., Norwich, Norfolk, UK. (Patent No. GB0424953.8, US7838230)
Technical Documents
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DNA连接酶作用于基因工程，用于连接两个DNA片段间的磷酸二酯键。
可分为以下几个类群:(1)依赖DNA的DNA聚合酶；(2)依赖RNA的DNA聚合酶；(3)依赖DNA的RNA聚合酶；(4)依赖RNA的RNA聚合酶。前两者是DNA聚合酶，它使DNA复制链按模板顺序延长。如在原核生物中仅就大肠杆菌中已被发现的就有三种(分别简称为PolⅠ，PolⅡ和PolⅢ等)；DNA聚合酶只能在有引物的基础上，即在DNA或RNA引物的3′-OH延伸，这DNA的合成方向记为5′→3′。换言之DNA聚合酶催化反应除底物(αNTP)外，还需要Mg2+ 、模板DNA和引物，迄今细胞内尚无发现可从单体起始DNA的合成。同样，上述(3)和(4)是催化RNA生物合成反应中最主要的RNA合成酶，它们以四种三磷酸核糖核苷(NTP)为底物，并需有DNA模板以及Mn2 及Mg2 的存在下，在前一个核苷酸3′-OH与下一个核苷酸的5′-P聚合形成3′，5′-磷酸二酯键，其新生链的方向也是5′→3′。RNA聚合酶也大量存在于原核和真核生物的细胞中。如大肠杆菌RNA聚合酶分子量4.8×105，由5条多肽链组成，分别命名为α，α，β，β′，和γ，全酶可用α2ββ′λ表示。真核生物RNA聚合酶分子大于5×105，由10～12个大小不等亚基组成。聚合酶除作为自然界生命活动中不可缺少的组分外，在实验室中大多用作生命科学研究的工具酶类之一。向左转|向右转
再来说真核生物,真核生物的DNA聚合酶分为α,β,γ,δ,ε,.首先我来说三个和原核生物中的Ⅰ,Ⅱ,Ⅲ功能相同的酶.ε类似于原核生物DNA聚合酶Ⅰ,β类似于原核生物DNA聚合酶Ⅱ,δ类似于原核生物DNA聚合酶Ⅲ.α具有引物酶活性,而γ则是作为复制真核生物线粒体内的DNA所需要的酶.
解旋酶：在DNA复制、转录时，作用于DNA双链，将双链DNA解开形成单链。
RNA聚合酶：在转录过程中，作用于游离的核糖核苷酸，将它们连接形成mRNA链
下面是六种不同耐热聚合酶的比较：
Taq：扩增效率最高的耐热DNA聚合酶，能很好的扩增6kb以下的DNA片段。扩增碱基出错率为10-5左右。
Pfu：目前保真度最高的耐热DNA聚合酶，碱基出错率为10-6，但扩增效率低于Taq酶，一般能很好的扩增2kb以下的片段。
TaqPlus：集扩增效率高和保真度好于一身。扩增效率比Pfu高，保真度比Taq好。能有效的扩增10kb以下的片段。
HotstartTaq：经过化学修饰的耐热DNA聚合酶。此酶在常温下，活性被化学基团封闭，要在94℃-95℃加热数分钟才能回复正常活力开始反应，避免了起始循环较低温度下的非特异性扩增，提高了反应的灵敏度和特异性。
LongTaq：具有3’-5’外切酶活性的耐热DNA聚合酶，它不但扩增效率高而且错配率低，对于简单模板可扩增长达40kb的模板，对复杂模板也可扩增长达15kb的片段。
TaqPlatinum：热启动高保真耐热DNA聚合酶。如果对保真度要求很高，而用Pfu扩增有难度，可选用TaqPlatinum，一般扩增长度可达4kb。
根据不同的实验目的选择最合适的酶，
克隆普通长度的目的DNA片段：Taq、TaqPlus
保真度要求较高，片段比较短，如点突变、基因筛选等：Pfu、TaqPlatinum
高保真长片段扩增，如构建基因图谱及分子遗传学研究等：LongTaq、TaqPlus
扩增基因组模板，需要降低背景：HotstartTaq、TaqPlatinum
扩增GC含量较高或二级结构较复杂的模板：TaqPlus、LongTaq、TaqPlatinum
实时荧光定量PCR反应：Taq、HotstartTaq、TaqPlatinum
从菌株或质粒模板，筛选鉴定目的克隆，扩增6kb以下的片段：Taq、TaqPlus、2×TaqPCRMasterMix
模板比较复杂或目的片段丰度低，用普通Taq酶扩增不出条带：2×TaqPCRMasterMix、2×PfuPCRMasterMix
聚合酶就是多功能的dna的制作机器
DNA聚合酶和DNA连接酶作用的位点都是3'5'磷酸二酯键；但DNA连接酶是作用在游离的DNA片段间，使其连接成为一条完整的DNA链，而DNA聚合酶则是将游离的脱氧核糖核苷酸连接成DNA片段。
