| Description | Aladdin's T7 DNA Ligase is a T7-derived, ATP-dependent dsDNA ligase recombinantly expressed in E. coli and purified using the PerfectProtein™ Technology Platform developed by aladdin. It ligates sticky ends more efficiently than blunt ends.Unlike T3 and T4 DNA Ligases, T7 DNA Ligase catalyzes Aladdin's T7 DNA Ligase is a T7-derived, ATP-dependent dsDNA ligase recombinantly expressed in E. coli and purified using the PerfectProtein™ Technology Platform developed by aladdin. It ligates sticky ends more efficiently than blunt ends.Unlike T3 and T4 DNA Ligases, T7 DNA Ligase catalyzes the formation of a phosphodiester bond between 5' phosphate and 3' hydroxyl groups of dsDNA only, but does not efficiently ligates blunt-end dsDNA. Addition of PEG6000 over 20% to the reaction can improve the ligation of blunt-end dsDNA. However, under regular ligation conditions blunt-end DNA ligation does not occur. Therefore, T7 DNA Ligase is ideal for molecular biology applications in which both blunt and sticky ends of DNA are are present but only sticky ends needs to be joined [1,2].Please refer to Figure 1 for the performance of this product in ligating sticky ends of dsDNA.Figure 1. Ligation of sticky-end DNA fragments with T7 DNA Ligase from aladdin and Competitor. A. Colonies of DH5ɑ transformed with the ligation products; B. Colony PCR of clones randomly selected from plates in figure A. The experimental results demonstrates that this product has comparable performance with the widely received Competitor product in ligating sticky-end DNA. This figure is for reference only, which may vary due to different experimental conditions.sApplication：Ligation of DNA fragments digested by restriction endonuclease, ligation of dsDNA and adapters, circularization of linear dsDNA, nick repair of dsDNA, site-specific mutagenesis, Golden Gate Assembly of DNA fragments, sticky-end specific ligation, etc.Source：Purified from E. coli with recombinant expression of DNA ligase from T7 phage.Definition of enzyme activity unit: One unit is defined as the amount of enzyme required for 50% ligation of 100ng HindIII fragments of λ DNA in a total reaction volume of 20µl in 30 minutes at 25°C in 1X T7 DNA Ligase Reaction Buffer.Purity: No DNA ligases other than T7 DNA Ligase, no DNA endonucleases and exonucleases, no RNase, no phosphodiesterase.Inactivation or inhibition：Ligation reactions without PEG6000 can be heat inactivated by incubation at 65℃ for 10 minutes.Precautions：ATP is a cofactor of T7 DNA Ligase, unlike E. coli DNA Ligase which uses NAD as a cofactor.T7 DNA Ligase does not effectively catalyse the ligation of blunt-end DNA fragments. For the ligation of blunt-end DNA, we recommend using the T4 DNA Ligase (, D7006).T7 DNA Ligase does not catalyze the ligation of ssDNA or RNA.The T7 DNA Ligase reaction contains 7.5% PEG6000. If the subsequent experiment is not compatible with PEG6000, a home-made ligation buffer without PEG6000 or the Ligation Buffer for T4 DNA Ligase (, D7006) can be used, but the activity of the T7 DNA Ligase will decrease by approximately 10-fold.We recommend using Pure™ Ultrapure Water (DNase/RNase-Free, Sterile) (, ST876) for the reaction.This product is for R&D only. Not for drug, household, or other uses.For your safety and health, please wear a lab coat and disposable gloves during the operation.Instructions for Use：1. Set up the ligation reaction in a nuclease-free microfuge tube on ice as follows:ReagentVolume2X Reaction Buffer10µlVector DNAXµl (0.020pmol)Insert DNAYµl (0.060pmol)Ultrapure Water (9-X-Y)µl T7 DNA Ligase (3KU/µl)1µl Total Volume20µlNote 1: The molar ratio of insert DNA to linearrized vector should be 3:1.Note 2: T7 DNA Ligase should be added last.2. Mix well by pipetting and centrifuge briefly to collect the liquid to the bottom of the tube.3. Incubate at 25℃ (or room temperature) for 15-30 minutes.4. Chill on ice and transform 5µl of ligation product into 50µl of competent cells. The remaining sample can be stored at -20℃.Note 1: Heat deactivation cannot be performed, as it will dramatically reduce transformation efficiency.Note 2: To analyze the ligation efficiency, the reaction product can be subjected to agarose/PAGE analysis. If DNA recovery from agarose gel is required, we recommend using the DNA Gel Recovery Kit (, D0056).FAQ:1. What is the length of sticky ends that can be ligated by T7 DNA Ligase?T7 DNA Ligase can effectively catalyse the ligation of 2bp or longer sticky ends and cannot ligate 1bp sticky ends. The T7 DNA Ligase is unable to ligate blunt-end dsDNA under typical reaction conditions. However, when the reaction contains high concentration of PEG6000 (20-30% w/v), T7 DNA Ligase also has measurable ligation activity for blunt-end dsDNA.2. Can the T7 DNA Ligase be used with PEG6000-free buffers?Yes. If PEG6000 cannot be included in the reaction, a 2X Reaction Buffer without PEG6000 can be prepared.3. What are the potential factors that can cause transformation failure when using T7 DNA Ligase for ligation?a. Lack of ATP or Mg2+ in the reaction. ATP easily degrades upon repeated freeze-thaw of this product. We recommend storing this product in aliquot to avoid repeated freeze-thaw, or adding an appropriate amount of ATP in this product after being used for multiple times to ensure ligation efficiency.b. The presence of high salt or EDTA in the reaction. We recommend purifying the DNA substrate before ligation to remove the interference.c. Phosphatases such as CIP, BAP or SAP used for dephosphorylation of the DNA substrate are not completely inactivated before ligation. The phosphatases should be completely deactivated or removed according to the recommended procedures.d. Too high a concentration of DNA in the reaction can result in the production of linear DNA only. The total concentration of DNA in the ligation reaction should be within 1-10µg/ml.e. Adding too much ligation product to competent cells can cause failure of the transformation. We recommend transforming 1-5µl of ligation product to 50µl of competent cells.f. Prolonged ligation in the presence of PEG6000 can produce large DNA fragments that inhibit transformation.g. The ligation product was not purified prior to electroporation. The presence of both salt and PEG6000 has a significant impact on electroporation. We recommend purifying the ligation product using a purification column before electroporation.h. Incomplete digestion of the vector will result in lack of target clones containing the insert.4. What other factors could cause a low transformation efficiency?a. The competent cells have too low transformation efficiency. New batch of competent cells should be used.b. Whether the ligated DNA contains an E. coli antagonistic inverted repeat or a tandem repeat.c. The insert DNA of mammalian or plant origin may contain methylated cytosines that can be degraded by a wide range of E. coli strains. We recommend using mcrA, mcrBC and mrr deficient E. coli competent cells for transformation.d. The constructed plasmid that is ＞10kb should be transformed with electroporation, instead of chemical transformation.5. What problems in restriction endonuclease digestion can lead to failure of the ligation reaction or subsequent transformation?a. The digestion is not complete. If digestion occurs at the end of a PCR fragment, there must be approximately 6 protection bases at 5' end of the recognition site. Meanwhile, test the activity of the restriction enzyme with a control substrate.b. The restriction endonuclease is not completely inactivated. If the restriction endonuclease cannot be heat inactivated, the DNA can be purified with an appropriate method.c. Restriction endonuclease generated star activity. We recommend analyzing the cleaved DNA by gel electrophoresis, reducing the amount of restriction endonuclease, or reducing the digestion time appropriately.d. DNA purification is recommended when DNA or restriction endonucleases contain nucleic acid exonucleases or phosphatases that destroy the ends of DNA fragments.6. How much DNA should be added when using T7 DNA Ligase?To improve the formation of circular DNA as well as the transformation efficiency, the total DNA concentration in the ligation reaction should be within 1-10µg/ml to ensure effective ligation. The molar ratio of insert DNA to linearised vector is recommended to be 3:1. Molar ratios lower than 2:1 will reduce ligation efficiency, while molar ratios higher than 6:1 will result in the insertion of multiple fragments. If the concentration of substrate DNA cannot be determined, multiple ratios can be tested.References: 1. Aidan J. Doherty. J Biol Chem. 1996 May 10;271(19):11083-9.2. A J Doherty. Nucleic Acids Res. 1996 Jun 15;24(12):2281-7... Read More | Inquire | Reverse transcriptases are enzymes encoded in retroviruses viral genome. The enzyme is responsible for transcription of the viral RNA to produce a dsDNA that can be inserted into the host genome.Reverse transcriptases are multifunctional enzymes. These enzymes exhibit an RNA and DNA directed Reverse transcriptases are enzymes encoded in retroviruses viral genome. The enzyme is responsible for transcription of the viral RNA to produce a dsDNA that can be inserted into the host genome.Reverse transcriptases are multifunctional enzymes. These enzymes exhibit an RNA and DNA directed polymerase activity. In addition reverse transcriptases catalyze the degradation of RNA in an RNA-DNA hybrid. The exonucleolytic activity proceeds in a 5' ---> 3' direction. The RNA or DNA directed activity requires a template (RNA or DNA) and a primer. The following is a schematic illustration of the reaction:Unit definition: One unit incorporates 1 nanomole of tritiated dTMP into acid insoluble productsusing poly(A)•oligo(dT) 12-18 as the template-primer in 20 minutes at 37° C.ApplicationsHIV reverse transcriptase is used for research on the AIDS primer. However it can be substituted for AMV reverse transcriptase, which is mainly used to transcribe mRNA into double stranded cDNA, that can be inserted into prokaryotic vectors. The enzyme can also be used with either single stranded DNA or RNA templates to make probes for use in hybridization experiments. It can be used for labeling the termini of DNA fragments with protruding 5' termini. The enzyme can also be used to sequence DNAs by the dideoxy chain termination method of Sanger when the Klenow fragment of E. coli DNA polymerase I, or the T7 DNA polymerase yield unsatisfactory results.Reagents0.05 M Tris, pH 8.3, containing 0.008 M MgCl21 mg/ml polyadenylic acid in water (poly A)DNA primer:Oligo d(T)12-181 µ mole dTTP/mL stock solution[methyl-3H]-Thymidine 5'-triphosphate (3H-dTTP)dTTP-3H-dTTP working mix: Add 1-2 µL 3H-dTTP per mL of 100 nmol/mL dTTP in order to obtain 1 to 1.5 x 105 cpm/mL1% bovine serum albumin10% perchloric acid1% perchloric acidBuffer substrate reaction mixture: Prepare fresh, immediately before use:For each 1mL of reaction mixture required mix:0.7 mL Tris/HCl, pH 8.3, 0.008M MgCl20.3 mL 1 mg/mL poly(A) RNA template0.005 mL 0.02 mg/mL oligo d(T)12-18 DNA primer0.02mL 1% BSAEnzymedilute as needed wtih 0.05M Tris/HCl, pH 8.3, 0.008M MgCl2 containing 0.1 mg/mL (1%) BSAProcedurePipette into each tube as follows:Buffer substrate mix：0.1 mLdTTP-3H3-dTTP：0.1 mLEnzyme：5-10 µLIncubate 20 minutes at 37° C. Stop reaction by adding 1 ml 10% cold perchloric acid. Filter through 0.2µ manifold filters used with Millipore vacuum manifold. Wash four times using 2mL 1% cold perchloric acid/wash. Transfer filter to scintillation vials. Add 2mL Cellosolve (or 2-methoxyethanol) to dissolve filter. Filters become opaque upon addition of Cellosolve. Make sure filters are dissolved before proceeding. Add 10mL scintillation cocktail and count.Calculation... Read More | Purity: >95%, by SDS-PAGE visualized with Coomassie® Blue Staining. Description： CD4, also known as L3T4, T4, and W3/25, is an approximately 55 kDa type I transmembrane glycoprotein that is expressed predominantly on thymocytes and a subset of mature T lymphocytes. It is a standard Purity: >95%, by SDS-PAGE visualized with Coomassie® Blue Staining. Description： CD4, also known as L3T4, T4, and W3/25, is an approximately 55 kDa type I transmembrane glycoprotein that is expressed predominantly on thymocytes and a subset of mature T lymphocytes. It is a standard phenotype marker for the identification of T cell populations. Mature human CD4 consists of a 371 amino acid (aa) extracellular region containing four immunoglobulin-like domains, a 22 aa transmembrane segment, and a 40 aa cytoplasmic domain. Within the ECD, human CD4 shares approximately 52% aa sequence identity with mouse and rat CD4. CD4 is expressed along with CD8 on double positive T cells during their development in the thymus. Either CD4 or CD8 expression is then lost, giving rise to single positive (SP) CD4+ or CD8+ mature T cells. CD4+ SP cells, also known as T helper cells, further differentiate into multiple subsets of CD4+ cells including Th1, Th2, Th17, Tfh, and Treg cells which regulate humoral and cellular immunity. CD4 is reexpressed on circulating CD8+ T cells upon activation and contributes to their cytotoxic effector activity. In human, CD4 is additionally expressed on macrophages, neutrophils, monocytes, NK cells, and neurons and glial cells in the brain. Similar CD4 distribution between species cannot be assumed as demonstrated by its presence on macrophages in human and rat but not in mouse. CD4 binds directly to MHC class II molecules on antigen presenting cells. This interaction contributes to the formation of the immunological synapse which is focused around the TCR-MHC class II-antigenic peptide interaction. Palmitoylation of two cysteine residues in the cytoplasmic tail of CD4 promotes the localization of CD4 in lipid rafts and its ability to augment TCR signaling via activation of the tyrosine kinase Lck. CD4 also functions as a chemotactic receptor for IL-16 and, in human, as a co-receptor for the gp120 surface glycoprotein of HIV-1... Read More | Recombinant Human Serum Albumin (rHSA) is an active compound and possesses an identical conformation to plasma derived HSA. Recombinant Human Serum Albumin (rHSA) has no difference between rHSA and plasma derived HSA. Recombinant Human Serum Albumin (rHSAAppearance:SolidBiological Activity:Recombinant Human Serum Albumin (rHSA) is an active compound and possesses an identical conformation to plasma derived HSA. Recombinant Human Serum Albumin (rHSA) has no difference between rHSA and plasma derived HSA. Recombinant Human Serum Albumin (rHSAAppearance:SolidBiological Activity:Recombinant Human Serum Albumin (rHSA) is an active compound and possesses an identical conformation to plasma derived HSA. Recombinant Human Serum Albumin (rHSA) has no difference between rHSA and plasma derived HSA. Recombinant Human Serum Albumin (rHSA... Read More |