TAP Growth Media, optimized for Chlamydomonas culture, 1 L - FAQs

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我正在使用藻类MAX Efficiency转化试剂转化衣藻。但是,转化效率非常低。如何能够对此进行改善?

请查看以下建议:

1. 为得到最佳结果,藻类细胞浓度应在1 x 106至2 x 106细胞/mL之间(OD范围为0.3-0.5)。细胞浓度不可超过3 x 106细胞/mL。可通过OD750检测细胞生长,线性范围将在0.2-1.2(在1 cm光路中)之间。如果OD值超出线性范围,请稀释并再次检测以获得准确读数。

公式为:细胞数= (OD750 – 0.088)/ 9 × 106 /mL

2. 线性DNA转化比环状DNA转化的效率高很多(有效率约高出70%)。
3. DNA的质量和浓度对于转化效率至关重要。您将需要使用PureLink HQ、PureLink HiPure或相同质量的质粒纯化试剂盒进行DNA纯化。使用小体积的浓缩纯化DNA要比使用大体积的低浓度DNA更好。(如果您在转化线性质粒,则在线性化之后,您将需要在转化前使用凝胶提取或PCR净化试剂盒对质粒进行纯化处理。)我们建议每次电穿孔使用2 µg的线性质粒DNA。
4. 质粒DNA是随机插入到基因组的。通常,只有20%的转化株会明显表达目的基因。我们建议首先通过菌落PCR对菌落进行筛选,确保启动子和目的基因的完全整合,随后通过筛选多个阳性克隆,挑选出表达水平最高的克隆。
5. 由于C. reinhardtii基因组具有非常高的GC含量(约62% GC),如果目的基因适应了高表达C. reinhardtii基因的密码子使用偏好,则重组基因的表达水平会明显改善。
6. 由于转化效率取决于构建体向基因组的随机整合,电穿孔结果将取决于目的基因的性质。您可尝试转化试剂盒中的对照载体,从而确认试剂盒及其电穿孔方法是有效的。

使用pChlamy_1或pChlamy_3载体时,由于出现基因沉默而得到较低的表达。你们有何建议?

很遗憾,基因沉默是藻类表达中的一个大问题。沉默程度取决于基因序列和从该基因表达到细胞中的蛋白的毒性。pChlamy_4载体专为避免发生常出现于C. reinhardtii的转基因沉默而设计。同时,该载体经过设计,可表达出带有博来霉素/Zeocin抗性基因(sh-ble)的转录融合蛋白。口蹄疫病毒(FMDV)2A肽段的自切序列位于抗生素抗性基因和目的基因之间。该序列可编码一个约20个氨基酸的短序列,介导发生适当切割并产生2个独立蛋白。我们使用该系统得到的阳性转化株,即使在有或无筛选压力下传代多次之后,依然能够维持高表达水平,其持续时间远远长于其他系统。

与基因工程试剂盒中的pChlamy_1或pChlamy_3相比,衣藻蛋白表达试剂盒中的pChlamy_4有什么不同?

pChlamy_4载体专为避免发生常出现于C. reinhardtii的转基因沉默而设计。同时,该载体经过设计可表达出带有博来霉素/Zeocin抗性基因(sh-ble)的转录融合蛋白。口蹄疫病毒(FMDV)2A肽段的自切割序列位于抗生素抗性基因和目的基因之间。该序列可编码一个约20个氨基酸的短序列,介导发生适当切割并产生2个独立蛋白。我们使用该系统得到的阳性转化株,即使在有或无筛选压力下传代多次之后,依然能够维持高表达水平,其持续时间远远长于其他系统。

我是否应该对目的基因的编码序列和3’UTR都进行克隆和插入?

pChlamy_1载体无终止密码子和3' UTR。pChlamy_3载体含有3’UTR,已被证明可增强蛋白表达。

在衣藻试剂盒中,载体上已经有一个ATG;是否需要使插入片段与ATG一起位于载体的读码框内?

需要。对于TOPO载体,您可通过设计引物,使编码序列与ATG一起位于载体的读码框内。

pChlamy_3载体是否含有目的基因的终止序列或3’ UTR?

是的,pChlamy_3载体在多克隆位点后含有一个3’ UTR。

我有一个旧版的pChlamy载体——pChlamy_1。你们是否建议在插入片段中加入3’UTR?

建议,如果您想使用pChlamy_1载体表达高水平的重组蛋白,您的插入片段需要在紧随终止密码子后的位置含有一个3’ UTR(非翻译区域)。

转化的预期时间常数是多少?

预期时间常数是15-20毫秒(平均为17毫秒)。

预期的转化效率是多少?

我们未报导衣藻细胞的转化效率,因为转化的最终结果是随机整合到基因组。电穿孔结果取决于目的基因。每个电穿孔反应中,对照载体应产生最少30个转录株。在每个挑选出的菌落中,目的基因阳性克隆数应不少于90%。

使用衣藻基因工程试剂盒进行整合的原理是什么?

整合是随机的。基因工程试剂盒是基于随机插入,这会导致目的基因快速丢失。蛋白表达试剂盒含有pChlamy_4载体,经过设计可表达出带有博来霉素/Zeocin抗性基因sh-ble的转录融合蛋白(Rasala et al., 2012)。口蹄疫病毒(FMDV)2A肽段的自切割序列位于抗生素抗性基因和目的基因之间。该序列可编码一个约20个氨基酸的短序列,介导发生适当切割并产生2个独立蛋白。我们使用该系统得到的阳性转化株,即使在有或无筛选压力下传代多次之后,依然能够维持高表达水平,其持续时间远远长于其他系统。

pChlamy载体转染是瞬时的还是稳定的?

这类载体的转染是稳定转染。

除了衣藻,pChlamy载体能否转化绿藻类?

很遗憾,我们尚未对其他藻类进行测试。

如何将阳性筛选的衣藻长期保存?

该试剂盒不是为长期保存阳性筛选克隆而设计的。大多数人在使用时将培养皿放在室温(不是4°C,因为它们需要光照)下的实验台上,根据需要反复划线。使用藻类的GeneArt低温保存试剂盒,可将藻株和克隆保存在–80°C数年。

细胞在送达时应该长什么样?

衣藻细胞应该是深绿色。浅绿色或无色(也可能是沿管侧面有一些液滴)细胞表示经过冻融或温度波动,而衣藻细胞对此极为敏感。

衣藻有细胞壁吗?

衣藻具有无细胞壁和有细胞壁两种类型;137c有细胞壁。

你们可提供哪种衣藻细胞株?

我们提供的是莱茵衣藻(Chlamydomonas reinhardtii)137c株,它被认为是野生型实验室株,交配类型为“mt +”。

衣藻细胞的保质期/有效期是多久?

衣藻细胞保存6个月后不会丧失活力。据估计,衣藻细胞的保存时间可能达到更久,但我们尚未数据证明保存一年后会丧失活力。

TAP培养基的配方是什么?

我们的预制TAP生长培养基专为衣藻优化(货号A1379801)。请查看以下配方:

TAP培养基
EDTA(二钠盐), EDTA, 0.005%, CAS: 60-00-4
七水硫酸锌, ZnSO4-7H2O, 0.002%, CAS: 7446-20-0
硼酸, H3BO3, 0.001%, CAS: 10043-35-3
四水氯化锰, MnCl2-4H2O, 0.005%, CAS: 1/5/7773
六水氯化钴, CoCl2-6H2O, 0.002%, CAS: 7791-13-1
五水硫酸铜, CuSO4·5H2O, 0.002%, CAS: 7758-98-7
七钼酸胺, (NH4)6Mo7O24·4H2O, 0.001%, CAS:12027-67-7
铁(II)硫酸盐, FeSO4·7H2O, 0.005%, CAS:7720-78-7
磷酸氢二钾, K2HPO4, 0.011%, CAS:11/4/7758
磷酸二氢钾, KH2PO4, 0.005%, CAS:7778-77-0
氯化铵, NH4Cl, 0.038%, CAS:12125-02-9
七水硫酸镁, MgSO4 . 7H2O, 0.010%, CAS:10034-99-8
二水氯化钙, CaCl2 . 2H2O, 0.005%, CAS:10035-04-8
Tris, (HOCH2)3CNH2, 0.242%, CAS:77-86-1
冰醋酸, CH3COOH, 0.11%, CAS:64-19-7

TAP培养基是否有利于任何其他类型的绿藻生长?

很遗憾,我们尚未在其他类型的绿藻中对TAP培养基进行测试。有证据表明,Chlorella可在维生素增强型TAP培养基中生长,但我们没有详细信息。

I am using the MAX Efficiency Transformation Reagent for Algae to transform Chlamydomonas. However, my efficiency is very low. Any suggestions on how to improve this?

Please see the following suggestions:

1. For best results, the algae need to be between 1 x 10e6 and 2 x 10e6 cells/mL (thus, an OD of 0.3-0.5). The concentration of the cells should not exceed 3 x 106 cells/mL. Cell growth can be measured by OD750 and the linear range will be between 0.2 and 1.2 (in 1 cm lightpass). If the OD is out of the linear range, please dilute the cells and measure again to get an accurate reading.
The formula is: cell number = (OD750 - 0.088)/9 million/mL
2. Transformation of linearized DNA is much more efficient (~70% more efficient) than transformation of circular DNA.
3. The quality and concentration of the DNA are critical to the transformation efficiency. You will want to use PureLink HQ, PureLink HiPure, or equivalent plasmid purification kits for pure DNA. It is better to have a small volume of concentrated pure DNA than a large volume of DNA of low concentration. (If you are transforming linearized plasmid, then after the linearization you will need to clean the plasmid up using either gel extraction or a PCR cleanup kit prior to transformation.) We recommend using 2 µg of linearized plasmid DNA per electroporation.
4. Insertion of the plasmid DNA into the genome occurs randomly. On average, only 20% of transformants will express the gene of interest at appreciable levels. We recommend first screening the colonies by colony PCR to ensure full integration of the promoter and gene of interest, followed by the screening of several positive clones for the expression of the gene of interest to pick the highest expressing clone.
5. Because the C. reinhardtii genome has a very high GC content (~62% GC), the expression levels of recombinant genes are significantly improved if the gene of interest is adapted to the preferred codon usage of highly expressed C. reinhardtii genes.
6. Since the transformation efficiency depends on the random integration of the construct into the genome, the results of the electroporation will depend on the nature of the gene of interest. You can try to transform the control vector that comes with the kit to confirm that the kit and their electroporation method are working correctly.

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

I'm getting low expression due to gene silencing using the pChlamy_1 or pChlamy_3 vector. What do you suggest I try?

Unfortunately, silencing is a big problem in algae. The extent of silencing depends on the sequence of the gene and the toxicity of the protein that expresses from that gene to the cell. Our pChlamy_4 vector was designed in order to circumvent the transgene silencing that often occurs in C. reinhardtii. This vector is also designed so that proteins are expressed as transcriptional fusions with the blemoycin/zeocin resistance gene (sh-ble). The self-cleaving sequence for the 2A peptide from the foot-and-mouth-disease-virus (FMDV) is placed between the antibiotic resistance gene and the gene of interest. It encodes a short ~20 amino acid sequence that mediates proper cleavage to yield two discrete proteins. With this system we have seen positive transformants maintain high expression levels for much longer than with other systems, even after many passages with or without selection pressure.

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

What is the difference between pChlamy_4 in the Chlamydomonas Protein Expression kit compared to pChlamy_1 or pChlamy_3 in the engineering kits?

The pChlamy_4 vector was designed in order to circumvent the transgene silencing that often occurs in C. reinhardtii. This vector is also designed so that proteins are expressed as transcriptional fusions with the blemoycin/zeocin resistance gene (sh-ble). The self-cleaving sequence for the 2A peptide from the foot-and-mouth-disease-virus (FMDV) is placed between the antibiotic resistance gene and the gene of interest. It encodes a short ~20 amino acid sequence that mediates proper cleavage to yield two discrete proteins. With this system we have seen positive transformants maintain high expression levels for much longer than with other systems, even after many passages with or without selection pressure.

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

Should I clone and insert not only the coding sequence but also the 3'UTR of my gene of interest?

The pChlamy_1 vector does not have the stop codon and the 3' UTR. The pChlamy_3 vector has the 3'UTR that has been shown to increase protein expression.

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

In the Chlamydomonas kit, there is already an ATG in the vector; does the insert need to be in frame with the ATG in the vector?

Yes. For the TOPO version, you can design the primer to make sure the coding sequence is in frame with the ATG in the vector.

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

Do the pChlamy_3 vectors contain a termination sequence or a 3' UTR for your gene of interest?

Yes, the pChlamy_3 vector contains a 3' UTR after the multiple cloning site.

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

I have an older version of the pChlamy vector, pChlamy_1. Do you recommend addition of a 3'UTR to the insert?

Yes, if you plan to use the pChlamy_1 vector to express high levels of recombinant protein, your insert also needs to contain a 3' UTR (untranslated region) immediately following the stop codon.

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

What is the expected time constant during transformation?

The expected time constant is 15-20 milliseconds (average is 17 milliseconds).

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

What is the expected transformation efficiency?

We don't report transformation efficiency of the Chlamydomonas cells, since the end result of transformation is random integration into the genome. The electroporation results will depend on the gene of interest. The control vector should produce a minimum of 30 transformants per electroporation reaction. Approximately 90% of colonies picked should be positive clones containing your gene of interest.

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

What is the mechanism of integration with the Chlamydomonas engineering kits?

Integration is at random. The engineering kit is based on a random insertion in which the gene of interest can be lost very quickly. For the protein expression kit, the pChlamy_4 vector is designed so proteins are expressed as transcriptional fusions with the bleomycin/zeocin resistance gene sh-ble (Rasala et al., 2012). The self-cleaving sequence for the 2A peptide from the foot-and-mouth disease virus (FMDV) is placed between the antibiotic resistance gene and the gene of interest. It encodes a short ˜20 amino acid sequence that mediates proper cleavage to yield two discrete proteins. With this system we have seen positive transformants maintain high expression levels for much longer than with other systems, even after many passages with or without selection pressure.

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

Is transfection with your pChlamy vectors transient or stable?

Transfection with these vectors is a stable transfection.

Can green algae other than Chlamydomonas be transformed with pChlamy vectors?

Unfortunately, we have not yet tested other algae.

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

How can I store my positively selected Chlamydomonas for long-term storage?

The kits are not designed for long-term storage of positive-selected clones. Most people keep the plates on their bench top at room temperature (not 4 degrees C, as they need light) while in use, re-streaking if necessary. The GeneArt Cryopreservation Kit for Algae can be used to preserve algal strains and clones for storage at -80 degrees C for years.

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

What should the cells look like upon arrival?

The Chlamydomonas cells should be dark green in color. Light green or even colorless (and maybe some droplets along the side of the vial) cells are indicative of freeze/thawing or fluctuations in temperature, which Chlamydomonas cells are extremely sensitive to.

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

Does Chlamydomonas have a cell wall?

There are both cell wall minus and positive strains; 137c has a cell wall.

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

What is the strain of the Chlamydomonas cells you offer?

We no longer offer any strains of Chlamydomonas. Our reagents and protocols were developed using Chlamydonas reinhardtii 137c. This is considered to be a wild type lab strain, mating type “mt +.”

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

What is the shelf life/competency of the Chlamydomonas cells?

After 6 months of storage, the Chlamydomonas cells did not lose their competency. It is expected that they may with longer storage times, but we have yet to gather data points for loss of competency after one year of storage.

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

What is the formulation of your TAP media?

We offer premade TAP growth media optimized for Chlamydomonas (Cat. No. A1379801). Please see the formulation below:

TAP Media
EDTA (Disodium Salt), EDTA, 0.005%, CAS: 60-00-4
Zinc Sulphate Heptahydrate, ZnSO4-7H2O, 0.002%, CAS: 7446-20-0
Boric Acid, H3BO3, 0.001%, CAS: 10043-35-3
Manganese Chloride Tetrahydrate, MnCl2-4H2O, 0.005%, CAS: 1/5/7773
Cobalt Chloride Hexahydrate, CoCl2-6H2O, 0.002%, CAS: 7791-13-1
Copper Sulphate Pentahydrate, CuSO4·5H2O, 0.002%, CAS: 7758-98-7
Ammonium heptamolybdate, (NH4)6Mo7O24·4H2O, 0.001%, CAS:12027-67-7
Iron(II) Sulphate, FeSO4·7H2O, 0.005%, CAS:7720-78-7
Potassium Phosphate Dibasic, K2HPO4, 0.011%, CAS:11/4/7758
Potassium dihydrogen phosphate, KH2PO4, 0.005%, CAS:7778-77-0
Ammonium chloride, NH4Cl, 0.038%, CAS:12125-02-9
Magnesium Sulfate Heptahydrate, MgSO4 . 7H2O, 0.010%, CAS:10034-99-8
Calcium Chloride Dihydrate, CaCl2 . 2H2O, 0.005%, CAS:10035-04-8
Tris, (HOCH2)3CNH2, 0.242%, CAS:77-86-1
Glacial Acetic Acid, CH3COOH, 0.11%, CAS:64-19-7

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

Is the TAP media good for growing any other kind of green algae?

Unfortunately, we have not tested TAP media with other kinds of green algae. There is an indication that Chlorella will grow if the TAP media is vitamin-fortified, but we don't have the specifics.

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

What type of algae can the MAX Efficiency Transformation Reagent for Algae be used for?

The MAX Efficiency Transformation Reagent for Algae was developed for transforming the pChlamy_4 vector into the Chlamydomonas reinhardtii 137c cells by electroporation.

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

What type of algae can the GeneArt Cryopreservation Kit for Algae be used for?

The GeneArt Cryopreservation Kit for Algae was developed for preserving the Chlamydomonas reinhardtii 137c cells. We have reports from some customers who were successfully able to preserve other algae cells.

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

What does the GeneArt Chlamydomonas Protein Expression Vector include?

It includes the pChlamy_4 vector. This vector has been tested for protein expression in Chlamydomonas reinhardtii 137c . You can get the Chlamydomonas reinhardtii 137c cells from the Chlamydomonas Resource Center (http://www.chlamycollection.org/).

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