PeppermintStick™ Phosphoprotein Molecular Weight Standards, 40 μL - FAQs

•降低电压、电流或缩短转印时间
•确保转膜缓冲液的甲醇浓度合适；可使用浓度为10–20%的甲醇，从而去除SDS-蛋白质复合物中的SDS，并促进蛋白质与膜的结合。
•确保转膜缓冲液的SDS浓度合适（若加入了SDS），SDS浓度不要超过0.02–0.04%。过多的SDS会阻碍蛋白质与膜的结合。过多的SDS会阻碍蛋白质与膜的结合。
•检查膜的孔径和靶标蛋白质的大小。小于10kDa的蛋白质很容易穿过0.45μm孔径的膜。如果您的目标蛋白质小于10 kDa，那么最好使用0.2μm孔径的膜。

•增加电压、电流或转印时间
•凝胶和SDS-蛋白质复合物中的SDS会促进蛋白质从凝胶中洗脱，但抑制蛋白质与膜的结合。这种抑制作用在硝化纤维素膜上的强度大于PVDF膜。对于难以从凝胶中洗脱的蛋白质，如大分子量蛋白质，可在转膜缓冲液中加入少量SDS以改善转印效果。我们建议在组装三明治前将凝胶置于含0.02–0.04% SDS的2x转膜缓冲液（无甲醇）中预平衡10分钟，然后使用含10%甲醇和0.01% SDS的1X转膜缓冲液进行转印。
•甲醇可去除SDS-蛋白质复合物中的SDS，促进蛋白质与膜的结合，但对凝胶本身有一些不良影响，会降低转印效率。甲醇可能导致孔径减小、某些蛋白质发生沉淀以及一些碱性蛋白质带正电荷或变为中性。应确保转膜缓冲液的甲醇浓度不高于10–20%，并使用高质量的分析级甲醇。

预染标准品具有与每种蛋白质共价结合的染料，这将导致标准品在不同的缓冲系统（即不同的凝胶）中迁移率不同。因此，使用预染标准品进行分子量估算将仅得出蛋白质的表观分子量。预染标准品可用于分子量估算、确认凝胶迁移和估算转膜效率，但对于需要精确估算分子量的应用，应使用非预染标准品。

•上样时，请注意确保相邻样品泳道没有交叉污染。
•确保每个泳道上标准品的量都是正确的。蛋白质上样过多会导致产生额外的条带，这个问题在使用银染凝胶时尤为突出。
•标准品储存不当或反复冻融会导致蛋白质降解。

建议如下：

•确保每个泳道上标准品的量都是正确的。蛋白质上样过多会导致模糊，这个问题在使用银染凝胶时尤为突出。
•条带在低百分比凝胶中不能很好地分辨。尝试使用更高百分比的凝胶。
•如果在转膜/检测后条带看起来不明显和模糊，可能是由于抗体浓度过高。遵循制造商建议的稀释度或通过斑点印迹确定最适抗体浓度。

建议如下：

•检查使用的凝胶类型/凝胶百分比。可能会由于凝胶类型和/或百分比的不同而不能看到所有条带。例如，蛋白质标准品的最小条带可能不能在非常低百分比的凝胶上分辨，而较高分子量条带可能不能在高百分比凝胶上分辨。
•检查蛋白质分子量标准品的有效日期。由于蛋白质降解，过期批次可能导致条带褪色或缺失。
•检查蛋白质分子量标准品的储存条件。不适当的储存条件会损害标准品中蛋白质的稳定性。
•确保蛋白质分子量标准品在上样到凝胶上之前未加热/煮沸。我们的蛋白质分子量标准品可直接上样，我们不建议将其加热/煮沸，因为这可能会导致标准品中的蛋白质降解。

- Decrease voltage, current or length of transfer time
- Make sure that the methanol concentration in the transfer buffer is proper; use a methanol concentration of 10-20% methanol removes the SDS from SDS-protein complexes and improves the binding of protein to the membrane.
- Make sure that the SDS concentration (if added) in the transfer buffer is proper, don't use more than 0.02-0.04% SDS. Using too much SDS can prevent binding of proteins to the membrane.
- Check the pore size of the membrane and the size of the target protein. Proteins smaller than 10 kDa will easily pass through a 0.45 µm pore size membrane. If proteins smaller than 10 kDa are of interest, it would be better to use a 0.2 µm pore size membrane.

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

- Increase voltage, current or length of time for transfer
- SDS in the gel and in the SDS-protein complexes promotes elution of the protein from the gels but inhibits binding of the protein to membranes. This inhibition is higher for nitrocellulose than for PVDF. For proteins that are difficult to elute from the gel such as large molecular weight proteins, a small amount of SDS may be added to the transfer buffer to improve transfer. We recommend pre-equilibrating the gel in 2X Transfer buffer (without methanol) containing 0.02-0.04% SDS for 10 minutes before assembling the sandwich and then transferring using 1X transfer buffer containing 10% methanol and 0.01%SDS.
- Methanol removes the SDS from SDS-protein complexes and improves the binding of protein to the membrane, but has some negative effects on the gel itself, leading to a decrease in transfer efficiency. It may cause a reduction in pore size, precipitation of some proteins, and some basic proteins to become positively charged or neutral. Make sure that the methanol concentration in the transfer buffer is not more than 10-20% and that high-quality, analytical grade methanol is used.

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

Pre-stained standards have a dye that is covalently bound to each protein that will result in the standard migrating differently in different buffer systems (i.e., different gels). As a result, using a pre-stained standard for molecular weight estimation will only give the apparent molecular weight of the protein. Pre-stained standards may be used for molecular weight approximation, confirming gel migration and estimating blotting efficiency but for accurate molecular weight estimation, an unstained standard should be used.

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

- While loading, take care to make sure that there is no cross-contamination from adjacent sample lanes.
- Make sure that the correct amount of standard is loaded per lane. Loading too much protein can result in extra bands and this is a problem especially with silver-stained gels.
- Improper storage of the standard or repeated freeze/thawing can result in protein degradation.

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

Here are some suggestions:

- Make sure that the correct amount of standard is loaded per lane. Loading too much protein can cause smearing and this is a problem especially with silver stained gels.
- Bands will not be as well resolved in low percentage gels. Try using a higher percentage gel.
- If the bands look smeary and non-distinct after a western transfer/detection, this may be due to the antibody being too concentrated. Follow the manufacturer's recommended dilution or determine the optimal antibody concentration by dot-blotting.

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

Here are some suggestions:

- Check the gel type/percentage of the gel that was used. Depending on the gel type and/or percentage, all the bands may not be seen. For example, the smallest bands of the protein standard may not resolve on a very low percentage gel whereas the higher molecular weight bands may not resolve on a high percentage gel.
- Check the expiration date on the protein standard. Expired lots may result in faded or missing bands due to protein degradation.
- Check the storage conditions for the protein standard. Improper storage conditions will compromise the stability of the proteins in the standard.
- Make sure that the protein standard was not heated/boiled prior to loading on the gel. Our protein standards are ready to load and we do not recommend heating/boiling them as this may cause degradation of proteins in the standard.

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

All proteins are single chain, monomeric proteins (no subunits). The phosphoproteins are both serine-phosphates. Ovalbumin has 2 phosphorylated residues and β-casein has 5 phosphorylated residues. We do not determine whether or not all the phosphates are present at all times for each lot and can only assume that a majority of each protein has all sites phosphorylated. Any protein extracted from a natural source may always have the potential for some dephosphorylation during extraction/purification or by natural cellular activity. For a more definitive phosphorylation number comparison to staining intensity, a synthesized peptide of known number of phosphates must be used. Please see below for details:

- β-galactosidase: 116,250 kDa; No phosphoprotein; No glycoprotein; Source - E. coli
- Bovine serum albumin: 66,200 kDa; No phosphoprotein; No glycoprotein; Source - Bovine serum
- Ovalbumin: 45,000 kDa; phosphoprotein present; glycoprotein present; Source - Chicken egg
- β-casein: 23,600 kDa; phosphoprotein present; No glycoprotein; Source - Bovine milk
- Avidin: 18,000 kDa; No phosphoprotein; glycoprotein present; Source - Chicken egg
- Lysozyme: 14,400 kDa; No phosphoprotein; No glycoprotein; Source - Chicken egg

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

For long-term storage, store the stock tube at either -20 degrees C or -80 degrees C. For short-term storage, store at 2-6 degrees C. The stock can be subjected to repeated freezing and thawing without any deleterious effects to the molecular weights of the proteins or their migration during electrophoresis.

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

Each of the six proteins is present at approximately 0.5 µg/µL concentration.

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Zymogram gels are essentially Tris-Glycine gels containing the substrate. Protein standards run based solely on the percentage of acrylamide and hence should run the same in both kinds of gels. It is quite possible though that if the standard is prestained, the proteins will appear a different color because of the staining (or pre-staining) of the Zymogram gels.

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

Our protein standards are not designed for protein quantitation.

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

Please find this information in the respective manuals for the individual protein standards.

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

Our protein standards are ready to load. We do not recommend heating them as this may cause protein degradation.

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

Except for our NativeMark Unstained Protein Standard (designed for native electrophoresis), all of the other unstained and prestained standards we offer (Invitrogen Sharp, SeeBlue, SeeBlue Plus2, BenchMark, HiMark) have been pre-reduced (by a proprietary method). Hence, you do not need to add reducing agent.

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