Biology Stack Exchange
Biology Stack Exchange

Questions tagged [lab-techniques]

Questions relating to protocols, procedures, and good practice when using laboratory equipment.

When asking questions on lab techniques, the following should be considered:

  • A clear outline of the experimental problem should be presented.
  • Standard names and units should be used for reagents and physical quantities.
  • If question is asking for troubleshooting, the current protocol employed should be explained stepwise.
  • The technique should be clearly important and specific to biology.
387 questions
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Pipetting: do human experimenters need liquid class information?

I've been working on a protocol standardization project where, among other things, we want protocols to be able to be run equivalently by both humans and robots. Something that I've noticed in doing so is that there's a radically different amount of…
jakebeal
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How long can I store extracted RNA?

If I extract RNA from a (leaf tissue) sample using a one-step phenol:chloroform extraction, how long can those samples be stored at -80°C? And how many times can I defrost and refreeze them before they will become degraded?
Rik Smith-Unna
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What is the difference between HPLC and FPLC and why is FPLC preferable for protein purification?

I've used HPLC (high performance liquid chromatography) before (once, so I'm barely even qualified to know what it stands for) so I was surprised when my labmate told me she would be using an alternate technique to isolate a protein. What exactly…
Emmie MC
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Why does an autoclave need to pressurize steam?

I've looked this up on other sites and they say that an autoclave needs high pressure in order to raise the boiling point of water so that you can achieve steam of a higher temperature. If you look at this diagram though, it seems to me as if it…
ad837
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What effect does vortexing have on a fluid sample that simple mechanical shaking does not?

Some protocols call for fluid samples to be mixed with a "vortexer" on the high setting. What effect does the vortexing have on fluid samples that mechanical shaking does not? Does it shear long molecules like DNA, for instance? A friend is…
Mac Cowell
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When running gels what is the difference between constant volts or constant amps?

In general, you want to be consistent with running your gels either at constant volts or constant amps. However, it is very clear that during the progression of both PAGE and agarose gels, the free parameter changes due to the change in resistance…
bobthejoe
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How long will a typical bacterial strain keep in a -80°C freezer?

I know that a -80°C freezer is the recommended means of long-term cell-line storage, and that cells will typically not last long in a -20°C freezer. But how long will a typical bacterial strain (e.g., E. coli DH5-alpha) actually stay good in a…
jakebeal
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Why do we add salt when precipitating DNA?

All the DNA extraction protocols I have seen involve adding salts to the extraction buffer. What is the purpose of the salts? What happens if they aren't included?
Rik Smith-Unna
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Are there issues with filling PCR tubes to capacity?

I'm planning to scale up a PCR reaction, and I'm wondering if filling the PCR tubes to the maximum volume of 200 ul would be a problem. It would mean a lot less pipetting as I would only need 1/4 of the tubes. The typical protocols I've seen always…
Mad Scientist
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Are bleach solutions still routinely used in biochemistry laboratories to rid surfaces of bacteria, viruses, certain enzymes, and nucleic acids?

Decades ago I would stop by biology and biochemistry laboratories to see what was up, and I noticed a ubiquitous presence of a squirt bottle of bleach solution. When I asked what it was for I would get different answers in different laboratories.…
uhoh
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Why should I degas my gel solution for polyacrylamide gels?

In protocols for polyacrylamide gel electrophoresis (PAGE) I often see instructions to degas the gel solution by putting it under vacuum for 10-15 minutes before polymerizing the gel. I usually don't do this, and when I tried it once I couldn't see…
Mad Scientist
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How sterile is sterile when working with nucleic acids to prevent contamination?

I am reading up on preparatory work on working with nucleic acids and a lot of the instructions speak on excessive procedures on cleaning environments with high %ethanol and making sure the equipment is nuclease free, and autoclaved. Are these…
Ro Siv
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What's happening in the "C" and "T" stripes of a covid test kit?

I have a COVID home test kit which produces C and T (control and test) stripes when the solution is applied to the strip. Something similar happens in pregnancy test kits. I understand the purpose of a control and test response, but what is the…
spraff
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How do I clean phenol contaminated RNA without losing any of the sample?

I recently extracted RNA from developing plant leaves for the first time, as part of a very long and intensive experiment. The samples were extremely precious because of the amount of effort that went into obtaining them (harvesting thousands of…
Rik Smith-Unna
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Does preservation in ethanol alter leaf litter mass?

I have benthic samples that were collected with an Ekman dredge from some small ponds. The samples contain quite a bit of coarse particulate organic matter (CPOM, basically dead leaves). I would like to quantify the amount of CPOM in the samples…
DQdlM
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