29
votes
Why does an autoclave need to pressurize steam?
An autoclave can sterilize both solids and liquids, whereas an oven with no pressure control is typically not suitable to sterilize liquids.
Not only do you need to heat the chamber to 121°C, but you ...
- 1,883
26
votes
How long will a typical bacterial strain keep in a -80°C freezer?
Richard Lenski's lab at Michigan State university has been doing long-term evolutionary research on E. coli and maintaining a "frozen fossil record" of their experimental populations every ...
- 4,571
23
votes
Accepted
Pipetting: do human experimenters need liquid class information?
In my experience it is very rare to see a protocol for humans that describes how to pipette a certain liquid, but I don't have as many years pipetting as others do.
In general, it is left to the ...
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23
votes
Pipetting: do human experimenters need liquid class information?
I work on software that controls one model of robotic pipetter. There are a few reasons why we use complex liquid class definitions:
One of the selling points of using a robot is high speed. You ...
- 471
15
votes
Are bleach solutions still routinely used in biochemistry laboratories to rid surfaces of bacteria, viruses, certain enzymes, and nucleic acids?
I'm a research post-doc working in a US-based microbiology research lab. We still use a relatively low-concentration bleach solution to decontaminate most liquid cultures before disposing of them, but ...
- 4,571
13
votes
Accepted
How sterile is sterile when working with nucleic acids to prevent contamination?
Short answer: Yes
Long answer: Depends what you are working with.
DNA: If you are working with DNA, its pretty stable and you can usually get away with a 70% ethanol wash/autoclave (mainly to ...
- 2,278
13
votes
When did mouth pipetting stop becoming a way to handle liquids in a lab?
Mouth pipetting, while almost unheard of in modern laboratories in developed countries, is still very much a current protocol in many parts of the world.
For example, this paper analyses the ...
- 9,434
13
votes
Accepted
Assembling small DNA parts using Golden Gate
Purely going off experience here having used golden gate assembly methods for 5+ years now, there is a definite lack of literature regarding small part assemblies. In my current lab, we use CIDAR ...
- 316
12
votes
Accepted
What is the role of glucose in plasmid isolation?
This is a common misconception: in fact, in the alkaline lysis method for plasmid isolation, the glucose does not act as an osmotic stabiliser.
Glucose is present in the resuspension buffer at 50 mM. ...
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11
votes
Good pipetting technique?
Here's some step-by-step advice on good pipetting technique:
Make sure the pipette is set for the correct volume
Ensure the tip is firmly attached
Keep the pipette vertical when pipetting
Slowly and ...
- 16.1k
11
votes
Accepted
How long will a typical bacterial strain keep in a -80°C freezer?
The reason you haven't found a definitive answer is that it depends on several factors.
The first factor that comes into play if we consider only ultra-low freezers (- 80 °C) is the organism you're ...
- 466
11
votes
Accepted
What's happening in the "C" and "T" stripes of a covid test kit?
This is a lateral flow assay.
[image source]
A sample is applied at one end of the strip and flows across to the other side by capillary action. It first encounters antibodies against the target ...
- 17.6k
10
votes
Are bleach solutions still routinely used in biochemistry laboratories to rid surfaces of bacteria, viruses, certain enzymes, and nucleic acids?
I can only speak from my experience in many labs in different countries: We never used bleach for cleaning or disinfecting surfaces like cell culture hoods or lab benches. For this purpose we ...
- 51.2k
10
votes
Accepted
Saturated Mutagenesis Screening
This sort of method is indeed quite useful and frequently used in synthetic biology: I've used a similar approach before to generate 5' insulators for promoters.
Calculating the exact theoretical ...
- 6,967
10
votes
Accepted
Tips for longer fragment size and higher purity of insect DNA
Insect samples are difficult to work with primarily because they contain a bunch of polysaccharides, like chitins, that are similar enough to nucleic acids that they can co-precipitate. Standard ...
- 9,338
9
votes
How sterile is sterile when working with nucleic acids to prevent contamination?
First of all, sterility is not necessary. It takes much more effort to reach this than just to wipe down everything with ethanol. What you need is a clean and controlled work environment (but this is ...
- 51.2k
9
votes
Accepted
"X" in stock solutions
1x is the final working concentration of the solution (it could be anything depending on the type of the solution). Stock solutions are made at a higher concentration; if it is 10 times more ...
- 35.2k
9
votes
Accepted
Why spin live fruit flies in centrifuge?
Correction of Poster’s Source
The article cited mistakenly refers to centrifugation, however the actual procedure used in the work — Karageorgi et al. Nature, 2 Oct 2019 — is vortexing, as ...
- 23.8k
9
votes
Alternative dyes for Gram staining
As you may have realized, crystal violet can be replaced by a lot of dyes since the ethanol will wash out the dye from the gram negative cells. Methylene blue is a nice choice - malachite green may ...
- 201
8
votes
Accepted
Magnetic-activated cell sorting vs. FACS
Magnetic-activated cell sorting (PDF download), or MACS, is a procedure developed by Miltenyi Biotec to separate cells from complex mixtures using antibody-coated magnetic nanoparticles. The ...
- 15.2k
8
votes
Is working with (nitrile) gloves around a bunsen burner safe?
new microbiology lab
What're the entry requirements for your lab? If you're working in BSL-2 or greater, the appropriate PPE ensemble is listed and required at all times while you're in there. ...
- 8,091
8
votes
Measuring luminescence in a fluorescence plate reader
I am René Inckemann and I am PhD student at the Max Planck Institute in Marburg, Germany. In my PhD I am using luminescence on a regular basis and I was also responsible to organize some of our ...
8
votes
Accepted
Measuring luminescence in a fluorescence plate reader
As the other answers here say, technically plate readers which are capable of fluorescent measurements can also make luminescent readings, but the sensitivity may be low (https://www.biotek.com/...
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8
votes
Assembling small DNA parts using Golden Gate
I don't have hard data to share regarding you question, but I can provide some anecdotal evidence. I have used golden gate assembly to build hundreds of plasmids using ~20bp annealed oligos, as well ...
- 81
7
votes
Accepted
Why calf thymus DNA is widely used instead any other body part?
I have crawled through google and many, many journal articles. What I can make of it, is:
"It is generally agreed that from mammalian cells (as, for example, calf thymus..." are capable of yielding ...
- 527
7
votes
Accepted
Measuring protein concentration, Bradford vs. Nanodrop?
That depends strongly on your protein and how exact you need this concentration. Both tests (Bradford and the measurement at 280nm) only do an approximation.
The measurement at 280nm relies on the ...
- 51.2k
7
votes
Sterilize/disinfect sugar for lab use
Autoclaving media with carbohydrates (or sugar solutions on its own) is not a good idea for two reasons:
The Maillard reaction: This occurs when you heat mixtures of amino acids and sugars. The ...
- 51.2k
7
votes
Is working with (nitrile) gloves around a bunsen burner safe?
Wearing gloves increases the risk of injury when working next to an open flame since they can melt onto your hand.
Not wearing gloves increases the risk of infection when working with pathogens.
As ...
- 17.6k
7
votes
Pipetting: do human experimenters need liquid class information?
Just to be clear, it has been many years since I have done real lab work, so I am certainly not an expert on the specific question. However, I have a fair amount of experience writing clear ...
- 71
6
votes
Using an analytical balance (0.0000 precision) to measure µg (micrograms)?
As others have said, that mass is too small to measure with a standard analytical scale. There are two options you could use:
Make a larger volume of your 200 ug/mL solution.
Make a concentrated ...
- 17.6k
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