Forgive me, but I’m continuing through a busy busy time both
in my life and in lab so posts are a bit sporadic and not on topic. I’ve read several ageing papers and will get
to writing those up soon, but since it has been so long since my last post, I
needed something quick! I was oddly
inspired for this post today while I was rushing to make a post doc ethics
meeting (no
jealousy, please). What inspired
me exactly? This thought:
My nail polish is missing. I’ll
stand on this chair so I can see my shelves clearly and maybe find it. I don’t want to borrow Tim’s again.
So,
there I was, standing on a swivel chair, hunting through bottles of buffers,
random scraps of parafilm, and glassware trying to find my clear nail polish. My motivating force was avoiding using Tim’s
(male,
correct). The whole thing struck
me as weird, both the fact that nail polish is an essential laboratory reagent
and that I didn’t want to use my male coworker’s stash. I started to wonder what other things in lab
are everyday products that would surprise people. I have a few!
Nail Polish (clear, thanks!)
In the Henrietta Lacksseries, I talked about how scientists grow cells in dishes (Figure 63.1).
We give them all sorts of nutrients (called media), place them in
incubators at the correct temperature, and let them grow in specially designed
(and sterile)
cell culture plates. If I can ever get a
camera to work on our microscope, I’ll take some pictures and tell you all
about cell culture!
Sometimes,
we want to do more with cells than merely grow them; sometimes, we want to
inspect the cells more deeply. In my Fluorescent Proteins
post, I talked about how scientists can put green fluorescent protein (GFP) inside cells.
I also explained that to “see” the GFP,
light of a specific wavelength must be used.
For this reason (among many others) scientists need a way to move
cells easily. Sure, we could walk around
with the cell culture plate as shown in Figure 63.1,
but you can imagine that with one false move the media would be all over the
microscope, which, especially a fancy one with lasers, is terribly
expensive. We’re in the business of
trying not to ruin instruments worth more than my house.
To
circumvent these problems, instead of growing cells directly on the dishes, we
place a small coverslip inside the plate.
A coverslip is a piece of glass ~ 0.5” x 0.5”. Cells will adhere to both the plate and the
slip during growth. When we’re ready, we
can take out the cover slip, permanently arrest the attached cells in their
current state, and finally place them face down on a microscope slide (Figure 63.2).
Walking around with a microscope slide is easy!
We don’t
want the cells to dry out on the cover slip.
Between the slip + cells and the microscope slide is a bit of liquid
called mounting media. It keeps the
cells somewhat hydrated and in the best possible shape for viewing. We don’t want the mounting media to
evaporate. To ensure that this doesn’t
happen, we paint all sides of the coverslip with nail polish to seal the
edges. Oddly, it has to be clear;
colored disrupts our ability to see the cells properly on the microscope.
Milk (evaporated)
Scientists
commonly use a technique called “Western Blotting.” I’m not going to get into what all this
entails right now; I’ll save it for a much longer explanation in a different
post. Instead, I’m just going to tell
you that it involves putting a lot of protein onto a piece of a paper (hence the word “blotting”)
and one protein on that paper we’ll call A. We then place the paper in a liquid containing
a different protein called B. We know
that A and B bind each other so B should end up stuck to the paper wherever
protein A is found.
Sounds
simple enough, yes? Not quite. The paper has a whole lot of other proteins
besides A. Proteins come in all
different shapes and sizes. Some are
sticky, some are lonely, and some are really similar to protein A. Protein B, while very much wanting to hook up
with Protein A, can get distracted along the way by all the types of proteins
on the paper. Scientists know this and
really want to minimize it so they do something called “blocking.”
Before
adding protein B to the paper, scientists set the paper in some milk, which is
full of other proteins. All those sticky,
lonely and similar to protein A proteins on the paper can get together with all
the random proteins from the milk. Then,
when protein B is added, the other problematic proteins are otherwise occupied
and protein B can find protein A more easily.
Acetone
I do
not work in an organic chemistry lab so acetone is not frequently pulled out
nor do I know the more fanciful uses for this solvent. But, I can tell you what I’ve used for it in
the past: drying glassware. Organic labs
have lots of glassware (some of it is custom-made for particular experiments; many
universities have glass-blowing facilities on campus to help create what the
organic chemists need) and it is constantly washed and reused. This is somewhat different from a
biochemistry/molecular biology lab (where I work) because we use a lot of
plastics. The difference? Sterility.
A
biochemistry lab needs many things to be sterile because we’re working with
living beings (cells, bacteria). It’s
essential to ensure that we aren’t contaminating one growth of bacteria or cells
with another. If we primarily used
glass, each piece would need to be washed and sterilized between uses. This is labor and time-intensive. Why do that when you can buy a pack of 100
sterile plastic tubes for $40?
Organic chemists aren’t worried
about sterility since they don’t work with live organisms. Their glassware merely needs to be clean and
dry. After being washed with soap and water,
the glassware is usually flushed with acetone and placed in a drying oven. The acetone serves to rinse out any water
left behind. Acetone evaporates much
faster than water so pieces only need to sit in the drying oven for a few
minutes to fully evaporate the acetone.
Fully drying pieces covered with water would take much longer.
Acetone is, as many women know, an
ingredient in nail polish remover (quite the theme today!). I know several women who have either flat out
used the acetone in lab to take off their nail polish or unintentionally
removed it after washing a lot of glassware.
Bleach & Tweezers
I don’t
think either of these products should be surprising. We commonly bleach anything that has come in
contact with bacteria or live cells.
This serves to kill off anything remaining alive before we pour liquids
down the sink. As a technician, I
frequently had to go run to the grocery store and pick up bleach because we
kept running out. Tweezers are used for
several purposes (all related to picking up things, oddly enough) but one of them is
to move coverslips around easily. We’ve
come full circle.
REFERENCES
Me, myself and I
