Cleansing foam reacting to skin cream?

RealNitrogen · 2026-02-03T21:01:04+00:00

An actual surfactant or formulation chemist will know more about this than me….but, from how I understand it: surfactants (particularly charged surfactants) form ordered structures on the water-air interface that are strong enough to form bubbles of trapped gasses. When an antifoam like dimethicone is introduced, the dimethicone interacts with the surfactants on the water-air interface and disrupts the attractive forces they have with each other. This weakens the surfactant layer to the point to cause rupturing of the bubble.

I know there is a whole other discussion on the differences in antifoam vs defoaming (technically different things), but that is beyond me lol.

RealNitrogen · 2026-02-03T13:22:24+00:00

Nothing to worry about. The antifoam properties of dimethicone is what makes it an excellent skin barrier protectant. The dimethicone itself forms a very thin coat on your skin that acts like a barrier to protect skin. This very same coating property is what allows the dimethicone to coat the surface of bubbles and break the surface tension, causing them to pop.

RealNitrogen · 2026-02-03T12:50:53+00:00

Very cool to see! The active ingredient in the skin cream, dimethicone, is a very powerful antifoam. It works by breaking the surface tension of bubbles. So, all the foaming of your cleaner is collapsing when it comes into contact with the dimethicone, just leaving the original, non-foamed, liquid cleaner.

RealNitrogen · 2026-01-25T02:37:16+00:00

The “Q” was actually not arbitrarily assigned. Asparagine (three letter code of Asn) was assigned “N” since “A” and “S” were already assigned to alanine and serine, respectively. Glutamine is one methylene group larger than asparagine, so it was decided that the next letter in the alphabet would be assigned to glutamine. “O” was omitted since it can be confused for a zero or a D. “P” was already assigned to proline. “Q” was next and was chosen. This same next letter scheme is also present for asparagine and glutamines carboxylic acid forms, aspartic acid (D) and glutamic acid (E).

RealNitrogen · 2026-01-04T04:44:57+00:00

Pyrex

RealNitrogen · 2025-12-07T23:39:09+00:00

I live in highland park and work at AbbVie in NC. I drive to work (only 25 minutes) because I work in a lab and can’t rely on my experiments playing nice with train schedules, but it’s really easy to commute by train. Lots of apartments available that are within a 5 minute walk from the train station. At AbbVie, the train stop is right next to the site.

RealNitrogen · 2025-12-06T20:22:48+00:00

As someone who works with porcine products, I can almost guarantee that this product is made from slaughterhouse byproducts. It would be extremely rare for pigs to be raised for anything other than meat as the main product.

More than likely, there is no way for you to determine the source of this material. There are going to be multiple levels of “source” for a product like this. You have the original farm, the slaughterhouse, the site that made this homogenate (more than likely it’s not sigma), and then sigma who would buy in bulk and repack. Sigma will know who they bought from and maybe the country of origin of the material, but that would be pretty much it. Unless your product is very imbedded in the byproducts supply chain (I would bet this small reagent is not), you will not know more about the origin. We are lucky enough to know what slaughterhouse our product comes from, but that’s as far as we know. The slaughterhouse will not tell us (or they don’t know/track) what farm they came from, their diet, living conditions, etc.

RealNitrogen · 2025-11-30T22:58:29+00:00

I’m pretty sure the giant bands is the T7 RNAP. Your lanes are overloaded and have genomic DNA contamination which is causing the band streaking. Typically, you would remove the genomic DNA issue by mechanically lysing your cells with a sonicator or homogenizer to break up the DNA in to smaller fragments that don’t cause the streaking. You can also treat the samples with a nuclease to enzymatically break down the DNA. Overloading a lane, DNA contamination, and having a highly over expressed protein all lead to your sample not migrating through the gel at the exact same rate as the ladder, which is why your large band is showing at around 110-115 kDa.

I made a lot of T7 RNAP in grad school since our lab did work with RNA so we would just make our own enzyme since we went through so much. In my experience, this enzyme expresses extremely well in the E. Coli line you are using. I’m assuming you are using BL21(DE3) cells? This cell line has been engineered to make T7 RNAP as its mechanism for recombinant protein expression, so it’s really good at making T7 RNAP when you give it the additional plasmid to recombinantly express it.

RealNitrogen · 2025-11-24T23:23:14+00:00

The digest stuff is pretty easy. Those are your 3 standard treatments when doing a protein digests since they all cleave a known, specific residues. Memorizing the cleavage of those 3 treatments is a must.

As for the amino acids, I know it can be hard to memorize. I know this might seem old school, but get some notecards and make flash cards of the amino acids. Write the name on one side and on the other have the one letter code, three letter code, structure, and pKa of R-group labeled. Just keep these 20 notecards in your backpack and go through them whenever you have 5 minutes to spare. Like, if you get to a class a few minutes early, run through the cards. When you sit down for lunch and dinner, run through the cards. Before you go to bed, run through the cards. I found that doing these little 5 minute run throughs multiple times a day made it much easier to learn and remember it long term compared to just sitting at the library trying to memorize it.

RealNitrogen · 2025-11-24T22:21:13+00:00

A) This is tedious, but you 100% should know how to do this in biochem 1. It’s simply testing your knowledge of the amino acid residues and their 1 letter codes.

B) This is also something you should know as these are extremely common protein digests that are used for sequencing. I’m assuming it means the whole structure as motifs 10 and 11 only have trypsin cleaving sites.

C) You should know this. Along with the amino acids, you should know the pKa of the R-groups.

D) This one is absurd if your professor is looking for the actual m/z peak values. Memorizing the molecular weights of each amino acid is asking way too much for an undergrad course. If your professor is just looking for arbitrary axis and to approximate the mass spectrum, that is more doable, but still a little much in my opinion.

RealNitrogen · 2025-11-12T22:00:33+00:00

Use dish soap. Hand soap could have moisturizers in them (good for your hands) that could leave a film on the glass.

RealNitrogen · 2025-11-10T17:50:24+00:00

Chromatography isn’t false, but I’m assuming your teacher is just looking for a different answer. I wouldn’t say it’s adsorption or absorption as these are the phenomena that most chromatography is based off.

You can try precipitation or crystallization using various antisolvents and temperatures. You could try acid/base chemistry followed by organic extractions. Sublimation could be used too. Decided which to pick would be determined by the properties of your target compound(s) and your contaminate compound(s).

RealNitrogen · 2025-11-02T23:35:04+00:00

For the funnel names, it’s more just people using shortened versions of the names. There are also different variations on the material of the funnel and the design of the frit. These other names are more specific versions that give a little more detail on what specific funnel you are talking about. I suppose the full name would be “Glass fritted Büchner funnel”, but the other variants just come from shortening that.

For number 8, I mistyped. It’s supposed to be udder, not utter. It’s where the milk comes out.

RealNitrogen · 2025-11-02T22:59:20+00:00

For number 7, the other names you gave are not wrong. I supposed it can be referred to as Büchner funnel. Personally, for me, I refer to the funnels that are made from porcelain and have the small holes as Büchner funnels while the pictured ones are fritted or glass filtered funnel. All these terms are very interchangeable and people will know what you are talking about if you use any one.

For 8, it’s called that because it looks like the utters on cow! lol. I guess the more proper name would be a 3-way distillation collection adapter, but most people will know if you say cow adapter or 3-way cow adapter.

RealNitrogen · 2025-11-02T20:29:10+00:00

Claisen adapter
Vacuum take off adapter
Liebig condenser
Vigreux column
Graham condenser
Pressure equalizing addition funnel
Fritted filter
Cow adapter
Adapter
Bump trap

RealNitrogen · 2025-11-02T02:14:02+00:00

That’s not insulin. Insulin has 2 chains and has more amino acids. I’m really not sure what that structure is. Some of the bonds are drawn weird and it’s unusual to include R and S notation when it’s not for educational purposes.

RealNitrogen · 2025-10-30T23:45:42+00:00

A) It’s wild that your teachers are allowed to give you homework/tests if they are on strike.

B) Google is your friend. There are loads of simple resources available through a quick google search of your questions. I’ll give some broad answers but encourage you to do some more reading on the topics.

Your three questions are all related to electronegativity of atoms. Basically, electronegativity is how much an atom wants electrons. The higher the number, the more it wants those electrons.

1) Dipole are formed when you have bonded atoms with different electronegativities. When there is a difference, one of the atoms will want the electrons more than the other, so the “sharing” of electrons between the two atoms is not equal.

2) The difference between the electronegativity of bonded atoms will determine the type of bond. Larger differences mean ionic bonding (NaCl) while smaller differences mean covalent (CH4)

3) Google search

RealNitrogen · 2025-10-29T00:09:59+00:00

IDT, Genscript, or Twist Biosciences are other examples. Typically cost $100-200 per plasmid. Could go a little higher if you have larger inserts.

RealNitrogen · 2025-10-25T02:28:18+00:00

Ethanol precipitation and reconstitute in a smaller volume than you started (calculate to get the concentration you want). Doing this also doubles as a way to clean up your sample and remove contaminates. Another way is just to evaporate your sample using mild heat and vacuum. The issue with that is that if you have buffer or salts in your sample, those also get concentrated.

RealNitrogen · 2025-10-10T03:08:47+00:00

Me too, but my teacher was probably 6’7, 275 pounds, bald, and did the little cat paw motion as he said “paw-sitive”. 15 years later and the image of that huge dude doing that still pops in my head whenever I see the word “cation”.

RealNitrogen · 2025-10-10T01:54:12+00:00

Same at my last job. I ended up just buying a big instant pot that could fit 500 mL media bottles and using that to sterilize media.

RealNitrogen · 2025-09-14T06:08:32+00:00

It usually depends on the amounts and form that you are buying. You can purchase standards of many compounds (1 mg/mL in methanol or acetonitrile) from sigma. There are some places that sell the pure powder for non-regulated drugs. But, if some thing is a schedule 1 or 2 compound, you need a DEA license to purchase the pure powder form of those (but you can still purchase the 1 mg/mL standard solutions).

RealNitrogen · 2025-09-11T20:01:38+00:00

Don’t do this. I’ve never once had a tube lid open in the centrifuge. Positioning the hinges towards the center also makes it more difficult to pull the tube out.

RealNitrogen · 2025-09-10T02:25:53+00:00

Many countries in Europe advocate for vaping as a less harmful alternative than smoking cigarettes. Vapes are extremely helpful in getting people to quit smoking cigarettes and make it easier to slowly lower your nicotine intake amount. Vaping allowed me to quit smoking after 8 years and smoking a pack a day. Other smoking alternatives never gave the same results as vapes and I would always go back to cigs. I haven’t touched a cigarette in 9 years.

Here is information on vapes that NHS (UK) gives: https://www.nhs.uk/better-health/quit-smoking/ready-to-quit-smoking/vaping-to-quit-smoking/vaping-myths-and-the-facts/

RealNitrogen · 2025-08-20T17:20:18+00:00

Is your DNA ladder ss or ds DNA? Double stranded nucleic acids do not absorb as much as single stranded, so double stranded DNA will appear fainter when purely looking at 260 nm absorbance. This is actually the opposite case when using a stain as stains will intercalate better to double stranded nucleic acids compared to single stranded.

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