27
votes
Are stable isotopes ever used in pharmaceuticals?
Deutetrabenazine.
As the linked article from Wikipedia notes:
Deutetrabenazine (trade name Austedo) is a vesicular monoamine
transporter 2 inhibitor which is used for the treatment of chorea
...
- 1,800
18
votes
Accepted
Why is the retention of ability to synthesize non essential amino acids of negative survival value?
It’s a very dubious argument in my opinion.
Whenever I see a question on this list arguing that higher organisms could save energy and DNA by such-and-such a hypothetical construct I want to scream. ...
- 25.7k
16
votes
Are stable isotopes ever used in pharmaceuticals?
The urea breath test for Helicobacter pylori uses urea labelled with carbon-13 or carbon-14 to detect the presence of the bacteria, which would metabolize it to carbon dioxide and be exhaled.
- 261
8
votes
Accepted
According to an online course, ribose and adenine can bond to make ATP. Is this true?
The structure shown is indeed of guanine, not adenine.
A nucleotide is defined as being composed of a nitrogenous base, a pentose sugar and phosphate (see, e.g. the Wikipedia entry). So the simplest ...
- 25.7k
7
votes
What is the energy of activation of uncatalyzed ATP hydrolysis reaction? Say in aquous solvent?
The activation energy of ATP hydrolysis at in the pH range 3–9 was determined by Kahn and Mohan in 1974 and found to be 28.0 to 20.7 kcal/mole. At neutrality (i.e. uncatalysed) it would appear to be:
...
- 25.7k
6
votes
Accepted
Are stable isotopes ever used in pharmaceuticals?
You should check the Wiki articles:
Isotopes in Medicine
Radiopharmaceutical
If we solely focus on carbon-13 based drugs then there is carbon-13 labeled ibrutinib, carbon-13 labeled midazolam/1′-...
- 1,214
6
votes
What is the energy of activation of uncatalyzed ATP hydrolysis reaction? Say in aquous solvent?
The 2014 paper of Wang and colleagues found the activation energy of ATP at 32.5 kcal/mol. See the reference for details. The image is figure 3 from the reference.
Reference:
QM/MM Investigation of ...
- 51.6k
6
votes
Why is the retention of ability to synthesize non essential amino acids of negative survival value?
The passage is saying that if you get enough of a nutrient in your diet, you don't need to synthesize it.
If you don't need to synthesize a nutrient, you don't need to waste energy on the machinery to ...
- 45.6k
5
votes
Is Eugene Koonin's probabilistic argument for the necessity of a multiverse to explain the origin of life sound?
There are two main problems here:
The logic assumes that a complete, simplified ribosome is the simplest possible useful unit, so has to spring up by a series of random events. This is extremely ...
- 203
5
votes
Allowed Deviations in fixed bond length and bond angles in peptides from the typical values
Single-conformation descriptions of the native-state ensemble, under ambient conditions, are expected to have close to ideal geometries. This is a result from Statistical Mechanics; the probability of ...
- 1,311
4
votes
Accepted
Free diving physiological changes
According to Libretexts Medicine link There are two types of chemoreceptors that help regulate breathing. Those with the most impact, the central chemoreceptors, can be desensitized. The relevant ...
- 326
3
votes
Accepted
How to calculate the osmolality of Hepes solution?
I assume this is a measured osmolality rather than a calculated one. It's challenging to calculate actual osmolality because of incomplete dissociation of the solutes, see for example https://en....
- 45.6k
3
votes
Accepted
Why can mitochondria make only 34 molecules (rather than 61 molecules) of ATP ？
The fundamental flaw in the poster’s logic is the implicit supposition that if a mitochondrial (or other) oxidation reaction has a standard Gibbs Free Energy change of -x kJ/mol, all of that can be ...
- 25.7k
3
votes
Accepted
Fate of GTP produced in the TCA cycle
There are direct enyzme-catalyzed pathways for reversible conversions among nucleoside diphosphates and triphosphates, via nucleoside-diphosphate kinases. See also https://archive.org/details/...
- 45.6k
3
votes
Aerobic respiration takes place in the mitochondria; anaerobic respiration takes place in the cytoplasm. Is there a biochemical reason for this?
The problems here would seem to be (1) a misconception of the biochemistry of anaerobic respiration — strictly anaerobic glycolysis or fermentation (see this Wikipedia article for explanation of the ...
- 25.7k
3
votes
Are there any plants that fix their own nitrogen?
Though it's not a land plant, and even does not fall into Archeaplastida, the haptophyte, Braarudosphaera bigelowii, has a nitrogen-fixing endosymbiont and recently confirmed as a fully dependent ...
3
votes
Why is iron transported across membranes in the ferrous form?
This is not my subject, but from scanning the introductions to a couple of reviews on the general topic of iron metabolism, the following factors seem to be important:
Ferric iron is less soluble ...
- 25.7k
3
votes
Accepted
What is the difference between digesting sugar and carbohydrates?
Scope of Answer
The original poster provided ample context for his question, which related to health considerations. It was perhaps for this reason, among others, that the question had not received an ...
- 25.7k
3
votes
Accepted
Why do monoclonal and polyclonal antibodies behave differently as labeled secondary antibodies?
The mechanism for this is (as stated in the first sentence of the quote) that in a monoclonal antibody all antibodies bind the same site (epitope), whereas in a polyclonal antibody you have a mix of ...
- 91
3
votes
Improving contrast between dot and paper in dot blot
In the absence of another answer, I'll transition my comments to an answer.
Please label your images.
Both an Abcam guide and a Thermo troubleshooting document suggest using a kit or DAB protocol ...
- 10.1k
2
votes
What is the purpose of DMT in plants?
Just pointing out that there is no evidence that endogenous DMT in humans is produced by the pineal gland. There has been much speculation, but the few studies that have measured DMT in human ...
- 21
2
votes
Can fermentation and aerobic respiration occur at the same time?
What happens at rest is that the muscle relies on blood glucose for energy supply. This involves glycolysis, Krebs' cycle and the ETC. In short, glucose is split into two trioses. The two trioses are ...
- 222
2
votes
Why doesn't the cell just use one messenger?
A simple explanation for why there are intermediate messengers between stimuli (in this case adrenaline) and the final effector (the kinase).
Multiple messengers in a signalling pathway create ...
- 109
2
votes
Accepted
How can saliva neutralise acids produced by bacterial cells in our mouth if it is itself acidic in nature?
Saliva is neutral, not acidic (6.8 is very barely acidic), and is a means to carry the acid away physically, and is also much less acidic than acid produced by bacteria, so is still effective in ...
- 401
2
votes
How come SSBPs in RPA don't bind primers?
From a 1994 review of E.coli single-stranded binding protein (SSBP) in Annual Reviews of Biochemistry, it would appear that at least 35 nucleotides (nt) of single-stranded DNA are required for binding ...
- 25.7k
2
votes
Accepted
Can humans metabolize D-malate?
I do not have specific proof, but I strongly suspect that the answer to this question is NO on the basis of the following arguments.
The overwhelming majority of sugars, amino acids, carboxylic acids
...
- 25.7k
2
votes
Can a non-pure culture be used for reliable rapid phenotypic diagnostic tests?
Isn't the answer in the quote you provided from Manual of Standards for Diagnostic Tests and Vaccines? The results won't be reliable.
Having pure cultures by re-streaking the ones you suspect and only ...
- 12k
2
votes
How does $\ce{H2CO3}$ form in the blood with a ratio of 1:20 with $\ce{HCO3-}$ if there are not enough $\ce{H+}$ ions
Bicarbonate and its conjugate acid buffer the blood due to their intrinsic behavior (pKa/pKb) of donating $H^{+}$ if there is too few (high pH) or taking up $H^{+}$ if there is too much (low pH).
You ...
- 1,597
2
votes
Why does harper states that aldehyde dehydrogenase is a oxidase? Is it a misnomer then?
In Harper's Illustrated Biochemistry 32nd edition Chapter 12 in the section "Other Oxidases Are Flavoproteins" there are several enzymes listed and described. Quoting from that paragraph:
...
- 45.6k
2
votes
Why is the retention of ability to synthesize non essential amino acids of negative survival value?
I don't see the cost of the synthetization machinery as relevant (in this case), either. There is selection pressure to turn off the production if it's not needed, since leaving it running would ...
- 151
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