Wikipedia:Reference desk/Archives/Science/2019 February 2

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February 2

Exact frequencies for hydroxyl lines (18 cm band)

Related to the "water hole" in SETI, what are the exact frequencies for the hydroxyl lines (hydroxyl radical (OH))?

The one for the hydrogen line is on Wikipedia with 14 significant digits:

1.4204057517667 GHz, 21.1061140542 cm

Progressively, I have found:

• 1612 MHz, 1665 MHz, 1667 MHz, and 1720 MHz
• 1612.2 MHz, 1665.4 MHz, 1667.4 MHz and 1720.5 MHz. The same in this source.
• 1612.231 MHz, 1665.402 MHz, 1667.359 MHz, and 1720.530 MHz (may not be reliable)

--Mortense (talk) 12:15, 2 February 2019 (UTC)

Because of hyperfine structure, hydroxyl may emit many dozens of gigahertz-range resonance frequencies. I pulled out my general-purpose reference book, Pacholczyk's Radio Astrophysics. Chapter 8.3 is entirely on the radio lines of the hydroxyl structure. Table 8.1 lists the eleven most prominent lines, at 1.6, 1.7, 6.0, and 4.7 GHz, with excruciating details (though his values differ from your most precise listing by a few kilohertz. As the author calls out, at these frequencies, you're characterizing so spectra precisely that you have to start accounting for all sorts of other physics that affect the line bandwidth - like the Doppler shift due to thermal noise - so, make sure you don't fall prey to false precision). Suffice to say, it takes a few dozen pages and some five or ten diagrams to list out all the various frequencies, and the physical explanations for them, and the equations that govern the exact frequencies. Particularly, the 21-cm and four strong 18-cm lines are attributed to the lambda doublet of the ground state. If you don't have one handy, now would be a good time to crack open your favorite text on physical chemistry, because it only gets more arcane from here. Nimur (talk) 23:21, 2 February 2019 (UTC)

I found figures with 2 more significant digits, 9, and the actual transitions, with sources (reference 29):

• 1612.23101 MHz, 1665.40184 MHz, 1667.35903 MHz, and 1720.5299 MHz (F'=1←F"=2, F'=1←F"=1, F'=2←F"=2, and F'=2←F"=1, respectively)

--Mortense (talk) 08:57, 3 February 2019 (UTC)

Enzyme workload and its performance.

Can felodipine still alter the serum concentration of nifedipine despite they're all sensitive substrates of CYP3A4 and not inhibitors among each other's metabolic pathways? My assumption is yes. I think co-administration of nifedipine and felodipine will decrease the metabolic rates of each other due to competition of the same enzyme given that the number of the CYP3A4 enzymes is limited. Just like when both are metabolized through CYP3A4 will result in traffic jam (as the capacity of CYP3A4 is constant) leading to reduced metabolism speed overall.

I know the combination is rarely seen. I just want to check the validity of my concept that if someone takes too much drugs that metabolized through same enzyme will lead to traffic jam and end up slow down the metabolism rate.

I searched some drug interaction programs and the results were mixed.

Thanks for your attention! --It's gonna be awesome!✎Talk♬ 16:09, 2 February 2019 (UTC)

I don't know the specific answer in your case, but bear in mind that besides competing for the same enzyme, drugs can also either inactivate the P450 enzyme that interacts with them, reducing its activity, or induce greater production of the enzyme, increasing its activity later on. Drugs might even interact at the multidrug transporter (see ATP-binding cassette transporter, e.g. the section on MDR1 ... I don't pretend to keep track) or in other ways in a cell. Conceptually you are on something of the right track but there are so many details that nothing but an empirical result for a specific situation will be reliable. Wnt (talk) 13:25, 4 February 2019 (UTC)

Thanks for the answer! --It's gonna be awesome!✎Talk♬ 09:32, 5 February 2019 (UTC)