https://phys.org/news/2019-08-molecules-ions-filter-potassium-channels.html
"...Researchers prove there are no water molecules between the ions in the selectivity filter of potassium channels..."
Although what they proved to be so certainly isn't intrinsically interesting at least from a purely academic point of view and most laypeople certainly wouldn't care whether water molecules move in those channels, what is far more impressive is that they managed to prove it at all as this is a very difficult thing to prove! And this isn't to mention the potential medical breakthroughs this insight might bring for diseases and disorders involving the potassium channel!
I find it surprising that they used nuclear magnetic resonance spectroscopy (NMR) to show that potassium ions move through the potassium channels without water molecules. Wouldn't this NMR have to have incredible resolution in its image to rule out the possibility there are water molecules there? Are there any NMR experts here that can tell me?
@humy
I found this on NMR, apparently higher frequencies give greater resolution and this one talks about magnetic fields at 1 Ghz but even that as a field would seem to me to give you maybe mm res non nm res.
Besides, this piece doesn't seem to use the right units, touting the high field strength of 1,020 Megahertz, a frequency measure not a field strength metric.
If the res is tied to frequency, then it looks to me like they would need Near IR frequencies or higher.
@sonhouse saidMaybe then they didn't image that directly (because not high enough frequency) but instead found a workaround in the form of some kind of ingenious indirect way of deducing from the image (and some other clue?) that there was no water molecules in the channel? Or at least deduce there was no water molecules MOVING in the channel, which would allow them to then deduce there was no water molecules in the channel?
@humy
I found this on NMR, apparently higher frequencies give greater resolution and this one talks about magnetic fields at 1 Ghz but even that as a field would seem to me to give you maybe mm res non nm res.
Besides, this piece doesn't seem to use the right units, touting the high field strength of 1,020 Megahertz, a frequency measure not a field strength metric.
If the res is tied to frequency, then it looks to me like they would need Near IR frequencies or higher.
If so, I would really like to know exactly how they did that.
@sonhouse saidHi sonhouse, NMR people talk about the characteristics of an NMR by the frequency at which the signal of TMS (tetramethylsinale) occurs.
@humy
I found this on NMR, apparently higher frequencies give greater resolution and this one talks about magnetic fields at 1 Ghz but even that as a field would seem to me to give you maybe mm res non nm res.
Besides, this piece doesn't seem to use the right units, touting the high field strength of 1,020 Megahertz, a frequency measure not a field strength metric.
If the res is tied to frequency, then it looks to me like they would need Near IR frequencies or higher.
@sonhouse saidoriginal paper available here:
@humy
Can you download the original paper?
https://advances.sciencemag.org/content/5/7/eaaw6756
This is in fact a really tricky application of a 2D NMR technique and the proof is actually quite indirect (but still convincing) on the actual magneitization time. You need to have some knowledge on protein chemistry and on advanced NMR-technique to understand that.
@ponderable saidOh this really looks hard to understand. Sorry I asked 🙂
original paper available here:
https://advances.sciencemag.org/content/5/7/eaaw6756
This is in fact a really tricky application of a 2D NMR technique and the proof is actually quite indirect (but still convincing) on the actual magneitization time. You need to have some knowledge on protein chemistry and on advanced NMR-technique to understand that.
@Ponderable
Ah, so it is kind of like a transponder or laser, input one frequency, in this case say a ghz and the energy of that ping activates the response which would be presumably a much higher frequency and therefore able to achieve greater resolution. Does that sound reasonable?
I never studied NMR, my expertise was in ion implanters, ion etchers, sputtering tools and a brief stint on electron microscopes, of course all in the world of semiconductor manufacturing so those kind of NMR technologies I never had a chance to encounter.
When I was an Apollo technician I was familiar with atomic clocks and tracking transponders on the craft, my job there was Tracking and Timing.
ATT they had a hydrogen clock which was the king of the mountain ATT, accurate to within one second in several million years.
Now the newest ones are thousands of times more accurate but one second in a million years was WOW time for me in 1970😉
The actual atomic clocks for Apollo were off the shelf HP clocks, only accurate to a mere one second in 2000 years. That was the cesium beam clock. Then a secondary clock if that one bit the dust (they never did) was a Rubidium clock, poor second, only accurate to one second in just 200 years😉 but that was not good enough, there was a third clock if both of those bit the dust, a highly thermally stabilized quartz clock, I guess accurate to around one second per year.
Those clocks were used to generate timing signals to switch data from the Apollo craft when one radio telescope would go under the horizon and lose signal, another one over the horizon would pick up that signal and you had 100 nanoseconds to get the signal transferred from one dish to another which they did quite regularly.
But NMR, never even saw one much less get my hands dirty on one😉