Ion semiconductor sequencing - hydrogen ion? water?

Question

[Salut]

Hi,

I am just having some issues with the principles of "Ion Semiconductor Sequencing" by Ion Torrent. As far as I understood it, the release of a hydrogen ion during polymerization is detected and knowing which nucleotide was added the sequence can be inferred.

My problem is, that during polymerization, it's not just a hydrogen ion that comes up, but also one OH-, forming H2O, as shown on this picture.

I think this formation of H2O happens instantly, so I am wondering how the detection of the hydrogen ion is possible. Are the sensors that sensitive that they can detect the hydrogen ion before H20 is formed?

I would be grateful for any answers, as I have not found anything about this "problem" yet and all graphics and explanations are totally based on "release of H+ is detected" not mentioning this theme at all...

Many thanks in advance!!

Answer 1

[Devon Ryan]

Well, part of the problem is that your image doesn't really show what's going on:

You can read the whole paper here. So in short, the hydrogen isn't immediately bound to a hydroxl group. If you look at figure 1 from their paper, you can get an idea of the bulk kinetics and amplitudes involved.

Edit: I should emphasize the fixed charge that's created. That's what's actually inducing the charge movement in the plate that the voltage clamp is picking up.