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Tin (Sn) isotopes for labeling

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DunjaM

Participant

Posts: 1

Joined: Tue May 25, 2021 12:25 am

Post Wed May 26, 2021 9:44 pm

Tin (Sn) isotopes for labeling

Hi everyone,

Does anyone have any experience with tin (Sn) isotopes for conjugating antibodies? We've tried loading DTPA, dota and nota with Sn but failed. There doesn't seem to be anything out there about tin for CyTOF. Just wondering if that's because people haven't had any success with it or maybe not many people have given it a shot. Any ideas as to which polymer/monomer/chelator might work for tin?

Thanks! :)
Dunja
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mleipold

Guru

Posts: 5796

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Wed May 26, 2021 11:33 pm

Re: Tin (Sn) isotopes for labeling

Hi Dunja,

My recollection is that 8-10 years ago, someone in the Nolan Lab at Stanford tried it, but they couldn't get it stably associated.

Which form of tin are you testing? Sn2+ or Sn4+?


One basic issue might be that tin has a couple common oxidation states (+2 and +4): https://www.britannica.com/science/tin
"Tin exists in two oxidation states, +4 and +2. Elemental tin is readily oxidized to the dipositive ion in acidic solution, but this Sn2+ ion is converted to the Sn4+ ion by many mild oxidizing agents, including elemental oxygen. Oxidation under alkaline conditions normally gives the tetrapositive (Sn4+) state."

Remember, chelate stability is dependent upon both size and charge: you can't have a chelator that's "too big" or "too small" for the metal ion, and the chelator generally charge-neutralizes (or close to) the metal ion.

So, if you chelate Sn2+ (maybe under acidic conditions?) and it gets oxidized, you'll get Sn4+ and that may not stably associate with the chelator anymore for both size and charge reasons.


It *does* look like stable Sn chelates can be made, though: https://patents.google.com/patent/US6231832B1/en


Mike
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ezunder

Participant

Posts: 4

Joined: Tue Oct 03, 2017 2:10 pm

Post Thu May 27, 2021 2:24 am

Re: Tin (Sn) isotopes for labeling

I was the one who tried this in Garry Nolan's lab. I tested Sn(II)Cl2 with the EDTA-based cell barcoding reagents Isothiocyanobenzyl-EDTA and BABE, but did not have good results. Cells were effectively barcode-labeled with these reagents, but they weren't clean enough to use: after pooling labeled and unlabeled cells, there was significant cross-contamination/leaching onto the unlabeled cells. The staining behavior was similar to just mixing un-chelated SnCl2 with cells, which makes me think that the Sn2+ wasn't effectively chelated by the EDTA molecules. It's certainly possible that all my tin oxidized before mixing with the bifunctional barcode molecules. I tried to mix them quickly, but I wasn't working under Argon/Nitrogen, just in Eppendorf tubes.

I also tried out DibutylTin-Diisothiocyanate, a Sn(IV) compound that in theory should have worked great for cell barcoding. Unfortunately, the performance of this was also disappointing - similar behavior to my SnCl2 tests.

I'd love to see someone get this to work. It would be great to be able to use all the Tin isotopes!

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