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139La in panels

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mleipold

Guru

Posts: 5774

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Wed Jun 08, 2022 9:09 pm

Re: 139La in panels

Hi Greg,

Back when we were trying to use 139La, we just bought it from Sigma: cat #203521.

The issue that we had was overall stability: you could make a conjugate with X8 or DN3, test that it's working properly, but then over the course of even a month or two, start seeing increased background (streaking) and decreased positive signal. It just wasn't worth it.

While the Tuning protocol of a CyTOF should keep LaO=155 below 3% of La=139 signal, if your marker is abundant enough, that <3% can still be a noticeable number and affect anything in the 155 channel. I had this happen years ago with one random sample that was hideously contaminated with lanthanum, and made the 155Gd channel (where I had CCR6, a low-abundance marker) completely uninterpretable.


Note: the DOTA chelator of the mDOTA live-dead and the DTPA chelator of X8/DN3 have different stability constants. This information can be found; unfortunately, the NIST 46 database is a downloadable database that has to be installed on a Win7 or earlier computer: https://data.nist.gov/od/id/mds2-2154

Thankfully, I found a colleague who had downloaded it years ago and the computer still worked. He told me: "The stability constant is LogK = 22.0 ± 3 for the La-DOTA complex and LogK = 19.49 for the La-DTPA complex. These two values would tell you the relative strength of the La complexes, but the effective stability constant (K_eff) in solution depends on the pH, the ionic strength of the solution, and the concentration of competitive ligands." I have attached the output he sent me.

In comparison, this table from Dojindo ( https://www.dojindo.eu.com/images/Produ ... stants.pdf ) lists the LogK of the other Lanthanides to be >= 22.4. Obviously, solution conditions impact stability, but this would be one explanation for why 139La-mDOTA live-dead seems to work more reliably, and for more people, than 139La-X8 for antibody staining.


IUPAC also has a similar database, but again is a downloadable thing:
https://www.degruyter.com/document/doi/ ... ml?lang=en
https://www.acadsoft.co.uk/scdbase/scdbase.htm


Why, in this day and age, IUPAC and NIST don't have online databases for this, or even just giant PDFs, I have *no* idea......


Mike
Attachments
StabilityConstants_LaDOTA_LaDTPA.pdf
(35.55 KiB) Downloaded 220 times
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mleipold

Guru

Posts: 5774

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Wed Jun 08, 2022 9:19 pm

Re: 139La in panels

To clarify:

"n comparison, this table from Dojindo ( https://www.dojindo.eu.com/images/Produ ... stants.pdf ) lists the LogK of the other Lanthanides to be >= 22.4."

That Dojindo table has DTPA values, not DOTA; I meant to say that the LogK of the other Lanthanides and *DTPA* is >=22.4 (ie, higher affinity than La and DTPA = 19.49)
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