Kd semantics

[kaj.stenberg from helsinki.fi.invalid]

DK <dk from no.email.thankstospam.net> wrote:
> In article <fomluv$bge$3 from oravannahka.helsinki.fi>, kaj.stenberg from helsinki.fi.invalid wrote:
>>This is probably trivial, but it confuces me:
>>
>>If the Kd for a ligand is mM it binds poorly, if the Kd is nM it binds
>>well. But in which case does one refer to the Kd as being "higher" or
>>"lower"?

> mM is "higher" than nM. However, sometimes people switch from 
> talking about Kd to talking about "affinity". Affinity is "higher" when
> Kd ~ nM. 

Thank you, "affinity" is of course unambigious, I did just not come to 
think of it. 

Just another thing: when can you start talking about a "real" (as in
specific) affinity? I am reading papers with a Kd in the ballpark of
tens of millimolar and find it hard to repeat the work so that I truly
believe in the results, since every random event seems to affect the 
curves fairly much.

-- 
Kaj