Free drug concentration

[carbonp]

If,
Free protein = [(Total protein - Total drug -Dissociation constant)] (+/-) under root of (Total protein - Total drug -Dissociation constant)^2 + 4 (dissociation Constant * Total Protein) divided by 2
If Total protein - 0.035 g /microliter,
Total drug - 3319.246 x 10^-15 moles/l (Molecular weight of drug - 337.41 g/mole)
Dissociation constant = 0.27 nM,
How to calculate the free protein, Above is quadratic equaltion,
As the unit dissociation constant of drug is in nM, while that of total protein and total drug is in different units, How to calculate the free protein ?

Is there any way to convert 0.27 nM in to some other unit that can be used for calculation?
Can any one please help,
Thanks in advance.

[JackBean]

First of all, I don't think, you are supposed to substract the diss. const. from the protein amount
What about multiplication?

[carbonp]

Sorry its addition of dissociation constant. but formula does not say multiplication of dissociation constant.

[JackBean]

Sorry, I don't get it.
Anyway, it doesn't make much sense to substract/add the dissociation constant from/to protein/drug amount