Coupling 12-aminododecanoic acid to Sepharose

[Tim Buss]

I am trying to make an affinity column by coupling 12-aminododecanoic
acid to Sepharose CL-4B. Does anybody know how to dissolve this stuff? 

I want to avoid acidifying it, and although it does dissolve in water
made alkaline with a few drops of 1M NaOH, it precipitates out when mixed
with coupling buffer (0.1M NaHCO3, pH8.5 0.5M NaCl).

Many thanks,

Tim Buss