[viviaa]

I‘m a bit confused on why L-Alanin is an non polar aminoacid but still soluble in water. Why is that? Does it have something to do with it‘s IEP?

[Borek]

"Polar" is a very handwavy concept, used in many highly imprecise rules of thumb. This is just one of these cases.

Compared with phenylalanine alanine is quite polar. Solubility of phenylalanine is still in the range of tens of grams per L.

[Babcock_Hall]

I am not familiar with the abbreviation IEP.  Would you please define it for me?  The side chain (-CH₃) of alanine is non-polar compared with some of the other side chains, such as -CH₂OH, the side chain of serine.  There is a very big difference, however, in how an alanyl residue in a polypeptide behaves versus the free amino acid alanine.  What intermolecular force (IMF) is present in free alanine but not in an alanyl residue?

[rolnor]

Yes, I agree, the term non-polar does not refere to the free amino acid, it referes to the side-chain