[URgEnthalpy]

I need to predict IEP of aminoacids derievatives but I can't find any calculator except these for proteins which I'm not interested in.
Is it even possible to calculate approx. IEP for compounds that aren't proteins built from aminoacids with known, experimentally designated IEPs?
Could you give me some examples of calculators that might help me?

[Babcock_Hall]

For non-natural amino acids with ionizing side chains, one has to classify the side-chain as a neutral acid or a cationic acid.  There is a different formula to calculate the pI, depending on this classification.  Offhand, I don't know of a good textbook treatment of this topic, nor do I know of a calculator.

[URgEnthalpy]

Okay so, let's simplify my problem is it possible to predict the following β-alanine derivatives:
1. 2-aminosuccinic acid
2. 2-(aminomethyl)malonic acid
3. 3-(carboxyamino)propanoic acid
4. 3-((carboxymethyl)amino)propanoic acid

I only know that the longer aliphatic chain of aminoacid (assuming amine gropu is at the other side to carboxylic group) the IEP is higher.
I assume that the more carboxylic acid groups the lower IEP will be, but have no idea how to predict it and what's worse how position of the group impact this.

[Babcock_Hall]

Unless I am missing something, 2-aminosuccinic acid is just another name for aspartic acid.  For aspartic and glutamic acids, pI = (pK₁ + pK_R)/2.  The meaning of pK_R is that it is the side-chain pK_a.  The main-chain carboxylic acid is pK₁.  A different formula is used for cationic acids, such as lysine or arginine.