[thedy]

Why is  not zwitterion soluble in water?Zwitterion has negative and positive charge,so in water it could be,because negative charge goes to positive charge of water and positive charge of zwitterion goes to negative charge of H2O.But in my book is written,that in isoelectric point,amino acid is not soluble.So where is the true?
I thought,that zwitterion behaves like NaCl lattice,for example.
Thanks

[sjb]

Why is  not zwitterion soluble in water?Zwitterion has negative and positive charge,so in water it could be,because negative charge goes to positive charge of water and positive charge of zwitterion goes to negative charge of H2O.But in my book is written,that in isoelectric point,amino acid is not soluble.So where is the true?
I thought,that zwitterion behaves like NaCl lattice,for example.
Thanks

In general, yes, you're right, so things like glycine have good solubility. However, don't forget that many amino acids also have a hydrophilic core (like phenylalanine), so this may override the ionic nature of the zwitterion (like the decreasing solubility of carboxylic acids from formic to stearic and beyond.

[AWK]

At pH=Pi amino acids show the lowest solubility, but it does not mean that they are insoluble at all.

[thedy]

In general, yes, you're right, so things like glycine have good solubility. However, don't forget that many amino acids also have a hydrophilic core (like phenylalanine), so this may override the ionic nature of the zwitterion (like the decreasing solubility of carboxylic acids from formic to stearic and beyond.

So,Am I right?And my book not?And phenyl is hydrophilic???Not non-polar?

At pH=Pi amino acids show the lowest solubility, but it does not mean that they are insoluble at all.

I m confused,sjb said,that I m right,but you are saying,that in Pi,amino acids have lowest solubility...Im totally out