A water wire in L-prolyl-L-serine monohydrate

Despite the extra functional group in the serine side chain, the crystal packing arrangement of the title compound {systematic name: (S)-3-hy­droxy-2-[(S)-pyrrolidine-2-carboxamido]­pro­pan­oic acid monohydrate}, C₈H₁₄N₂O₄·H₂O, is essentially the same as observed for a series of L-Pro-L-Nop peptide hydrates, where Nop is a strictly nonpolar residue. This is rendered possible by a monoclinic P2₁ packing arrangement with Z′ = 2 that deviates from ortho­rhom­bic P2₁2₁2₁ symmetry only for the seryl hy­droxy groups, which form infinite O—H...O—H hydrogen-bonded chains along the 5.3 Å a axis. At the same time, cocrystallized water mol­ecules form parallel water wires.

An unexpected tetra­gonal unit cell for N-(L-2-amino­butyr­yl)-L-serine

The title dipeptide, incorporating the nonproteinogenic amino acid residue L-2-aminobutyric acid, forms an extensively disordered, compact crystal packing arrangement in the tetragonal space group I4.

N-(L-2-Amino­penta­noyl)-L-phenyl­alanine dihydrate, a hydro­phobic dipeptide with a nonproteinogenic residue

The title dipeptide has a nonproteinogenic N-terminal residue. The crystal structure is divided into distinct hydro­phobic and hydro­philic layers, the latter encompassing cocrystallized water mol­ecules connecting the charged N- and C-terminal groups.