1. The inhibition of pepsin-catalysed hydrolysis of N-acetyl-l-phenylalanyl-l-phenylalanylglycine by products and product analogues was studied. 2. The non-competitive nature of the inhibition by the product N-acetyl-l-phenylalanine confirms an ordered release of products, and points to a common mechanism (involving an amino-enzyme) for pepsin-catalysed transpeptidation and hydrolysis reactions...

Microcystins are hepatotoxic cyclic peptides produced by several cyanobacterial genera worldwide. In 2008, our research group identified eight new glycine-containing microcystin congeners in two hydro-terrestrial mat samples from the McMurdo Dry Valleys of Eastern Antarctica. During the present study, high-resolution mass spectrometry, amino acid analysis and micro-scale thiol derivatization we...

The asymmetric unit of the title salt, C(5)H(6)ClN(2) (+)·C(2)F(3)O(2) (-), contains two independent 2-amino-5-chloro-pyridinium cations and two independent trifluoro-acetate anions. The F atoms of both anions are disordered over two sets of positions, with occupancy ratios of 0.672 (12):0.328 (12) and 0.587 (15):0.413 (15). In the crystal, the cations and anions are linked via N-H⋯O and C-H⋯O ...

In the title compound, C(8)H(8)BrNO(2), the dihedral angle between the aromatic ring and the methyl acetate side chain is 5.73 (12)°. The mol-ecular conformation is stabilized by an intra-molecular N-H⋯O hydrogen bond, generating an S(6) ring. In the crystal, mol-ecules are connected by N-H⋯O inter-actions, generating zigzag chains running along the b-axis direction.

The title compound, C(8)H(8)ClNO(2), is almost planar, with an r.m.s. deviation of 0.0410 Å from the plane through the non-hydrogen atoms. In the crystal structure, inter-molecular N-H⋯O hydrogen bonds link the mol-ecules into chains along the b axis. An intra-molecular N-H⋯O hydrogen bond results in the formation of a six-membered ring.

In the title salt, C6H9N2(+)·C2F3O2(-), the F atoms of the anion are disordered over two sets of sites, with refined occupancies in a ratio of 0.505 (17):0.495 (17). In the crystal, cations and anions are linked via N-H⋯O hydrogen bonds, forming R2(2)(8) ring motifs. The ionic units are linked into a two-dimensional network parallel to (100) by N-H⋯O and weak C-H⋯O hydrogen bonds. The crystal s...

In the title salt, C(6)H(9)N(2) (+)·NO(3) (-), the 2-amino-5-methyl-pyridinium cation and the nitrate anion are cyclically linked through pyridinium and amine N-H⋯O hydrogen bonds [graph set R(4) (3)(12)]. These units are extended into a zigzag chain structure lying parallel to the a axis, through a second cyclic R(2) (2)(8) association involving amine N-H⋯O and aromatic C-H⋯O hydrogen bonds to...

In the crystal structure of the title salt, C(5)H(6)ClN(2) (+)·C(7)H(5)O(3) (-), the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl-ate O atoms via a pair of N-H⋯O hydrogen bonds, forming R(2) (2)(8) ring motifs. These motifs are centrosymmetrically paired via N-H⋯O hydrogen bonds, forming a complementary donor-donor-acceptor-acceptor (DDAA) array. A t...

In the title compound, C(5)H(6)BrN(2) (+)·C(2)F(3)O(2) (-), the F atoms of the anion are disordered over two sets of sites, with occupancies of 0.59 (2):0.41 (2). In the crystal structure, the anions and cations are linked into a two-dimensional network parallel to (100) by N-H⋯O and C-H⋯O hydrogen bonds. Within this network, the N-H⋯O hydrogen bonds generate R(2) (2)(8) ring motifs.