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A small library of pyrrolidinesulphonylaryl molecules has been synthesized via an efficient 4-step route, and members evaluated for their ability to inhibit IL-6 signalling. One molecule (6a) was found to have promising activity against IL-6/STAT3 signalling at the low micromolar level, and to selectively inhibit phosphorylation of STAT3 (but not STAT1) in IL-6 stimulated MDA-MB-231 breast cancer and HeLa cell lines. It was also selectively cytostatic in MDA-MB-231 (STAT3-dependent) versus A4 (STAT3-null) cells suggesting STAT3-specific inhibitory properties.

Conformational change in polymers including proteins is central to many molecular processes. Defining conformational states, however, remains a difficult and increasingly common problem, with many existing methods based on arbitrary or potentially unrepresentative measures. Furthermore, the expanding length of molecular dynamics simulations and direct observation of transitions between different energy basins suggest that this issue will only become evermore important. Methods commonly used to characterize conformational states include principal component analysis, root-mean-square deviation-based clustering, and geometric measurements such as hinge angles and distances. Here we present a method where the eigenvector frequencies derived from a Gaussian network model (Bahar, I.; Atilgan, A. R.; Erman, B. Folding Des. 1997, 2, 173-181) of a trajectory of structures from a molecular dynamics simulation are used to describe the state of the protein at each time point. We apply the method to three proteins that share the same fold as the type II periplasmic binding proteins: The lysine-arginine-ornithine-binding protein, the glutamine-binding protein, and the ligand-binding domain from the NR1 N-methyl-D-aspartate receptor. We find that the method can distinguish different states in good agreement with a variety of previous analyses and additionally provides information on the dynamic properties of that system at a given time point.

The precise nature of redox modulation of N-methyl-d-aspartate (NMDA) receptors is still unclear, although it is thought to be related to the formation and breaking of disulfide bonds. Recent structural data demonstrated the way in which disulfide bonds in the ligand-binding core of the NR1 subunit are arranged. However, the structures were not able to reconcile existing experimental data that examined the effects of mutating these cysteine residues. We have used molecular dynamics (MD) simulations of a series of in silico mutations to try and address this in terms of the current structure of the NR1 ligand-binding domain. A double mutation that removes the disulfide bridge between C744 and C798 gives rise to greater interlobe mobility which was predicted from the crystal structure information but, unexpectedly, also appears to predispose the receptor toward greater flexibility in the hinge region. Removal of the disulfide bond between C454 and C420 did not show any appreciable difference from the "wild-type" simulation, suggesting that removal of this would not change receptor properties, which is in agreement with experimental findings. Furthermore, the position of the C454 side chain could be characterized into discrete rotamers, which may reflect the observation of alternative density in the crystal structure for this residue. Simulations in which two of the disulfide bonds are removed via mutations to alanine (C420A and C436A) resulted in a tendency of the protein to adopt a partially closed conformation.

The mechanism of partial agonism at N-methyl-d-aspartate receptors is an unresolved issue, especially with respect to the role of protein dynamics. We have performed multiple molecular dynamics simulations (7 × 20 ns) to examine the behavior of the ligand-binding core of the NR1 subunit with a series of ligands. Our results show that water plays an important role in stabilizing different conformations of the core and how a closed cleft conformation of the protein might be stabilized in the absence of ligands. In the case of ligand-bound simulations with both full and partial agonists, we observed that ligands within the binding cleft may undergo distinct conformational changes, without grossly influencing the degree of cleft closure within the ligand-binding domain. In agreement with recently published crystallographic data, we also observe similar changes in backbone torsions corresponding to the hinge region between the two lobes for the partial agonist, d-cycloserine. This observation rationalizes the classification of d-cycloserine as a partial agonist and should provide a basis with which to predict partial agonism in this class of receptor by analyzing the behavior of these torsions with other potential ligands.