A metal complex that binds alpha-amino acids with high and predictable stereospecificity

Artificial synthetic receptors as regulators of protein activity

Superimposed snapshots of a MD simulation for the ternary complex between G6PD, a molecular clip and included NADP⁺ cofactor.

Molecular recognition of organic ammonium ions in solution using synthetic receptors

Ammonium ions are ubiquitous in chemistry and molecular biology. Considerable efforts have been undertaken to develop synthetic receptors for their selective molecular recognition. The type of host compounds for organic ammonium ion binding span a wide range from crown ethers to calixarenes to metal complexes. Typical intermolecular interactions are hydrogen bonds, electrostatic and cation-π interactions, hydrophobic interactions or reversible covalent bond formation. In this review we discuss the different classes of synthetic receptors for organic ammonium ion recognition and illustrate the scope and limitations of each class with selected examples from the recent literature. The molecular recognition of ammonium ions in amino acids is included and the enantioselective binding of chiral ammonium ions by synthetic receptors is also covered. In our conclusion we compare the strengths and weaknesses of the different types of ammonium ion receptors which may help to select the best approach for specific applications.

Colorimetric sensing of alpha-amino acids and its application for the "label-free" detection of protease

A new indirect approach to explore sensitive colorimetric sensors toward alpha-amino acids is proposed: the pink solution of 1 and copper ions changed to colorless immediately upon the addition of alpha-amino acids. As the hydrolysis of bovine serum albumin (BSA) with the aid of trypsin produces alpha-amino acids, the complex of 1/Cu(2+)/BSA could act as a label-free, sensitive, selective sensor toward trypsin. The detection process could be visually observed by naked eyes.

Enantiomerically pure chiral {Fe28} wheels

Wheels of steel: Two enantiomerically pure chiral {Fe(28)} wheel-like aggregates have been synthesized from the acetate buffer solution containing ferric ions and chiral tartrate ligands (see picture). These compounds are the largest chiral ferric aggregates isolated to date.

Structural dynamic of a self-assembling peptide d-EAK16 made of only D-amino acids

We here report systematic study of structural dynamics of a 16-residue self-assembling peptide d-EAK16 made of only D-amino acids. We compare these results with its chiral counterpart L-form, l-EAK16. Circular dichroism was used to follow the structural dynamics under various temperature and pH conditions. At 25 degrees C the d-EAK16 peptide displayed a typical beta-sheet spectrum. Upon increasing the temperature above 70 degrees C, there was a spectrum shift as the 218 nm valley widens toward 210 nm. Above 80 degrees C, the d-EAK16 peptide transformed into a typical alpha-helix CD spectrum without going through a detectable random-coil intermediate. When increasing the temperature from 4 degrees C to 110 degrees C then cooling back from 110 degrees C to 4 degrees C, there was a hysteresis: the secondary structure from beta-sheet to alpha-helix and then from alpha-helix to beta-sheet occurred. d-EAK16 formed an alpha-helical conformation at pH0.76 and pH12 but formed a beta-sheet at neutral pH. The effects of various pH conditions, ionic strength and denaturing agents were also noted. Since D-form peptides are resistant to natural enzyme degradation, such drastic structural changes may be exploited for fabricating molecular sensors to detect minute environmental changes. This provides insight into the behaviors of self-assembling peptides made of D-amino acids and points the way to designing new peptide materials for biomedical engineering and nanobiotechnology.