Application of Combinatorial Procedures in the Search for Serine-Protease-Like Activity with Focus on the Acyl Transfer Step

Recursive deconvolution of a 729-membered peptide library has identified three active sequences, in which both Ser and His are present in one of the two tripeptidic chains generated on a steroidal scaffold (see structural formula), for the cleavage of an activated p-nitrophenyl ester. This combinatorial approach aims at searching for serine-protease-like activity.     

A Carbohydrate-based Synthetic Approach to Diverse Structurally and Stereochemically Complex Chiral Polyheterocycles

Chiral polyheterocycles are one of the most frequently encountered scaffolds in natural products and in current drugs repertoire. A carbohydrate-based diversity oriented synthetic (DOS) approach has been employed for gaining access to many structurally diverse and stereochemically complex rigid polyheterocyclic molecules with multiple chiral hydroxyl groups to enhance aqueous solubility. Inexpensive chiral pool of D-Glucose has been judiciously exploited to get access of complex chiral polyheterocyclic structures using inexpensive, common achiral reagents and domino-Knoevenagel hetero-Diels-Alder (DKHDA) reaction as one of the key synthetic tools. Stereochemistry of newly generated stereocenters of polycyclic structures are unambiguously determined through NMR and X-ray crystallographic study. A chemoinformatic comparison (PCA and PMI) with 40 branded blockbuster drugs showed that newly generated polyheterocycles have good three-dimensional scaffold diversity and most of these pass the Lipinski filter of drug-likeness.     

Tripodal naphthalene ether ligand: Solid-state anion recognition and fluorescence studies

The simple tripodal amine ligand Tris-[2-(naphthalen-1-yloxy)-ethyl]-amine (L₁) was screened for anion recognition. Four crystal structures confirmed the inorganic as well as organic anion recognition in the solid state. Solid-state structures are results of supramolecular self-assembly and 3D molecular network involves C–HO and C–Hπ bonding in the crystal lattice. In the solid state, it forms a strong C–HCl and C–HO type interactions with the anions. This anion recognition was also confirmed by steady state fluorescence spectroscopy. In complex 4, L₁ is confined between 2D hydrogen bonded sheet formed by pyromellitic acid anion. L₁ shows unusually high selectivity toward nitrate in solution resulting in both a dramatic color change and a concomitant quenching of luminescence.     

Perspectives from above and beyond the proton drip-line

This paper will review the dramatic increase in our knowledge of one and two proton unbound nuclei [1] such as recoil decay tagging [2] are revealing unique insights into the structure of nuclei beyond the proton drip-line. These studies of excited states provide complementary information to proton radioactivity studies, particularly regarding the role of deformation [3]. Radioactive beams are being used to study two-proton unbound resonances and to study explosive nuclear astrophysical reactions in the region of the proton drip-line.     

Endocrine disruption: molecular interactions of chlorpyrifos and its degradation products with estrogen receptor

Structural Chemistry - Chlorpyrifos is an extensively used organophosphate pesticide showing broad-spectrum effectiveness on various target pests. Long-term sublethal exposure to this pesticide is...     

Spatio‐temporal dynamics in nondiffractive Bessel ultrafast laser nanoscale volume structuring

Nondiffractive ultrafast optical beams with quasi‐stationary characteristics enable new regimes and scales in light‐matter interactions. We discuss the action of ultrashort Bessel laser beams in bulk fused silica, emphasizing excitation dynamics with energy localization beyond diffraction limit. We shed light on relaxation channels leading to one‐dimensional structures with nanoscale sections and morphologies ranging from densified matter to nanosized cavities. Space‐ and time‐resolved absorption and phase‐contrast microscopy reveals two main carrier relaxation paths. Fast exciton trapping in self‐induced matrix deformations results in positive index contrast driven by swift accumulation of non‐bridging oxygen hole centers and defect‐driven structural rearrangements. High excitation densities determine thermomechanical paths, with onset of phase transitions and the release of pressure waves. High‐aspect‐ratio nanosized channels are thus created via rarefaction and liquid cavitation, accompanied by molecular decomposition and generation of oxygen deficiency. The characteristic electronic relaxation identifies the nature of structural transitions up to the onset of phase transformation. Temporal pulse dispersion regulation allows driving unique carrier dynamics with precise control over energy deposition down to the 100 nm scale. Extreme high‐aspect‐ratio uniform void structures can thus be fabricated in conditions of sub‐micron transverse light confinement.