An Alternate [2×2] Grid Constructed Around TiO4N2 Units

The formation of a tetranuclear self-assembled species constructed around a TiO₄N₂ motif is reported. This aggregate is generated from Ti(OⁱPr)₄, 2,2’-bipyrimidine (bpym) and a bis-biphenol strand (L²H₄) where two 2,2’-biphenol units are connected with a biphenyl spacer. The solid-state structure of the [Ti₄(L²)₄(bpym)₄] architecture reveals the formation of an unprecedented chiral alternate [2×2] grid. In addition to the structural characterization of the [Ti₄(L²)₄(bpym)₄] architecture, geometry optimisation on various possible isomeric tetrameric assemblies ([2×2] grid, alternate [2×2] grid, circular helicate or cyclic hemihelicate) is performed using DFT calculations. These results confirm the higher stability of the alternate [2×2] grid over the other possible tetranuclear isomers and allow examining the replacement of the bpym ligands by two novel diimine chelates within the tetranuclear assembly (2,2’-bipyridine=bipy and 2,2’-bipyrazine=bipyraz). From this initial theoretical investigation, the competition between these three nitrogen ligands in the course of the self-assembly process is next evaluated. Overall, this investigation shows that the exclusive formation of the alternate [2×2] grid is driven by CH⋅⋅⋅N interactions.     

Investigating a Boronate-Affinity-Guided Acylation Reaction for Labelling Native Antibodies

The excellent molecular recognition capabilities of monoclonal antibodies (mAbs) have opened up exciting opportunities for biotherapeutic discovery. Taking advantage of the full potential of this tool necessitates affinity ligands capable of conjugating directly with small molecules to a defined degree of biorthogonality, especially when modifying natural Abs. Herein, a bioorthogonal boronate-affinity-based Ab ligand featuring a 4-(dimethylamino)pyridine and an S-aryl thioester to label full-length Abs is reported. The photoactivatable linker in the acyl donor facilitated purification of azide-labelled Ab (N₃-Ab) was quantitatively cleaved upon brief exposure to UV light while retaining the original Ab activity. Click reactions enabled the precise addition of biotin, a fluorophore, and a pharmacological agent to the purified N₃-Abs. The resulting immunoconjugate showed selectivity against targeted cells. Bioorthogonal traceless design and reagentless purification allow this strategy to be a powerful tool to engineer native antibodies amenable to therapeutic intervention.     

Radiological chronometry of uranium metal samples

Radiological chronometry is an important tool in nuclear forensics that uses several methods to determine the length of time that has elapsed since a material was last purified. One of the chronometers used in determining the age of metallic uranium involves measuring the fractional ingrowth of ²³⁰Th from its parent ²³⁴U with the assumption that the uranium metal contained no impurities, especially thorium, when it was purified. The affects of different etching procedures were evaluated for the removal of surface oxidation with three different types of uranium metal samples to determine whether the etching procedure affects the radiological age. The sample treated with a rigorous etching procedure had exhibited the most reliable radiological age while less rigorous etching yields a radiological age from 15 years to hundreds of years older than the known age. Any excess thorium on the surface of a uranium metal sample presents a bias in age determination and the sample will appear older than the true age. Although this research demonstrates the need for rigorous surface etching, a bias in the radiological age could have arisen if the uranium in the metal was heterogeneously distributed.     

How Many Water Molecules Does it Take to Dissociate HCl?

The potential energy surfaces of the HCl(H₂O)_n (n is the number of water molecules) clusters are systematically explored using density functional theory and high‐level ab initio computations. On the basis of electronic energies, the number of water molecules needed for HCl dissociation is four as reported by some experimental groups. However, this number is five owing to the inclusion of entropic factors. Wiberg bond indices are calculated and analyzed, and the results provide a quadratic correlation and classification of clusters according to the nondissociated, partially dissociated, and fully dissociated character of the H?Cl bond. Our computations show that if temperature is not controlled during the experiment, the values obtained for the dipole moment (or for any measurable property) are susceptible to change, providing a different picture of the number of water molecules needed for HCl dissociation in a nanoscopic droplet.     

Infinite non-conformal iterated function systems

We consider a class of iterated function systems consisting of a countable infinity of non-conformal contractions, extending both the self-affine limit sets of Lalley and Gatzouras as well as the infinite iterated function systems of Mauldin and Urbański. Natural examples include the sets of points in the plane obtained by taking the binary expansion along the vertical and the continued fraction expansion along the horizontal and deleting certain pairs of digits. We prove that the Hausdorff dimension of the limit set is equal to the supremum of the dimensions of compactly supported ergodic measures, which are given by a Ledrappier and Young type formula. In addition we consider the multifractal analysis of Birkhoff averages for countable families of potentials. We obtain a conditional variational principle for the level sets.     

A Simple Efficient Synthesis of 5,8-Isoquinolinedione

5,8-Isoquinolinedione was synthesized from 5-hydroxyisoquinoline by nitrosation at C-8, reduction of the nitroso group and oxidation of the resultant 5-hydroxy-8-aminoisoquinoline.