Ratios of some domination parameters in trees

We determine upper bounds on the ratios of several domination parameters in trees.     

Establishing the selective phospholipid membrane coordination,permeation and lysis properties for a series of ‘druggable’ supramolecular self-associating antimicrobial amphiphiles

The rise of antimicrobial resistance remains one of the greatest global health threats facing humanity. Furthermore, the development of novel antibiotics has all but ground to a halt due to a collision of intersectional pressures. Herein we determine the antimicrobial efficacy for 14 structurally related supramolecular self-associating amphiphiles against clinically relevant Gram-positive methicillin resistant Staphylococcus aureus and Gram-negative Escherichia coli. We establish the ability of these agents to selectively target phospholipid membranes of differing compositions, through a combination of computational host:guest complex formation simulations, synthetic vesicle lysis, adhesion and membrane fluidity experiments, alongside our novel ¹H NMR CPMG nanodisc coordination assays, to verify a potential mode of action for this class of compounds and enable the production of evermore effective next-generation antimicrobial agents. Finally, we select a 7-compound subset, showing two lead compounds to exhibit ‘druggable’ profiles through completion of a variety of in vivo and in vitro DMPK studies.

A combination of computational and synthetic phospholipid vesicle/nanodisc assays are used to investigate the mode of action for a class of antimicrobial agents, while a range of DMPK studies establish agent druggability.     

Carbon nucleophilic displacements on kamiya's azetidinone disulfide: Synthesis of c-2 modified penicillins

Novel carbon nucleophilic displacement reactions on Kamiya's azetidinone disulfide $\text{2}$ and the synthesis of the C-2 modified penams $\text{25}$, $\text{26}$ and $\text{27}$ from the intermediates $\text{8}$, $\text{9}$, and $\text{11}$ are described.     

The diastereospecific aprotic conjugate addition reactions of allylic anions-mechanistic aspects.

A ten-membered cyclic “chair-chair” - or “$\text{trans}$-decalyl”-like TS is proposed to account for the diastereospecific aprotic conjugate addition reactions of allylic carbanions bearing polar, charge-stabilizing groups.     

Structures of the intermediates formed in the ring-opening reaction of 2-chloro-3-nitropyridine

The reaction of 2-chloro-3-nitropyridine with two equivalents of hydroxide ion was studied by NMR and X-ray crystallography. On the basis of NMR coupling constants, the originally formed ring-opened intermediate is the pseudo-cis form, as predicted by the SN(ANRORC) mechanism. However, the first intermediate is unstable and isomerizes to a second intermediate, which was isolated. The pseudo-trans geometry of the second intermediate [3-pentenenitrile, 2-nitro-5-oxo, ion(-1), sodium] explains why additional base does not lead to the ring-closing reaction as observed with 2-chloro-5-nitropyridine.     

Constructing bounded remainder sets and cut-and-project sets which are bounded distance to lattices

For any irrational cut-and-project setup, we demonstrate a natural infinite family of windows which gives rise to separated nets that are each bounded distance to a lattice. Our proof provides a new construction, using a sufficient condition of Rauzy, of an infinite family of non-trivial bounded remainder sets for any totally irrational toral rotation in any dimension.     

Theoretical study of hydrogen abstraction and sulfur insertion in the reaction H2S + S

The reaction of H2S + S has been characterized at the multireference configuration interaction level with the geometries optimized using the aug-cc-pVTZ basis set and the single-point energy calculated using the aug-cc-pV(Q+d)Z basis set. As in the analogous reaction of H2 + S, the presence of an intersystem crossing enables products (SH + SH) to be formed on the singlet surface through S insertion, which bypasses the triplet barrier (19.1 kJ mol-1 relative to SH + SH) of the H abstraction route. This provides theoretical evidence for SH + SH formation without barrier beyond endothermicity at sufficiently low temperatures. The H abstraction route, however, is expected to be competitive at higher temperatures due to a much higher Arrhenius pre-exponential factor (6.9 x 10(14) cm3 mol-1 s-1 derived from TST calculation) than that of S insertion channel (3.7 x 10(13) cm3 mol-1 s-1, derived by a least-squares fit to the measurements). With a slightly higher transition-state barrier than that of the H abstraction channel, the production of S2 + H2 is less favored due to proceeding via intersystem crossing and insertion. While the formation of HSS + H is energetically unfavorable relative to SH + SH, recombination channels producing H2SS or the more stable HSSH are expected to occur under collisional stabilization conditions at high pressures.