Jasper Adamson

Negative area compressibility in silver(I) tricyanomethanide

The molecular framework Ag(tcm) (tcm(-) = tricyanomethanide) expands continuously in two orthogonal directions under hydrostatic compression. The first of its kind, this negative area compressibility behaviour arises from the flattening of honeycomb-like layers during rapid pressure-driven collapse of the interlayer separation.

Changes in the mitochondrial function and in the efficiency of energy transfer pathways during cardiomyocyte aging

The role of mitochondria in alterations that take place in the muscle cell during healthy aging is a matter of debate during recent years. Most of the studies in bioenergetics have a focus on the model of isolated mitochondria, while changes in the crosstalk between working myofibrils and mitochondria in senescent cardiomyocytes have been less studied. The aim of our research was to investigate the modifications in the highly regulated ATP production and energy transfer systems in heart cells in old rat cardiomyocytes. The results of our work demonstrated alterations in the diffusion restrictions of energy metabolites, manifested by changes in the apparent Michaelis–Menten constant of mitochondria to exogenous ADP. The creatine kinase (CK) phosphotransfer pathway efficiency declines significantly in senescence. The ability of creatine to stimulate OXPHOS as well as to increase the affinity of mitochondria for ADP is falling and the most critical decline is already in the 1-year group (middle-age model in rats). Also, a moderate decrease in the adenylate kinase phosphotransfer system was detected. The importance of glycolysis increases in senescence, while the hexokinase activity does not change during healthy aging. The main result of our study is that the decline in the heart muscle performance is not caused by the changes in the respiratory chain complexes activity but mainly by the decrease in the energy transfer efficiency, especially by the CK pathway.

Shortfall of B3LYP in Reproducing NMR J CH Couplings in Some Isomeric Epoxy Structures with Strong Stereoelectronic Effects: A Benchmark Study on DFT Functionals

Unprecedented scatter plots of calculated versus measured NMR 2,3 JCH coupling constants in six densely oxygen functionalized epoxides are found with some B3LYP protocols, an effect attributed to stereoelectronic effects. Hence, 26 other exchange-correlation density functionals (xc DFs) are benchmarked in this work. Very good results are achieved with mPW1PW91 and PBE0 in conjunction with the pcJ-1 basis set (BS) of moderate size. A thorough statistical analysis of 53 relationships between the predicted and observed 2,3 JCH datasets is presented. The effects of some xc DFs, including their x and c parts, and BSs on the calculation results are discussed, also in the context of DFT modeling of electron-density distributions. Moreover, related 1 JCH datasets predicted with 11 different DF methods are considered and compared with the experimental data. Finally, some proposals for further improvement of existing DFs based on the available n JCH (n=1-3) values are briefly outlined, in line with recent results on the DFT electron densities.

Competing hydrostatic compression mechanisms in nickel cyanide

We use variable-pressure neutron and X-ray diffraction measurements to determine the uniaxial and bulk compressibilities of nickel(II) cyanide, Ni(CN)2. Whereas other layered molecular framework materials are known to exhibit negative area compressibility, we find that Ni(CN)2 does not. We attribute this difference to the existence of low-energy in-plane tilt modes that provide a pressure-activated mechanism for layer contraction. The experimental bulk modulus we measure is about four times lower than that reported elsewhere on the basis of density functional theory methods [Phys. Rev. B 83 (2011) 024301].

Hydrogen bond order/disorder in a polar one-dimensional confined ice

Ice is one of the most well-studied substances yet forming a polar, bulk phase, where the water molecule dipoles are all aligned, has proved to be challenging. One approach is to confine the water in nanotubes, such that the molecules are restricted in orientation [1], however this hinders their use as ferroelectric devices – the primary application of polar ices. An alternative is to exploit the voids in nanoporous crystalline hosts but there are, as yet, no reported confined ice systems where the water molecules are able to switch between paraelectric and ferroelectric states whilst retaining a crystalline structure. One such porous system is 2,3,6,7,10,11hexahydroxytriphenylene (HHTP) tetrahydrate, where columnar stacks of the HHTP molecules are arranged in a pseudo-square arrangement and the water molecules occupy the pores, forming one-dimensional, meso-helical chains. The structure, determined previously [2], crystallises in Pbcn, however this places inversion centres within the water chains leading to unphysical intermolecular H...H contacts. A variable-temperature single-crystal X-ray diffraction investigation is described where careful consideration of the data shows how long-range dipole ordering within and between the water chains is induced, by varying temperature, transforming the crystal structure to the polar Pna21 space group [3]. Subsequent reassessment of the ambient temperature structure reveals a superposition of opposing polarisation states.