Ultrafast 2D-IR spectroscopy of haemoproteins

Applications of ultrafast two-dimensional infrared (2D-IR) spectroscopy to study the structural dynamics of haem-containing proteins are reviewed. The 2D-IR experiments discussed exploit diatomic ligands bound to the haem as reporters on the dynamic protein environment in the electronic ground-state. This is possible because fluctuations of the protein give rise to inhomogeneous broadening of the ligand stretching vibrational mode that is manifest as spectral diffusion in a time-resolved 2D-IR measurement. Methods for measuring and quantifying spectral diffusion data are introduced, prior to a discussion of recent results focussing on the influence of protein structure, water ingress into the haem pocket and substrate binding on the measured dynamics. Particular emphasis will be placed on proteins featuring the ferric oxidation state of the haem ligated by a nitric oxide molecule, though comparisons with other haem systems will be drawn throughout

Protection of cattle from Culicoides spp. in Australia by shelter and chemical treatments

Trials were conducted in three regions of Australia to investigate the potential for improvised shelters and chemical treatments to reduce feeding by Culicoides on cattle and thereby minimise the risk of bluetongue transmission during transport of cattle to ports. Various designs and combinations of roofs and walls were placed around penned cattle. Chemical treatments were applied to other penned cattle. Culicoides were collected from the cattle by vacuum samplers or by light traps in the pens. Roofs alone did not consistently reduce the numbers of Culicoides brevitarsis or C. fulvus and increased the numbers of C. actoni collected. Walls alone reduced the numbers of C. wadai but not C. brevitarsis. Roofs and walls in combination reduced the numbers of C. brevitarsis and C. wadai. The chemical treatments ‘Flyaway’ (a blend of repellents) and fenvalerate reduced the numbers of C. brevitarsis and C. wadai up to 52 h post treatment

Global QCD analysis and dark photons

Published: September 15, 2023We perform a global QCD analysis of high energy scattering data within the JAM Monte Carlo framework, including a coupling to a dark photon that augments the Standard Model (SM) electroweak coupling via kinetic mixing with the hypercharge B boson. We first set limits on the dark photon mass and mixing parameter assuming that the SM is the true theory of Nature, taking into account also the effect on g – 2 of the muon. If instead we entertain the possibility that the dark photon may play a role in deep-inelastic scattering (DIS), we find that the best fit is preferred over the SM at 6.5σ, even after accounting for missing higher order uncertainties. The improvement in χ² with the dark photon is stable against all the tests we have applied, with the improvements in the theoretical predictions spread across a wide range of x and Q². The largest improvement corresponds to the fixed target and HERA DIS data, while the best fit yields a value of g – 2 which significantly reduces the disagreement with the latest experimental determination.N. T. Hunt-Smith, a W. Melnitchouk, a, b N. Sato, b A. W. Thomas, a X. G. Wanga and M. J. Whitea on behalf of the Jefferson Lab Angular Momentum (JAM) collaboratio

Tunable supramolecular gel properties by varying thermal history

YesThe possibility of using differential pre‐heating prior to supramolecular gelation to control the balance between hydrogen‐bonding and aromatic stacking interactions in supramolecular gels and obtain consequent systematic regulation of structure and properties is demonstrated. Using a model aromatic peptide amphiphile, Fmoc‐tyrosyl‐leucine (Fmoc‐YL) and a combination of fluorescence, infrared, circular dichroism and NMR spectroscopy, it is shown that the balance of these interactions can be adjusted by temporary exposure to elevated temperatures in the range 313–365 K, followed by supramolecular locking in the gel state by cooling to room temperature. Distinct regimes can be identified regarding the balance between H‐bonding and aromatic stacking interactions, with a transition point at 333 K. Consequently, gels can be obtained with customizable properties, including supramolecular chirality and gel stiffness. The differential supramolecular structures also result in changes in proteolytic stability, highlighting the possibility of obtaining a range of supramolecular architectures from a single molecular structure by simply controlling the pre‐assembly temperature.FP7 Ideas: European Research Council. Grant Number: 25877

Comprehensive analysis of epigenetic clocks reveals associations between disproportionate biological ageing and hippocampal volume

The concept of age acceleration, the difference between biological age and chronological age, is of growing interest, particularly with respect to age-related disorders, such as Alzheimer’s Disease (AD). Whilst studies have reported associations with AD risk and related phenotypes, there remains a lack of consensus on these associations. Here we aimed to comprehensively investigate the relationship between five recognised measures of age acceleration, based on DNA methylation patterns (DNAm age), and cross-sectional and longitudinal cognition and AD-related neuroimaging phenotypes (volumetric MRI and Amyloid-β PET) in the Australian Imaging, Biomarkers and Lifestyle (AIBL) and the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Significant associations were observed between age acceleration using the Hannum epigenetic clock and cross-sectional hippocampal volume in AIBL and replicated in ADNI. In AIBL, several other findings were observed cross-sectionally, including a significant association between hippocampal volume and the Hannum and Phenoage epigenetic clocks. Further, significant associations were also observed between hippocampal volume and the Zhang and Phenoage epigenetic clocks within Amyloid-β positive individuals. However, these were not validated within the ADNI cohort. No associations between age acceleration and other Alzheimer’s disease-related phenotypes, including measures of cognition or brain Amyloid-β burden, were observed, and there was no association with longitudinal change in any phenotype. This study presents a link between age acceleration, as determined using DNA methylation, and hippocampal volume that was statistically significant across two highly characterised cohorts. The results presented in this study contribute to a growing literature that supports the role of epigenetic modifications in ageing and AD-related phenotypes

The effect of temperature and solvation on the ultrafast dynamics of n-methylacetamide

The ultrafast dynamics of N-methylacetamide (NMA), a peptide-linkage model compound, are reported for the first time as a function of temperature and dilution. The rotational-diffusive timescale of NMA was observed to behave in a manner inconsistent with established hydrodynamic theory for simple liquids, exhibiting sharp decreases at elevated temperatures and low concentrations. These were associated with non-stoichiometric changes in far-infrared and terahertz Raman transition strengths. The data is consistent with a model in which neat NMA forms hydrogen bonded aggregates, featuring cooperative effects upon the polarizability and dipole moment that are disrupted by increased temperature or decreased NMA mole fraction

Terahertz-pulse emission by laser excitation of surface plasmons in a metal grating

Metallic nanostructures have been prepared by depositing thin layers of gold onto a fused-silica transmission grating. Excitation with 800-nm femtosecond laser pulses in air results in the emission of terahertz radiation with an angle-dependent efficiency and a third-order dependence on input power. Nanostructures consisting of metal nano-pyramids on glass as well as silver nano-pyramid arrays covered in gold also exhibit terahertz emission. We will show that the source of the terahertz radiation in all of these cases is surface-plasmon-assisted multiphoton ionisation and ponderomotive acceleration in the evanescent laser field

The dynamics of water-protein interaction studied by ultrafast optical Kerr-effect spectroscopy

Changes in the ultrafast dynamics and terahertz Raman spectrum accompanying a helix-to-coil transition of a homo-polypeptide have been observed for the first time. Formation of the -helix is associated with a shift to lower frequency of a broad Raman band attributable to solvent-peptide intermolecular hydrogen bonding. This band facilitates direct spectroscopic observation of so-called hydration water near a peptide and yields the first quantitative estimate of the time scale of the ultrafast dynamics in the solvation shell, which range from 0.18 to 0.33 ps (185-100 cm-1) depending on the secondary structure of the peptide. Such fast motions of solvent molecules have been referred to as the "lubricant of life" and are thought to play key roles in determining structure and activity of proteins