PCCP Blog

Structural characterisation of powdered solids remains a significant challenge in modern chemistry. Graeme Day, Lyndon Emsley and co-workers have used a combination of computational and solid state NMR approaches to determine the structures of powdered samples of small organic compounds.

The group show that their ab initio approach can successfully be used to identify the structures of cocaine, flutamide and flufenamic acid in their recent PCCP paper.

Read this HOT article today:

Powder crystallography of pharmaceutical materials by combined crystal structure prediction and solid-state 1H NMR spectroscopy
Maria Baias, Cory M. Widdifield, Jean-Nicolas Dumez, Hugh P. G. Thompson, Timothy G. Cooper, Elodie Salager, Sirena Bassil, Robin S. Stein, Anne Lesage, Graeme M. Day and Lyndon Emsley
DOI: 10.1039/C3CP41095A

Scientists from the USA provide important insights into the complex mechanism of amyloid-induced membrane disruption in their recent PCCP article, which will be included in our soon-to-be-published themed issue on biophysical studies of protein misfolding and amyloid diseases.

Zheng et al. investigated the adsorption, orientation and suface interaction of the p3 pentamer with lipid bilayers composed of both pure zwitterionic POPC and mixed anionic POPC-POPG lipids using molecular dynamics simulations.

A pathological hall-mark of Alzheimer’s disease is the co-existence of extracellular plaques of amyloid-β and intracellular tangles of tau protein in the brain. It is generally thought that the interactions of Aβ oligomers with neuronal membranes are responsible for brain cell death and subsequent damage to learning and memory functions, but the exact details of the process are unclear. This work is valuable for future development of therapeutic agents and approactes to disrupt Aβ adsorption, aggregation and surface interaction on the membrane.

Read this HOT article today:

Molecular interactions of Alzheimer amyloid-β oligomers with neutral and negatively charged lipid bilayers
Xiang Yu, Qiuming Wang, Qingfen Pan, Feimeng Zhou and Jie Zheng
DOI: 10.1039/C3CP44448A

You may be interested to see our online collection of biophysics and biophysical chemistry in PCCP.

Joakim Jämbeck and Alexander Lyubartsev from Stockholm University describe an effective and novel way to account for atomic polarization in simulations of the partitioning of small molecules between water and lipid bilayers.

Their approach is a useful tool for rational drug design and for understanding anesthetic and toxic action.

Read this HOT article today:

Implicit inclusion of atomic polarization in modeling of partitioning between water and lipid bilayers
Joakim P. M. Jämbeck and Alexander P. Lyubartsev
DOI: 10.1039/C3CP44472D

The plasmons of bimetallic nanorods appear by cursory inspection to be independent of the composition! Pure gold, silver-gold-silver, pure silver, it matters not.
The ratio (length) of the nanorod, which is gold, can be varied from 0 nm to 200 nm in the 200 nm long nanorods, without changing the shape or position of the plasmonic bands. It happens to be coincidental that 200 nm long rods give this result, as the dielectric function of silver and gold are similar at the energies the plasmonic resonances are found at in 200 nm long nanorods.

A team of Korean scientist have been investigating mixed-metal nanorods, either 100 nm or 200 nm long. They find that the interfaces between the metals have little effect on the plasmonic resonances in the system. The single most important factor is the match of the dielectric function for the two metals, if the functions match the composition of the metal nanorod can be varied without any effect in the plasmons. A very interesting conclusion.

by Dr Thomas Just Sørensen

For the full details of this exciting article see:

Localized plasmon resonances of bimetallic AgAuAg nanorods
Sung-Hyun Ahn, Deok-Soo Kim, Daeha Seo, Wonjun Choi, Gi-Ra Yi, Hyunjoon Song, Q-Han Park and Zee Hwan Kim
DOI: 10.1039/C2CP43365F

This article is part of the PCCP themed collection on Optical studies of single metal nanoparticles. Check out the rest of the articles today.

Scientists from Israel and Japan have found a simple and effective route to the fabrication of stable Au island films, which are very useful in the field of localized surface plasmon resonance (LSPR) sensing. They additionally present a detailed kinetic study of the formation of gold nano-islands from gold films and their subsequent embedding into a glass substrate during annealing, in their recent PCCP paper.

The group used a combination of in-situ high temperature spectroscopy, high-resolution scanning electron microscopy, atomic force microscopy, cross-sectional transmission electron microscopy, and simulations using the Multiple Multipole Program approach to show that the morphological transformation of Au films proceeds via three processes exhibiting different time scales. They found that the embedding process is strongly temperature-dependent, but not dependant on the annealing atmosphere.

Discontinuous films of certain metals, such as gold, show a characteristic absorption band in the optical spectrum, attributed to excitation of localised surface plasmons, which can be influenced by the effective refractive index (RI) of the surrounding environment. This makes nanostructured metal films useful in chemical and biological sensing, as it is possible to quantify analyte binding to the metal surface by monitoring changes in the surface plasmon extinction band resulting from the local RI changes. A common problem in the preparation of reliable LSPR transducers for sensing, is poor adhesion between nanostructured Au films and substrates.

Read this HOT PCCP article today:

Mechanism of morphology transformation during annealing of nanostructured gold films on glass
Tanya Karakouz, Alexander B. Tesler, Takumi Sannomiya, Yishay Feldman, Alexander Vaskevich and Israel Rubinstein
DOI: 10.1039/C3CP50198A

Jos Oomens, Renato Zenobi and co-workers have investigated the structures and energetic properties of four common oxazine dyes using both experimental and theoretical approaches. The structural information obtained in the gas phase provides an important step towards an in-depth understanding of the fluorescent properties of the dyes.

The group studied Nile red, Nile blue A, cresyl violet and brilliant cresyl blue using both infrared multiple photon dissociation spectroscopy and quantum chemical calculations. Nile red is a commonly used probe for the investigation of many chemically important systems and, despite its well-characterised fluorescence in solution and widespread use, its gas-phase fluorescence has not been observed before. The group determined the true structure of the protonated fluorophore and, out of the many possible sites, they found that that the site of protonation of Nile red is at the carbonyl oxygen.

Significant differences can exist between the fluorescence properties of an isolated ion in the gas phase and its solvated counterpart. As these differences can be unpredictable, a definitive structural description of a gaseous flourophore is essential for the prediction of the associated fluorescent properties.

Read more in this PCCP article:

Infrared multiple photon dissociation (IRMPD) spectroscopy of oxazine dyes
Robert J. Nieckarz, Jos Oomens, Giel Berden, Pavel Sagulenko and Renato Zenobi
DOI: 10.1039/C3CP00158J