PCCP Blog

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

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

Diau, Yeh et al. studied the effects of the 4-tert-butylpyridine (TBP) additive in the electrolyte on the performance of two different porphyrin sensitizers from both photoelectric and photophysical points of views.

The scientists from Taiwan carried out time-resolved investigations of thin-film samples using femtosecond fluorescence up-conversion spectroscopy, charge extraction and transient photoelectric measurements of the corresponding devices. The two push-pull porphyrin sensitizers, which had different anchoring groups, showed similar device performance without TBP. Upon addition of TBP, the power conversion efficiency of the device containing one dye increased, and the device containing the other decreased.

Read more in this HOT PCCP article today:

The influence of electron injection and charge recombination kinetics on the performance of porphyrin-sensitized solar cells: effects of the 4-tert-butylpyridine additive
Yu-Cheng Chang, Hui-Ping Wu, Nagannagari Masi Reddy, Hsuan-Wei Lee, Hsueh-Pei Lu, Chen-Yu Yeh and Eric Wei-Guang Diau
DOI: 10.1039/C3CP44555K

Scientists from Wuhan University of Technology have found that the visible-light absorption and photocatalytic activities of B-, C- and B/C-doped anatase TiO₂ are not only influenced by the energy gaps and the distributions of energy states, but also by the locations of Fermi levels and the energies of the band gap edges. They also found that the stability of the doped TiO2 was dependant on its growth conditions.

Jiaguo Yu, Peng Zhou and Qin Li used density functional theory calculations to investigate the structures, formation energies and electronic properties of B-, C- and B/C-doped anatase TiO2. Their study provides insights into the design and synthesis of multi-doped TiO2 with desirable electronic properties, important in areas such as heterogeneous catalysis.

Read this HOT article:

New insight into the enhanced visible-light photocatalytic activities of B-, C- and B/C-doped anatase TiO2 by first-principles
Jiaguo Yu, Peng Zhou and Qin Li
DOI: 10.1039/C3CP44651D

Remi Chauvin and Christine Lepetit give the topological resonance energy (TRE) acyclic reference of any π-cyclic molecule, for 36 years merely defined by an abstract matching polynomial, a real chemical structure: the Mobius-twisted head-to-tail metathesis cyclo-dimer of the parent ring.

The aromaticity of a cyclically conjugated molecular system can be qualitatively defined as its tendency to resist the loss of its cyclic character under constraint or relief of external perturbations, or fundamentally quantified as the difference between the energy of the cyclic system and the energy of some acyclic reference. This acyclic reference is rigorously defined as the abstract reference of the TRE, but might not exist as a chemical species. In their recent PCCP paper, Chauvin and Lepitit report the long-sought chemical nature of TRE, and of topological aromaticity.

Read the details in this HOT article today:

The fundamental chemical equation of aromaticity
Remi Chauvin and Christine Lepetit
DOI: 10.1039/C2CP44075J

Hernandez and Schmidt investigate the role of anisotropic water-carbon interactions on water in low-diameter carbon nanotubes (CNTs) in their recent PCCP paper, and demonstrate the importance of the anisotropy. Extensive simulations provide a comprehensive picture of the effects of the interaction anisotropy on the structure and dynamics of water confined in narrow, single-walled CNTs.

Carbon based materials are generally accepted as being hydrophobic, but the calculated water-graphene interaction is found to be non-negligible and, moreover, orientation-dependant. The authors firstly calibrated new parameters for a Lennard-Jones potential, emphasising the anisotropy in the carbon-water interaction. They then performed molecular dynamics studies, using these parameters, of water inside various CNTs to examine properties such as structure, Lindemann index, mean square displacements and H-bonding patterns.

In contrast to previous simulations employing spherical interaction models, they found that the water molecules tend to form denser clusters displaying liquid-like behaviour, allowing for self-diffusion along the CNT axis.

Structures and hydrogen-bonding networks of water molecules inside CNTs can be radically different to those found in bulk water, due to the fact that the water molecules are confined in tubes with diameters not much larger than their own size. A central issue in many applications of CNTs is the possibility of conveying or storing fluids, hence the importance of understanding these systems.

Read about these fascinating results in this article:

Anisotropy of the Water-Carbon Interaction: Molecular Simulations of Water in Low-Diameter Carbon Nano-Tubes
Burkhard Schmidt
DOI: 10.1039/C3CP44278K

A recent theoretical study by Zhijan Wu, Aimin Ren and co-workers predicts novel BODIPY derivatives with interesting and potentially very useful nonlinear optical properties.

The group studied a series of aza-BODIPY fluorophores with structures expected to have large two-photon cross-sections at telecommunication wavelengths. They found that it is possible to finely tune the linear and non-linear optical properties by chemical modification of the aza-BODIPY core and peripheral moieties, resulting in excellent, original candidates for nonlinear transmission and fluorescent labelling materials.

Read the full paper:

New insights into two-photon absorption properties of functionalized aza-BODIPY dyes at telecommunication wavelengths: a theoretical study
Xiaoting Liu, Jilong Zhang, Kai Li, Xiaobo Sun, Zhijian Wu, Aimin Ren and Jikang Feng
DOI: 10.1039/C3CP44435J

Janina Kneipp and co-authors report SERS spectra of hemoglobin using silver and gold nanoparticles in red blood cells in their recent PCCP paper, which shed light on the interactions of nanoparticles with red blood cells.

The group used small nanoparticle concentrations compared to the concentration of hemoglobin molecules, similar to the situation upon nanoparticle entry into the hemoglobin-rich environment of the red blood cell. They demonstrated the dependence of the SERS spectra on the type and size of nanoparticle used as the SERS substrate. They confirmed that the nanoparticles interact with blood cells via interaction with hemoglobin and are also in contact with many other red blood cell components. Interestingly, the evidence shows nanoparticle-induced structural changes in the lipid bilayer of the red blood cells.

Understanding these interactions are of great importance, as silver nanoparticles, found everywhere in everyday life, display high cytotoxicity. The uptake of nanoparticles into red blood is also intriguing as it does not occur by endocytosis.

Read the detail in this article today:

SERS reveals the specific interaction of silver and gold nanoparticles with hemoglobin and red blood cell components
Daniela Drescher, Tina Büchner, Don McNaughton and Janina Kneipp
DOI: 10.1039/C3CP43883J

If you enjoyed this article, keep an eye out for our themed issue on plasmonics and spectroscopy, which is soon to be published.