Cross‐Linking/Mass Spectrometry for Studying Protein Structures and Protein–Protein Interactions: Where Are We Now and Where Should We Go from Here?

Structural mass spectrometry (MS) is gaining increasing importance for deriving valuable three‐dimensional structural information on proteins and protein complexes, and it complements existing techniques, such as NMR spectroscopy and X‐ray crystallography. Structural MS unites different MS‐based techniques, such as hydrogen/deuterium exchange, native MS, ion‐mobility MS, protein footprinting, and chemical cross‐linking/MS, and it allows fundamental questions in structural biology to be addressed. In this Minireview, I will focus on the cross‐linking/MS strategy. This method not only delivers tertiary structural information on proteins, but is also increasingly being used to decipher protein interaction networks, both in vitro and in vivo. Cross‐linking/MS is currently one of the most promising MS‐based approaches to derive structural information on very large and transient protein assemblies and intrinsically disordered proteins.     

Where gold meets a hydrogen bond?

This is a short survey of the area of the hydrogen bonding where the noble and coinage metal gold enters its manifold of the proton acceptors. It is largely focused on the nonconventional hydrogen bonds that are formed in the complexes of the auride anion Au⁻ with HF, (HF)₂, H₂O, (H₂O)₂, NH₃, and (NH₃)₂, as mostly experimentally investigated to date. A thorough comparison of the experimental and computational data on these nonconventional hydrogen bonds is the main motif of the present work.     

Where can i find a computational chemist?

The Computational Perspective

Where can i find a computational chemist?     

The Physics and Radiochemistry of Solar Neutrino Detectors: What Have We Learned and What Can We Expect?

The situation in solar neutrino science has changed drastically in the past decade, with results now available from five neutrino experiments that use different methods to look at different regions of the solar-neutrino energy-spectrum. While the goal of all of these experiments is physics, they all rely heavily on chemistry and radiochemistry. Three of these experiments are radiochemical, the ³⁷Cl detector and the two different forms of ⁷¹Ga detectors used in GALLEX and SAGE are based on the chemical isolation and counting of the radioactive products of neutrino interactions. The other two, Kamiokande and its improved successor, Super- Kamiokande, detect neutrinos in real time; however, they also depend sensitively on radiochemistry in that (as in all the solar neutrino detectors) radioactive contaminants must be controlled at very low levels. It is noteworthy that all of these experiments (a) have detected solar neutrinos, but (b) all report deficits of the observed neutrinos relative to the predictions of standard solar models — the so-called "solar neutrino problem". In this paper, I review the basic principles of operation of these neutrino detectors, report their recent results, and discuss some of the interpretations that are now in vogue. I then describe some of the new neutrino detectors that are under construction or being developed, and discuss the kinds of new results we might expect to see in the early years of the new millennium.     

Where on Earth has our water come from?

The presence of water in the Earth has long been an enigma. However, computer modelling techniques have shown that the adsorption of water onto the fractal surfaces of interplanetary dust particles, which are present in the planetary accretion disk, is sufficiently strong to provide a viable origin of terrestrial water.     

Hairy Core–Shell Nanoparticles via RAFT: Where are the Opportunities and Where are the Problems and Challenges?

The preparation of hairy core–shell nanoparticles including (crosslinked) micelles, unimolecular micelles such as star polymers with block structures in each arm and surface grafted nanoparticles such as inorganic particles via the RAFT process are discussed. The RAFT process is certainly a highly versatile process. However, it should not be forgotten that RAFT polymerization is a process, i.e., superimposed on a conventional free radical process. Furthermore, the livingness of the process is dependent on the accessibility of the RAFT group, which can be hampered in certain approaches such as star synthesis and surface grafting from nanoparticles. Nevertheless, the RAFT process is a versatile toolbox that offers good solutions to a range of problems in the preparation of hairy nanoparticles.

     

Do We Understand the Recyclability of Ionic Liquids?

Recycling of “green” solvents : Recycling of ionic liquids with high efficiency is of key importance on going from the laboratory‐scale to large‐scale industrial application of these solvents.

     

Particle dynamics and particle heat and mass transfer in thermal plasmas. Part I. The motion of a single particle without thermal effects

A particle injected into a thermal plasma will experience a number of effects which are not present in an ordinary gas. In this paper effects exerted on the motion of a particle will be reviewed and analyzed in the context of thermal plasma processing of materials. The primary purpose of this paper is an assessment of the relative importance of various effects on particle motion.Computer experiments are described, simulating motion of a spherical particle in a laminar, confined plasma jet or in a turbulent, free plasma jet. Particle sizes range from 5 to 50 µm, and as sample materials alumina and tungsten are considered.The results indicate that (i) the correction term required for the viscous drag coefficient due to strongly varying properties is the most important factor; (ii) non-continuum effects are important for particle sizes <10 µm at atmospheric pressure and these effects will be enhanced for smaller particles and/or reduced pressures; (iii) the Basset history term is negligible, unless relatively large and light particles are considered over long processing distances; (iv) thermophoresis is not crucial for the injection of particles into thermal plasmas; (v) turbulent dispersion becomes important for particle <10 µm in diameter.     

Atomic and molecular emission spectroscopy on an expanding argon/methane plasma

A supersonically expanding cascaded arc plasma in argon is analyzed axperimentally by emission spectroscopy. The thermal cascaded arc plasma is allowed to expand through a conically shaped nozzle in the arc anode into the vacuum vessel. In the nozzle monomers (C _n H _v ) are injected. The monomers are dissociated and ionized by the argon carrier plasma, and transported toward a substrate by means of the expansion. Emission spectroscopy is used to obtain temperatures and particle densities. By varying external parameters (e.g., arc power, gas flow rates) plasma parameters can be linked with (e.g. parameters (e.g., refractive index).     

Structure and thermal behaviors of poly(vinyl alcohol)/surfactant composites: Investigation of molecular interaction and mechanism

Poly(vinyl alcohol) (PVA) is a promising biocompatible polymer, whose applicability is limited by its narrow processing window. Here, we adopted a facile approach to broaden the processing windows of PVA based on phosphoric ester of poly(ethylene oxide) (10) nonylphenyl (NP‐10P). Thermal analysis shows that both the melting temperature (T_m) and the glass transition temperature (T_g) of PVA decrease noticeably as NP‐10P content increases, indicating good miscibility of NP‐10P with PVA. The thermal degradation kinetics suggests composites display excellent thermal stability compared with neat PVA. The pyrolysis mechanism of PVA before and after modification with NP‐10P varies from chain unzipping degradation followed by chain random scission to chain random scission. The processing window of PVA is broadened from 9°C to 98°C with low content NP‐10P (5 wt%). Moreover, the composites maintain significant mechanical performance and transparency. This work provides an environmentally friendly and economical method to improve the possibility of thermal melt processing for PVA.     

Thermal plasma materials processing—Applications and opportunities

Thermal plasma processing of materials is a rapidly growing area of research. The commercialization of these processes, however, has been limited by the lack of fundamental understanding of how the various processes work. Research has historically focused on developing models of fluid flow and heat transfer to particles injected into either DC arc or RF plasma jets. These models in the past have simplified boundary conditions to meet computational limitations. Recent advances in models have now been made, allowing evaluations of more of the plasma process variables. Supersonic flow modeling in a DC jet and modeling of the effects of particle loading (particulate feed rate) have been accomplished and are reviewed here. Materials processing using thermal plasmas has been separated into the categories of synthesis, melting, and deposition, and is discussed in view of the processing effects on the resultant material structures. Process modeling leading to process understanding is reviewed with an emphasis on process control and optimization. Commercialization of plasma processes requires controls and process transducers which result from experimentation and process models. Approaches to develop process controls from the current technical base are presented.     

Manipulating morphology and orientation in thermally responsive block copolymer thin films

We demonstrate the use of combined thermal annealing and solvent vapor annealing (SVA) to tune the morphology of thermally responsive block copolymer (BCP) thin films. The BCP, poly(styrene‐b‐tert‐butyl acrylate) (PS‐b‐PtBA), undergoes a chemical deprotection to poly(styrene‐b‐acrylic anhydride) (PS‐b‐PAH) above a temperature threshold, giving rise to a structural and morphological transition. Our experiments systematically examine different thermal annealing and SVA protocols with two solvents (tetrahydrofuran and acetone) and map the resulting morphologies. Assessments of these processing protocols were accelerated using temperature gradients. Our results demonstrate that the final nanoscale morphologies after SVA are determined by the changes in the relative solvent/polymer interactions and surface tensions of the polymer blocks that accompany deprotection. Because of these driving forces, certain processing combinations led to irreversible morphological states, whereas others present opportunities for further manipulation. Accordingly, our study reveals that the morphology of this thermally sensitive BCP can be altered through judicious choice of annealing protocol. The protocols that combine equal numbers of SVA and thermal annealing (TA) steps are not necessarily equivalent, and the order of the SVA relative to TA is a deciding factor in the final morphology. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Differential scanning calorimetry (DSC) analysis of human plasma in melanoma patients with or without regional lymph node metastases

Melanoma malignum (MM) is a common type of skin cancer, and its incidence is increasing in the general population. We aimed to detect blood plasma components with differential scanning calorimetry (DSC) in 15 white adult MM patients, who had histopathologically diagnosed, operable cutaneous MM without any distant metastases. We observed that thermal changes (second T _m , calorimetric enthalpy) in blood plasma showed correlation with tumor thickness and the extent of regional invasion. Further studies are needed to elucidate these relationships, but our preliminary work has provided DSC should be a new tool for the early diagnosis and monitoring of MM patients.     

Application of TEM and XPS in the interpretation of the kinetics of deuterium evolution from ultrathin TiD<Subscript><Emphasis Type="BoldItalic">y</Emphasis></Subscript>/Pd films evaporated on quartz

The kinetics of thermal evolution of deuterium from ultrathin TiD _y /Pd bilayer films has been studied by means of thermal desorption mass spectrometry (TDMS). Using a combination of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy, we made a study of the complex structural and chemical transformations of the TiD _y /Pd film as a result of TDMS-induced evolution of deuterium and simultaneous annealing of this film. Both preparation and TDMS processing of the TiD _y /Pd bilayer films were performed in situ under UHV conditions. It was found that the high-temperature TDMS processing of an ultrathin TiD _y /Pd film, which was carried out in a relatively short time, leads to a significant film structure transformation. Energy-filtered TEM mapping of cross-section images and EDX analysis revealed extensive interdiffusion of Ti and Pd within the Ti–Pd bi-layer film. This process leads to a progressive change in chemical composition within the surface and subsurface area of the film during the TDMS processing. As the temperature of TDMS heating increases, segregation of Ti at the Pd top layer surface becomes significant. As a result, the kinetics of deuterium desorption is progressively changed during TDMS; at lower temperatures, the kinetics is limited by recombinative processes at the Pd surface, at temperatures beyond 500 K, it becomes dominated by interdiffusion of Ti into the Pd surface.     

Poly(ethylene sulfide). II. Thermal degradation and stabilization

High molecular weight poly(ethylene sulfide) undergoes severe thermal degradation at the high temperatures (220–260°C) required for processing in injection-molding equipment. Thermal degradation of the polymer is accompanied by gas evolution and a decrease in melt viscosity. Stabilization of poly(ethylene sulfide) can be effectively accomplished by addition of small concentrations of certain 1,2-polyamines, preferably together with certain zinc salts as coadditives. Use of this stabilizer system inhibits thermal degradation to a remarkable extent, making it possible to mold the polymer at these high temperatures and obtain excellent physical and mechanical properties. Investigation of the thermal degradation process was carried out. The rate at which gases evolved from unstabilized poly(ethylene sulfide) resins of various molecular weights and preparative histories and from model compounds of the same organic backbone structure was measured at temperatures ranging from 220 to 260°C. Rate of gas evolution from the resins, irrespective of chain length or preparation, was found to be constant at 230°C. The evolved gases, analyzed by infrared spectroscopy and gas chromatography, contained ethylene. Nearly identical apparent activation energies were found for the gas evolution reaction from the resin and model compounds. The ΔE^* values were in good agreement with ΔE^* determined by other techniques, 58 ± 2 kcal/mole. This is about the energy requirement expected for the homolytic cleavage of a carbon–sulfur bond of the type present in a poly(ethylene sulfide) structure. The rate and analytical data indicate that the degradative mechanism at processing (molding) temperatures is primarily due to the organic structure of the polymer. A mechanism of thermal stabilization is proposed in which the polyamine and zinc salt, in presence of molten polymer at processing temperatures, form a two-centered electron transfer complex, capable of reacting with both radicals of the homolytically cleaved bond, “healing” the scission, so to speak.     

Effects of structure on properties of some new aromatic-aliphatic polybenzimidazoles

Polybenzimidazoles were prepared in poly(phosphoric acid) from isophthalic, m- and p-phenylene diacetic, succinic, adipic, suberic, and sebacic acids and 3,3′-diaminobenzidine, 3,3′,4,4′-tetraaminodiphenyl ether and 3,3′,4,4′-tetraaminodiphenylmethane. The thermal, mechanical, and bonding properties were studied. A 3:1 copolymer of isophthalic and m-phenylenediacetic acid with 3,3′-diaminobenzidine showed the best results as far as isothermal oxidation resistance and thermal and processing characteristics.     

Improved Glass Transition Temperature towards Thermal Stability via Thiols Solvent Additive versus DIO in Polymer Solar Cells

The halogen‐free solvent additive, 1,4‐butanedithiol (BT) has been incorporated into PTB7‐Th:PC₇₁BM, leading to higher power conversion efficiency (PCE) value as well as substantially enhanced thermal stability, as compared with the traditional 1,8‐diiodooctane (DIO) additive. More importantly, the improved thermal stability after processing with BT contributes to a higher glass transition temperature (T _g) of PTB7‐Th, as determined by dynamic mechanical analysis. After thermal annealing at 130 °C in nitrogen atmosphere for 30 min, the PCE of the specimen processed with BT reduces from 9.3% to 7.1%, approaching to 80% of its original value. In contrast, the PCE of specimens processed with DIO seriously depresses from 8.3% to 3.8%. These findings demonstrate that smart utilization of low‐boiling‐point solvent additive is an effective and practical strategy to overcome thermal instability of organic solar cells via enhancing the T _g of donor polymer.