The analysis of C4–C11 hydrocarbons in naphtha and reformate with a new apolar fused silica column

This paper deals with the separation of alkanes, naphthenes, and aromatic compounds in naphtha and reformate, on a newly developed apolar high resolution GC column. The selectivity of this apolar phase has been compared with those of squalane, DB-1, and SE-30. A total of 95 hydrocarbons were reliably identified, mostly by GC-MS. Repeated measurements of Kováts retention indices are presented as evidence for the reproducible manufacture of fused silica columns coated with this phase.     

Thin surfactant layers at the solid interface

The formation of surfactant layers on solid surfaces is an important process in many industrial applications. The structure of these layers influences the properties of the solid in processing and use. We summarize the literature data on the structure of surfactant layers at the solid/liquid interface and our own results characterizing the interactions between solid surfaces and solutions or emulsions. Ideas are presented for the processes taking place at the solid surface during drying by heat treatment. An outlook is given of how to investigate surfactant layers on dry surfaces. Received: 11 July 1999/Accepted: 2 May 2000     

Filterable Agents for Hyperpolarization of Water,Metabolites, and Proteins

Hyperpolarization is generated by dissolution dynamic nuclear polarization (d‐DNP) using a polymer‐based polarizing agent dubbed FLAP (filterable labeled agents for polarization). It consists of a thermo‐responsive poly(N‐isopropylacrylamide), also known as pNiPAM‐COOH, labeled with nitroxide radicals. The polymer powder is impregnated with an arbitrary solution of interest and frozen as is. Dissolution is followed by a simple filtration, leading to hyperpolarized solutions free from any contaminants. We demonstrated the use of FLAP to hyperpolarize partially deuterated water up to P(¹H)=6 % with a long relaxation T₁ >36 s characteristic of high purity. Water hyperpolarization can be transferred to drugs, metabolites, or proteins that are waiting in an NMR spectrometer, either by exchange of labile protons or through intermolecular Overhauser effects. We also show that FLAPs are suitable polarizing agents for ¹³C‐labeled metabolites such as pyruvate, acetate, and alanine.     

EXPERIMENTAL STUDY OF CONVECTIVE HEAT TRANSFER INSTABILITIES IN TRANSIENT RESPONSE ALONG A COUNTERCURRENT HEAT EXCHANGER

This article deals with experimental investigations to reveal the effect of combined natural and forced convection in a horizontal tubular countercurrent heat exchanger in both transient and steady states. In transient response, the temperature profiles of hot fluid in a cross section of the inner tube show the influence of buoyancy forces and radial conduction. These profiles are distorted in time and lead to the appearance of oscillating temperature along the inner tube of the heat exchanger. The transient Richardson dimensionless number is calculated to show these effects. Also, a spectral analysis using the discrete Fourier transform has been performed to characterize these temperature instabilities. Using this technique, the influence of flow rates of hot and cold fluids is investigated.     

Environment-Responsive Peptide Dimers Bind and Stabilize Double-Stranded RNA

Double-stranded RNAs (dsRNA) possess immense potential for biomedical applications. However, their therapeutic utility is limited by low stability and poor cellular uptake. Different strategies have been explored to enhance the stability of dsRNA, including the incorporation of modified nucleotides, and the use of diverse carrier systems. Nevertheless, these have not resulted in a broadly applicable approach thereby preventing the wide-spread application of dsRNA for therapeutic purposes. Herein, we report the design of dimeric stapled peptides based on the RNA-binding protein TAV2b. These dimers are obtained via disulfide formation and mimic the natural TAV2b assembly. They bind and stabilize dsRNA in the presence of serum, protecting it from degradation. In addition, peptide binding also promotes cellular uptake of dsRNA. Importantly, peptide dimers monomerize under reducing conditions which results in a loss of RNA binding. These findings highlight the potential of peptide-based RNA binders for the stabilization and protection of dsRNA, representing an appealing strategy towards the environment-triggered release of RNA. This can broaden the applicability of dsRNA, such as short interfering RNAs (siRNA), for therapeutic applications.     

The aid of calorimetry for kinetic and thermal study

Journal of Thermal Analysis and Calorimetry - Phosphoric acid, a non-renewable chemical, is used in different industries. Production of this chemical from natural phosphate can be done by two...     

Thermal risk assessment for the epoxidation of linseed oil by classical Prisleschajew epoxidation and by direct epoxidation by H2O2 on alumina

Journal of Thermal Analysis and Calorimetry - Substitution of fossil feedstock by vegetable oils is growing due to environmental constraints and oil depletion. Among the different valorization...     

On the problem of water adsorption on alkali halide cleavage planes,investigated by secondary ion mass spectroscopy

In the epitaxial growth of thin metallic films, atomic beam scattering and other work on (001) cleavage planes of alkali halides, the problem of water adsorption (physically or chemically) and its consequences often arose. In this paper (001) planes of LiF, NaF and NaCl were investigated in a UHV apparatus by secondary ion mass spectroscopy (SIMS) under a variety of conditions: air and vacuum cleaved, with and without heat annealing, with and without exposure to water at various crystal temperatures. The main results are: cleaved crystal surfaces are free of water and hydroxide layers even in the submonolayer region under UHV conditions. Water vapour at a partial pressure of 10^?9 Torr will only adsorb on cooled cleavage planes: for LiF below 200 K, for NaF below 250 K and for NaCl below 260 K, the adsorption energy for the fluorides being in the 200 meV region. Thicker layers of adsorbed water on LiF (001) will grow according to the Weber-Volmer mechanism. The formation of hydroxide layers on the fluorides is possible only under extremely forced conditions. Direct evidence is given that the “active sites” for the adsorption of H₂O consist in surplus Li metal atoms on the surface. Heat treatment in UHV at temperatures up to the melting point for several hours removes these active sites and yields crystal surfaces which do not adsorb water even if cooled. Cleavage planes of the water soluble NaCl showed a somewhat different behaviour.     

Direct profiling of myelinated and demyelinated regions in mouse brain by imaging mass spectrometry

One of the newly developed imaging mass spectrometry (IMS) technologies utilizes matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to map proteins in thin tissue sections. In this study, we evaluated the power of MALDI IMS as we developed it in our (Bruker) MALDI TOF (Reflex IV) and TOF-TOF (Ultraflex II) systems to study myelin patterns in the mouse central nervous system under normal and pathological conditions. MALDI IMS was applied to assess myelin basic protein (MBP) isoform-specific profiles in different regions throughout the mouse brain. The distribution of ions of m/z 14,144 and 18,447 displayed a striking resemblance with white matter histology and were identified as MBP isoform 8 and 5, respectively. In addition, we demonstrated a significant reduction of the MBP-8 peak intensity upon MALDI IMS analysis of focal ethidium bromide-induced demyelinated brain areas. Our MS images were validated by immunohistochemistry using MBP antibodies. This study underscores the potential of MALDI IMS to study the contribution of MBP to demyelinating diseases.     

Identification of new regional marker proteins to map mouse brain by 2-D difference gel electrophoresis screening

To screen for new region-specific protein markers we compared the proteome maps of the primary visual and somatosensory areas V1 and S1 in mouse brain using 2-D difference gel electrophoresis (2-D DIGE). Twenty-three protein spots showed a statistically significant difference in expression level between V1 and S1, with 52% appearing more abundantly in V1. Twenty-six proteins were mass spectrometrically identified in 22 spots. To assess the validity of this list of potential areal markers generated by 2-D DIGE, the effective area-specific distribution profile of creatine kinase brain subtype (CKB), a protein with a clearly higher expression level in S1, was monitored with in situ hybridization. The mRNA expression profile of CKB displayed a clear area-specific distribution, which allowed demarcation of S1 and its topographical borders with neighboring neocortical areas. This proteomic study demonstrates the innovative application of 2-D DIGE and MS to select new regional markers for neuroscience research.