Symposium overview the Shell Conference on computer-aided molecular modelling

The Shell Conference on ... series began in 1985 and meetings are held approximately twice a year. The idea behind the conferences is to bring together invited scientists from both universities and industry, and representatives from different Shell Research laboratories, to create a forum to discuss the future directions of the chosen research area. These meetings have embraced a wide range of topics of interest to Shell Research as a whole.This particular conference, organised by the Analytical Department of the Koninklijke/ShellLaboratorium, Amsterdam (KSLA), was held on 4–6 October, 1987 at Hoenderloo in the Netherlands. The aim was to review the state-of-the-art and to discuss the future of molecular modelling and design. The programme itself consisted of a series of presentations on prescribed topics, panel discussions, and software and hardware demonstrations. Many of the presentations given consisted of overviews, experiences, advice and predictions for the future. The panel sessions, which involved the speakers within that session and a discussion leader who summarised some of the points made in an introduction, encouraged even further discussion and speculation. This overview attempts to catch the flavour of the meeting and convey some personal views that were expressed and conclusions drawn.     

High-speed color cinematography of chain self-ignition in the hydrogen,methane, and isobutylene oxidation reactions

The spatial development of chain self-ignition in the oxidation of stoichiometric mixtures of hydrogen, methane, and isobutylene with oxygen at total pressures of 10–100 Torr and T = 750–1000 K has been investigated by high-speed color cinematography. The spatial development of the chain process is governed by the properties of the reactor surface and by the heating time of the combustible mixture. A numerical simulation of the process has been carried out.     

Lewis acid catalyzed allylboration: discovery, optimization, and application to the formation of stereogenic quaternary carbon centers

A full account of the development of the first catalytic manifold for the additions of allylboronates to aldehydes is described. The thermal additions (both diastereospecific and enantioselective) of 2-carboxyester 3,3-disubstituted allylboronates 1 to both aromatic and aliphatic aldehydes give biologically and synthetically important exo-methylene butyrolactones 2 containing a beta-quaternary carbon center. Although the thermal reaction requires 14 d at room temperature to reach completion, the presence of certain metal salts allows for a 12-16 h reaction while preserving the diastereospecificity observed in the uncatalyzed process. Preliminary mechanistic studies on the origin of the catalytic effect are described as well as stereoselective transformations of lactones 2 into cyclic and acyclic stereotriads with potential usefulness as synthetic intermediates.     

5-Hydroxymethylcytosine, the sixth base of the genome

5-Hydroxymethylcytosine (hmC) was recently discovered as a new constituent of mammalian DNA. Besides 5-methylcytosine (mC), it is the only other modified base in higher organisms. The discovery is of enormous importance because it shows that the methylation of cytosines to imprint epigenetic information is not a final chemical step that leads to gene silencing but that further chemistry occurs at the methyl group that might have regulatory function. Recent progress in hmC detection--most notably LC-MS and glucosyltransferase assays--helped to decipher the precise distribution of hmC in the body. This led to the surprising finding that, in contrast to constant mC levels, the hmC levels are strongly tissue-specific. The highest values of hmC are found in the central nervous system. It was furthermore discovered that hmC is involved in regulating the pluripotency of stem cells and that it is connected to the processes of cellular development and carcinogenesis. Evidence is currently accumulating that hmC may not exclusively be an intermediate of an active demethylation process, but that it functions instead as an important epigenetic marker.     

Thermodynamics in process development in the chemical industry - importance, benefits, current state and future development

Phase equilibrium thermodynamics is one of the most important fundamental sciences for process development in the chemical industry. The outstanding results achieved by thermodynamics in the last decades have let to a profound change in working methods for the development of thermal separation processes. However, there remains a large number of unsolved problems in the field of phase equilibrium thermodynamics which often represent a significant restriction to process development for the chemical engineer. Current deficiencies are illustrated with some significant examples and desired developments for the future are suggested.     

A foldamer at the liquid/graphite interface: the effect of interfacial interactions, solvent, concentration, and temperature

The unfolding process and self-assembly of a foldable oligomer (foldamer 1) at the liquid/graphite interface were investigated by scanning tunnelling microscopy. At the level of molecular conformation, we identified several molecular conformations (A(z), B, C, D, E) that represent intermediate states during unfolding, which may help to elucidate the unfolding process at the liquid/graphite interface. Adsorption at the interface traps the intermediate states of the unfolding process, and STM has proved to be a powerful technique for investigating folding and unfolding of a foldamer at the molecular level, which are not accessible by other methods. The STM observations also revealed that varying the solvent and/or concentration results in different self-assemblies of foldamer 1 as a result of variations in molecular conformations. The solvent and concentration effects were attributed to the changes in existing states (extended or folded) of foldamers in solution, which in turn affect the distribution of adsorbed molecular conformations at the interface. This mechanism is quite different from other systems in which solvent and concentration effects were also observed.     

Enzymatic modification of lignocellulosic substances for the production of fiberboards

The object of the research is the development of enzyme systems for the enzymatic modification of wood fiber materials as well as fiber materials from annual plants for the production of glue-free fiberboards. The project is aimed first at the process development for the enzymatic modification and second at the development of cellulase/hemicellulase complexes on the basis of stillage as a substrate and inducer for the enzymatic modification. The results demonstrate that it is possible to substitute synthetic resins by means of activation and biocatalytic cross-linking of fibers with hydrolytic enzyme systems, in particular, for the production of medium-density fiberboards. The article is published in the original.     

In between worlds: G.N. Lewis, the shared pair bond and its multifarious contexts

In this paper, I will look at the rather convoluted discovery process which gave birth to the concept of the shared electron pair bond as developed by G.N. Lewis, to be subsequently appropriated by the American founders of quantum chemistry, and highlight the complex relations between conceptual development and the different contexts in which ideas are created and presented. I will show how the successive installments of Lewis's model of the chemical bond were supported by and gained credence from an epistemological background in which Lewis explored the relations of chemistry to physics. Furthermore, they were shaped by the changing public contexts in which the successive metamorphoses of the ideas took place and their epistemological background was outlined and explored. The complexities which are always associated with a discovery process can therefore be illuminated if one pays attention to different interactive realms-the conceptual, epistemological, and the presentational one.     

Separation, characterization, and quantitation of process-related substances of the anti-hypertensive drug doxazosin mesylate by reversed-phase LC with PDA and ESI-MS as detectors

A simple and rapid reversed-phase liquid chromatography (LC) method with photodiode array (PDA) and electrospray ionization (ESI)-mass spectrometry (MS) as detectors was developed and validated to separate, identify, and quantitate the related substances of Doxazosin mesylate (DXZN) for monitoring the reactions involved during process development. The high-performance liquid chromatography profiles of related-substances of DXZN are used as fingerprints to follow the procedures used in the manufacturing units. The separation is accomplished on an Inertsil ODS-3 column with acetonitrile-ammonium acetate (10 mM, pH 4.0) as the mobile phase, using a gradient elution mode and monitoring the eluents by a photodiode array detector at 265 nm at ambient temperature. LC-ESI-MS-MS is used to identify the additional impurities formed during the synthesis. The identified impurities were synthesized and characterized by UV, Fourier transform-IR, 1H NMR, and MS data. The detection limits for the impurities are 0.74 - 4.14 x 10(-9) g, and the method is found to be suitable not only for the monitoring of synthetic reactions, but also for quality assurance of DXZN in bulk drugs and formulations.     

Nonaqueous Lyotropic Ionic Liquid Crystals: Preparation,Characterization, and Application in Extraction

A class of new ionic liquid (IL)‐based nonaqueous lyotropic liquid crystals (LLCs) and the development of an efficient IL extraction process based on LC chemistry are reported. The nonaqueous LLCs feature extraordinarily high extraction capacity, excellent separation selectivity, easy recovery, and biocompatibility. This work also demonstrates that the introduction of self‐assembled anisotropic nanostructures into an IL system is an efficient way to overcome the intrinsically strong polarity of ILs and enhances the molecular recognition ability of ILs. The distribution coefficients of IL‐based LLCs for organic compounds with H‐bond donors reached unprecedented values of 50–60 at very high feed concentrations (>100 mg mL^?1), which are 800–1000 times greater than those of common ILs as well as traditional organic and polymer extractants. The IL‐based nonaqueous LLCs combining the unique properties of ILs and LCs open a new avenue for the development of high‐performance extraction methods.     

The recirculation zone at the entrance of a falling liquid film: Consequences for the surfactant adsorption problem

When a surfactant solution emerges from a slot to form a falling liquid film, an adsorption process occurs which generates a gradient in surface concentration. This concentration gradient gives rise to a gradient in the surface tension which retards the development of the velocity profile. Experimental measurements of the surface velocity, theoretical analysis of the adsorption process, and visual observation of the entrance region all indicate the existence of a double-vortex recirculation zone at the head of the entrance region. The surfactant adsorption process is largely controlled by the flow field in the recirculation zone as the downstream vortex provides a mechanism of convective transport from the bulk to the surface phase.     

Separation of the unique proteins of wheat protein fractions by capillary electrophoresis

Summary The wheat maturation process was monitored by high-performance capillary electrophoresis. The different protein components of the albumin, globulin, gliadin and glutenin fractions from the Osborne extraction procedure were analysed. The wheat sample was a Hungarian winter wheat, cultivar Martonvásári 23. The protein fractions were analysed by capillary zone electrophoresis using a low pH phosphate buffer containing a polymeric additive and organic modifiers. The albumins and gliadins as well as glutenins showed a characteristic pattern of development during the maturation process. For these fractions the development occurred at different stages of maturation. The formation of protein fractions of wheat at different stages of maturation—and thus the entire maturation process—could be well characterised by high-performance capillary electrophoresis. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September, 1–3, 1999     

Principles of Water Electrolysis and Recent Progress in Cobalt-, Nickel-, and Iron-Based Oxides for the Oxygen Evolution Reaction

Water electrolysis that results in green hydrogen is the key process towards a circular economy. The supply of sustainable electricity and availability of oxygen evolution reaction (OER) electrocatalysts are the main bottlenecks of the process for large-scale production of green hydrogen. A broad range of OER electrocatalysts have been explored to decrease the overpotential and boost the kinetics of this sluggish half-reaction. Co-, Ni-, and Fe-based catalysts have been considered to be potential candidates to replace noble metals due to their tunable 3d electron configuration and spin state, versatility in terms of crystal and electronic structures, as well as abundance in nature. This Review provides some basic principles of water electrolysis, key aspects of OER, and significant criteria for the development of the catalysts. It provides also some insights on recent advances of Co-, Ni-, and Fe-based oxides and a brief perspective on green hydrogen production and the challenges of water electrolysis.     

Chemical,technological, and rheological properties of hydrocolloids from sesame (Sesamum indicum) with potential food applications

BackgroundHydrocolloids are hydrophilic biopolymers which are widely used in the food industry due to their functional properties. In the present study, sesame hydrocolloids (Sesamum indicum) were obtained and, consequently, their physicochemical, proximal composition, functional, and rheological properties were evaluated to establish their potential applications in the food industry. Methods: Hydrocolloids were obtained from sesame seeds at 80 °C on evaluating the pH at 3, 7, and 10 and specific flour: water ratios during the solubilization process. Results: The hydrocolloids obtained had a good relationship between carbohydrates and proteins, which increased their potential use in the development of colloidal systems. The samples had high water holding capacity, solubility, and appropriate emulsifying and foaming properties. The hydrocolloids showed non-Newtonian shear-thinning behavior, adjusted to the Carreau-Yasuda model. Based on the dynamic viscoelastic rheological test, samples were characterized as a gel-like state when storage modulus values were higher than the loss modulus in the frequency and temperature ranges investigated. Conclusion: The findings revealed that sesame seeds can be considered appropriate raw material for extracting hydrocolloids as an alternative for obtaining natural food ingredients with interesting functional and rheological properties, with further applications in the development and formulation of micro-structured products.     

A validation concept for purity determination and assay in the pharmaceutical industry using measurement uncertainty and statistical process control

 The analytical chemists in process development in the pharmaceutical industry have to solve the difficult problem of producing high quality methods for purity determination and assay within a short time without a clear definition of the substance to be analyzed. Therefore the quality management is very difficult. The ideal situation would be that every method is validated before use. This is not possible because this would delay the development process. A process-type quality development approach with an estimation type fast validation (measurement uncertainty) is therefore suggested. The quality management process consists of the estimation of measurement uncertainty for early project status. Statistical process control (SPC) is started directly after measurement uncertainty estimation and a classical validation for the end of the project. By this approach a process is defined that allows a fast and cost-efficient way of supporting the development process with the appropriate quality at the end of the process and provides the transparency needed in the development process. The procedure presented tries to solve the problem of the parallelism between the two development processes (chemical and analytical development) by speeding up the analytical development process initially. Received: 25 March 1997 · Accepted: 17 May 1997     

Recent advances in the polymerisation of propylene

Since its discovery, the field of olefin polymerization using Ziegler-Natta catalysts has undergone rapid development both in terms of industrial catalysis as well as fundamental understanding of this polymerization process. This paper reviews some aspects of the recent developments with specific regard to propylene polymerizations. Presented at the Symposium on ’Polymer Science and Engineering during the Annual Meeting of the Academy, Nainital, October 1982     

Fluid Extraction of Hops,Spices, and Tobacco with Supercritical Gases

This report provides an introduction to the principal methods of extraction with supercritical gases, illustrated by the processing of some natural products with carbon dioxide. The combination of pressure and temperature as process parameters makes it possible to vary the solvent power of the medium within certain ranges as desired without having to change the composition of the solvent, as would be necessary in conventional solvent extraction. The problem-free handling of carbon dioxide and also of the products obtained open up possibilities whose development has only just started.     

Block copolymer solution self-assembly: Recent advances,emerging trends,and applications

The self-assembly process of block copolymers (BCPs) in solution has been at the focus of extended scientific research over the past several decades owing to the astonishing morphological diversity and attainable complexity of the resulting nanoassemblies, including spheres, cylinders, lamellae, vesicles, and many other complex, bicontinuous or even hierarchical structures. The ever-increasing sophistication in the development of synthetic chemistry methods and techniques has led to a myriad of available macromolecules with varying chemical compositions, architectures, features, and properties. This assortment of characteristics has led in turn to a plethora of intriguing self-organized polymeric nanostructures, with countless possible applications in several nanotechnological fields relevant to physics, chemistry, material science, nanomedicine, and biomaterials. The present review aims to illuminate the importance and fascinating potential of BCPs solution self-assembly by highlighting recent advances and emerging trends in the field, as well as significant application-oriented progress, through characteristic contemporary examples.