Ion spectroscopy: Where did it come from; where is it now; and where is it going?

The ASMS conference on ion spectroscopy brought together at Asilomar on October 16–20, 2009 a large group of mass spectrometrists working in the area of ion spectroscopy. In this introduction to the field, we provide a brief history, its current state, and where it is going. Ion spectroscopy of intermediate size molecules began with photoelectron spectroscopy in the 1960s, while electronic spectroscopy of ions using the photodissociation “action spectroscopic” mode became active in the next decade. These approaches remained for many years the main source of information about ionization energies, electronic states, and electronic transitions of ions. In recent years, high-resolution laser techniques coupled with pulsed field ionization and sample cooling in molecular beams have provided high precision ionization energies and vibrational frequencies of small to intermediate sized molecules, including a number of radicals. More recently, optical parametric oscillator (OPO) IR lasers and free electron lasers have been developed and employed to record the IR spectra of molecular ions in either molecular beams or ion traps. These results, in combination with theoretical ab initio molecular orbital (MO) methods, are providing unprecedented structural and energetic information about gas-phase ions.     

Fluorine in the Earth and the solar system,where does it come from and can it be found?

This review (1) presents a summary of the distribution of fluorine in different fluid (surficial, subterranean, metamorphic, and magmatic–hydrothermal–geothermal) and solid (oceanic and continental crust, mantle, and core) domains of the Earth, and various extraterrestrial materials and bodies (meteorites, planets and moons, and the Sun); (2) it provides an estimate of the total fluorine abundance for the Earth and in its dominant reservoirs contributing to the Earth's fluorine endowment; and (3) it discusses key observations that could further improve our understanding of fluorine abundances and geochemical systematics.     

Metrology for metalloproteins—where are we now, where are we heading?

The use of the amount of certain proteins in biological samples as markers for distinguishing between a healthy and a diseased state has become increasingly important in clinical diagnosis. As about 30 % of all proteins contain metals in one form or another, either as a cofactor or covalently bound as part of the protein, some of these proteins are regularly analyzed in clinical laboratories. With the increasing number of measurements of those proteins performed all over the world, the necessity of obtaining reliable and comparable results is becoming a focal point for scientists and politicians. Directives such as the EC directive covering in vitro diagnostic medical devices (Directive 98/79/EC) and standards such as EN ISO 17511:2003 demand the traceability of the results obtained for analytes in samples of human origin. However, no reference measurement procedures with results traceable to the SI exist for many metalloproteins. In this article, the situation for a few important metalloproteins, such as hemoglobin, transferrin, superoxide dismutase, ceruloplasmin, and C-reactive protein, for which specific efforts have been made in recent years to achieve comparable and traceable results worldwide, is discussed. These proteins also serve as examples of the difficulties scientists face when they wish to quantify proteins and the pitfalls they should avoid to achieve reliable results.

The impact of flow injection on modern chemical analysis: has it fulfilled our expectations? And where are we going?

Presenting a condensation of the opening lecture of the 12th ICFIA conference, this communication presents a view of the impact that flow injection analysis (FIA) has had on modern analytical chemistry, evaluated both within the academic community and outside it, i.e. in “industry”. The ensuing developments of FIA, encompassing sequential injection analysis (SIA) and bead injection lab-on-valve (BI-LOV), are described and their individual features discussed. Finally, some recent results of the activities from the author’s own research group are briefly mentioned.     

Five-coordinate Fe(III)NO and Fe(II)CO porphyrinates: where are the electrons and why does it matter?

Recent years have seen dramatic growth in our understanding of the biological roles of nitric oxide (NO). Yet, the fundamental underpinnings of its reactivities with transition metal centers in proteins and enzymes, the stabilities of their structures, and the relationships between structure and reactivity remains, to a significant extent, elusive. This is especially true for the so-called ferric heme nitrosyls ([FeNO](6) in the Enemark-Feltham scheme). The Fe-CO and C-O bond strengths in the isoelectronic ferrous carbonyl complexes are widely recognized to be inversely correlated and sensitive to structural, environmental, and electronic factors. On the other hand, the Fe-NO and N-O bonds in [FeNO](6) heme complexes exhibit seemingly inconsistent behavior in response to varying structure and environment. This report contains resonance Raman and density functional theory results that suggest a new model for FeNO bonding in five-coordinate [FeNO](6) complexes. On the basis of resonance Raman and FTIR data, a direct correlation between the nu(Fe)(-)(NO) and nu(N)(-)(O) frequencies of [Fe(OEP)NO](ClO(4)) and [Fe(OEP)NO](ClO(4)).CHCl(3) (two crystal forms of the same complex) has been established. Density functional theory calculations show that the relationship between Fe-NO and N-O bond strengths is responsive to FeNO electron density in three molecular orbitals. The highest energy orbital of the three is sigma-antibonding with respect to the entire FeNO unit. The other two comprise a lower-energy, degenerate, or nearly degenerate pair that is pi-bonding with respect to Fe-NO and pi-antibonding with respect to N-O. The relative sensitivities of the electron density distributions in these orbitals are shown to be consistent with all published indicators of Fe-N-O bond strengths and angles, including the examples reported here.     

O-alkyl resorcarenes: where are we now?

This review describes the current position in the emerging field of direct synthesis of O-alkyl resorcarenes through the use of O-protected precursors. The use of this approach for the selective synthesis of the diastereoisomers of resorc[4]arenes, the synthesis of parent resorcarenes and pyrogalloranes and the preparation of chiral partially alkylated resorc[4]arenes are highlighted. The applications of such molecules, with regard to their role as ligand platforms, for binding of cations, organic electron acceptors and in chiral discrimination are discussed.     

Metrological traceability: I make it 42; you make it 42; but is it the same 42?

The paper reproduces a talk given at a 2-day symposium on quality assurance in chemistry held in Brisbane, Australia in 2005. Intended for an audience of analysts in the field, the theme of the symposium drew inspiration from the series of books by Douglas Adams “The Hitchhiker's Guide to the Galaxy”. An introduction to basic concepts of metrological traceability is followed by a discussion of practical steps to ensure metrological traceability of field measurement results. The relationship between metrological traceability and comparability of measurement results is discussed. To achieve metrological traceability in the field, the use of appropriate certified reference materials for calibration is recommended. Examples of atmospheric carbon dioxide and roadside breathalyzer measurements are given.

Improving the intrinsic activity of electrocatalysts for sustainable energy conversion: where are we and where can we go?

As we are in the midst of a climate crisis, there is an urgent need to transition to the sustainable production of fuels and chemicals. A promising strategy towards this transition is to use renewable energy for the electrochemical conversion of abundant molecules present in the earth''s atmosphere such as H₂O, O₂, N₂ and CO₂, to synthetic fuels and chemicals. A cornerstone to this strategy is the development of earth abundant electrocatalysts with high intrinsic activity towards the desired products. In this perspective, we discuss the importance and challenges involved in the estimation of intrinsic activity both from the experimental and theoretical front. Through a thorough analysis of published data, we find that only modest improvements in intrinsic activity of electrocatalysts have been achieved in the past two decades which necessitates the need for a paradigm shift in electrocatalyst design. To this end, we highlight opportunities offered by tuning three components of the electrochemical environment: cations, buffering anions and the electrolyte pH. These components can significantly alter catalytic activity as demonstrated using several examples, and bring us a step closer towards complete system level optimization of electrochemical routes to sustainable energy conversion.

We evaluate the improvements over the past two decades in intrinsic activity of electrocatalysts for sustainable energy conversion, and highlight opportunities from tuning the electrolyte.     

PDLC shutters: where has this technology gone?

A Commentary on the paper ”Response times and voltages for PDLC shutters?, by Bao‐Gang Wu, John H. Erdman and J. William Doane. First published in Liquid Crystals, 5, 1453‐1465 (1989).     

An insight into iTRAQ: where do we stand now?

The iTRAQ (isobaric tags for relative and absolute quantification) technique is widely employed in proteomic workflows requiring relative quantification. Here, we review the iTRAQ literature; in particular, we focus on iTRAQ usage in relation to other commonly used quantitative techniques e.g. stable isotope labelling in culture (SILAC), label-free methods and selected reaction monitoring (SRM). As a result, we identify several issues arising with respect to iTRAQ. Perhaps frustratingly, iTRAQ's attractiveness has been undermined by a number of technical and analytical limitations: it may not be truly quantitative, as the changes in abundance reported will generally be underestimated. We discuss weaknesses and strengths of iTRAQ as a methodology for relative quantification in the light of this and other technical issues. We focus on technical developments targeted at iTRAQ accuracy and precision, use of 4-plex over 8-plex reagents and application of iTRAQ to post-translational modification (PTM) workflows. We also discuss iTRAQ in relation to label-free approaches, to which iTRAQ is losing ground.     

Diet and metabolic syndrome: where does resistant starch fit in?

Metabolic syndrome is a term linking the clinical profiles of some of the world's major health problems today: obesity, heart disease, and diabetes. It is predicated on dietary patterns, and particularly on the delivery of fuel. The effects may be seen first in the development of abdominal obesity and insulin resistance leading to Type 2 diabetes mellitus and coronary heart disease. This review examines the role resistant starch might play in the prevention and management of these conditions. Beginning with a definition of resistant starch, a critical review of the scientific literature is presented. Current knowledge suggests that resistant starch in the diet may assist in the prevention and management of conditions associated with the metabolic syndrome via its potential effects on delaying the delivery of glucose as fuel with subsequent fat utilization and appetite control benefits. There is still a great deal of research to be undertaken in this area, but it is clearly warranted, given the position of starches in the global food supply and the potential impact on population health.     

Nonlinear electrophoresis of point-like particles--is it possible?

A new universal method for the generation of nonlinear electrophoretic mobility of a packet of any particles is suggested. The method is based on the investigation of particle packet dynamics under the influence of an external force. The system under consideration is a homogeneous and isotropic medium with traps for these particles. Packet dynamics is described by a linear diffusion equation. The measured packet parameters are the position and the velocity of a packet maximum. It is shown that these parameters are nonlinear in the external field under definite limitations on the trap properties. This statement is proved both theoretically and experimentally for the simple model of diffusive substrate, the so-called comb structure. The prospects of designing new supporting substrates (microfluidic systems) with a nonlinear response are discussed.     

A decade of yeast surface display technology: where are we now?

Yeast surface display has become an increasingly popular tool for protein engineering and library screening applications. Recent advances have greatly expanded the capability of yeast surface display, and are highlighted by cell-based selections, epitope mapping, cDNA library screening, and cell adhesion engineering. In this review, we discuss the state-of-the-art yeast display methodologies and the rapidly expanding set of applications afforded by this technology.     

High-resolution continuum source graphite furnace atomic absorption spectrometry: Is it as good as it sounds? A critical review

The recent arrival of high-resolution continuum source atomic absorption spectrometry represents a potential revolution in this field, in particular for direct analysis of complex samples. This review tries to illustrate the main advantages of this technology, paying particular attention to the development of direct solid sampling methods. Three solid sampling applications will be discussed, each one of them highlighting one of the main advantages of this technique. The review also intends to clarify some misconceptions on the true potential of the instrumentation that is currently commercially available, such as its performance for multielemental analysis.     

How well can new-generation density functionals describe protonated epoxides where older functionals fail?

In a recent article, Carlier et al. (J. Org. Chem. 2006, 71, 1592) examined the prediction of several DFT functionals and showed that the most popular density functional, B3LYP, and 15 others fail badly for the prediction of the structure of protonated 2-methyl-1,2-epoxypropane. In this note, we compare the performance of several recently developed density functionals for the calculation of structures and energetics of protonated cyclic ethers, including epoxides. We found that several of the newly developed DFT methods perform better than B3LYP or any of the other 17 functionals examined by Carlier. We conclude that a recently published functional, M05-2X, has greatly improved performance for an unsymmetrical protonated epoxide, and we recommend this functional for studies that involve protonated epoxides and protonated ethers.     

The ester group: how hydrofluoroalkane-philic is it?

Pressurized metered-dose inhalers (pMDIs) have been recognized as potential devices for the delivery of systemically acting drugs, including biomolecules, to and through the lungs. Therefore, the development of novel excipients capable of imparting stability to suspension formulations in hydrofluoroalkane (HFA) propellants is of great relevance because many of the drugs of interest are poorly soluble in HFAs. In this work, we use ab initio calculations and chemical force microscopy (CFM) to determine the HFA-philicity of the biodegradable and biocompatible ester moiety quantitatively. The complementary information obtained from the binding energy calculations and adhesion force measurements are used to gain microscopic insight into the relationship between the chemistry of the moiety of interest and its solvation in HFA. A lactide (LA)-based copolymer surfactant was synthesized and characterized, and its ability to stabilize a dispersion of micronized budesonide in HFA227 was demonstrated. These results corroborate the ab initio calculations and CFM and show that the LA-based moiety is a suitable candidate for enhancing the stability of dispersions in HFA-based pMDIs.     

Thermochemical kinetics: does it still give insights?

This tutorial review revisits the subject of the seminal book written by Sidney Benson in 1968. A short summary of the nature of the subject is presented, including its place in the wider world of quantitative chemistry. A number of themes are selected to illustrate its previous and continuing usefulness in evaluating numerical values of important quantities, and probing ideas of reaction mechanism. These include strain enthalpies for biradical combination, chain reactions, why some reactions don't occur and the involvement of carbenes in hydrocarbon rearrangements.