Predicting properties of new ionic liquids: density functional theory and experimental studies of tetra-alkylammonium salts of (thio)carboxylate anions, RCO2⁻, RCOS⁻ and RCS2⁻

Density functional theory calculations of alkyl-carboxylate anions and their sulfur substituted variants are presented here as an aid for the development of new ionic liquids. Electron transfer both within the anion, and between the anion and cation of an ion pair, are described using natural bond order analysis, using tetraethylammonium as a common cation. The overall stabilising effect of this electron transfer is quantified for the series of anions, and is found to correlate with clear trends in ion-pair binding energy. These and other electronic properties determine which compounds are synthesised, and experimental results validate the computational results. In combination with tetraethylammonium, a carboxylate with an unsaturated alkyl chain produces an ionic liquid at room temperature. However, computations suggest that sulfur substituted anions will produce a lower melting point and perhaps more fluid ionic liquid, but one which would be less stable against oxidation.     

Archaeolithoporella and Tubiphytes : Affinties and Paleoecology in Permian Reefs of South China

Archaeolithoporella is one of the most important Permian reef-building organisms, but itsaffinity has long been controversial. It was first reported in Japan and was considered as a coralline red alga. Since then it has been recognized in Permian reefs in other parts of the world. Many researchers have studied the materials they had found and the Japanese holotype specimen. Most have concluded that it is a problematic alga. or just a problematica because of weak criteria for definition. Some have even considered it inorganic. However, relict cellular structures and microtubular laminae found in well-preserved specimens from Permian reefs in South China strongly support a coralline red algal affinity for the genus.In situ preserved Archaeolithoporella is restricted within the typical framework facies and it occurs most abundantly in syndepositionally cemented framestones. This suggests that Archaeolithoporella required a firm substrate and clear but agitated sea water. Archaeolithoporella is often found     

Gel- and Solid-State-Structure of Dialanine and Diphenylalanine Amphiphiles: Importance of C⋅⋅⋅H Interactions in Gelation

To investigate the role of the capping group in the solution and solid-state self-assembly of short peptide amphiphiles, dialanine and diphenylalanine have been linked via the N-terminus to a benzene (phenyl) and 3-naphthyl capping groups using three different methylene linkers; (CH₂)_n, n=0–4 for the benezene and 0, 1 and 2 for the naphthalene capping group. Atomic force microscopy (AFM), oscillatory rheology, circular dichroism (CD), and IR analysis have been employed to understand the properties of these peptide-based hydrogels. Several X-ray structures of these short peptide gelators give useful conformational information regarding packing. A comparison of these solid state structures with their gel state properties yielded greater insights into the process of self-assembly in short peptide gelators, particularly in terms of the important role of C⋅⋅⋅H interactions appear to play in determining if a short aromatic peptide does form a gel or not.     

Free Radicals in the Photolysis and Radiolysis of Polymers: IV. Radicals in γ- and UV-Irradiated Wood and Lignin

Free radicals formed in the radiolysis and photolysis of wood and lignin were studied using X-band and D-band EPR measurements. It was found that singlet spectra at g 2, which appeared upon the low-temperature (77 K) - and UV irradiation of wood and lignin, or singlets detected in a posteffect on heating the irradiated samples belong to radicals having conjugated carbon–carbon bonds. Formyl radicals in -irradiated wood and peroxide radicals in - and UV-irradiated wood were detected for the first time using EPR spectra. The radiation-chemical and quantum yields of radical formation reactions were determined. In wood at 77 K, G _R 3.2 1/100 eV and _R 2 × 10^–3.     

Theory of chemical bonds in metalloenzymes XII: Electronic and spin structures of metallo–oxo and isoelectronic species and spin crossover phenomena in oxygenation reactions

The broken-symmetry (BS) and multideterminant approaches to atomic oxygen (O), molecular oxygen (O₂) and iron–oxo (Fe(IV)O) core in P450 have elucidated electronic structures of the ground triplet and excited singlet states, which indicate isoelectronic characteristics of the species. The dissociation processes of the O–O and Fe–O double bonds are also examined to clarify the radical character, namely O-atom property responsible for radical mechanism of hydroxylations of alkanes and epoxidation of alkenes. This isolobal analogy has indeed enabled us to propose possible reaction mechanisms of oxygenation reactions by the Fe(IV)O species on the basis of available theoretical and experimental results for O and O₂. Similarly, an isolobal analogy of the σ^* bond among Fe(IV)O, dioxirane, peracids, etc. indicates the common electrophilic property for the oxygenation reactions. The small energy gaps between the high- and low-spin states of the transition structures and intermediates generated in the oxygenation reactions are found to be origins for spin crossover phenomena along the reaction pathways of these reactions.     

Applications of cellular automata: attractors and fractals in analytical chemistry?

A cellular automaton is a discrete dynamic system of simple construction, yet capable of exhibiting complex self-organizing behavior. A cellular automaton can be used to model differential systems by assuming that time and space are quantized, and that the dependent variable takes on a finite set of possible values. Cellular-automaton behavior falls into four distinct universality classes, analogous to (1) limit points, (2) limit cycles, (3) chaotic attractors (fractals), and (4) 'universal computers'. The behavior of members of each of these four classes is explored in the context of digital spectral filtering. The utility of class 2 behavior in experimental data analysis is demonstrated with a laboratory example.     

Reduction and alkylation of proteins in preparation of two-dimensional map analysis: why, when, and how?

The standard procedure adopted up to the present in proteome analysis calls for just reduction prior to the isoelectric focusing/immobilized pH gradient (IEF/IPG) step, followed by a second reduction/alkylation step in between the first and second dimension, in preparation for the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) step. This protocol is far from being optimal. It is here demonstrated, by matrix assisted laser desorption/ionization-time of flight (MALDI-TOF)-mass spectrometry, that failure to reduce and alkylate proteins prior to any electrophoretic step (including the first dimension) results in a large number of spurious spots in the alkaline pH region, due to "scrambled" disulfide bridges among like and unlike chains. This series of artefactual spots comprises not only dimers, but an impressive series of oligomers (up to nonamers) in the case of simple polypeptides such as the human alpha- and beta-globin chains, which possess only one (alpha-) or two (beta-) -SH groups. As a result, misplaced spots are to be found in the resulting two-dimensional (2-D) map, if performed with the wrong protocol. The number of such artefactual spots can be impressively large. In the case of analysis of complex samples, such as human plasma, it is additionally shown that failure to alkylate proteins results in a substantial loss of spots in the alkaline gel region, possibly due to the fact that these proteins, at their pI, regenerate their disulfide bridges with concomitant formation of macroaggregates which become entangled with and trapped within the polyacrylamide gel fibers. This strongly quenches their transfer in the subsequent SDS-PAGE step.     

“The Fitness of Their Union”: Travel and Health in the Letters of Humphry and Jane Davy

The letters of Humphry Davy and his circle, to be published shortly, shed new light on his marriage to Jane Apreece. This paper examines the journeys undertaken by the couple, together and separately, with particular attention to the therapeutic benefits they sought from travel. I argue that their increasingly divergent itineraries reflected a growing understanding that Humphry and Jane had different humoral temperaments or constitutions, leading them to seek different climatic conditions to cure their ailments. While Jane’s temperament was classified as melancholic, requiring her to travel to warmer and sunnier climes during the English winter, Humphry’s was believed to be sanguine, meaning he had to avoid excessive heat along with stimulating food and drink. He relied on classical ideas about individuals’ different humoral constitutions, and the therapies appropriate to them, while measuring atmospheric variables to determine the best places to restore his health. The Davys’ letters reveal the beliefs about bodily differences and atmospheric conditions that shaped their therapeutic travels.     

The polarographic determination of indium in zinc-base alloys : The determination of indium in zinc and in “lead-free” zinc alloys

The use of a potassium iodide base electrolyte for the separation of the polarographic steps due to indium and cadmium is discussed and theoretical data relating to the interference of the step due to lead with that due to indium are presented. An experimental study is given together with details of the attempted removal of lead interference. A method is presented for the polarographic determination of indium in zinc alloys, applicable when the lead concentration is small compared with that of indium.     

Host–guest system of Vitamin B10 in β-cyclodextrin: characterization of the interaction in solution and in solid state

Conventional drugs are usually formulated for the immediate release of the medicinal substances and for obtaining the desired therapeutic effect. The aim of this paper was to investigate the possible interactions between Vitamin B10 and β-cyclodextrin (β-CD), to determine the physical-chemical characteristics and the interactions present in the corresponding inclusion compound. The so-obtained compounds were characterized by X-ray diffraction, DSC and FTIR spectroscopy. ¹H NMR and UV–vis spectroscopic methods were employed to study the inclusion process in aqueous solution. The X-ray powder diffraction patterns demonstrate the inclusion compound formation, especially for the lyophilized product where the amorphous phase dominates. The existence of the inclusion compounds obtained by different methods was confirmed by comparing with DSC and FTIR data of the pure compounds and the (1:1) Vitamin B10:β-CD physical mixture (pm). ¹H NMR measurements on aqueous solutions of Vitamin B10 and β-CD in D₂O allowed us to establish the corresponding Vitamin B10’s and cyclodextrin’s protons implied in the complexation process. 2D NMR spectroscopy established the geometry of the inclusion complex. ¹H NMR, UV–Vis and fluorescence data were used to obtain the stoichiometry and the stability constant of the complex.     

Streaming potential and protein transmission ultrafiltration of single proteins and proteins in mixture: β-lactoglobulin and lysozyme

A study of single proteins, β-lactoglobulin and lysozyme of different sizes and electrical characteristic as a function of pH, ionic strength and nature of salt (NaCl or CaCl₂) allows to evaluate the filtration performances. Streaming potential measurements confirm that proteins contribute to the net charge of the system and that the protein tranfer through mineral membranes is governed by ionic and steric exclusion phenomena.This work shows the correlation between protein transmission and streaming potential values which takes into account steric and ionic exclusion. The ionic repulsion decreases the transmission. This one depends on membrane net charge characterised by streaming potential, which depends on the solution composition. This model, which does not take into account interactions between protein and membrane fouling leads to an overestimation of calculated transmission values when proteins are in a mixture. However, it allows a correct estimation of transmission variations versus the studied variables: pH and ionic strength.     

Organotrihalide Complexes: α-Nucleophiles and Effective Oxidizing Agents in Decomposition Reactions of Organophosphorus Compounds in Water and Surfactant Micelles

We have studied the nucleophilic and oxidative reactivity of the system HOBr/BrO^–, in water and in the presence of different types of surfactants, relative to 4-nitrophenyldiethylphosphate, 4-nitrophenyl- 4´-toluenesulfonate (nucleophilic substitution), and 4-nitrophenol (oxidation). As the source of "active" bromine, we used organotrihalide complexes. The micellar effects of the surfactants in nucleophilic substitution reactions are adequately described within both a pseudophase distribution model and an ion-exchange model. Just transferring the reaction from water to micelles of a cationic surfactant leads to an increase in the observed rates of reaction of the BrO^– ion with esters by up to a factor of 20-30 and an increase in the rate for reaction of HOBr with nitrophenol by up to a factor of 5, while the HOBr/BrO^– system is one of the most effective systems in decomposition of organophosphorus compounds.     

Inclusion complexes of Sulconazole with β-cyclodextrin and hydroxypropyl β-cyclodextrin: characterization in aqueous solution and in solid state

Complexation between sulconazole (SULC), an imidazole derivative with in vitro antifungal and antiyeast activity, and β-cyclodextrins (β-CD and HP-β-CD) was studied in solution and in solid states. Complexation in solution was evaluated using solubility studies and nuclear magnetic resonance spectroscopy (¹H-NMR). In the solid state, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and RX diffraction studies were used. Solubility studies suggested the existence of inclusion complex between SULC and β-CD or HP-β-CD. ¹H-NMR spectroscopy studies showed that the complex formed occurs by complexation of imidazole ring into inner cavity. DSC studies showed the existence of a complex of SULC with β-CD. The TGA and RX studies confirmed the DSC results of the complex. Solubility of SULC in solid complexes was studied by the dissolution method and it was found to be much more soluble than the uncomplexed drug.     

Pollution characteristics of atmospheric fine particles and their secondary components in the atmosphere of Shenzhen in summer and in winter

Two field measurements for atmospheric fine particles were conducted in Baoan district of Shenzhen during the summer and winter in 2004. Totally 30 sets of 24 h samples were collected, and then the mass concentrations and chemical compositions were determined. The seasonal varia- tions and secondary pollution characteristics of fine particles during the sampling periods were dis-cussed with meteorological factors. The results show that seasonal variations of atmospheric particles are significant in Shenzhen. The average mass concentrations of PM2.5 and PM10 in summer were 35 μg·m-3 and 57 μg·m-3, respectively, and those in winter were 99 μg·m-3 and 135 μg·m-3, respec-tively. The concentrations of both PM2.5 and PM10 in winter increased 184% and 137%, respectively, compared to those in summer. PM2.5 accounted for 61% and 75% of PM10 in summer and in winter, respectively, indicating severe fine particle pollution in Shenzhen. During the summer and winter sampling periods, the mean OC/EC ratios were 3.4 and 1.6, respectively. The estimated secondary organic carbon (SOC) averagely accounted for 56% and 6% of the total OC in summer and in winter, respectively, which implies a major contribution of SOC to OC in summer. During the continuous high temperature period in summer, both the concentrations and fractions of secondary aerosol compo-nents in PM2.5 were highly elevated, suggesting severe secondary pollution again. The prevailing wind was from South China Sea in summer, and the air quality was good. The prevailing wind in winter was from Mainland China to the north, and the polluted air mass led to poor air quality.     

Synthesis and in Vitro Cytotoxicity of a Novel Conjugate of Polyamide and Phospholipid

Small molecules with the ability to target predetermined sequences of DNA would be valuable tools in molecular biology and potentially in human medicine1-3. Synthetic polyamides consisting of N-methylpyrrole (Py), N-methylimidazole (Im) have received spec…     

Role of hydration in determining the structure and vibrational spectra of L-alanine and N-acetyl L-alanine N′-methylamide in aqueous solution: a combined theoretical and experimental approach

In this work we have utilized recent density functional theory Born-Oppenheimer molecular dynamics simulations to determine the first principles locations of the water molecules in the first solvation shell which are responsible for stabilizing the zwitterionic structure of L-alanine. Previous works have used chemical intuition or classical molecular dynamics simulations to position the water molecules. In addition, a complete shell of water molecules was not previously used, only the water molecules which were thought to be strongly interacting (H-bonded) with the zwitterionic species. In a previous work by Tajkhorshid et al. (J Phys Chem B 102:5899) the L-alanine zwitterion was stabilized by 4 water molecules, and a subsequent work by Frimand et al. (Chem Phys 255:165) the number was increased to 9 water molecules. Here we found that 20 water molecules are necessary to fully encapsulate the zwitterionic species when the molecule is embedded within a droplet of water, while 11 water molecules are necessary to encapsulate the polar region with the methyl group exposed to the surface, where it migrates during the MD simulation. Here we present our vibrational absorption, vibrational circular dichroism and Raman and Raman optical activity simulations, which we compare to the previous simulations and experimental results. In addition, we report new VA, VCD, Raman and ROA measurements for L-alanine in aqueous solution with the latest commercially available FTIR VA/VCD instrument (Biotools, Jupiter, FL, USA) and Raman/ROA instrument (Biotools). The signal to noise of the spectra of L-alanine measured with these new instruments is significantly better than the previously reported spectra. Finally we reinvestigate the causes for the stability of the P_π structure of the alanine dipeptide, also called N-acetyl-L-alanine N′-methylamide, in aqueous solution. Previously we utilized the B3LYP/6-31G* + Onsager continuum level of theory to investigate the stability of the NALANMA4WC Han et al. (J Phys Chem B 102:2587) Here we use the B3PW91 and B3LYP hybrid exchange correlation functionals, the aug-cc-pVDZ basis set and the PCM and CPCM (COSMO) continuum solvent models, in addition to the Onsager and no continuum solvent model. Here by the comparison of the VA, VCD, Raman and ROA spectra we can confirm the stability of the NALANMA4WC due to the strong hydrogen bonding between the four water molecules and the peptide polar groups. Hence we advocate the use of explicit water molecules and continuum solvent treatment for all future spectral simulations of amino acids, peptides and proteins in aqueous solution, as even the structure (conformer) present cannot always be found without this level of theory. Festschift in Honor of Philip J. Stephens’ 65th Birthday. During the proof stage of this article a very relevant article has been published by M. Losada and Y. Xu titled “Chirality transfer through hydrogen-bonding: Experimental and ab initio analyses of vibrational circular dichroism spectra of methyl lactate in water” in Phys Chem Chem Phys 2007, 9: 3127–3135. In that work they confirm that the effects of water are seen in the VCD spectra and hence it is fundamental to include explicit water molecules in modeling studies of the vibrational spectra of biomolecules in aqueous solution.     

Detection and Determination of Released Ions in the Presence of Nanoparticles: Selectivity or Strategy?

Metallic nanoparticles can release ionic species, but also both species can occur in the same samples. Therefore, there is a need of efficient and cost‐effective methods to determine these ionic species in the presence of the corresponding nanoparticles. Electroanalytical techniques open the door to this selective detection of NPs and their ions. In this work, a methodology that allows the direct determination of ionic silver (Ag⁺) in the presence of silver nanoparticles based on anodic stripping voltammetry was implemented. Silver nanoparticles were determined, after acidic digestion of the sample, by difference with respect to the total content of silver. The method was validated in terms of specific identification of silver ions, linearity, working range, limit of detection, limit of quantification, recovery, repeatability and ruggedness. All parameters are adequate for an analytical method following Eurachem recommendations. The validated method was used to determine the concentration of Ag⁺ and total silver in two commercial products of colloidal silver. The results were compared with those obtained by atomic absorption spectrometry in combination with an ultrafiltration step for isolation of ionic silver. There were no significant differences in the results. The proposed methodology benefits from the intrinsic selectivity of the electroanalysis methods, allowing to eliminate the steps of pretreatments of the samples, which are necessary in other techniques. The novelty of the article lies in the direct determination of Ag (I) ions in the presence of AgNPs, without the use of previous separation steps.     

Determination of Cd and Pb in Honey by SF‐ICP‐MS: Validation Figures and Uncertainty of Results

Abstract

A method based on microwave‐assisted acid digestion of honey and quantification of Cd and Pb by Sector Field Inductively Coupled Plasma Mass Spectrometry was in‐house validated and the combined uncertainty was estimated according to the Eurachem/Citac Guide. Limits of detection and quantification were 0.07 and 0.20 ng g^?1 for Cd, and 0.70 and 2.10 ng g^?1 for Pb; recovery was 103.9% for Cd and 98.5% for Pb; repeatability was 10.7% for Cd and 18.5% for Pb; within‐laboratory reproducibility was 15.2% for Cd and 21.4% for Pb. Relative combined uncertainty in honey was 15% for Cd and 22% for Pb, with the main contribution coming from the within‐laboratory reproducibility. The method showed robustness when subjected to different working conditions and when applied to various Italian honeys. Cadmium content ranged 0.2–1.37 ng g^?1 and Pb 4.6–30.5 ng g^?1 in flower honeys, while the highest concentrations were presented by honeydew honeys.     

Inclusion Complexation of Carbaryl and β-Cyclodextrin in Solution and in the Solid State

This study was carried out with the aim ofinvestigating the interactions between-cyclodextrin and carbaryl, a carbamatepesticide, and their effect on some physico-chemicalproperties of carbaryl, such as aqueous solubility andlipophilicity. The interactions between carbaryl and-cyclodextrin were thoroughly investigated bothin solution and in the solid state. The effect of-cyclodextrin on the aqueous solubility ofcarbaryl was evaluated by the phase solubility method.The amount of carbaryl dissolved increased linearlywith the addition of -cyclodextrin according toan A_L type plot and without precipitation of thecomplex. The apparent stability constant of thecomplex was 289 ± 21 M^-1, assuming a 1 : 1stoichiometry; this value was confirmed by a methodbased on circular dichroism measurements.Equimolar carbaryl/-cyclodextrin solid systemswere prepared by physical-mixing and freeze-drying,and fully characterised by Differential ScanningCalorimetry, X-ray powder diffractometry and FourierTransform Infra-Red analysis. The results of the solidstate study demonstrated that the freeze-drying methodyields a system with a high degree of amorphisationand yields an inclusion complex.The dissolution profile of the pesticide was affectedby the physico-chemical properties of each solidsystem, the freeze-dried form dissolving more rapidly. However, the physical association of-cyclodextrin and carbaryl enhanced the aqueoussolubility of the insecticide as well.     

Sequence-based analysis of 5′UTR and coding regions of CASP3 in terms of miRSNPs and SNPs in targetting miRNAs

Apoptosis is described as a mechanism of cell death occurring after adequate cellular harm. Deregulation of apoptosis occurs in many human conditions such as autoimmune disorders, ischemic damage, neurodegenerative diseases and different cancer types. Information relating miRNAs to cancer is increasing. miRNAs can affect development of cancer via many different pathways, including apoptosis. Polymorphisms in miRNA genes or miRNA target sites (miRSNPs) can change miRNA activity. Although polymorphisms in miRNA genes are very uncommon, SNPs in miRNA-binding sites of target genes are quite common. Many researches have revealed that SNPs in miRNA target sites improve or decrease the efficacy of the interaction between miRNAs and their target genes. Our aim was to specify miRSNPs on CASP3 gene (caspase-3) and SNPs in miRNA genes targeting 5′UTR and coding exons of CASP3, and evaluate the effect of these miRSNPs and SNPs of miRNA genes with respect to apoptosis. We detected 141 different miRNA binding sites (126 different miRNAs) and 7 different SNPs in binding sites of miRNA in 5′UTR and CDS of CASP3 gene. Intriguingly, miR-339-3p’s binding site on CASP3 has a SNP (rs35372903, G/A) on CASP3 5′UTR and its genomic sequence has a SNP (rs565188493, G/A) at the same nucleotide with rs35372903. Also, miR-339-3p has two other SNPs (rs373011663, C/T rs72631820, A/G) of which the first is positioned at the binding site. Here, miRSNP (rs35372903) at CASP3 5′UTR and SNP (rs565188493) at miR-339-3p genomic sequence cross-matches at the same site of binding region. Besides, miR-339-3p targets many apoptosis related genes (ZNF346, TAOK2, PIM2, HIP1, BBC3, TNFRSF25, CLCF1, IHPK2, NOL3) although it had no apoptosis related interaction proven before. This means that miR-339-3p may also have a critical effect on apoptosis via different pathways other than caspase-3. Hence, we can deduce that this is the first study demonstrating a powerful association between miR-339-3p and apoptosis upon computational analysis.