Tailoring the electrochemical charge storage properties of carbonaceous support by redox properties of heteropoly acids: where does the synergy come from?

Journal of Solid State Electrochemistry - The synergistic effects between two Keggin-type heteropoly acids (HPAs) and carbon surface were examined and elucidated. An improved high rate capability...     

Synthesis of protected ω-mercapto amino acids: precursors for incorporation of elongated cysteines into peptides

A series of protected ω-mercapto amino acids with side-chain lengths ranging from 3–5 methylene units has been synthesized via nucleophilic substitution of ω-bromo-α-azido acids by 4-methoxy-α-toluenethiol followed by reduction of the azido functionality with SnCl₂. These enantiomerically pure protected cysteine analogues can be used to optimize the length of disulfide connections in cyclically constrained peptide pharmacophores.     

Synthesis of bridged sugar amino acids: a new entry into conformationally locked δ- and ε-amino acids

The synthesis of three methylene bridged sugar amino acids is described. Key transformations in the synthetic strategy are a CO-insertion on fully protected ribose, an aldol condensation with formaldehyde and an oxetane forming cyclisation step. A novel Leu-enkephalin analogue containing the δ-SAA 1 was prepared using standard solution phase peptide chemistry.     

Is it possible to predict the average surface hydrophobicity of a protein using only its amino acid composition?

Hydrophobicity is one of the most important physicochemical properties of proteins. Moreover, it plays a fundamental role in hydrophobic interaction chromatography, a separation technique that, at present time, is used in most industrial processes for protein purification as well as in laboratory scale applications. Although there are many ways of assessing the hydrophobicity value of a protein, recently, it has been shown that the average surface hydrophobicity (ASH) is an important tool in the area of protein separation and purification particularly in protein chromatography. The ASH is calculated based on the hydrophobic characteristics of each class of amino acid present on the protein surface. The hydrophobic characteristics of the amino acids are determined by a scale of aminoacidic hydrophobicity. In this work, the scales of Cowan-Whittaker and Berggren were studied. However, to calculate the ASH, it is necessary to have the three-dimensional protein structure. Frequently this data does not exist, and the only information available is the amino acid sequence. In these cases it would be desirable to estimate the ASH based only on properties extracted from the protein sequence. It was found that it is possible to predict the ASH from a protein to an acceptable level for many practical applications (correlation coefficient > 0.8) using only the aminoacidic composition. Two predictive tools were built: one based on a simple linear model and the other on a neural network. Both tools were constructed starting from the analysis of a set of 1982 non-redundant proteins. The linear model was able to predict the ASH for an independent subset with a correlation coefficient of 0.769 for the case of Cowan-Whittaker and 0.803 for the case of Berggren. On the other hand, the neural model improved the results shown by the linear model obtaining correlation coefficients of 0.831 and 0.836, respectively. The neural model was somewhat more robust than the linear model particularly as it gave similar correlation coefficients for both hydrophobicity scales tested, moreover, the observed variabilities did not overcome 6.1% of the mean square error. Finally, we tested our models in a set of nine proteins with known retention time in hydrophobic interaction chromatography. We found that both models can predict this retention time with correlation coefficients only slightly inferior (11.5% and 5.5% for the linear and the neural network models, respectively) than models that use the information about the three-dimensional structure of proteins.     

Divergent synthetic routes to biologically relevant types of compounds: chiral polyfunctional γ-lactams and amino acids

Divergent and versatile synthetic routes leading to the title compounds are described. They start from a common chiral precursor derived from (−)-(S)-verbenone and afford polyfunctional γ-lactams and γ- and ε-amino acids. The cyclobutane moiety in these molecules acts as a chiral and polyfunctional platform providing stereogenic centres with unambiguous absolute configuration that control the chirality of the newly produced asymmetric carbons. Furthermore, it affords functional groups and carbon chains suitable not only to create the basic skeleton of the desired products but additional functional groups. These features confer on these derivatives a great versatility for further uses in the development of new drugs and as synthetic building blocks.     

I2-mediated α-selective Ferrier glycosylation approach to synthesis of O-glycosyl amino acids

I₂ is an effective promoter for the synthesis of 2,3-unsaturated glycosides via Ferrier glycosylation. This reaction was used in the present work for the synthesis of O-glycosylated Fmoc amino acid building blocks. This metal-free reaction afforded the desired products with good to excellent yields with good α-selectivity.     

Modeling of lithium-ion batteries is becoming viral: where to go?

Journal of Solid State Electrochemistry - We briefly summarize the most popular theoretical/computational techniques being used to model lithium-ion batteries and suggest some future...     

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.     

Computational study of the reaction of P+ with acetylene: does spin-crossing play a significant role?

A computational study of the reaction of P(+)((3)P) with acetylene has been carried out. The only exothermic products correlating with the reactants are PCCH(+)((2)Π) + H((2)S). Two different pathways leading to these products that are apparently barrier-free have been found. Both pathways involve isomerization into open-chain intermediates followed by direct elimination of a hydrogen atom. The possibility of spin-crossing has been considered because the species on the singlet surface are considerably more stable than those on the triplet one. On the singlet surface, there are other possible channels for the reaction, namely, cyclic PC(2)H(+)((2)A') + H((2)S) and CCP(+)((1)Σ) + H(2) ((1)Σ(g)(+)). A computational kinetic study shows that, in agreement with the experimental evidence, the major products are PCCH(+)((2)Π) + H((2)S) at all temperatures. Only at very high temperatures is CCP(+)((1)Σ) + H(2) ((1)Σ(g)(+)) formed in non-negligible amounts. Therefore, only PCCH(+) should be formed in the interstellar medium.     

P–C bond formation: synthesis of phosphino amino acids by palladium-catalysed cross-coupling

(4-Diethylphosphanyl)- and (4-diphenylphosphanyl)-derivatives of d- and l-phenylalanine have been synthesised using a palladium-catalysed cross-coupling giving the desired products in very high yields and without racemisation.     

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.     

T3P (propylphosphonic anhydride) mediated conversion of Nα-protected amino/peptide acids into thioacids

A general, mild and an efficient protocol, which makes use of T3P as an acid activator for the synthesis of N^α-protected amino/peptide thioacids from corresponding acids in the presence of finely ground Na₂S as hydrosulfide ion donor is described. The protocol employed significantly increases the overall efficiency as the yield, reaction duration and purity of even sterically hindered amino acids.     

Preparation of modified peptides: direct conversion of α-amino acids into β-amino aldehydes

A direct method for the transformation of α-amino acids into β-amino aldehydes was developed, and applied to the modification of the C-terminal residue of peptides. The method takes place in good yields and under mild conditions. The application of this methodology to the preparation of small peptides with γ-amino alcohol units, which are precursors of analogues of peptaibol antibiotics, is also described.     

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.     

Synthesis and incorporation into cyclic peptides of tolan amino acids and their hydrogenated congeners: construction of an array of A-B-loop mimetics of the Cε3 domain of human IgE

The disruption of the human immunolobulin E-high affinity receptor I (IgE-FcεRI) protein-protein interaction (PPI) is a validated strategy for the development of anti asthma therapeutics. Here, we describe the synthesis of an array of conformationally constrained cyclic peptides based on an epitope of the A-B loop within the Cε3 domain of IgE. The peptides contain various tolan (i.e., 1,2-biarylethyne) amino acids and their fully and partially hydrogenated congeners as conformational constraints. Modest antagonist activity (IC(50) ～660 μM) is displayed by the peptide containing a 2,2'-tolan, which is the one predicted by molecular modeling to best mimic the conformation of the native A-B loop epitope in IgE.     

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.     

Electrochemistry: quo vadis or where should we head to?

Journal of Solid State Electrochemistry -     

Thermodynamics of Binding of α:-Cyclodextrin to Straight-Chain Alkyl Derivatives in Aqueous Solution

Apparent standard Gibbs energy, enthalpy, entropy, and heatcapacity data of the interactions of -cyclodextrin (CD) to some n-carboxylatesH(CH₂)_nCOO^- (n = 4–6), are determined by isothermal titration microcalorimetryat different temperatures in phosphate buffer, pH 9.0, assuming a 1 : 1 model indilute solution. Modelling of contributions of the thermodynamic properties of the solutionindicates that CD undergoes conformational change upon binding to homologousseries of n-carboxylates, n-alcohols, ,-alkane dicarboxylates and ,-alkane diols.