Comparison of an antibody and its recombinant derivative for the detection of the small molecule explosive 2,4,6-trinitrotoluene

Antibodies are commonly used as recognition elements in immunoassays because of their high specificity and affinity, and have seen extensive use in competitive assays for the detection of small molecules. However, these complex molecules require production either in animals or by mammalian cell cultures, and are not easily tailored through genetic manipulation. Single chain antibodies (scFv), recombinantly expressed molecules consisting of only the antibody's binding region joined via a linking peptide, can provide an alternative to intact antibodies. We describe the characterization of a new monoclonal antibody (mAb), 2G5B5, able to detect the small molecule explosive 2,4,6-trinitrotoluene (TNT) and the scFv derived from its variable regions. The mAb and scFv were tested by surface plasmon resonance to determine their affinity for an immobilized TNT surrogate; dissociation constants were determined to be 1.5 × 10⁻¹³ M and 4.8 × 10⁻¹⁰ M respectively. Circular dichroism was used to determine their melting temperatures. The mAb is more stable melting at ∼75 °C while the scFv melts at ∼65 °C. The recognition elements were incorporated into a competitive assay format using a bead-based multiplexing platform to examine their sensitivity and specificity. The scFv was able to detect TNT ∼10-fold more sensitively than the mAb in this assay format, allowing detection of TNT concentrations down to at least 1 μg L⁻¹. The 2G5B gave similar detection limits to a commercial anti-TNT mAb, but was less specific, recognizing 1,3,5-trinitrobenzene (TNB) equally well as TNT.     

Investigating microcrystalline cellulose crystallinity using Raman spectroscopy

Cellulose - Microcrystalline cellulose (MCC) is a semi-crystalline material with inherent variable crystallinity due to raw material source and variable manufacturing conditions. MCC crystallinity...     

Bacterial cellulose/triethanolamine based ion-conducting membranes

New bacterial cellulose (BC)–triethanolamine (TEA) ion-conducting membranes have been prepared and characterized. The samples were obtained by soaking BC membranes in triethanolamine aqueous solutions and drying. The scanning electron microscopy pictures revealed that the incorporation of TEA in BC membranes covers the cellulose microfibrils. Raman spectra exhibited BC and TEA characteristic group frequencies and thermal analysis evidenced an influence of TEA content on the sample thermal stability. The ion-conductivity as a function of the temperature showed an Arrhenius behavior increasing from 1.8 × 10^?5 S/cm at room temperature to 7.0 × 10^?4 S/cm at 80 °C for the BC–TEA 1 M sample.     

Reliable radical stabilization energies from diffusion Monte Carlo calculations

We assess the performance of variational (VMC) and diffusion (DMC) quantum Monte Carlo methods for calculating the radical stabilization energies of a set of 43 carbon-centered radical species. Even using simple single-determinant trial wavefunctions, both methods perform exceptionally well, with mean absolute deviations from reference values well under the chemical accuracy standard of 1 kcal/mol. In addition, the use of DMC results in a highly concentrated spread of errors, with all 43 results within chemical accuracy at the 95% confidence level. These results indicate that DMC is an extremely reliable method for calculating radical stabilization energies and could be used as a benchmark method for larger systems in future.     

Improving the Switching Capacity of Glyco-Self-Assembled Monolayers on Au(111)

Self-assembled monolayers (SAMs) decorated with photoisomerizable azobenzene glycosides are useful tools for investigating the effect of ligand orientation on carbohydrate recognition. However, photoswitching of SAMs between two specific states is characterized by a limited capacity. The goal of this study is the improvement of photoswitchable azobenzene glyco-SAMs. Different concepts, in particular self-dilution and rigid biaryl backbones, have been investigated. The required SH-functionalized azobenzene glycoconjugates were synthesized through a modular approach, and the respective glyco-SAMs were fabricated on Au(111). Their photoswitching properties have been extensively investigated by applying a powerful set of methods (IRRAS, XPS, and NEXAFS). Indeed, the combination of tailor-made biaryl-azobenzene glycosides and suitable diluent molecules led to photoswitchable glyco-SAMs with a significantly enhanced and unprecedented switching capacity.     

Seasonal Variability of a Caryophyllane Chemotype Essential Oil of Eugenia patrisii Vahl Occurring in the Brazilian Amazon

Eugenia patrisii Vahl is a native and non-endemic myrtaceous species of the Brazilian Amazon. Due to few botanical and phytochemical reports of this species, the objective of the present work was to evaluate the seasonal variability of their leaf essential oils, performed by GC and GC-MS and chemometric analysis. The results indicated that the variation in oil yields (0.7 ± 0.1%) could be correlated with climatic conditions and rainy (R) and dry seasons (D). (E)-caryophyllene (R = 17.1% ± 16.0, D = 20.2% ± 17.7) and caryophyllene oxide (R = 30.1% ± 18.4, D = 14.1% ± 19.3) are the major constituents and did not display significant differences between the two seasons. However, statistically, a potential correlation between the main constituents of E. patrisii essential oil and the climatic parameters is possible. It was observed that the higher temperature and insolation rates and the lower humidity rate, which are characteristics of the dry season, lead to an increase in the (E)-caryophyllene contents, while lower temperature and insolation and higher humidity, which occur in the rainy season, lead to an increase in the caryophyllene oxide content. The knowledge of variations in the E. patrisii essential oil composition could help choose the best plant chemical profile for medicinal purposes.     

Characterization of the raw essential oil eugenol extracted from <Emphasis Type="Italic">Syzygium</Emphasis> <Emphasis Type="Italic">aromaticum</Emphasis> L.

Eugenol is the main volatile compound extracted oil from clove bud, Syzygium aromaticum L., and used in traditional medicine, as a bactericide, fungicide, anesthetic, and others. Its extraction was performed using hydrodistillation which is the most common extraction technique. Its components and thermal behavior were evaluated using gas chromatography (GC) and differential scanning calorimetry (DSC), which provide a better characterization of these natural compounds. This extracted product was compared to the standard eugenol results. The GC results suggested ~90% eugenol was found in the total extracted oil, and some of its boiling characteristics were 270.1 °C for peak temperature and 244.1 J g⁻¹ for the enthalpy variation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Advances in electrochemical detection for study of neurodegenerative disorders

Several severe neurodegenerative disorders, including Alzheimer’s disease, Parkinson’s disease, and prion-associated transmissible spongiform encephalopathies, have been linked to dysregulation of specific proteins capable of self-assembly into deleterious fibrillar aggregates termed amyloids. A wide range of analytical techniques has been used to clarify the mechanisms of these protein-misfolding processes, in the hope of developing effective therapeutic treatment. Most of these studies have relied heavily on conventional methods of protein characterization, notably circular dichroism spectroscopy, thioflavin T fluorescence, transmission electron microscopy, and atomic force microscopy, which are particularly suitable for monitoring later-stage aggregate formation. Although electrochemical methods of protein detection have existed for some time, they have only recently gained prominence as a powerful tool for studying the early stages of protein aggregation during which the more toxic soluble amyloid species form. Electrochemical detection methods include direct detection of intrinsic redox-active amino acid residues, protein-catalyzed hydrogen evolution, use of extrinsic β-sheet binding mediators, and impedance spectroscopy. In this review, we evaluate the use of electrochemistry for study of protein aggregation related to neurodegenerative disorders.

Engineered-membranes: A novel concept for clustering of native lipid bilayers

A strategy for clustering of native lipid membranes is presented. It relies on the formation of complexes between hydrophobic chelators embedded within the lipid bilayer and metal cations in the aqueous phase, capable of binding two (or more) chelators simultaneously Fig. 1. We used this approach with purple membranes containing the light driven proton pump protein bacteriorhodopsin (bR) and showed that patches of purple membranes cluster into mm sized aggregates and that these are stable for months when incubated at 19 °C in the dark. The strategy may be general since four different hydrophobic chelators (1,10-phenanthroline, bathophenanthroline, Phen-C10, and 8-hydroxyquinoline) and various divalent cations (Ni²⁺, Zn²⁺, Cd²⁺, Mn²⁺, and Cu²⁺) induced formation of membrane clusters. Moreover, the absolute requirement for a hydrophobic chelator and the appropriate metal cations was demonstrated with light and atomic force microscopy (AFM); the presence of the metal does not appear to affect the functional state of the protein. The potential utility of the approach as an alternative to assembled lipid bilayers is suggested.