Recent trends and advances in microbial electrochemical sensing technologies: An overview

Microbial electrochemical systems utilize the electrochemical interaction between microorganisms and electrode surfaces to convert chemical energy into electrical energy, offering a promise as technologies for wastewater treatment, bioremediation, and biofuel production. Recently, growing research attention has been devoted to the development of microbial electrochemical sensrs as biosensing platforms. Microbial electrochemical sensors are a type of microbial electrochemical technology (MET) capable of sensing through the anodic or the cathodic electroactive microorganisms and/or biofilms. Herein, we review and summarize the recent advances in the design of microbial electrochemical sensing approaches with a specific overview and discussion of anodic and cathodic microbial electrochemical sensor devices, highlighting both the advantages and disadvantages. Particular emphasis is given on the current trends and strategies in the design of low-cost, convenient, efficient, and high performing METs with different biosensing applications, including toxicity monitoring, pathogen detection, corrosion monitoring, as well as measurements of biological oxygen demand, chemical oxygen demand, and dissolved oxygen. The conclusion provides perspectives and an outlook to understand the shortcomings in the design, development status, and sensing applications of microbial electrochemical platforms. Namely, we discuss key challenges that limit the practical implementation of METs for sensing purposes and deliberate potential solutions, necessary developments, and improvements in the field.     

Bromine-Promoted Glycosidation of Conformationally Superarmed Thioglycosides

Presented herein is a study of the conformation and reactivity of highly reactive thioglycoside donors. The structural studies have been conducted using NMR spectroscopy and computational methods. The reactivity of these donors has been investigated in bromine-promoted glycosylations of aliphatic and sugar alcohols. Swift reaction times, high yields, and respectable 1,2-cis stereoselectivity were observed in a majority of these glycosylations.     

A fingerprint of a heterogeneous data set

Advances in Data Analysis and Classification - In this paper, we describe the fingerprint method, a technique to classify bags of mixed-type measurements. The method was designed to solve a...     

Identification of Protein Functional Regions

Protein sequence stores the information relative to both functionality and stability, thus making it difficult to disentangle the two contributions. However, the identification of critical residues for function and stability has important implications for the mapping of the proteome interactions, as well as for many pharmaceutical applications, e. g. the identification of ligand binding regions for targeted pharmaceutical protein design. In this work, we propose a computational method to identify critical residues for protein functionality and stability and to further categorise them in strictly functional, structural and intermediate. We evaluate single site conservation and use Direct Coupling Analysis (DCA) to identify co-evolved residues both in natural and artificial evolution processes. We reproduce artificial evolution using protein design and base our approach on the hypothesis that artificial evolution in the absence of any functional constraint would exclusively lead to site conservation and co-evolution events of the structural type. Conversely, natural evolution intrinsically embeds both functional and structural information. By comparing the lists of conserved and co-evolved residues, outcomes of the analysis on natural and artificial evolution, we identify the functional residues without the need of any a priori knowledge of the biological role of the analysed protein.     

Direct reduction of nitrite to N2 on a Pt(100) electrode in alkaline media

The selective reduction of NO(2)(-) to N(2) in 0.1 M NaOH was obtained at a Pt(100) electrode in a narrow but distinct potential region. This is the first report of such selectivity for this reaction on Pt(100), which is known to be the most catalytically active platinum surface toward NO(2)(-) reduction in alkaline media. Both ammonia and nitrous oxide are ruled out as possible reaction intermediates on the basis of online electrochemical mass spectrometry. Based on earlier work on ammonia oxidation, NH(2) adsorbates are speculated to be involved in the reaction mechanism.     

Molecular modeling of Protein A affinity chromatography

The properties of the complex between fragment B of Protein A and the Fc domain of IgG were investigated adopting molecular dynamics with the intent of providing useful insight that might be exploited to design mimetic ligands with properties similar to those of Protein A. Simulations were performed both for the complex in solution and supported on an agarose surface, which was modeled as an entangled structure constituted by two agarose double chains. The energetic analysis was performed by means of the molecular mechanics Poisson Boltzmann surface area (MM/PBSA), molecular mechanics generalized Born surface area (MM/GBSA), and the linear interaction energy (LIE) approaches. An alanine scan was performed to determine the relative contribution of Protein A key amino acids to the complex interaction energy. It was found that three amino acids play a dominant role: Gln 129, Phe 132 and Lys 154, though also four other residues, Tyr 133, Leu 136, Glu 143 and Gln 151 contribute significantly to the overall binding energy. A successive molecular dynamics analysis of Protein A re-organization performed when it is not in complex with IgG has however shown that Phe 132 and Tyr 133 interact among themselves establishing a significant π–π interaction, which is disrupted upon formation of the complex with IgG and thus reduces consistently their contribution to the protein–antibody bond. The effect that adsorbing fragment B of Protein A on an agarose support has on the stability of the protein–antibody bond was investigated using a minimal molecular model and compared to a similar study performed for a synthetic ligand. It was found that the interaction with the surface does not hinder significantly the capability of Protein A to interact with IgG, while it is crucial for the synthetic ligand. These results indicate that ligand–surface interactions should be considered in the design of new synthetic affinity ligands in order to achieve results comparable to those of Protein A right from the ligand design stage.     

Comparative study of oxaprozin complexation with natural and chemically-modified cyclodextrins in solution and in the solid state

The complexing, solubilizing and amorphizing abilities toward oxaprozin (a poorly water-soluble anti-inflammatory agent) of some β-cyclodextrin derivatives (hydroxypropyl-βCd, heptakis-2,6-di-O-methyl-βCd (DIMEB) amorphous randomly substituted methyl-βCd (RAMEB) and semi-crystalline methyl-βCd (CRYSMEΒ)) were investigated and compared with those of natural (α-, β-, γ-) cyclodextrins. The role of both the cavity size, the amorphous or crystalline state and the presence and type of substituent on the ability of cyclodextrins in establishing effective interactions with the drug has been evaluated. Equimolar drug-cyclodextrin solid systems were prepared by blending, kneading, co-grinding, sealed-heating, coevaporation, and colyophilization. Drug-carrier interactions were studied in both the liquid and solid state by phase-solubility analysis, differential scanning calorimetry, X-ray powder diffractometry, FT-IR spectroscopy and scanning electron microscopy. βCd showed the best performance among the natural Cds, indicating that its cavity was the most suitable for accommodating the drug molecule. The presence of substituents on the rim of the βCd cavity significantly improved its complexing and solubilizing effectiveness towards the drug, and methylated derivatives were better than the hydroxy-propylated ones The amorphous nature of the partner was also important: among the examined methyl-derivatives, RAMEB proved to be the most effective in performing solid state interactions and in improving drug wettability and dissolution properties.     

Bubble Divergences from Cellular Cohomology

We consider a class of lattice topological field theories, among which are the weak-coupling limit of 2d Yang–Mills theory, the Ponzano–Regge model of 3d quantum gravity and discrete BF theory, whose dynamical variables are flat discrete connections with compact structure group on a cell 2-complex. In these models, it is known that the path integral measure is ill-defined in general, because of a phenomenon called ‘bubble divergences’. A common expectation is that the degree of these divergences is given by the number of ‘bubbles’ of the 2-complex. In this note, we show that this expectation, although not realistic in general, is met in some special cases: when the 2-complex is simply connected, or when the structure group is Abelian – in both cases, the divergence degree is given by the second Betti number of the 2-complex.