Volume 32, Issue 3

Protein tyrosine nitration is a post-translational modification (PTM) that can occur in biological systems under conditions of oxidative stress. This PTM can impact protein structure and function and has been linked to diseases such as Alzheimer’s disease, cardiomyopathy, and arthritis. In order to understand the role that 3-nitrotyrosine (3NT) plays in disease states, a better understanding at the macromolecular level is necessary. Proteomics is a powerful approach that can simultaneously measure hundreds to thousands of proteins in normal or diseased states and thus can be helpful in the analysis of 3NT-modified proteins. Recently, some attention has been focused on the development of proteomic workflows that provide enrichment, characterization, and relative quantification of 3NT-modified proteins. These approaches rely on gel electrophoresis, liquid chromatography, and mass spectrometry (MS) techniques. This review provides an overview of current proteomics approaches for 3NT-modified proteins and highlights current MS-based methods for quantification of this PTM.

Botulinum neurotoxins (BoNTs) cause the disease botulism, which can be lethal if untreated. There are seven known serotypes of BoNT, A–G, defined by their response to antisera. Many serotypes are distinguished into differing subtypes based on amino acid sequence and immunogenic properties, and some subtypes are further differentiated into toxin variants. Toxin characterization is important as different types of BoNT can respond differently to medical countermeasures for botulism, and characterization of the toxin can aid in epidemiologic and forensic investigations. Proteomic techniques have been established to determine the serotype, subtype, or toxin variant of BoNT. These techniques involve digestion of the toxin into peptides, tandem mass spectrometric (MS/MS) analysis of the peptides, and database searching to identify the BoNT protein. These techniques demonstrate the capability to detect BoNT and its neurotoxin-associated proteins, and differentiate the toxin from other toxins that are up to 99.9% identical in some cases. This differentiation can be accomplished from toxins present in a complex matrix such as stool, food, or bacterial cultures and no DNA is required.

Binding affinity is measured by dissociation constant, K d , which uses concentration as units. The universal concentration units facilitate direct comparison of affinities for different binding events. However, K d is a thermodynamic parameter, which lacks kinetic information of a binding event. In addition, K d does not reveal the mechanical property of the binding, which emerges as a critical element for many physiologically significant processes such as DNA replication, RNA transcription, and protein translation. Here we propose a new parameter, mechanical affinity, to delineate kinetic and mechanical features of a binding event. The mechanical affinity is equivalent to the work required to dissemble the chemical binding between a ligand and a receptor. During this process, it must cover dissipated heat that originates from the relative movement between a ligand and a receptor. Because dissipated heat varies with unfolding direction or rate of mechanical perturbation, the mechanical affinity is a function of these two variables. Screening of chemicals using rupture force of a ligand-receptor complex or mechanical affinity is discussed at the end of this review. The interrogation on the mechanical interaction between a ligand and a receptor provides a new perspective not available in conventional thermodynamic evaluation of binding processes.

This review looks at the advancements in the development of a sensor for technetium (Tc) that is applicable to characterizing and monitoring the vadose zone and associated subsurface water. Subsurface contamination by Tc is of particular concern for two reasons: the long lifetime of its most common isotope 99 Tc (half-life=2×10 5 years) and the fast migration in soils of pertechnetate (TcO 4 - ), which is considered to be the dominant 99 Tc species in ground water. TcO 4 – does not have a characteristic spectral signature which prevents its rapid, sensitive, and economic in situ detection. To address this problem, a novel spectroelectrochemical sensor has been designed, that combines three modes of selectivity (electrochemistry, spectroscopy, and selective partitioning) into a single sensor to substantially improve specificity, which is critical in the specific detection of an analyte in the presence of potential interfering species. The sensor consists of a basic spectroelectrochemical configuration: a waveguide with an optically transparent electrode (OTE) that is coated with a thin chemically-selective film that preconcentrates the analyte. The key to adapting this generic sensor to detect TcO 4 - and Tc complexes lies in the development of chemically-selective films that preconcentrate the analyte and, when necessary, chemically convert it into a complex with electrochemical and spectroscopic properties appropriate for sensing. The chemically selective films can be combined with ligands which are capable of reacting with TcO 4 - to form coordination complexes, the spectral properties of which can be used to enhance the sensitivity of detection. The first half of this review describes the general concept of the sensor and the rationale for the selection of its specific components, and the development and characterization of the sensor for the different detection modules. The second half summarizes the synthesis and characterization of complexes relevant for the detection of technetium, and the progress in the utilization of the sensor module for the effective detection of these complexes.

Mercury is one of the most important metals to environmental researchers due to its toxicity. In recent years, many authors determined the concentration of mercury and its different forms in the environment, such as soil, water, atmosphere and biota, with various analytical techniques, such as atomic absorption spectrometry, spectrophotometry, voltammetry, inductively coupled plasma mass spectrometry, inductively coupled plasma atomic emission spectrometry, spectrofluorometry and chromatography. The objective of this paper is to summarize the recent understanding of the available techniques for the analysis and speciation of mercury in environmental and biological samples reported worldwide during 2010–2011. We tabulated all the analytical parameters of about 129 research papers published in reputable international journals during 2010–2011 about mercury determination and speciation studies.

Because of its broad usage in industry and medical science, as well as the potential toxicity in the environment, the detection of sulfide, including hydrogen sulfide, metal sulfide and organic sulfide, has long attracted the attention of scientists working in diverse areas. Compared with other detection methods, electrochemical detection represents a highly sensitive, rapid, affordable, and simple technique. In this regard, the main objective of this report is to provide an up-to-date review of the electrochemical detection of sulfide. This review details different electrochemical approaches investigated between 2010 and 2012, together with the development of various electrodes. In addition to the commonly used techniques, such as, anodic stripping voltammetry (ASV), amperometry, cyclic voltammetry (CV), photoelectrochemical methods, and electrochemical detection methods coupled with other devices, have also been discussed, within the context of detection limit, linear detection range, and applicable conditions.