Current Analytical Chemistry - Volume 2, Issue 4, 2006

This review outlines the mass spectrometric methods used to identify disulfide functionality in peptides, particularly cleavages from peptide (M-H)- parent anions. A brief introduction to characteristic negative ion fragmentations of peptides is given, including (i) the α and β cleavages which provide data analogous to that provided by Y+2 and B cleavages of MH+ ions, (ii) characteristic side chain cleavages, and (iii) γ backbone cleavages initiated from anion sites on the side chains of certain residues (e.g. Ser, Thr, Cys, Asp, Asn, Glu and Gln). The cystine disulfide functionality is difficult to identify from positive ion fragmentations of an MH+ parent cation of an underivatised peptide. However, the -S-S- group is readily identified by the diagnostic loss of the elements of H2S2 from the (M-H)- anion of the peptide. This process is anion directed (from that cystine backbone enolate anion closest to the Nterminal end of the peptide). The stepwise process is exothermic (by 4.6 kcal mol-1; calculations at the HF/6-31G(d)//AM1 level of theory) with a barrier of 9.1 kcal mol-1 to the highest energy transition state. If one of the cystine residues is Cterminal with a terminal CO2H moiety, the presence of a pronounced peak corresponding to the fragmentation sequence [(M-H)- - (H2S2 + CO2)]- identifies this functionality. The studied fragmentation processes are charge initiated; there is no evidence for the operation of any charge-remote processes.

In this review, a full discussion and update of the state-of-the-art of separation techniques interfaced to plasma spectrometers for speciation analysis of non-metallic elements, such as iodine, chlorine, bromine and fluorine as well as phosphorus and sulfur is presented. The plasma-based techniques covered include inductively coupled plasma mass spectrometry (ICP-MS) microwave-induced plasma optical emission spectrometry (MIP-OES), and inductively coupled plasma optical emission spectrometry (ICP-OES). Also, different variants of plasma sources, such as low power plasmas and glow discharge (GD) sources are described and compared with respect to their capabilities in elemental speciation. Recent advances and alternative mass analyzers (collision/reaction cell; time-of-flight; double-focusing sector field) are also included. The discussion is centralized on the application of the hyphenated methodologies involving several types of separations such as liquid chromatography, gas chromatography and electrophoresis coupled to plasma-based detectors for speciation analysis of non-metals. This is presented in different sections considering the analysis of several matrices including environmental, biological and food samples, as well as a last section related to the use of halogenated compounds for plasma studies.

Nicotinamide containing cofactors are ubiquitous in biological systems. As a result, when studying nicotinamide dependent systems in vitro or in vivo, isotopically labeled nicotinamide cofactors are often used to reveal the mechanism of the biological system of interest. The reduced form of these cofactors is labile and is sensitive to light, oxygen, pH, temperature and other factors. Consequently, their synthesis, purification, analysis, and preservation have been an ongoing challenge. Due to these stability issues, studies using nicotinamide cofactors, especially those utilizing the reduced forms, have been relegated to repetitive cycles of synthesizing the needed material just prior to experimental use. Such practice is not practical in studies utilizing complex isotopic labeling patterns. Many of the efforts that have been reported for synthesis, separation and long-term preservation of the various nicotinamide cofactors, led to procedures that are no longer practical or cost effective while others present the best solutions available today. Some of these efforts are presented and compared in this mini-review. Herein we describe our analytical and synthetic methodologies for the synthesis, separation, purification, analysis and long term preservation of labile nicotinamide cofactors, which achieve excellent versatility, yields, purity, HPLC resolution, and long term stability.

Compare with normal liquid chromatography (LC), high-speed ion chromatography (IC) has the benefits of fast analysis, fast method development, and increased mass sensitivity. These benefits start to attract more and more researchers' attention. This review covers recent developments in high-speed IC field, mainly focus on application of the inorganic anions and cations determination; the review show that high-speed IC mostly use monolithic stationary phases at high eluent flow-rates.

Lanthanide complexes have been used for fluorescent labels to the wide variety of analytical methods including high performance liquid chromatography, immunoassay, and fluorescent imaging with time-resolved fluorometric measurements. Introduction of a time-resolved fluorometric measurement has been permitted the easy distinction of a specific long-lived fluorescence signal from short-lived natural background fluorescence present in most biological samples, reaction wells and optical components. Recently, new fluorescent labels and new instruments have been reported for timeresolved fluorescence including high performance liquid chromatography as in environmental analysis as river water, clinical chemistry as allergen assay, and a biochemical analysis as in staining method of proteins on polyacrylamide gel. The time-resolved fluorometric detection methods using new fluorescent labels improved the detection sensitivity compared to those of previously-described methods. This paper reviews those developments of applications of lanthanide fluorescent labels for various purposes: time-resolved fluorometric high performance liquid chromatography, timeresolved fluorescent immunoassay, and protein staining in recent years.

In this paper, the desirable physical-chemical properties of ionic liquids, the method of ionic liquids used as running electrolytes or modifier in aqueous and non-aqueous capillary electrophoresis were introduced. The potential of capillary electrophoresis based on ionic liquids was discussed throughout the paper. The application status of capillary electrophoresis based on ionic liquids in the analysis of the bioactive components in traditional Chinese herbs, polyphenols, basic proteins, metal ions, and so on were reviewed and summarized with the illustrative use of recent literatures. In addition, the foreground of capillary electrophoresis based on ionic liquids, as well as its difficulties was also discussed.

The management of phosphorus (P) as a non-renewable resource is receiving increasing attention at the dawn of the new millennium. The importance of phosphate as a nutrient, the environment phosphate load in areas with intens livestock production and the depletion of the high quality phosphate resources are accentuating the need of a holistic and global phosphorus-resource management and understanding of the physiological roles, the biosynthesis and the breakdown of phosphorylated compounds in plants. Two important routes towards improved P-resource management are genetic engineering of plants towards improved P bioavailability and the application of microbial phytases to increase the bioavailability of phytate-P in monogastric animals. The present review gives an overview on these P-management approaches and discusses the arsenal of analytical techniques that can be used to analyze P and P-compounds. This analytical capability is an important determinant in the development of more advanced and more effective approaches towards Presource management.