Speciation biological systems

The techniques and methods that could be applied to chemical speciation in biological systems are surveyed and the limitations are highlighted. In addition, changes that occur in the samples that may have a detrimental effect on the results are examined. 

A multidisciplinary approach is required in order to achieve total speciation. This approach is not only desirable but essential for the proper design of the experiments and interpretation of the results. Over the next few years, it is to be expected that more information relevant to speciation studies would become available. Thk would lead to a more informed choice of methods and techniques. In addition, on the basis of this knowledge, accurate computer simulation of the distribution of species in a wider variety of biological systems could be accomplished. 

Szpunar, Lobinski el al. have reported on several hyphenated techniques (especially CE-ICP-MS and HPLC-ICP-MS) for elemental speciation in biological systems,51-54 describing e.g. the quasi-simultaneous determination of more than 30 selenopeptides using HPLC-ICP-MS. 

In the past, most analytical problems related to environmental or biological systems were addressed by measuring the total concentrations of the elements. However, at present, there is an increasing awareness of the importance of the chemical form in which an element is present (e.g. the oxidation state, the nature of the ligands or even the molecular structure) since its chemical, biological and toxicological properties critically depend on it. Hence there is a clear need for rapid and robust analytical tools to perform chemical speciation, and atomic spectroscopy is undoubtedly one of the most important tools for such studies. 

J. Szpunar, R. Lobinski and A. Prange, Hyphenated techniques for elemental speciation in biological systems, Appl. Spectrosc., 57, 2003, 102A-112A. 

An important aspect of metal-microbe interactions, but one that is rarely addressed, is metal speciation and metal bioavailability. It is the metal species present and their relative bioavailability rather than total metal concentration in the environment that determines the overall physiological and toxic effects on biological systems (Bernhard, Brinckman Sadler, 1986 Hughes Poole, 1989 Morrison, Batley Florence, 1989). 

The evolutionary fate of parasitic flat-worms lies intimately intertwined with the taxa they currently utilize, the taxa they can but have not yet utilized and the selective pressures driving speciation within and between parasites and their hosts. As with any other biological system, if time and conditions permit, natural selection will maintain diversity. Host switching, host speciation, vicariant events affecting parasites and/or hosts, an increase in host population size and dispersal and drug resistance are just some of the factors that will maintain or even promote the success of parasites and subsequently drive diversity in the hosts. 

Part II considers speciation in specific compartments of the environment viz. the atmosphere, biological systems, soils, sediments and natural waters, and with particular aspects of the speciation of environmentally important radionuclides. Two new chapters have been added to make the coverage even more comprehensive. These new chapters are Chapter 10, Chemical Speciation in Soib and Related Materials by Selective Chemical Extraction by the editors, and Chapter 12, Speciation in Seawater by R.H. Byrne of the University of South Florida. 

The number of analytical methods developed for the study of the distribution of metal- and metalloid-containing species in the last decade has been impressive. However, a majority of these are as yet to be applied to real biological materials. With the greater appreciation of the pre- and post-sampling factors that influence chemical speciation, and the development of appropriate quality control materials the results of these studies will become more reliable. Consequently, the use of chemical speciation data will become indispensable to accurate environmental impact assessment, and to our understanding of the roles that metals and metalloids play in biological systems. 

Details of the intracellular speciation of Si and the mechanisms of its intracellular transport prior to condensation remain uncertain in all of the biological systems studied. Several possible alternatives have been suggested, including association with an intracellular carrier or ionophore17, covalent complex formation by condensation with alcohols, polyols or... 

The principle of the isotope dilution analysis (IDA) is described in Section 6.4. Due to its advantages as a definitive and accurate analytical method for the determination of element concentration via isotope ratio measurements, IDA is being increasingly applied in mass spectrometry, especially in ICP-MS and LA-ICP-MS as one of the most frequently used techniques. For example, the isotope dilution technique is employed in species analysis in biological systems, " e.g., for the determination of mercury species in tuna material,or in aquatic systems. Further applications of the isotope dilution technique are the determination of selenomethionine in human blood serum by capillary HPLC-ICP (ORC) MS ° or sulfur speciation in gas oil, diesel or heating fuel by LA-ICP-MS. Evans and co-workers have reported on the high accuracy analysis of sulfur in diesel fuel by IDA. ICP-SFMS has been employed for Si species analysis in biological or clinical samples and... 

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