High-frequency and high-field electron paramagnetic resonance (HFEPR): a new spectroscopic tool for bioinorganic chemistry.

This minireview describes high-frequency and high-field electron paramagnetic resonance (HFEPR) spectroscopy in the context of its application to bioinorganic chemistry, specifically to metalloproteins and model compounds. HFEPR is defined as frequencies above ~100 GHz (i.e., above W-band) and a resonant field reaching 25 T and above. The ability of HFEPR to provide high-resolution determination of g values of S = 1/2 is shown; however, the main aim of the minireview is to demonstrate how HFEPR can extract spin Hamiltonian parameters [zero-field splitting (zfs) and g values] for species with S > 1/2 with an accuracy and precision unrivalled by other physical methods. Background theory on the nature of zfs in S = 1, 3/2, 2, and 5/2 systems is presented, along with selected examples of HFEPR spectroscopy of each that are relevant to bioinorganic chemistry. The minireview also provides some suggestions of specific systems in bioinorganic chemistry where HFEPR could be rewardingly applied, in the hope of inspiring workers in this area.

Spectrophotometric characterisation of the Cu(II):PPi system: implementation as a method for measuring pyrophosphate (PPi) in solution

El pirofosfato (PPi) tiene una importante función en numerosos procesos biológicos. Participa en muchas reacciones enzimáticas catalizadas por transferasas, hidrolasas, ligasas o sintetasas. La interacción en solución del Cu(II) con pirofosfato (PPi) modifica el espectro de absorción del catión. Se describen las interacciones químicas involucradas en el cambio de absorbancia, se identifican los coeficientes de absorción de las diferentes especies en solución y proponemos un modelo del sistema químico Cu(II)-PPi. Ya que los cambios en el espectro de absorción son dependientes de la concentración, nosotros proponemos un método para cuantificar PPi en soluciones acuosas basado en la modificación del espectro de absorción de Cu(II) en presencia PPi. Los cambios en la absorción pueden ser monitorizados y utilizados para cuantificar PPi en solución. La determinación es simple, rápida y barata. El límite de detección del método es 0,1 ìmol de PPi en las condiciones del ensayo. Además es posible usar este método en sistema biológicos que contienen proteínas, nucleótidos, EDTA o magnesio

The interaction of Cu(II) with pyrophosphate (PPi) in solution modifies the absorption spectrum of the cation. We provide here a proper description of the chemical interactions involved in the absorbance shift, identify the absorption coefficients of the species in solution and afford a model of the Cu(II)-PPi chemical system. Since the changes in the absorption spectrum are concentration dependent, we describe a new method for quantifying PPi in aqueous solutions, based on the modification of the Cu(II) absorption spectrum in the presence of PPi. Changes in absorptivity can be monitored and used to quantify PPi in solution. The determination is simple, fast and cheap. The detection limit of the method is 0.1 ìmol of PPi in the assay conditions. The presence of orthophosphate does not interfere in the determination of PPi. Furthermore, it is possible to use this method in biological systems containing proteins, nucleotides, EDTA or magnesium

Mass spectrometry in bioinorganic analytical chemistry.

A considerable momentum has recently been gained by in vitro and in vivo studies of interactions of trace elements in biomolecules due to advances in inductively coupled plasma mass spectrometry (ICP MS) used as a detector in chromatography and capillary and planar electrophoresis. The multi-isotopic (including non-metals such as S, P, or Se) detection capability, high sensitivity, tolerance to matrix, and large linearity range regardless of the chemical environment of an analyte make ICP MS a valuable complementary technique to electrospray MS and MALDI MS. This review covers different facets of the recent progress in metal speciation in biochemistry, including probing in vitro interactions between metals and biomolecules, detection, determination, and structural characterization of heteroatom-containing molecules in biological tissues, and protein monitoring and quantification via a heteroelement (S, Se, or P) signal. The application areas include environmental chemistry, plant and animal biochemistry, nutrition, and medicine.

[Handling of biological material before trace element determination]. / Alcuni aspetti del trattamento di materiale biologico prima della determinazione di elementi in traccia.

The various steps of the analytical process are taken into account with particular reference to problems arising in sampling biological materials, their storage, pretreatment, digestion (when necessary) and determination. Emphasis is laid on the fact that the availability of analytical equipment with exceptional detection power is not always flanked by an equivalent ability to control phenomena of contamination and/or loss of analytes as well as to check and guarantee the accuracy of experimental data. In this context, proper use of the most popular analytical techniques for the determination of trace elements and the adoption of strict procedural conditions for data reliability are briefly discussed.

[Assessment of factors causing pre-analytic variabililty]. / Esame dei fattori di variabilità preanalitici.

Preanalytical variability can affect the results of trace element determinations. Even using sensitive and reliable analytical methods, the analysis of a contaminated specimen can only lead to erroneous results. Analyte contents in a sample can be altered during collection, storage and pretreatment, including simple dilution. Anticoagulants, plastic and glassware used for collection and storage, reagents, including water, and the laboratory environment itself, under particular conditions, can significantly contribute to this variability. The most common sources of contamination of biological matrices and some preventive measures are discussed. Operative procedures for the collection and storage of biological samples, specifically designed in dependence of analyte and matrix type, are reported.

[Instrumental analysis of trace elements]. / Analisi strumentale di elementi in traccia.

The study of trace elements in human medicine and toxicology requires very low concentration of these elements to be determined in biological matrices. Among the analytical methodologies of major impact there are isotopic dilution mass spectrometry, neutron activation analysis, anodic stripping voltammetry, inductively coupled plasma atomic emission spectrometry and electrothermal atomization atomic emission spectrometry. This last, in particular, provides high sensitivity and reliability for the determination of numerous elements. Instrumental and methodological improvements leading to these achievements include the adoption of the so-called stabilized temperature platform furnace, the introduction of universal matrix modifiers, oxygen charring steps and background correction systems based on the Zeeman effect.