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Accuracy profile is a graphical method, which allows to validate an analytical method. It defines a validity of a concentration range for a given accuracy. With this tool, quantitative determinations of macroelements and microelements (Al, Ca, Fe, K, Mg, Mn, Na, P, S, and Zn) in plant samples were evaluated by the use of a wavelength‐dispersive X‐ray fluorescence instrument. The method uses a simple preparation procedure with only drying, grinding, and pressing samples. The measured samples were reference materials with known mineral contents. The calibration procedure was established by employing plant materials issued from interlaboratory studies. Matrix effects were corrected by employing the method of the influence coefficients on the basis of the computerized routine program linked to the equipment. The accuracy profiles of the method show the measurements (trueness and precision) collected under intermediate precision conditions and aim to compute an acceptability interval where a known proportion of future results will be located. The various types of accuracy profile behavior were exemplified. In comparison with an inductively coupled plasma optical emission spectrometry method, the use of X‐ray fluorescence offers a good alternative, faster, and better precision. Inversely, inductively coupled plasma optical emission spectrometry offers an approach well suited for the trueness of measurements with very low matrix effects. [ABSTRACT FROM AUTHOR]

The El Manatí archaeological site in Veracruz State, Mexico, is famous for its deposits of ceremonial stone axes and beads from the Olmec culture. Some of these have been considered to be in jadeite-jade, but this rock type in these artefacts has never before been physico-chemically verified. A portable Raman spectrometer was employed in situ inside the Centro-INAH Veracruz reserve for this remote analytical operation of non-destructive direct hand-held analysis to identify some of the mineral species present. The key points of interest were as follows: which objects can correctly be called 'jade' because they contain the high-pressure minerals jadeite or omphacite and, if so, with what mol. % Jd (Jd%) in the solid-solution jadeite-diopside-hedenbergite. The Jd% value was then quantified from the wavenumber shift of the symmetric Si-O-Si Raman vibration band. Although some artefacts did not yield any usable Raman spectra, exploitable spectra were obtained from 41 stone axes or beads. Jadeite was found in 13 artefacts and omphacite in another 11. Jd% varied from 95 to 38% such that many of these jades are actually omphacite-jade rather than jadeite-jade. The complicated terminology of jades is thus re-examined. A partial correlation is shown to exist between the Jd% value and the density of the artefacts. These results provide important, hitherto unknown, mineralogical data for archaeologists studying artefacts at different horizons at different sites of Mesoamerican cultures. These results also allow these artefacts to be now labelled correctly in their Museum reserve or exhibition display. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Lactoferrin and transferring were submitted in their metal-free forms as well as in their iron-saturated forms to various concentrations of urea, in the presence or absence of 2-mercaptomethanol. The progressive unfolding of the proteins was followed by their optical activity in the visible region. The change in the three-dimensional structure of lactoferrin when binding iron was found to be more profound than in transferring whose stability is more dependent on disulphide bridges. In the absence of 2-mercaptoethanol, the concentrations of urea which caused 50% denaturation at pH 7.4 were found to be respectively 4 M for apolactoferrin, 4.9 M for apotransferrin, 5.5 M for Fe·transferring and 8 M for Fe·lactoferrin. In the presence of 2-mercaptoethanol, these values became respectively 2 M for apotransferrin, 2.5 M for apolactoferrin, 3.9 M for Fe·transferring and 6.7 M for Fe·lactoferrin. The loss of iron-binding ability, estimated from absorbance at 460 nm, was found to follow strictly the evolution of the [m′]546 parameter. [ABSTRACT FROM AUTHOR]

A molecular weight of 75000 was computed for human lactoferrin on the basis of a sedimentation coefficient s20,w0 = 4.93, a partial specific volume &vsline;20 = 0.715 and a diffusion coefficient D20,w0 = 5.6 x 10-7 cm² x sec-1. A molecular weight of 76800 ± 1600 was estimated from electrophoreses in agarose acrylamide gel containing sodium dodecylsulphate. No decrease of the molecular weight was observed when the reduced and alkylated or aminoethylated protein was submitted to 6 M urea, indicating that the molecule of lactoferrin consists of a single polypeptide chain. From the analysis of the amino acid composition of human lactoferrin a theoretical molecular weight of 76400 was computed by means of a statistical test. A comparison of the amino acid compositions of human lactoferrin and transferrin suggests that the two proteins are more closely related to one another than was suspected before. [ABSTRACT FROM AUTHOR]

By means of a spectrophotometric titration method it was found that six of the tyrosyl residues of the metal-binding proteins lactoferrin and transferrin were titratable by alkali in the metal-lee protons but not in their iron protein complexes, suggesting the involvement of three tyrosyl groups in each of the two binding sites present in these proteins. Seemingly discordant estimates of the number of binding tyrosyls were obtained using the difference spectra of the lactoferrin · Tb3+ vs lactoferrin, lactoferrin · Fe3+ vs lactoferrin, transferrin · Tb3+ vs transferrin or transfferin · Fe3+ vs transferriin. However, such discrepancies as were found could be explained in the light of the ligand-field theory and need not invalidate the conclusions based on alkali-titration data. [ABSTRACT FROM AUTHOR]