Sr isotope measurements in beef-analytical challenge and first results.

The strontium isotope ratio ((87)Sr/(86)Sr) in beef, derived from 206 European cattle, has been measured. These cattle were located in 12 different European regions within France, Germany, Greece, Ireland, Italy, Spain and the UK. As animal protein is known to be a difficult material on which to conduct Sr isotope analysis, several investigations were undertaken to develop and improve the sample preparation procedure. For example, Sr isotope analysis was performed directly on freeze-dried meat and defatted dry mass from the same samples. It was found that enormous differences-sometimes exceeding the measurement uncertainty-could occur between the fractions and also within one sample even if treated in the same manner. These variations cannot be definitely allocated to one cause but are most likely due to inhomogeneities caused by physiological and biochemical processes in the animals as post mortem contamination during analytical processing could be excluded. For further Sr isotope measurements in meat, careful data handling is recommended, and for the authentic beef samples within this project, it was decided to use only freeze-dried material. It can be demonstrated, however, that Sr isotope measurements in beef proteins are a valuable tool for authentication of geographic origin. Although partly overlapping, some of the European sampling sites could be discriminated even by only using (87)Sr/(86)Sr.

Methods for peak assignment in low-resolution multidimensional NMR cross-correlation relaxometry.

Several NMR protocols are presented for assigning peaks in complex T1-T2 spectra, including the effects of varying the spectrometer frequency and the CPMG pulsing rate. Extensions into a third dimension based on chemical-shift; diffusion- and field-cycled weighted T1-T2 cross-correlation methods are also explored as a means of peak assignment. We illustrate the power of these novel techniques with reference to simple aqueous sucrose solutions, but the methodology should be generally applicable.

Allergens of the cupin superfamily.

The cupin family comprises a family of proteins possessing a common beta-barrel structure that is thought to have originated in a prokaryotic ancestor. This structural motif is found as a single domain in fungal spherulins, fern sporulins and the germins/oxalate oxidase proteins of plants, while the globular storage proteins of plants, called legumins (11 S) and euvicilins (7 S), are two-domain cupins. The 11 S globulins are hexameric heteroligomeric proteins of M (r) approximately 360000, with each subunit comprising an acidic 30000-40000- M (r) polypeptide that is disulphide-linked to a 20000- M (r) basic polypeptide. A number of cupins have been identified as major plant food allergens, including the 7 S globulins of soybean (beta-conglycinin), peanut (conarachin; Ara h 1), walnut (Jug r 2) and lentil, and the 11 S globulins of peanut (arachin; Ara h 3), soybean (glycinin) and possibly also coconut and walnut. Other members of the cupin superfamily have not been identified as allergens, with the exception of one germin (germination-specific protein) from pepper. Cupins are generally very stable proteins. A summary of our current knowledge of allergenic seed storage globulins will be presented, together with an overview of cupin structure and stability properties, as illustrated by the allergenic soya globulins, glycinin and beta-conglycinin.