Electron spin resonance (ESR) spectroscopy study of cheese treated with accelerated electrons

The generation, accumulation and decay of free radicals in six varieties of cheese, irradiated (0–4 kGy) in an electron accelerator, have been studied by electron spin resonance (ESR) spectroscopy. Remarkably, the ESR spectra of all untreated cheeses showed only one singlet signal with a g-factor of 2.0064 ± 0.0005. Surprisingly, the ESR spectra of irradiated samples presented a new signal with g-factor of 2.0037 ± 0.0003 which was independent of the type of cheese, and which might be due to free radicals from the radiolysis of proteins. Surface regression models (P < 0.0001) established the relationship among signal intensity, absorbed dose (0, 1, 2 and 4 kGy) and storage time (0–180 days) for the different types of cheese. Results suggested that the analysis by ESR (or electron paramagnetic resonance, EPR) is suitable to evaluate, either qualitatively or quantitatively, the irradiation treatment of different types of cheese.Sección Deptal. de Farmacia Galénica y Tecnología Alimentaria (Veterinaria)Fac. de VeterinariaTRUEpu

Electron spin resonance (ESR) spectroscopy study of dry-cured ham treated with E-beam

The generation, accumulation and decay of free radicals in muscle and fat fractions from three varieties of Spanish dry-cured ham treated (0–4 kGy) in an electron accelerator have been studied by electron spin resonance (ESR) spectroscopy. In the ESR spectra from fat fractions, a well-resolved triplet signal corresponding to an alkyl radical was found only in treated samples. Linear regression models (P 0.05) differences were found between ESR spectra from untreated (0 kGy) and treated (0–4 kGy) samples. Results suggest that the analysis of ESR spectrum in fat samples can be used to evaluate the E-beam treatment of dry-cured hamMICINNCARNISENUSASección Deptal. de Farmacia Galénica y Tecnología Alimentaria (Veterinaria)Fac. de VeterinariaTRUEpu

Covalent Attachment of Heme to the Protein Moiety in an Insect E75 Nitric Oxide Sensor

We have recombinantly expressed and purified the ligand binding domains (LBDs) of four insect nuclear receptors of the E75 family. The Drosophila melanogaster and Bombyx mori nuclear receptors were purified as ferric hemoproteins with Soret maxima at 424 nm, whereas their ferrous form had a Soret maximum at 425 nm that responds to ·NO and CO binding. In contrast, the purified LBD of Oncopeltus fasciatus displayed a Soret maximum at 415 nm for the ferric protein that shifted to 425 nm in its ferrous state. Binding of ·NO to the heme moiety of D. melanogaster and B. mori E75 LBD resulted in the appearance of a peak at 385 nm, whereas this peak appeared at 416 nm in the case of the O. fasciatus hemoprotein, resembling the behaviour displayed by its human homolog Rev-erbβ. HPLC analysis revealed that, unlike the D. melanogaster and B. mori counterparts, the heme group of O. fasciatus is covalently attached to the protein through the side-chains of two amino acids. The large sequence homology with O. fasciatus E75 led us to clone and express the LBD of Blattella germanica, which established that its spectral properties closely resemble those of O. fasciatus and that it also has the heme group covalently bound to the protein. Hence, ·NO/CO regulation of the transcriptional activity of these nuclear receptors might be differently controlled among various insect species. In addition, covalent heme binding provides strong evidence that at least some of these nuclear receptors function as diatomic gas sensors rather than heme sensors. Finally, our findings expand the classes of hemoproteins in which the heme group is normally covalently attached to the polypeptide chain