Method for the quantification of underivatized amino acids on dry blood spots from newborn screening by HPLC-ESI-MS/MS

In our study we have developed an HPLC-ESI-MS/MS method for qualitative and quantitative analysis of underivatized amino acids on dry blood spots. The sensitive and specific instrumental performances permitted the chromatographic separation of 40 amino acids and their isomers within 10 min. The method has been set up for cases of suspected metabolic diseases revealed by newborn screening. What is new is that it is applied on the same blood spots used for newborn screening, instead of plasma, in order to avoid involvement of doctors, increased anxiety for parents, stress for patients for plasma collection, long time of waiting and further costs for analysis.     

Cbl-b Is a Novel Physiologic Regulator of Glycoprotein VI-dependent Platelet Activation

Cbl-b, a member of the Cbl family of E3 ubiquitin ligases, plays an important role in the activation of lymphocytes. However, its function in platelets remains unknown. We show that Cbl-b is expressed in human platelets along with c-Cbl, but in contrast to c-Cbl, it is not tyrosine-phosphorylated upon glycoprotein VI (GPVI) stimulation. Cbl-b, unlike c-Cbl, is not required for Syk ubiquitylation downstream of GPVI activation. Phospholipase Cγ2 (PLCγ2) and Bruton''s tyrosine kinase (BTK) are constituently associated with Cbl-b. Cbl-b-deficient (Cbl-b^−/−) platelets display an inhibition in the concentration-response curve for GPVI-specific agonist-induced aggregation, secretion, and Ca²⁺ mobilization. A parallel inhibition is found for activation of PLCγ2 and BTK. However, Syk activation is not affected by the absence of Cbl-b, indicating that Cbl-b acts downstream of Syk but upstream of BTK and PLCγ2. When Cbl-b^−/− mice were tested in the ferric chloride thrombosis model, occlusion time was increased and clot stability was reduced compared with wild type controls. These data indicate that Cbl-b plays a positive modulatory role in GPVI-dependent platelet signaling, which translates to an important regulatory role in hemostasis and thrombosis in vivo.     

The functional links between prion protein and copper

Prion diseases are fatal neurodegenerative disorders associated with the conversion of the cellular prion protein (PrPC) into a pathologic isoform. Although the physiological function of PrPC remains unknown, evidence relates PrPC to copper metabolism and oxidative stress as suggested by its copper-binding properties in the N-terminal octapeptide repeat region. This region also reduces copper ions in vitro, and this reduction ability is associated with the neuroprotection exerted by the octarepeat region against copper in vivo. In addition, the promoter region of the PrPC gene contains putative metal response elements suggesting it may be regulated by heavy metals. Here we address some of the evidence that support a physiological link between PrPC and copper. Also, in vivo experiments suggesting the physiological relevance of PrPC interaction with heparan sulfate proteoglycans are discussed.     

Hydroxamic acids in Secale cereale L. and the relationship with their antifeedant and allelopathic properties

Contents of the hydroxamic acids 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA), and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) in leaves and roots of 14 cultivars of rye, Secale cereale L., were determined. Dynamics of accumulation in three cultivars were evaluated. DIBOA was the main cyclic hydroxamic acid in leaves but the contents differed significantly between the cultivars. Both DIBOA and DIMBOA were present in the roots. Maximum concentration of DIBOA in leaves and DIMBOA in roots was reached between 48-54 h and 54-72 h after germination, respectively. Antifeedant activity of DIBOA towards the aphid Rhopalosiphum padi and the feeding behavior were studied by electronic recording in barley leaves treated with different contents of DIBOA. The deleterious activity of DIBOA could arise by starvation and/or a toxic effect. Additionally, allelopathic potential of pure DIBOA and aqueous extracts of leaves and roots of rye (Tetra-Baer) on the germination of lettuce (Lactuca sativa) and rye (Tetra-Baer) seeds was evaluated. A high percentage of germination inhibition of pure DIBOA and the extracts of leaves and roots was observed. The activity is in agreement with the contents of hydroxamic acids in the plants. The substrates had no allelopathic effect on rye seeds.     

The crystal structure of a thermophilic glucose binding protein reveals adaptations that interconvert mono and di-saccharide binding sites

Periplasmic binding proteins (PBPs) comprise a protein superfamily that is involved in prokaryotic solute transport and chemotaxis. These proteins have been used to engineer reagentless biosensors to detect natural or non-natural ligands. There is considerable interest in obtaining very stable members of this superfamily from thermophilic bacteria to use as robust engineerable parts in biosensor development. Analysis of the recently determined genome sequence of Thermus thermophilus revealed the presence of more than 30 putative PBPs in this thermophile. One of these is annotated as a glucose binding protein (GBP) based on its genetic linkage to genes that are homologous to an ATP-binding cassette glucose transport system, although the PBP sequence is homologous to periplasmic maltose binding proteins (MBPs). Here we present the cloning, over-expression, characterization of cognate ligands, and determination of the X-ray crystal structure of this gene product. We find that it is a very stable (apo-protein Tm value is 100(+/- 2) degrees C; complexes 106(+/- 3) degrees C and 111(+/- 1) degrees C for glucose and galactose, respectively) glucose (Kd value is 0.08(+/- 0.03) microM) and galactose (Kd value is 0.94(+/- 0.04) microM) binding protein. Determination of the X-ray crystal structure revealed that this T. thermophilus glucose binding protein (ttGBP) is structurally homologous to MBPs rather than other GBPs. The di or tri-saccharide ligands in MBPs are accommodated in long relatively shallow grooves. In the ttGBP binding site, this groove is partially filled by two loops and an alpha-helix, which create a buried binding site that allows binding of only monosaccharides. Comparison of ttGBP and MBP provides a clear example of structural adaptations by which the size of ligand binding sites can be controlled in the PBP super family.     

Occurrence of Ochratoxin A-Producing Fungi in Commercial Corn Kernels in Argentina

Potentially ochratoxigenic Aspergillus and Penicillium species were identified and the natural occurrence of ochratoxin A (OTA) in corn kernels was evaluated. Likewise, the capacity to produce OTA by Aspergillus section Nigri and Circumdati was investigated. A total of 50 corn samples for human consumption was collected in the south of Córdoba Province. The surface-disinfected method for mycobiota determination was used. The OTA detection was performed by HPLC. OTA production was tested in strains belonging to section Nigri and Circumdati. Statistical analysis demonstrated that the specie A. flavus was isolated in higher frequency (p<0.01) from corn kernels in DRBC and DG18 media. The percentage of corn kernels contaminated by A. niger var. niger was similar in DRBC and DG18 media. The frequency of grains contaminated by A. flavus and A. niger var. awamori was higher than A. niger var. niger and A. japonicus var. japonicus (p<0.01) in DG18 media. The other potentially ochratoxigenic species, A. ochraceus, was isolated between 5% and 10% of the corn kernels in DG18 and DRBC media, respectively. The OTA producing species P. verrucosum was not isolated. All samples of corn were OTA negative (<1 ng g⁻¹). Thirty strains (25%) of the black Aspergillus were OTA producers. From four strains of A. ochraceus isolated, only one produced OTA. Due to the storage variable conditions could not be adequate in this substrate, the presence of ochratoxigenic strains of section Nigri and OTA needs to be evaluated for a longer time to establish the toxicological risk for human beings. The contamination of stored corn kernels with A. flavus and Aspergillus section Nigri was significant.     

Carbohydrate metabolism and fruit quality are affected in frost-exposed Valencia orange fruit

Exposure of citrus fruit to frost often results in the development of freeze injury during their maturation in planta. This work was aimed to analyze changes in the biochemistry and enzymology of carbohydrate metabolism in freeze-injured orange fruit ( Citrus sinensis var. Valencia late) and the involvement of oxidative stress in frost damage. The activities of pyrophosphate-dependent phosphofructokinase, phosphoenolpyruvate carboxylase and several fermentative enzymes increased in frost-exposed (FE) fruit, while NADP-malic enzyme and the mitochondrial isoform of NAD-malate dehydrogenase showed a reduction in their activities. Western blot analysis indicated a correlation between activity levels and protein content. Respiration rate in whole fruit was reduced by 40%, whereas the flavedo showed a more pronounced decline (53%). Volatile compound (i.e. ethanol and acetaldehyde) content was significantly higher in FE fruit than in control, as was that of l -malate (three-fold). Additionally, FE fruit showed a marked decrease in the maturity index (24%) because of a higher titratable acidity (39%). Evidence is presented that oxidative stress is involved in freeze-induced damage of orange fruit, where oxidative damage to lipids and proteins, and a greater electrolyte leakage in the flavedo were also observed. The results suggest that freezing temperatures provoke a notable metabolic switch in citrus fruit toward a fermentative stage, resulting in low-quality fruits.