Peptide fractionation is extremely important in proteomics approaches. Full proteome characterization is desired from complex organisms, and with growing interest in post-translational modifications an extended protein sequence coverage is required. Peptide fractionation techniques have the great challenge of feeding current mass spectrometers in a way in which these issues are met. Peptide fractionation can be divided into three simple components: the column characteristics; the mobile phase; and peptide properties (charge, polarity, hydrophobicity and size). The current challenges are in the combination of these three components to allow comprehensive proteomics studies to be improved.

Caffeine is one of the most widely consumed psycho-stimulants. The study of the beneficial effects of caffeine consumption to decrease the risk of developing several neuropsychiatric pathologies is receiving increasing attention. Thus, accurate and sensitive methods have been developed, mainly by LC-MS/MS, in order to quantify caffeine and its metabolites. These quantifications of caffeine and its metabolites by LC-MS/MS require a considerable effort to select or find a surrogate matrix, without the compounds of interest, to be used in the calibration curves. Thus, we evaluated the possibility of using calibration curves prepared in solvent instead of calibration curves prepared in human plasma. Results show that the calibration curves prepared in solvent and in human plasma were similar by comparing their slopes and interceptions, and the accuracy and precision were within the limits of acceptance for both calibration curves. This work demonstrates that, by using internal standards, it is possible to use a calibration curve in solvent instead of a calibration curve in plasma to perform an accurate and precise quantification of caffeine and theobromine.

Ag⁺had stronger effects than AgNPs on the growth ofPseudomonassp. M1. Responses of metabolic, energetic and stress pathways to Ag⁺and AgNP exposure suggested distinct mechanisms of toxicity.

Caffeine may be protective against Alzheimer’s disease (AD) by modulating amyloid-β (Aβ) metabolic pathways. The present work aimed to study a possible association of caffeine consumption with the cerebrospinal fluid (CSF) biomarkers, particularly Aβ. The study included 88 patients with AD or mild cognitive impairment. The consumption of caffeine and theobromine was evaluated using a validated food questionnaire. Quantification of caffeine and main active metabolites was performed with liquid chromatography coupled to tandem mass spectrometry. The levels of Aβ _1 - 42 , total tau, and phosphorylated tau in the CSF were determined using sandwich ELISA methods and other Aβ species, Aβ _X - 38 , Aβ _X - 40 , and Aβ _X - 42 , with the MSD Aβ Triplex assay. The concentration of caffeine was 0.79±1.15 μ g/mL in the CSF and 1.20±1.88 μ g/mL in the plasma. No correlation was found between caffeine consumption and Aβ ₄₂ in the CSF. However, a significant positive correlation was found between the concentrations of theobromine, both in the CSF and in the plasma, with Aβ ₄₂ in the CSF. Theobromine in the CSF was positively correlated with the levels of other xanthines in the CSF, but not in the plasma, suggesting that it may be formed by central metabolic pathways. In conclusion, caffeine consumption does not modify the levels of CSF biomarkers, and does not require to be controlled for when measuring CSF biomarkers in a clinical setting. Since theobromine is associated with a favorable Aβ profile in the CSF, the possibility that it might have a protective role in AD should be further investigated.