A Comprehensive Analytical Review of Polyphenols: Evaluating Neuroprotection in Alzheimer's Disease.

Alzheimer's Disease (AD), a prevalent neurodegenerative disorder, is the primary cause of dementia. Despite significant advancements in neuroscience, a definitive cure or treatment for this debilitating disease remains elusive. A notable characteristic of AD is oxidative stress, which has been identified as a potential therapeutic target. Polyphenols, secondary metabolites of plant origin, have attracted attention due to their potent antioxidant properties. Epidemiological studies suggest a correlation between the consumption of polyphenol-rich foods and the prevention of chronic diseases, including neurodegenerative disorders, which underscores the potential of polyphenols as a therapeutic strategy in AD management. Hence, this comprehensive review focuses on the diverse roles of polyphenols in AD, with a particular emphasis on neuroprotective potential. Scopus, ScienceDirect, and Google Scholar were used as leading databases for study selection, from 2018 to late March 2024. Analytical chemistry serves as a crucial tool for characterizing polyphenols, with a nuanced exploration of their extraction methods from various sources, often employing chemometric techniques for a holistic interpretation of the advances in this field. Moreover, this review examines current in vitro and in vivo research, aiming to enhance the understanding of polyphenols' role in AD, and providing valuable insights for forthcoming approaches in this context.

The Potential of Plum Seed Residue: Unraveling the Effect of Processing on Phytochemical Composition and Bioactive Properties.

Bioactive compounds extracted from plum seeds were identified and quantified, aiming to establish how the brandy manufacturing process affects the properties and possible cascade valorization of seed residues. Extraction with n-hexane using Soxhlet has provided oils rich in unsaturated fatty acids (92.24-92.51%), mainly oleic acid (72-75.56%), which is characterized by its heart-healthy properties. The fat extracts also contain tocopherols with antioxidant and anti-inflammatory properties. All the ethanol-water extracts of the defatted seeds contain neochlorogenic acid (90-368 µg·g-1), chlorogenic acid (36.1-117 µg·g-1), and protocatechuate (31.8-100 µg·g-1) that have an impact on bioactive properties such as antimicrobial and antioxidant. Anti-amyloidogenic activity (25 mg·mL-1) was observed in the after both fermentation and distillation extract, which may be related to high levels of caffeic acid (64 ± 10 µg·g-1). The principal component analysis showed that all plum seed oils could have potential applications in the food industry as edible oils or in the cosmetic industry as an active ingredient in anti-aging and anti-stain cosmetics, among others. Furthermore, defatted seeds, after both fermentation and distillation, showed the greatest applicability in the food and nutraceutical industry as a food supplement or as an additive in the design of active packaging.

Effect of Storage and Drying Treatments on Antioxidant Activity and Phenolic Composition of Lemon and Clementine Peel Extracts.

Obtaining polyphenols from horticultural waste is an emerging trend that enables the valorization of resources and the recovery of value-added compounds. However, a pivotal point in the exploitation of these natural extracts is the assessment of their chemical stability. Hence, this study evaluates the effect of temperature storage (20 and -20 °C) and drying methods on the phenolic composition and antioxidant activity of clementine and lemon peel extracts, applying HPLC-DAD-MS, spectrophotometric methods, and chemometric tools. Vacuum-drying treatment at 60 °C proved to be rather suitable for retaining the highest antioxidant activity and the hesperidin, ferulic, and coumaric contents in clementine peel extracts. Lemon extracts showed an increase in phenolic acids after oven-drying at 40 °C, while hesperidin and rutin were sustained better at 60 °C. Hydroethanolic extracts stored for 90 days preserved antioxidant activity and showed an increase in the total phenolic and flavonoid contents in lemon peels, unlike in clementine peels. Additionally, more than 50% of the initial concentration was maintained up to 51 days, highlighting a half-life time of 71 days for hesperidin in lemon peels. Temperature was not significant in the preservation of the polyphenols evaluated, except for in rutin and gallic acid, thus, the extracts could be kept at 20 °C.

Valorization of Prunus Seed Oils: Fatty Acids Composition and Oxidative Stability.

Prunus fruit seeds are one of the main types of agri-food waste generated worldwide during the processing of fruits to produce jams, juices and preserves. To valorize this by-product, the aim of this work was the nutritional analysis of peach, apricot, plum and cherry seeds using the official AOAC methods, together with the extraction and characterization of the lipid profile of seed oils using GC-FID, as well as the measurement of the antioxidant activity and oxidative stability using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging method. Chemometric tools were required for data evaluation and the obtained results indicated that the main component of seeds were oils (30-38%, w). All seed oils were rich in oleic (C18:1n9c) and linoleic (C18:2n6c) acids and presented heart-healthy lipid indexes. Oil antioxidant activity was estimated in the range IC50 = 20-35 mg·mL-1, and high oxidative stability was observed for all evaluated oils during 1-22 storage days, with the plum seed oil being the most antioxidant and stable over time. Oxidative stability was also positively correlated with oleic acid content and negatively correlated with linoleic acid content. Therefore, this research showed that the four Prunus seed oils present interesting healthy characteristics for their use and potential application in the cosmetic and nutraceutical industries.

A combined analytical-chemometric approach for the in vitro determination of polyphenol bioaccessibility by simulated gastrointestinal digestion.

In this study, an integrated characterisation through polyphenol and caffeine content and antioxidant activity was combined with chemometric analysis to assess the effects of simulated in vitro gastrointestinal digestion on the bioaccessibility of these bioactive compounds from nine different tea infusions. Tea infusions were characterised based on total flavonoids, total polyphenols and antioxidant activity, together with the determination of individual polyphenol content. Fourteen phenolic compounds, including phenolic acids, stilbenes and flavonoids, were selected based on their reported bioactivity and high accessibility, attributed to their low molecular weight. Both polyphenols and caffeine were initially monitored in raw tea infusions and through the different digestion stages (salivary, gastric and duodenal) by capillary high performance liquid chromatography coupled to diode array detection (cHPLC-DAD) and/or HPLC coupled to a triple quadrupole mass analyser (HPLC-MS/MS). Multivariate analysis of the studied bioactives, using principal component analysis and cluster analysis, revealed that the decaffeination process seems to increase the stability and concentration of the compounds evaluated during digestion. The greatest transformations occurred mainly in the gastric and duodenal stages, where low bioactivity indices (IVBA) were shown for resveratrol and caffeic acid (IVBA = 0%). In contrast, the polyphenols gallic acid, chlorogenic acid and quercetin gave rise to their availability in white, green and oolong infusion teas (IVBA > 90%). Furthermore, highly fermented black and pu-erh varieties could be designated as less bioaccessible environments in the duodenum with respect to the tested compounds.

Neuroprotective activity of selenium nanoparticles against the effect of amino acid enantiomers in Alzheimer's disease.

Alzheimer's disease (AD), the most prevalent neurodegenerative disease, is characterized by extracellular accumulation of amyloid-beta protein (Aß), which is believed to be the very starting event of AD neurodegeneration. In this work, D-Phe, D-Ala, and D-Glu amino acids, which are the non-occurring enantiomeric form in the human body, and also D-Asp and DL-SeMet, have proved to be amyloidogenic regarding Aß42 aggregation in TEM studies. These amyloidogenic amino acid enantiomers also widened Aß42 fibrils up to 437% regarding Aß42 alone, suggesting that Aß42 aggregation is enantiomerically dependent. To inhibit enantiomeric-induced amyloid aggregation, selenium nanoparticles stabilized with chitosan (Ch-SeNPs) were successfully synthesized and employed. Thus, Ch-SeNPs reduced and even completely inhibited Aß42 aggregation produced in the presence of some amino acid enantiomers. In addition, through UV-Vis spectroscopy and fluorescence studies, it was deduced that Ch-SeNPs were able to interact differently with amino acids depending on their enantiomeric form. On the other hand, antioxidant properties of amino acid enantiomers were evaluated by DPPH and TBARS assays, with Tyr enantiomers being the only ones showing antioxidant effect. All spectroscopic data were statistically analysed through experimental design and response surface analysis, showing that the interaction between the Ch-SeNPs and the amino acids studied was enantioselective and allowing, in some cases, to establish the concentration ratios in which this interaction is maximum.

Perioperative Continuous Noninvasive Cardiac Output Monitoring in Cardiac Surgery Patients by a Novel Capnodynamic Method.

OBJECTIVES: To test the clinical performance of a novel continuous noninvasive cardiac output (CO) monitoring based on expired carbon dioxide kinetics in cardiac surgery patients. DESIGN: A prospective feasibility pragmatic clinical study. SETTING: A single-center, large community hospital. PARTICIPANTS: Thirty-two patients undergoing cardiac surgery were studied during the intraoperative (before cardiopulmonary bypass) and postoperative (in the intensive care unit before extubation) periods. INTERVENTIONS: CO was measured simultaneously by the continuous capnodynamic method and by transpulmonary thermodilution during changes in the patient's hemodynamic and/or respiratory conditions. MEASUREMENTS AND MAIN RESULTS: The current recommended comparative statistics for CO measurement methods were analyzed, including bias, precision, and percentage error obtained from Bland-Altman analysis, and concordance between methods obtained from the four-quadrant plot analysis to evaluate the trending ability. Bias ± limits of agreement and percentage error were -0.6 (-1.9 to +0.8; 95% CI of 3.73-5.25) L/min and 31% (n = 147 measurements) for the intraoperative period, -0.8 (-2.4 to +0.9; 95% CI of 3.03-5.21) L/min and 41% (n = 66) for the postoperative period, and -0.6 (-2.1 to +0.8; 95% CI of 3.74-5.00) L/min and 34% (n = 213) for the pooled data. The trending analysis obtained a concordance of 82% (n = 65) for the intraoperative and 71% (n = 24) for the early postoperative periods. Aggregation of both data sets gave a concordance of 79% (n = 89). CONCLUSIONS: The continuous capnodynamic method was reliable and in good agreement with the reference method, and had an accuracy and trending ability good enough to make it a possible future alternative for hemodynamic monitoring in the studied population of elective adult cardiac surgery patients.

Effects of three biochars on copper immobilization and soil microbial communities in a metal-contaminated soil using a metallophyte and two agricultural plants.

Biochar (BC) is a porous, carbonaceous material produced by slow pyrolysis of biomass under oxygen-limited conditions. BC production has been attracting research interest because it modifies soil physicochemical characteristics and improves the growth of plants in problem soils. These benefits may be best actualized for soils contaminated by metals, where remediation is hampered by metal toxicity to both plants and soil microbial communities. The objectives of this study were to evaluate the impact of the addition of chicken manure biochar (CMB), oat hull biochar (OHB), or pine bark biochar (PBB) on copper (Cu) bioavailability in a Cu-contaminated soil, the effectiveness of these BCs promoting plant growth, and its effects on soil microbial communities supporting these plants. A sandy soil (338 mg Cu kg-1) was amended with CMB, OHB, and PBB, and the metallophyte Oenothera picensis or the agricultural species Solanum lycopersicum and Lolium perenne were grown for 3 months. The BCs produced an increase in soil pH, reduced the exchangeable Cu, and increased Cu bound to organic matter and residual fractions. All BCs enhanced the quality of contaminated soil and increased the plant biomass production, notably for S. lycopersicum, which grew until 12 times more than plants in non-amended soil. While BC addition reduced the concentration of Cu in soil pore water, the amendment did not reduce the concentrations of Cu in shoot tissues. BC additions also stimulated soil microorganisms, increasing basal respiration and DHA activity and modifying microbial communities, especially in soils supporting L. perenne. These results indicate that BCs represent an effective tool to remediate Cu-contaminated sandy soils.

Ability of selenium species to inhibit metal-induced Aß aggregation involved in the development of Alzheimer's disease.

Extracellular accumulation of amyloid beta peptide (Aß) is believed to be one of the main factors responsible for neurodegeneration in Alzheimer's disease (AD). Metals could induce Aß aggregation, by their redox activity or binding properties to amyloid ß fibrils, leading to their accumulation and deposition outside neurons. For this reason, metal chelation may have an acknowledged part to play in AD prevention and treatment. In the current work, the role of different selenium species, including selenium nanoparticles, in Aß aggregation, was studied by evaluating their metal-chelating properties and their ability both to inhibit metal-induced Aß1-42 aggregation fibrils and to disaggregate them once formed. Transition biometals such as Fe(II), Cu(II), and Zn(II) at 50 µM were selected to establish the in vitro models. The DPPH assay was used to determine the antioxidant capacity of the evaluated selenium species. Selenium nanoparticles stabilized with chitosan (Ch-SeNPs) and with both chitosan and chlorogenic acid polyphenol (CGA@ChSeNPs) showed the highest antioxidant properties with EC50 of 0.9 and 0.07 mM, respectively. UV-Vis and d1(UV-Vis) spectra also revealed that selenium species, in particular selenomethionine (SeMet), were able to interact with metals. Regarding Aß1-42 incubation experiments, Fe(II), Cu(II), and Zn(II) induced Aß aggregation, in a similar way to most of the evaluated selenium species. However, Ch-SeNPs produced a high inhibition of metal-induced Aß aggregation, as well as a high disaggregation capacity of Aß fibrils in both the presence and absence of biometals, in addition to reducing the length and width (20% of reduction in the presence of Zn(II)) of the generated Aß fibrils. Graphical abstract.

Estimation of residual renal function using beta-trace protein: Impact of dialysis procedures.

Beta-trace protein (BTP), a low molecular weight protein of 23-29 kDa, has been proposed as a promising biomarker to estimate residual renal function (RRF) in patients on maintenance hemodialysis (HD). Indeed, BTP is cleared by native kidney but not during conventional HD session. By contrast, the removal rate of BTP using convective processes (mainly hemodiafiltration [HDF]) and peritoneal dialysis (PD) has been little or not investigated. Therefore, an aim of this study was to evaluate the impact of dialysis procedures (high-flux HD, on-line post-dilution HDF and PD) on BTP removal in comparison with beta-2 microglobulin (B2M) and cystatin C (CYSC) removals after a single session. In addition, the ability of BTP to predict RRF in PD was assessed. This observational cross-sectional study included a total of 82 stable chronic kidney disease patients, 53 patients were on maintenance dialysis (with n = 26 in HD and n = 27 in HDF) and 29 were on PD. Serum concentrations of BTP, B2M, and CYSC were measured (a) before and after a single dialysis session in HD and HDF anuric patients to calculate reduction percentages, (b) in serum, 24-hour-dialysate and 24-hour-urine in PD patients to compute total, peritoneal, and urinary clearance. RRF was estimated using four equations developed for dialysis patients without urine collection and compared to the mean of the urea and creatinine clearances in PD. The concentrations of the three studied molecules were significantly reduced (P < .001) after dialysis session with significantly higher reduction ratio using HDF compared to HD modality (P < .001): BTP 49.3% vs 17.5%; B2M 82.3% vs 69.7%; CYSC 77.4% vs 66% in HDF and HD, respectively. In non-anuric PD patients, B2M and CYSC were partly removed by peritoneal clearance (72.3% and 57.6% for B2M and CYSC, respectively). By contrast, BTP removal by the peritoneum was negligible and a low bias for the BTP-based equation to estimate RRF (-1.4 mL/min/1.73 m2 ) was calculated. BTP is significantly removed by high-flux HD or HDF, thereby compromising its use to estimate RRF. By contrast, BTP appears as a promising biomarker to estimate RRF in PD patients since it is not affected by peritoneal clearance, unlike B2M and CYSC, and it is well correlated to RRF.

Enzymatic esterification of oleic acid by Candida rugosa lipase immobilized onto biochar.

The immobilization of Candida rugosa lipase (CRL) onto biochar was studied in a series of batch experiments. CRL sorption behavior was evaluated as a function of pH, enzyme concentration, temperature and ionic strength. As the immobilized lipase was used for the catalytic esterification of oleic acid, its resistance to solvents and thermal stability were evaluated. CRL adsorption increased by increasing temperature, and with higher pH, reaching a maximum at pH 7.0. Immobilization increased lipase stability at 40 °C by more than 80% when compared to the free enzyme. Moreover, immobilized CRL showed high stability in the presence of tert-butanol, which prevents premature deactivation of the enzyme caused by alcohols during the reaction. Immobilization of CRL increased the oleic acid conversion rate. Our results suggest that biochar is a highly promising material for the immobilization of CRL lipase for the catalytic production of esters.

The HIV-1 Vpr Protein: A Multifaceted Target for Therapeutic Intervention.

The human immunodeficiency virus type 1 (HIV-1) Vpr protein is an attractive target for antiretroviral drug development. The conservation both of the structure along virus evolution and the amino acid sequence in viral isolates from patients underlines the importance of Vpr for the establishment and progression of HIV-1 disease. While its contribution to virus replication in dividing and non-dividing cells and to the pathogenesis of HIV-1 in many different cell types, both extracellular and intracellular forms, have been extensively studied, its precise mechanism of action nevertheless remains enigmatic. The present review discusses how the apparently multifaceted interplay between Vpr and host cells may be due to the impairment of basic metabolic pathways. Vpr protein modifies host cell energy metabolism, oxidative status, and proteasome function, all of which are likely conditioned by the concentration and multimerization of the protein. The characterization of Vpr domains along with new laboratory tools for the assessment of their function has become increasingly relevant in recent years. With these advances, it is conceivable that drug discovery efforts involving Vpr-targeted antiretrovirals will experience substantial growth in the coming years.

Cryopreserved CD90+ cells obtained from mobilized peripheral blood in sheep: a new source of mesenchymal stem cells for preclinical applications.

Mobilized peripheral blood (MPB) bone marrow cells possess the potential to differentiate into a variety of mesenchymal tissue types and offer a source of easy access for obtaining stem cells for the development of experimental models with applications in tissue engineering. In the present work, we aimed to isolate by magnetic activated cell sorting CD90+ cells from MPB by means of the administration of Granulocyte-Colony Stimulating Factor and to evaluate cell proliferation capacity, after thawing of the in vitro culture of this population of mesenchymal stem cells (MSCs) in sheep. We obtained a median of 8.2 ± 0.6 million of CD90+ cells from the 20-mL MPB sample. After thawing, at day 15 under in vitro culture, the mean CD90+ cells determined by flow cytometry was 92.92 ± 1.29 % and cell duplication time determined by crystal violet staining was 47.59 h. This study describes for the first time the isolation, characterization, and post-in vitro culture thawing of CD90+ MSCs from mobilized peripheral blood in sheep. This population can be considered as a source of MSCs for experimental models in tissue engineering research.

Two-dimensional liquid chromatography for direct chiral separations: a review.

Separation of enantiomers remains a challenge owing to their identical physical and chemical properties in an achiral environment, and research on specialized separation techniques such as multidimensional achiral-chiral liquid chromatography continues to resolve individual enantiomers in complex samples. Recent advances in application of multidimensional liquid chromatography applied to chiral analysis are reviewed. For this reason, benefits of achiral-chiral coupling are shown, with emphasis in applications on biological and pharmaceutical fields as well as pesticide analysis. A description of standard instrumental setup in both heart-cut and comprehensive multidimensional liquid chromatography is shown. The most broadly used chiral stationary phases for multidimensional liquid chromatography are summarized. An extensive overview of different interface designs applied to complex samples is presented.

Evaluation of Rheological Properties of Asphalt Binder Modified with Biochar from Oat Hulls.

In this study, the effect of biochar from oat hulls (BO) on the rheological properties of a PG 64-22 asphalt binder was evaluated using a full factorial design, which included the following factors: pyrolysis temperature (PT) (300 °C and 500 °C), BO particle size (<20 µm and <75 µm), and the amount of BO (2.5%, 5%, and 7.5%). First, the morphological and physicochemical properties of BO were analyzed by comparing it with graphite powder (CFG) and commercial activated carbon (CAC). The physicochemical properties of the modified asphalt binder were then evaluated using confocal laser microscopy, scanning electron microscopy (SEM-EDX), and Fourier-transform infrared spectroscopy (FTIR). Its storage stability was also evaluated. Subsequently, the rutting parameter G*/sin(δ) and the Fraass breaking point were analyzed to select asphalt binders that extended their viscoelastic range. The asphalt binders selected were those with 2.5%, 5%, and 7.5% BO, produced at a PT of 300 °C with a particle size <20 µm (BO300S). Next, the rheological properties of the selected samples were evaluated by testing for rotational viscosity, rutting parameter G*/sin(δ), multiple stress creep recovery (MSCR), fatigue parameter G*·sin(δ), and creep stiffness by bending beam rheometry (BBR). The rheological aging index according to rutting parameter G*/sin(δ) (RAI) was also evaluated. These tests were conducted in different states of the asphalt binder: original, short-term aged, and long-term aged. According to the results, the application of BO300S significantly increased the resistance of the asphalt binder to rutting and rotational viscosity, proportional to the amount added to the asphalt binder. Moreover, low modifier percentages improved fatigue resistance, outperforming CFG and CAC. In addition, it performs well at low service temperatures, registering better resistance than the control asphalt binders.

Unravelling the in vitro and in vivo potential of selenium nanoparticles in Alzheimer's disease: A bioanalytical review.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by progressive cognitive decline and the accumulation of beta-amyloid plaques and tau tangles in the brain. Current therapies have limited efficacy, prompting the search for novel treatments. Selenium nanoparticles (SeNPs) have emerged as promising candidates for AD therapy due to their unique physicochemical properties and potential therapeutic effects. This review provides an overview of SeNPs and their potential application in AD treatment, as well as the main bioanalytical techniques applied in this field. SeNPs possess antioxidant and anti-inflammatory properties, making them potential candidates to combat the oxidative stress and neuroinflammation associated with AD. Moreover, SeNPs have shown the ability to cross the blood-brain barrier (BBB), allowing them to target brain regions affected by AD pathology. Various methods for synthesizing SeNPs are explored, including chemical, physical and biological synthesis approaches. Based on the employment of algae, yeast, fungi, and plants, green methods offer a promising and biocompatible alternative for SeNPs production. In vitro studies have demonstrated the potential of SeNPs in reducing beta-amyloid aggregation and inhibiting tau hyperphosphorylation, providing evidence of their neuroprotective effects on neuronal cells. In vivo studies using transgenic mouse models and AD-induced symptoms have shown promising results, with SeNPs treatment leading to cognitive improvements and reduced amyloid plaque burden in the hippocampus. Looking ahead, future trends in SeNPs research involve developing innovative brain delivery strategies to enhance their therapeutic potential, exploring alternative animal models to complement traditional mouse studies, and investigating multi-targeted SeNPs formulations to address multiple aspects of AD pathology. Overall, SeNPs represent a promising avenue for AD treatment, and further research in this field may pave the way for effective and much-needed therapeutic interventions for individuals affected by this debilitating disease.

Unlocking the in vitro neuroprotection of sloe residues phenolic extracts by bioanalytical and chemometric strategies.

Wild fruits, particularly the underutilized sloe (Prunus spinosa), are gaining interest as natural antioxidants, with residues from liqueur production being a source of bioactive compounds. This study proposes a sustainable approach for valorizing sloe residues, seeds and skins, by employing an innovative green extraction method. HPLC-ESI-QTOF and spectrophotometric techniques were used to explore the phenolic profile, highlighting the predominance of quercetin, 2,3-dihydroxybenzoic and ferulic acids (9.7-57 µg·g-1). In addition, the presence of Cu, Zn and Ca was confirmed by atomic absorption spectroscopy. Simultaneously, their neuroprotective potential against Alzheimer's disease (AD) was studied by exploring the inhibition of beta-amyloid aggregation and oxidative stress cytoprotection in SH-SY5Y cell line, standing out 1 µg·g-1 and 10 µg·g-1 extracts of sloe skin. Phenolic composition was correlated with bioactivities by means of multivariate analysis. These results contributed to highlight the potential of this bio-residue as a neuroprotective agent against AD in pharmaceutical and nutraceutical industries.

HIV-1 Vpu protein mediates the transport of potassium in Saccharomyces cerevisiae.

Human immunodeficiency virus type 1 (HIV-1) Vpu is an integral membrane protein that belongs to the viroporin family. Viroporins interact with cell membranes, triggering membrane permeabilization and promoting release of viral particles. In vitro electrophysiological methods have revealed changes in membrane ion currents when Vpu is present; however, in vivo the molecular mechanism of Vpu at the plasma membrane is still uncertain. We used the yeast Saccharomyces cerevisiae as a genetic model system to analyze how Vpu ion channel impacts cellular homeostasis. Inducible expression of Vpu impaired cell growth, suggesting that this viral protein is toxic to yeast cultures. This toxicity decreased with extracellular acidic pH. Also, Vpu toxicity diminished as the extracellular K(+) concentration was increased. However, expression of the Vpu protein suppresses the growth defect of K(+) uptake-deficient yeast (Δtrk1,2). The phenotype rescue of these highly hyperpolarized cells was almost total when they were grown in medium supplemented with high concentrations of KCl (100 mM) at pH 7.0 but was significantly reduced when the extracellular K(+) concentration or pH was decreased. These results indicate that Vpu has the ability to modify K(+) transport in both yeast strains. Here, we show also that Vpu confers tolerance to the aminoglycoside antibiotic hygromycin B in Δtrk1,2 yeast. Our results suggest that Vpu interferes with cell growth of wild-type yeast but improves proliferation of the hyperpolarized trk1,2 mutant by inducing plasma membrane depolarization. Furthermore, evaluation of the ion channel activity of the Vpu protein in Δtrk1,2 yeast could aid in the development of a high-throughput screening assay for molecules that target the retroviral protein.

Determination of salbutamol by direct chiral reversed-phase HPLC using teicoplanin as stationary phase and its application to natural water analysis.

A direct chiral LC-UV method was optimized for the determination of salbutamol (SAL) ß2 -agonist in environmental water. Two commercially available columns were evaluated: teicoplanin Chirobiotic-T™ (150 × 2.1 mm i.d., 5 µm) and vancomycin Chirobiotic-V™ (150 × 2.1 mm i.d., 5 µm). Finally, teicoplanin chiral stationary phase was selected for SAL enantiomer resolution. In order to preserve its integrity and maintain the column performance for longer time, the use of additives such as triethylamine (TEA) in the mobile phase was avoided. Experimental design was applied to simultaneously evaluate the influence of several parameters involved in enantiomer separation and to establish the conditions for acceptable resolution and performance in short analysis time. Optimum mobile phase was methanol-20 mM ammonium acetate buffer at pH 4.5 (98:2, v/v). A solid-phase extraction procedure for sample pre-concentration and clean-up allowed the determination of chiral SAL residues in natural water samples spiked at low concentrations in the range 1.0-20 ng mL(-1) . Reproducible recoveries, between 77 and 98%, were obtained and matrix effect was negligible. Injection of sample solutions at low elution strength permitted the SAL enantioresolution in the natural water complex matrix with satisfactory sensitivity and precision.