Directly observed 15N NMR spectra of uniformly enriched proteins

The proteins cytochrome c2, cytochrome c', and ribulosebisphosphate carboxylase/oxygenase from Rhodospirillum rubrum were enriched in 15N by growth of the organism on 15NH4Cl. The proteins were purified to homogeneity and studied by 15N NMR. Longitudinal and transverse relaxation times as well as the nuclear Overhauser effects were determined for various groups of the proteins which vary in molecular weight from 13,000 to 114,000. The values of these parameters for the amide resonances or for groups thought to be rigid were consistent with the molecular weights of the proteins. Relaxation times of the amino-terminal alpha-amino groups and the side chain nitrogen atoms of arginine and lysine were consistent with much more rapid motion. Nitrogen atoms having bound protons were generally found to be decoupled from the protons by chemical exchange. Demonstrable 1H-15N coupling was taken as an indication that exchange was hindered, either by hydrogen bonding interactions or by inaccessibility of the group to solvent. Histidine side chain nitrogen atoms, which experience a large chemical shift upon protonation/deprotonation, were often found to be broadened beyond detectability by chemical exchange and tautomerization. Strategies for improving sensitivity and for obtaining specific peak assignments are also discussed.     

Effect of cod liver oil supplementation on plasma lipids, lipoproteins, lipase activity and platelet aggregation in normotensive and hypertensive volunteers

No significant change in plasma levels of total cholesterol (TC), triglycerides, phospholipids, very-low-density lipoprotein cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL-C), lipase activity and TC/HDL-C ratio could be observed in both normotensive and hypertensive individuals after cod liver oil supplementation. Measure of platelet aggregation rates did not also show any significant change after cod liver oil ingestion in both normotensive and hypertensive individuals. The results suggest that supplementation of normal diets with 600 mg cod liver oil per day for 50 days neither affects plasma lipids, lipoproteins and lipase activity nor affects platelet aggregation in both normotensive and hypertensive individuals.     

Revealing the polar lipidome,pigment profiles,and antioxidant activity of the giant unicellular green alga,Acetabularia acetabulum

Marine algae are one of the most important sources of high-value compounds such as polar lipids, omega-3 fatty acids, photosynthetic pigments, or secondary metabolites with interesting features for different niche markets. Acetabularia acetabulum is a macroscopic green single-celled alga, with a single nucleus hosted in the rhizoid. This alga is one of the most studied dasycladalean species and represents an important model system in cell biology studies. However, its lipidome and pigment profile have been overlooked. Total lipid extracts were analyzed using hydrophilic interaction liquid chromatography-high resolution mass spectrometry (HILIC-HRMS), tandem mass spectrometry (MS/MS), and high-performance liquid chromatography (HPLC). The antioxidant capacity of lipid extracts was tested using DPPH and ABTS assays. Lipidomics identified 16 polar lipid classes, corresponding to glycolipids, betaine lipids, phospholipids, and sphingolipids, with a total of 191 lipid species, some of them recognized by their bioactivities. The most abundant polar lipids were glycolipids. Lipid classes less studied in algae were identified, such as diacylglyceryl-carboxyhydroxymethylcholine (DGCC) or hexosylceramide (HexCer). The pigment profile of A. acetabulum comprised carotenoids (17.19%), namely cis-neoxanthin, violaxanthin, lutein and β,β-carotene, and chlorophylls a and b (82.81%). A. acetabulum lipid extracts showed high antioxidant activity promoting a 50% inhibition (IC₅₀) with concentrations of 57.91 ± 1.20 μg · mL⁻¹ (438.18 ± 8.95 μmol Trolox · g⁻¹ lipid) in DPPH and 20.55 ± 0.60 μg · mL⁻¹ in ABTS assays (918.56 ± 27.55 μmol Trolox · g⁻¹ lipid). This study demonstrates the potential of A. acetabulum as a source of natural bioactive molecules and antioxidant compounds.     

Inactivation of (Na-++K-+)-stimulated ATPase by a cytotoxic protein from cobra venom in relation to its lytic effects on cells.

The mechanism of action of the cytotoxic protein P6 isolated from cobra venom (Naja naja) which shows preferential cytotoxicity particularly to Yoshida sarcoma cells has been studied by its effects on the membrane-bound enzyme (Na-++K-+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) of a variety of cell systems. Evidence obtained with Yoshida sarcoma cells, dog and human erythrocytes and three tissue culture cell lines KB (human oral carcinoma), Hela (human cervix carcinoma) and L-132 (human lung embryonic) shows that inhibition of (Na-++K-+)-ATPase by the P6 protein can be correlated with its lytic activity. (Na-++k-+)-ATPase of Yoshida sarcoma membrane fragments inactivated by P6 protein could be reconstituted by the addition of phosphatidylserine and phosphatidic acid. It is conceivable that lysis of cells by the P6 protein may be due to an imbalance of K-+ and Na-+ in the cell which leads to swelling and disintegration of the membrane structure. Observations indicate that the P6 protein combines with membrane constituents of susceptible cells. The overall evidence suggests that both the specificity of its protein structure and the highly basic nature of the P6 protein are factors which enable it to compete with the lipid moiety maintaining the (Na-++k-+)-ATPase of the susceptible cells in proper conformation for activity.     

Improvement of homologous GH10 xylanase production by deletion of genes with predicted function in the Aspergillus nidulans secretion pathway

Filamentous fungi are important cell factories for large-scale enzyme production. However, production levels are often low, and this limitation has stimulated research focusing on the manipulation of genes with predicted function in the protein secretory pathway. This pathway is the major route for the delivery of proteins to the cell exterior, and a positive relationship between the production of recombinant enzymes and the unfolded protein response (UPR) pathway has been observed. In this study, Aspergillus nidulans was exposed to UPR-inducing chemicals and differentially expressed genes were identified by RNA-seq. Twelve target genes were deleted in A. nidulans recombinant strains producing homologous and heterologous GH10 xylanases. The knockout of pbnA (glycosyltransferase), ydjA (Hsp40 co-chaperone), trxA (thioredoxin) and cypA (cyclophilin) improved the production of the homologous xylanase by 78, 171, 105 and 125% respectively. Interestingly, these deletions decreased the overall protein secretion, suggesting that the production of the homologous xylanase was specifically altered. However, the production of the heterologous xylanase and the secretion of total proteins were not altered by deleting the same genes. Considering the results, this approach demonstrated the possibility of rationally increase the production of a homologous enzyme, indicating that trxA, cypA, ydjA and pbnA are involved in protein production by A. nidulans.     

Correction to: Determining ecosystem functioning in Brazilian biomes through foliar carbon and nitrogen concentrations and stable isotope ratios

Biogeochemistry - The initial online publication contained typesetting mistakes in the author information. The original article has been corrected.     

Short-term effects of winter warming and acidification on phytoplankton growth and mortality: more losers than winners in a temperate coastal lagoon

Hydrobiologia - Changes in temperature and CO2 are typically associated with climate change, but they also act on shorter time scales, leading to alterations in phytoplankton physiology and...     

Meta-omics analysis indicates the saliva microbiome and its proteins associated with the prognosis of oral cancer patients

Saliva is a biofluid that maintains the health of oral tissues and the homeostasis of oral microbiota. Studies have demonstrated that Oral squamous cell carcinoma (OSCC) patients have different salivary microbiota than healthy individuals. However, the relationship between these microbial differences and clinicopathological outcomes is still far from conclusive. Herein, we investigate the capability of using metagenomic and metaproteomic saliva profiles to distinguish between Control (C), OSCC without active lesion (L0), and OSCC with active lesion (L1) patients. The results show that there are significantly distinct taxonomies and functional changes in L1 patients compared to C and L0 patients, suggesting compositional modulation of the oral microbiome, as the relative abundances of Centipeda, Veillonella, and Gemella suggested by metagenomics are correlated with tumor size, clinical stage, and active lesion. Metagenomics results also demonstrated that poor overall patient survival is associated with a higher relative abundance of Stenophotromonas, Staphylococcus, Centipeda, Selenomonas, Alloscordovia, and Acitenobacter. Finally, compositional and functional differences in the saliva content by metaproteomics analysis can distinguish healthy individuals from OSCC patients. In summary, our study suggests that oral microbiota and their protein abundance have potential diagnosis and prognosis value for oral cancer patients. Further studies are necessary to understand the role of uniquely detected metaproteins in the microbiota of healthy and OSCC patients as well as the crosstalk between saliva host proteins and the oral microbiome present in OSCC.