Determination of specific and non-specific protein-protein interactions for beta-lactoglobulin by analytical ultracentrifugation and membrane osmometry experiments

Protein-protein interactions are essential for the understanding of biological processes. Specific protein aggregation is an important aspect for many biological systems. In particular, electrostatic interactions play the key role for protein-protein interactions, as many amino acids have pH-dependent charge states. Moreover, protein dissociation is directly related to the solution pH, ionic strength, temperature and protein concentration. The subtle interplay between different specific and non-specific interactions is demonstrated for beta-lactoglobulin (BLG) with a focus on low salt concentrations, thus mimicking technically relevant processing conditions. BLG is a well-characterized model system, proven to attain its monomer-dimer equilibrium strongly dependent upon the pH of the solution. In this manuscript, we present a unique combination of analytical ultracentrifugation and membrane osmometry experiments, which quantifies specific and non-specific interactions, i.e. in terms of the dimer dissociation constants and the second osmotic virial coefficient, at pH 3 and 7 and sodium chloride concentrations of 10 mM and 100 mM. This provides direct insight to protein-protein interactions for a system with a concentration-dependent monomer-dimer equilibrium. Moreover, using a coarse-grained extended DLVO model in combination with molecular dynamics simulations, we quantify non-specific monomer-monomer, monomer-dimer and dimer-dimer interactions as well as the binding free energy of BLG dimerization from theoretical calculations. The experimentally determined interactions are shown to be mainly governed by electrostatic interactions and further agree with free energy calculations. Our experimental protocol aims to determine non-specific and specific interactions for a dynamically interacting system and provides an understanding of protein-protein interactions for BLG at low salt concentrations.

Development of

Novel zero-trans frying shortenings were formed by enzymatic transesterification by exploring a palm stearin and canola oil mixture and stearic acid as substrates. Both immobilized (Novozym 435, Lipase PS “Amano” IM) and non-immobilized (Lipomod TM 34P) enzymes were applied as biocatalysts. Palmitic acid, the fatty acid which defines the proper type of crystal formation, was present at the 15% level in the reaction mixtures. The novel structured lipids had comparable physical properties and offered similar frying performance to those of commercial shortening. Needle-shaped crystals were predominant both in the transesterification products and the commercial frying shortening. Furthermore, solid fat content profiles of the zero-trans structured lipids produced by Novozym 435 and Lipase PS “Amano” IM were close to those of the commercial shortening.

P6463Prognostic value of respiratory index (RI) in hemodinamically stable patients with acute pulmonary embolism: the RI-MODEL study

Background

The accuracy of the 2014 ESC model to predict 30-day mortality in hemodynamically stable patients with acute pulmonary embolism (PE) is relatively limited.

Purpose

The aims of this study in hemodynamically stable patients with acute PE were i) to evaluate the prognostic value of a novel respiratory index (RI) (oxygen saturation in air to respiratory rate ratio) and ii) to assess the accuracy of the RI-model (simplified Pulmonary Embolism Severity Index [sPESI] + RI), both in predicting 30-day mortality.

Methods

A collaborative database of hemodynamically stable patients with PE was divided into two cohorts (derivation and validation) with equal numbers of patients, based on a temporal criterion. Study outcome was 30-day all-cause-death. Discrimination and calibration were assessed in the derivation and validation cohorts by the c-statistics and by the Hosmer-Lemeshow test, respectively.

Results

30-day all-cause-death occurred in 7.5% of the 319 patients in the derivation cohort (mean age 72 years, females 53%). The RI was an independent predictor of 30-day mortality (p=0.004). A RI ≤3.8 was associated with an increased death rate compared to higher RI values (15.4% vs 5.0%, OR 3.4, 95% CI 1.5–8.1). When the RI≤3.8 was integrated in the sPESI, the novel RI-model showed a good discriminatory power (c-statistics 0.703, 95% CI 0.603–0.803).

In the 319 patients of the validation cohort (30-day mortality 6.9%, mean age 71 years, females 55%) the discriminatory power of the RI-model was confirmed (c-statistics 0.838, 95% CI 0.768–0.907).

The RI-model and the 2014 ESC model had a c-statistics of 0.772 (95% CI 0.709–0.834) and of 0.687 (95% CI 0.620–0.753) in the overall population, respectively.

Conclusion

In this study, the RI independently predicted 30-day mortality in hemodynamically stable patients with acute PE. A clinical model including RI showed a better discriminatory value than 2014 ESC model and could be used for risk stratification in these patients.

P5588Early versus delayed oral anticoagulation in patients with acute pulmonary embolism: determinants and outcome

Background

Whether early oral anticoagulant treatment is appropriate for patients with acute pulmonary embolism (PE) regardless of PE severity is undefined. The aim of this study in patients with acute PE at intermediate risk of death were: I) to assess the determinants for the use of early vs delayed vs no oral anticoagulants in patients with acute PE and II) to assess the association between timing of oral anticoagulation and in-hospital mortality.

Methods

Prospective cohorts of patients with acute PE at intermediate risk of death according to the European Society of Cardiology Guidelines 2014 were merged in a collaborative database. The initiation of oral anticoagulation was classified as early (≤3 days) or delayed (between day 3 and 10 from diagnosis). Patients treated with parenteral anticoagulants for longer than 10 days were also included. In-hospital death was the primary study outcome.

Results

Overall, 557 patients were included in the study, 23 received thrombolytic treatment during the hospital stay. The mean duration of parenteral anticoagulation was 7±8 days (5 median), 348 patients were initiated on a direct oral anticoagulant and 79 on a vitamin K antagonist during the hospital stay. Initiation of oral anticoagulants occurred early or delayed in 209 (37%) and 218 (39%) patients, respectively and never occurred during the first 30 days in 130 (23%).

Intermediate-low risk patients more commonly received early and intermediate high delayed oral anticoagulation. Simplified PESI score of zero (OR 1.9, 95% CI 1.3–2.7) was independently associated with early oral anticoagulation; among sPESI components absence of cancer (OR 5.9, 95% CI 3.3–10) and heart rate <110 (OR 1.8, 95% CI 1.01–3.16) were independent predictors of early initiation of oral anticoagulants. The presence of both right ventricle dysfunction and injury was associated with delayed initiation of oral anticoagulants.

The incidence of death was 5.5%. Death occurred in 32 patients and was not related to the duration of parenteral anticoagulation (OR 1.01 per day, 95% CI 0.98–1.06) nor to right ventricle dysfunction but to sPESI 1 (OR 3.32, 95% CI 1.14–9.66). These results were partially confirmed in the 435 intermediate risk patients without cancer (OR 1.03, 95% CI 0.99–1.08 for days of parenteral treatment; OR 4.17, 95% CI 0.95–18 for sPESI 1).

Conclusion

The clinical severity of PE and not the timing of initiation of oral anticoagulants are associated with in-hospital death in patients with intermediate risk PE. Randomized studies are needed to definitively assess the role of heparin lead-in in patients with PE at intermediate risk for death.

Oxygen saturation or respiratory rate to improve risk stratification in hemodynamically stable patients with acute pulmonary embolism

Essentials In acute pulmonary embolism (PE), risk stratification is essential to drive clinical management. Improving the 2014-ESC risk stratification strategy is crucial in hemodynamically stable patients. Oxygen saturation and respiratory rate improve risk stratification in hemodynamically stable PE. Simple and routine tests improve risk stratification of hemodynamically stable PE. SUMMARY: Background In patients with acute pulmonary embolism (PE), risk stratification for short-term death is recommended to drive clinical management. A risk stratification strategy combining the simplified Pulmonary Embolism Severity Index (PESI), echocardiography and troponin was proposed by the European Society of Cardiology (ESC) in 2014. The identification of hemodynamically stable patients at increased risk of death by this strategy needs improvement. Objective To assess whether further stratification by serial cut-off values of oxygen saturation or respiratory rate improves the accuracy of the ESC risk stratification strategy in hemodynamically stable PE patients. Methods Prospective cohorts of hemodynamically stable patients with PE were merged in a collaborative database. The accuracy of risk stratification for 30-day mortality by the original and a modified 2014 ESC strategy was assessed. Results Overall, 255 patients (27%) were categorized as low, 510 (54%) as intermediate-low and 181 (19%) as intermediate-high risk according to the original 2014 ESC strategy. Thirty-day mortality was 1.2% in low, 10% in intermediate-low and 11% in intermediate-high-risk patients. By adding oxygen saturation in air of < 88%, the discriminatory power of the 2014 ESC model improved for 30-day mortality (c-statistics, 0.71; 95% confidence interval [CI], 0.65-0.77 vs. 0.63, 95% CI, 0.56-0.69) and for PE-related death (c-statistics, 0.75; 95% CI, 0.69-0.81 vs. 0.63, 95% CI 0.56-0.69). Conclusions Simple and routine tests, such as oxygen saturation or respiratory rate, could be added to the 2014 ESC strategy for risk stratification to identify hemodynamically stable PE patients at increased risk of death who are potentially candidates for more aggressive treatment.

Influence of Ca/Mg ratio on phytoextraction properties of Salix viminalis. II. Secretion of low molecular weight organic acids to the rhizosphere

A hydroponic experiment in a phytotron was performed to investigate the effect of two different Ca/Mg ratios (4:1 and 1:10) and trace element ions (Cd, Cu, Pb and Zn) in solution on the efficiency of low molecular weight organic acid (LMWOA) formation in Salix viminalis rhizosphere. Depending on the Ca/Mg ratio and presence of selected trace elements at 0.5mM concentration, the amount and kind of LMWOAs in the rhizosphere were significantly affected. In physiological 4:1 Ca/Mg ratio the following complex of acids was observed: malonic (Pb, Zn), citric, lactic, maleic and succinic (Zn) acids. Under 1:10 Ca/Mg ratio, citric (Cd, Zn), maleic and succinic (Cd, Cu, Pb, Zn) acids were seen. Additionally, high accumulation of zinc and copper in all systems was observed, with the exception of those where one of the metals was at higher concentration. Summing up, the results indicate a significant role of LMWOAs in Salix phytoremediation abilities. Both effects can be modulated depending on the mutual Ca/Mg ratio.

Influence of pleural macrophages on proliferative activity and apoptosis regulating proteins of malignant cells

Malignant tumors contain numerous macrophages as a major component of the leukocytic infiltrate. Only few studies have evaluated the interaction between products secreted by macrophages and tumor cells. Our objective was to study soluble factors produced by pleural macrophages. We sampled pleural effusions from patients with cancer and used human tumor cell lines as targets. Pleural macrophages were cultured and the supernatants were used as a conditioned medium for cultures of human cell lines A549, HT29, HCT116, SW620, MCF7, MDA-MB231, JURKAT, and HL60. We investigated apoptosis, proliferative activity, and expression of apoptosis regulating proteins Fas, Bcl2, Caspase-3, and survivin of malignant cells cultured in the conditioned medium. Our findings raise the possibility that macrophages from malignant pleural effusions can act as a factor inhibiting apoptosis of malignant cells.

Contractile elements of Lemna trisulca L. glycerinated cell models during chloroplast translocations

Electron microscopy of Lemna glycerinated cell models depicts contractile elements during chloroplast translocations. One contractile element, the thin ectoplasmic layer, is < or = 0.4 microm thick, pressed against plasma membrane-cell wall. Thin ectoplasmic layer contains numerous oriented filaments and some appear to be actin and myosin. Another contractile element is the outer chloroplast membrane which envelops each chloroplast and joins or fuses with the thin ectoplasmic layer. Chloroplast interconnections are formed between two or more chloroplasts by outer chloroplast membranes; they enhance chloroplast communications, translocations, and molecular exchanges.

ATP depletion, purine riboside triphosphate accumulation and rat thymocyte death induced by purine riboside

Purine riboside (purine-1-D-ribofuranoside, nebularine), an adenosine analog, exerts cytotoxic effect both in vivo and in vitro. However, exact biochemical mechanism for its toxicity and sensitivity of lymphoid cells remains unknown. The present experiments have examined the sequential metabolic changes leading to cell death, induced in cultured rat thymocytes during incubation with purine riboside. Among 22 analogs tested, purine-riboside and tubercidin were most toxic as determined by trypan blue exclusion and lactate dehydrogenase leakage from the cells. 2-Chloroadenosine and 2'-deoxyadenosine were only moderately toxic, whereas other analogs tested were without effect on cell viability. In the presence of purine riboside, more than 90% of ATP was lost after 2 h of incubation. Hypoxanthine accumulated in the medium and the formation of purine-riboside triphosphate exceeded 4-fold the physiological concentration of ATP in the cell. Inhibition of adenosine kinase by 5-iodotubercidin reversed the cytotoxic effect of purine riboside. Interestingly, cells virtually deprived of ATP after 2 h of incubation with purine riboside maintained high nucleotide energy charge value and high viability. Purine riboside triphosphate was capable to replace ATP in stimulation of glycolysis in cell-free thymus extract. We conclude that for a short time (a few hours) purine riboside triphosphate formed in the cell may serve in the absence of ATP as an intermediate of cellular energy metabolism in rat thymocytes. However, possibly due to toxic effects of purine-riboside triphosphate, cells were finally dying. Thus, ATP depletion and adenosine kinase mediated purine riboside phosphates formation are the principle causes of rat thymocytes death exposed to purine riboside.

Liver regeneration attenuates increased voluntary alcohol intake evoked by the liver damage

Liver dysfunction induced in Wistar rats either surgically (by construction of portocaval anastomosis) or chemically (by chronic administration of thioacetamide) led to increased voluntary alcohol intake. Alcohol preference could be attenuated by liver regeneration that was triggered by a two-thirds hepatectomy done on cirrhotic rats. The brain serotonin system was activated in portocaval anastomosis rats and unchanged in thioacetamide-treated rats, thus suggesting that serotonin is not likely to be implicated in the mechanism(s) underlying development of alcohol preference in these rats. Also, tetrahydro-beta-carboline could possibly be excluded from consideration. Neither change in the brain concentration or distribution of tetrahydrobetacarboline after long-term treatment with thioacetamide could be found.