Drop motion during mass transfer accompanied by interphase convection

The article deals with the experimental study of the mass transfer of acetic acid from the dispersed phase (butyl acetate) to the continuous phase (water). The experiments were carried out on a laboratory column with single floating drops. The presence of the Marangoni effect during the movement of drops and its influence on the trajectories of movement of drops and the kinetics of mass transfer during extraction are shown. The influence of the Marangoni effect is most clearly observed when the driving force of the process is 0.1...0.2 mol/l

Environments of the Four Tryptophans in the Extracellular Domain of Human Tissue Factor: Comparison of Results from Absorption and Fluorescence Difference Spectra of Tryptophan Replacement Mutants with the Crystal Structure of the Wild-Type Protein

The local environments of the four tryptophan residues of the extracellular domain of human tissue factor (sTF) were assessed from difference absorption and fluorescence spectra. The difference spectra were derived by subtracting spectra from single Trp-to-Phe or Trp-to-Tyr replacement mutants from the corresponding spectrum of the wild-type protein. Each of the mutants was capable of enhancing the proteolytic activity of factor Vila showing that the mutations did not introduce major structural changes, although the mutants were more susceptible to denaturation by guanidinium chloride. The difference spectra indicate that the Trp residues are buried to different extents within the protein matrix. This evaluation was compared with the x-ray crystal structure of sTF. There is excellent agreement between predictions from the difference spectra and the environments of the Trp residues observed in the x-ray crystal structure, demonstrating that difference absorption and particularly fluorescence spectra derived from functional single-Trp replacement mutants can be used to obtain information about the local environments of individual Trp residues in multi-tryptophan proteins

DROP MOTION DURING MASS TRANSFER ACCOMPANIED BY INTERPHASE CONVECTION

Received: 04.11.2021. Revised: 16.06.2022. Accepted: 16.06.2022. Available online: 22.06.2022.The article deals with the experimental study of the mass transfer of acetic acid from the dispersed phase (butyl acetate) to the continuous phase (water). The experiments were carried out on a laboratory column with single floating drops. The presence of the Marangoni effect during the movement of drops and its influence on the trajectories of movement of drops and the kinetics of mass transfer during extraction are shown. The influence of the Marangoni effect is most clearly observed when the driving force of the process is 0.1...0.2 mol/l

Gramicidin Increases Lipid Flip-Flop in Symmetric and Asymmetric Lipid Vesicles

© 2019 Biophysical Society Unlike most transmembrane proteins, phospholipids can migrate from one leaflet of the membrane to the other. Because this spontaneous lipid translocation (flip-flop) tends to be very slow, cells facilitate the process with enzymes that catalyze the transmembrane movement and thereby regulate the transbilayer lipid distribution. Nonenzymatic membrane-spanning proteins with unrelated primary functions have also been found to accelerate lipid flip-flop in a nonspecific manner and by various hypothesized mechanisms. Using deuterated phospholipids, we examined the acceleration of flip-flop by gramicidin channels, which have well-defined structures and known functions, features that make them ideal candidates for probing the protein-membrane interactions underlying lipid flip-flop. To study compositionally and isotopically asymmetric proteoliposomes containing gramicidin, we expanded a recently developed protocol for the preparation and characterization of lipid-only asymmetric vesicles. Channel incorporation, conformation, and function were examined with small angle x-ray scattering, circular dichroism, and a stopped-flow spectrofluorometric assay, respectively. As a measure of lipid scrambling, we used differential scanning calorimetry to monitor the effect of gramicidin on the melting transition temperatures of the two bilayer leaflets. The two calorimetric peaks of the individual leaflets merged into a single peak over time, suggestive of scrambling, and the effect of the channel on the transbilayer lipid distribution in both symmetric 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and asymmetric 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1,2-dimyristoyl-sn-glycero-3-phosphocholine vesicles was quantified from proton NMR measurements. Our results show that gramicidin increases lipid flip-flop in a complex, concentration-dependent manner. To determine the molecular mechanism of the process, we used molecular dynamics simulations and further computational analysis of the trajectories to estimate the extent of membrane deformation. Together, the experimental and computational approaches were found to constitute an effective means for studying the effects of transmembrane proteins on lipid distribution in both symmetric and asymmetric model membranes

SIMULATION OF RISING DROPLET MOVEMENT WITH MOVING MESH METHODS

In this paper movement of rising benzene droplets was studied experimentally and numerically. The moving mesh methods were used to simulate drop movement. Comparison of experimental and numerical results was performed with respect to instantaneous velocities and shape of rising droplets

MARANGONI CONVECTION INFLUENCE ON MASS TRANSFER ACROSS SPHERICAL INTERFACIAL BOUNDARY

In this paper the influence of Marangoni convection on mass transfer across spherical interfacial boundary was consideredin detail. Considered issues allow to make a conclusion about necessary conditions of extraction performance to enhance mass transfer. Research results give an opportunity to define the parameters, which have a crucial influence of mass transfer intensification

Comparative analysis of local stimulation methods of reparative osteogenesis

Objective To determine the ratio of the main growth factors when using various methods of local stimulation of reparative osteogenesis.Material and methods The study consisted of two parts: in the first part a comparative analysis of the content of growth factors by ELISA was carried out (PDGF – platelet derived growth factor, TGF – transforming growth factor, VEGF – vascular endothelial growth factor, IGF – insulin-like growth factor, BMP6 and BMP7 – morphogenetic proteins 6 and 7), capable of stimulating reparative osteogenesis in blood plasma, plateletrich plasma, red bone marrow and bone autoregenerate. The second part presented the results of approbation of the autoregenerate obtained according to the original method in the framework of an acute experiment on animals.Results The most important cytokines affecting the process of reparative osteogenesis are fibroblast growth factor – FGF1 and bone morphogenetic protein 7 – BMP7. Based on the results of a comparative enzymelinked immunosorbent assay, it has been established that the autoregenerate, obtained by the original method, and a bone marrow aspirate concentrate have the highest osteogenic potential.Conclusion Autoregenerate is an effective and promising means of local stimulation of reparative osteogenesis, and its transplantation is a simple and highly effective procedure

Transcriptional dysregulation of Interferome in experimental and human Multiple Sclerosis

Recent evidence indicates that single multiple sclerosis (MS) susceptibility genes involved in interferon (IFN) signaling display altered transcript levels in peripheral blood of untreated MS subjects, suggesting that responsiveness to endogenous IFN is dysregulated during neuroinflammation. To prove this hypothesis we exploited the systematic collection of IFN regulated genes (IRG) provided by the Interferome database and mapped Interferome changes in experimental and human MS. Indeed, central nervous system tissue and encephalitogenic CD4 T cells during experimental autoimmune encephalomyelitis were characterized by massive changes in Interferome transcription. Further, the analysis of almost 500 human blood transcriptomes showed that (i) several IRG changed expression at distinct MS stages with a core of 21 transcripts concordantly dysregulated in all MS forms compared with healthy subjects; (ii) 100 differentially expressed IRG were validated in independent case-control cohorts; and (iii) 53 out of 100 dysregulated IRG were targeted by IFN-beta treatment in vivo. Finally, ex vivo and in vitro experiments established that IFN-beta administration modulated expression of two IRG, ARRB1 and CHP1, in immune cells. Our study confirms the impairment of Interferome in experimental and human MS, and describes IRG signatures at distinct disease stages which can represent novel therapeutic targets in MS

Acute respiratory failure in immunocompromised patients : outcome and clinical features according to neutropenia status

Abstract Background The impact of neutropenia in critically ill immunocompromised patients admitted in a context of acute respiratory failure (ARF) remains uncertain. The primary objective was to assess the prognostic impact of neutropenia on outcomes of these patients. Secondary objective was to assess etiology of ARF according to neutropenia. Methods We performed a post hoc analysis of a prospective multicenter multinational study from 23 ICUs belonging to the Nine-I network. Between November 2015 and July 2016, all adult immunocompromised patients with ARF admitted to the ICU were included in the study. Adjusted analyses included: (1) a hierarchical model with center as random effect; (2) propensity score (PS) matched cohort; and (3) adjusted analysis in the matched cohort. Results Overall, 1481 patients were included in this study of which 165 had neutropenia at ICU admission (11%). ARF etiologies distribution was significantly different between neutropenic and non-neutropenic patients, main etiologies being bacterial pneumonia (48% vs 27% in neutropenic and non-neutropenic patients, respectively). Initial oxygenation strategy was standard supplemental oxygen in 755 patients (51%), high-flow nasal oxygen in 165 (11%), non-invasive ventilation in 202 (14%) and invasive mechanical ventilation in 359 (24%). Before adjustment, hospital mortality was significantly higher in neutropenic patients (54% vs 42%; p = 0.006). After adjustment for confounder and center effect, neutropenia was no longer associated with outcome (OR 1.40, 95% CI 0.93–2.11). Similar results were observed after matching (52% vs 46%, respectively; p = 0.35) and after adjustment in the matched cohort (OR 1.04; 95% CI 0.63–1.72). Conclusion Neutropenia at ICU admission is not associated with hospital mortality in this cohort of critically ill immunocompromised patients admitted for ARF. In neutropenic patients, main ARF etiologies are bacterial and fungal infections

Acute respiratory failure in immunocompromised patients:outcome and clinical features according to neutropenia status

Background: The impact of neutropenia in critically ill immunocompromised patients admitted in a context of acute respiratory failure (ARF) remains uncertain. The primary objective was to assess the prognostic impact of neutropenia on outcomes of these patients. Secondary objective was to assess etiology of ARF according to neutropenia. Methods: We performed a post hoc analysis of a prospective multicenter multinational study from 23 ICUs belonging to the Nine-I network. Between November 2015 and July 2016, all adult immunocompromised patients with ARF admitted to the ICU were included in the study. Adjusted analyses included: (1) a hierarchical model with center as random effect; (2) propensity score (PS) matched cohort; and (3) adjusted analysis in the matched cohort. Results: Overall, 1481 patients were included in this study of which 165 had neutropenia at ICU admission (11%). ARF etiologies distribution was significantly different between neutropenic and non-neutropenic patients, main etiologies being bacterial pneumonia (48% vs 27% in neutropenic and non-neutropenic patients, respectively). Initial oxygenation strategy was standard supplemental oxygen in 755 patients (51%), high-flow nasal oxygen in 165 (11%), non-invasive ventilation in 202 (14%) and invasive mechanical ventilation in 359 (24%). Before adjustment, hospital mortality was significantly higher in neutropenic patients (54% vs 42%; p = 0.006). After adjustment for confounder and center effect, neutropenia was no longer associated with outcome (OR 1.40, 95% CI 0.93–2.11). Similar results were observed after matching (52% vs 46%, respectively; p = 0.35) and after adjustment in the matched cohort (OR 1.04; 95% CI 0.63–1.72). Conclusion: Neutropenia at ICU admission is not associated with hospital mortality in this cohort of critically ill immunocompromised patients admitted for ARF. In neutropenic patients, main ARF etiologies are bacterial and fungal infections.SCOPUS: ar.jinfo:eu-repo/semantics/publishe