Nascent Ones Research Articles

Polyamide thin-film composite membranes with enhanced interfacial stability for durable organic solvent nanofiltration

Polyamide thin-film composite (TFC) membranes present a promising option for organic solvent nanofiltration (OSN) due to their superior advantages in facile fabrication and high separation efficiency. However, existing TFC-based OSN membranes are heavily limited by their weak interfacial stability in organic solvents, because many solvent-resistant porous supports are hydrophobic and have poor interfacial compatibility to polyamide. Herein, we report a polyamide TFC membrane with enhanced interfacial stability and durable OSN performance, by multifunctional surface modification and in-situ interfacial polymerization on a hydrophobic and solvent-resistant polypropylene substrate. Distinct from nascent ones, the polypropylene substrates modified by tannic acid/aminopropyltriethoxysilane coating possess excellent hydrophilicity and more functional groups, in which the former allows for the in-situ synthesis of integral polyamide layers via interfacial polymerization and the latter greatly enhances the binding strength between the polyamide layer and PP substrate by 30 times. With this method, the TFC membranes exhibit excellent thermal stability in 80 °C dimethylformamide solution. Meanwhile, the TFC membranes display high ethanol permeance (9.2 L m−2 h−1 bar−1) and acid fuchsin rejection (98.5 %), outperforming the performance of most OSN membranes reported. This straightforward method, robust structural stability, and extraordinary performance make the TFC membranes a step closer to commercial OSN membranes.

Green synthesis, characterization and drug-loaded iron oxide nanoparticles derived from Nerium oleander flower extract as a nanocarrier for in vitro antibacterial efficacy

Application of drug conjugated iron oxide hematite (α-Fe2O3) nanoparticles are of tremendous interest in biomedicine nowadays. Meanwhile, green production of iron oxide nanoparticles is gaining favour due to its sustainability, ease of usage, and biocompatibility. Therefore, this work reports on the use of hexahydrate ferric chloride and nerium oleander flower extract to synthesize nanoscaled hematite (α-Fe2O3) iron oxide particles conjugated with various drugs for antibacterial agents. Diverse morphological, physicochemical, structural, optical, and magnetic characteristics have been characterized using FESEM, EDX, XRD, UV–vis, FTIR, Raman and vibrating sample magnetometer. The synthesis of the polyshaped iron oxide nanoparticles, with average sizes ranging from 47.2 ± 20 nm, was accomplished. Furthermore, temperature-dependent variations in magnetic behavior were observed during calcination. The XRD and Raman spectra revealed hematite (α-Fe2O3) type formation of iron oxide nanoparticles. Only calcinated IO-NPs at high temperatures (700 °C) demonstrated low coercivity and residual magnetism, which revealed weak ferromagnetic ordering; other calcinated samples, including nascent ones, showed incredibly weak ferromagnetic ordering. Besides, the effectiveness of drug-encapsulated iron oxide nanoparticles against bacteria in vitro was examined. It was interesting to observe that gentamycin-coated IO-NPs tended to be more susceptible to S. aureus than E. coli bacteria, but streptomycin-conjugated IO-NPs showed the reverse trend. However, as compared to the nascent sample and the high temperature (700 °C) calcinated sample, both antibiotic-loaded IO-NPs displayed better inhibitory abilities.

Momentum, Imitation and Partner Selection in Nascent and Mature Product Markets

AbstractDetermining which partners to ally with is a key strategic decision for managers. Many studies suggest that firms select alliance partners by rationally evaluating their quality, but it is possible that information asymmetry and managers’ limited cognitive capacity actually drive firms to adopt behavioural strategies like momentum and imitation to make decisions. This study examines how momentum and imitation affect firms’ selection of partners in nascent and mature product markets. We suggest that the absolute, relative and interactive impacts of momentum and imitation on alliance partner selection decisions change as a product market evolves from its nascent stage to maturity. Evidence from 13,071 partner selection decisions initiated by Chinese fund firms largely supports these predictions. Specifically, as a nascent product market moves towards maturity, the effect of momentum on partner selection decisions becomes weaker, while that of imitation grows stronger. However, momentum is more influential than imitation in both nascent and mature product markets. Momentum diminishes the effect of imitation on partner selection decisions in nascent and mature product markets, but this substitute effect is weaker in mature product markets than in nascent ones.

Established and Nascent Entrepreneurs: Comparing the Mental Health, Self-Care Behaviours and Wellbeing in Singapore.

Mental health problems currently affect a quarter of the world's population. Recent research in western societies has started to examine the relationship between entrepreneurship and mental health problems such as Attention Deficit Hyperactivity Disorder (ADHD) and dyslexia. However, little has been done to categorize entrepreneurs into different types and investigate how their levels of mental health and well-being correspond to these types. This study divided entrepreneurs into established and nascent categories and examined this topic in Singapore. By distributing two sets of surveys, a total of 834 responses were collected, with 346 responses from established entrepreneurs and 488 responses from nascent ones. The results showed that the nascent entrepreneurs' levels of well-being were found to be much lower than those of the established entrepreneurs. Furthermore, entrepreneurs with ADHD or dyslexia symptoms generally had a much lower level of life satisfaction, compared with those without. However, the self-care behaviours observed in this sample differed somewhat from observations made in western societies, which might be explained by the different cultures and habits in Singaporean society. The findings not only highlight the need for relevant organizations to support nascent entrepreneurs but serve to remind veteran entrepreneurs to practice more healthy self-care behaviours.

Formation of a protein corona on the surface of extracellular vesicles in blood plasma.

In this study we tested whether a protein corona is formed around extracellular vesicles (EVs) in blood plasma. We isolated medium‐sized nascent EVs of THP1 cells as well as of Optiprep‐purified platelets, and incubated them in EV‐depleted blood plasma from healthy subjects and from patients with rheumatoid arthritis. EVs were subjected to differential centrifugation, size exclusion chromatography, or density gradient ultracentrifugation followed by mass spectrometry. Plasma protein‐coated EVs had a higher density compared to the nascent ones and carried numerous newly associated proteins. Interactions between plasma proteins and EVs were confirmed by confocal microscopy, capillary Western immunoassay, immune electron microscopy and flow cytometry. We identified nine shared EV corona proteins (ApoA1, ApoB, ApoC3, ApoE, complement factors 3 and 4B, fibrinogen α‐chain, immunoglobulin heavy constant γ2 and γ4 chains), which appear to be common corona proteins among EVs, viruses and artificial nanoparticles in blood plasma. An unexpected finding of this study was the high overlap of the composition of the protein corona with blood plasma protein aggregates. This is explained by our finding that besides a diffuse, patchy protein corona, large protein aggregates also associate with the surface of EVs. However, while EVs with an external plasma protein cargo induced an increased expression of TNF‐α, IL‐6, CD83, CD86 and HLA‐DR of human monocyte‐derived dendritic cells, EV‐free protein aggregates had no effect. In conclusion, our data may shed new light on the origin of the commonly reported plasma protein ‘contamination’ of EV preparations and may add a new perspective to EV research.

Targeted Mass Spectrometry-Based Approach for the Determination of Intrinsic Internalization Kinetics of Cell-Surface Membrane Protein Targets.

Successful development of targeted therapeutics aimed at the elimination of diseased cells relies on the target properties and the therapeutics that target them. Currently, target properties have been evaluated through antibody-dependent semiquantitative approaches such as flow cytometry, Western blotting, or microscopy. Since antibodies can alter target properties following binding, antibody-dependent approaches provide at best skewed measurements for target intrinsic properties. To circumvent, here we attempted to develop an antibody-free targeted mass spectrometry-based (ATM) strategy to measure the surface densities and the intrinsic rates (Kint) of CD38 internalization in multiple myeloma cell lines. Using cell-surface biotinylation in conjunction with differential mass tagging to separate inward CD38 molecules from the outbound and nascent ones, the ATM approach revealed diversities in measured CD38 Kint values of 0.239 min-1 S.E. ± 0.076, 0.109 min-1 S.E. ± 0.032, and 0.058 min-1 S.E. ± 0.001 for LP1, NCIH929, and MOLP8 cell lines, respectively. Together with CD38 surface densities, intrinsic Kint values aligned well with the tumor penetration model and supported the outcomes for tumor regression in mouse xenografts upon drug treatment. Additionally, the ATM approach can evaluate molecules with fast Kint as we determined for CTLA4 protein. We believe that the ATM approach has the potential to evaluate diverse cell-surface targets as part of the pharmacological assessment in drug discovery.

Non-thermal rate constants of quenching and vibrational relaxation in the OH manifold

Knowledge of molecular energy-transfer processes is a key ingredient for using laser-induced fluorescence, LIF, as a quantitative optical diagnostic method at high pressure. At present, rate constants of electronic quenching and vibrational energy transfer in the OH manifold for many colliders are known only in the condition of thermal equilibrium of the rotational population of the A electronic state. However, this condition is seldom met in molecular gases. Therefore, the rotational distributions in the OH manifold are often non-thermal and close to the nascent ones. In the present work, a new set of rate constants has been measured in the condition of non-thermal rotational distribution, for the excitation of three rotational levels, N′ = 0, 1, 2, of OH with CO2, CO, O2, CH4 and H2 as colliders. For N′ = 2 the temperature dependence of the rate constants has also been measured for the first time from 300 to over 2000 K. These new data are crucial for the quantification of OH by LIF in gas discharges at high pressure and to fully exploit the CET-LIF (collision energy transfer LIF) technique for measuring the CO2 dissociation as a function of time in a nanosecond repetitively pulsed discharge.

Using Quality of Service Delivery to Evaluate Federal Government of Nigeria Policy on Public Service Outsourcing: A Case of Public Healthcare Institutions, Nigeria

It is a normal practice in all works of life to evaluate or assess the impacts or effects of policies made by individuals, groups and organizations, more especially, the public policies of governments. By assessing some of these policies, especially, nascent ones such as this one, gaps could be established between the policy framework and impacts such could create on the people or institutions which they are meant to serve. This could also serve as post critical analysis for the policy stakeholders. This study is set out to evaluate the public service outsourcing of the Federal Republic of Nigeria, using quality of service delivery questionnaires as the major assessment instrument. A descriptive survey research was adopted for the study, and correlation design as its method was used for data analysis. Pearson Moment Correlation Coefficient was used to determine its internal consistency. Three sets of questionnaire were designed to service the population sample size of 319 (Three Hundred and Nineteen) in the study areas. The SPSS assisted result from the study shows strong correlate of 0.828, at 0.01 level (2-tailed) between public service outsourcing and quality of service delivery.

Characterizing alternative food networks in China

Amid the many food safety scandals that have erupted in recent years, Chinese food activists and consumers are turning to the creation of alternative food networks (AFNs) to ensure better control over their food. These Chinese AFNs have not been documented in the growing literature on food studies. Based on in-depth interviews and case studies, this paper documents and develops a typology of AFNs in China, including community supported agriculture, farmers’ markets, buying clubs, and recreational garden plot rentals. We unpacked the four standard dimensions of alternativeness of AFNs into eight elements and used these to examine the alternativeness of AFNs in China. We argue first that the landscape of alternativeness varies among different networks but the healthfulness of food is the most prominent element. Second, there is an inconsistency in values between AFN initiators and customers, which contributes to the uneven alternativeness of Chinese AFNs. Third, Chinese AFNs are strongly consumer driven, a factor that constrains their alternativeness at present. The inclusion of “real” peasants in the construction of AFNs in China is minimal. This paper adds to the existing literature on AFNs with an analysis of recent initiatives in China that have not been well documented before. By unpacking the dimensions of alternativeness into specific elements, this paper also provides an analytical framework for examining the alternativeness of AFNs especially nascent ones that have not developed a full spectrum of alternativeness.

Acrylonitrile-based copolymer membranes containing reactive groups: Surface modification by the immobilization of biomacromolecules

Asymmetric membranes fabricated from poly(acrylonitrile- co-maleic acid) (PANCMA) were immobilized with heparin and/or insulin to improve their surface properties. These biomacromolecule-immobilized PANCMA membranes were prepared by the amination of the membrane surface with ethylenediamine, followed by the reaction of the amino groups with heparin and/or insulin in the presence of 1-ethyl-3-(3-dimethyl amidopropyl) carbodiimide. The surface-modified membranes were analyzed by X-ray photoelectron spectroscopy to confirm the immobilization of the biomacromolecules. Morphological changes on the membrane surface and in the cross section were characterized by scanning electron microscopy. The surface hydrophilicity and hemocompatibility of the studied membranes were evaluated on the basis of water contact angle, platelets adhesion and cell attachment measurements. It was found that, after the immobilization of the biomacromolecules, the water contact angle and the amount of adhered platelets and macrophages on the membrane decreased significantly when compared with the nascent ones, indicating the improvement of surface hydrophilicity. Furthermore, the heparin immobilized membrane showed the best hemocompatibility among the corresponding membranes studied.

Adsorption and Activity of Candida rugosa Lipase on Polypropylene Hollow Fiber Membrane Modified with Phospholipid Analogous Polymers

Efforts have recently been made toward the study of interactions of phospholipid with various enzymes. It seems that phospholipids may be directly involved in regulating the enzyme activity. In this work, three phospholipid analogous polymers (PAPs), containing hydrophobic octyloxy, dodecyloxy, and octadecyloxy groups (abbreviated as 8-PAP, 12-PAP, and 18-PAP, respectively), were tethered on polypropylene hollow fiber microfiltration membrane (PPHFMM) to create a biocompatible interface for lipase immobilization. Lipase from Candida rugosa was immobilized on these PPHFMMs by adsorption. The adsorption capacity, activity, and thermal stability of enzyme on the PAP-modified PPHFMMs were compared with those of enzyme on the nascent ones. It was found that, as for the PAP-modified PPHFMMs, the adsorption capacities of lipase are lower than that of the nascent ones, while the activity retention of immobilized lipase increases from 57.5% to 74.1%, 77.5%, and 83.2% respectively for the 8-PAP-, 12-PAP-, and 18-PAP-modified PPHFMMs. In addition, the experimental results of thermal stability show that the residual activity of the immobilized lipase at 50 degrees C for 2 h is 62% for the 8-PAP-modified PPHFMM, 59% for the 12-PAP-modified PPHFMM, and 66% for the 18-PAP-modified PPHFMM, which are also higher than that of the nascent ones.

Adsorption immobilization of Candida rugosa lipases on polypropylene hollow fiber microfiltration membranes modified by hydrophobic polypeptides

Poly(γ-ethyl- l-glutamate) (PELG) and poly(γ-stearyl- l-glutamate) (PSLG), two polypeptides with short and long hydrophobic side chains, respectively, were tethered on the polypropylene hollow fiber microfiltration membrane (PPHFMM) surface through the ring opening polymerization of N-carboxyanhydride of γ-ethyl- l-glutamate (γ-stearyl- l-glutamate) initiated by amino groups. Lipases from Candida rugosa were immobilized on these membranes by adsorption. Results on the basis of the enzyme adsorption capacity, activity and thermal stability were compared with those of the nascent PPHFMM. It was found that, as for the modified PPHFMM, the adsorption capacities of lipase are lower than that of the nascent ones, but the activity retention of the immobilized enzymes increases from 57% to 72% and to 62%, respectively for the PSLG-modified and PELG-modified PPHFMM. In addition, the experimental results of thermal stability show that the residual activity of the immobilized lipases at 50 °C for 2 h is respectively 64% for the PELG-modified PPHFMM and 58% for the PSLG-modified PPHFMM, which are higher than that of the nascent ones.

A comparative study on lipase immobilized polypropylene microfiltration membranes modified by sugar-containing polymer and polypeptide

Two protocols were used to modify polypropylene microfiltration membrane (PPMM): (a) a sugar-containing polymer was grafted onto the membrane surface by the plasma-induced polymerization of α-allyl glucoside (AG) and (b) poly(γ-stearyl l-glutamate) (PSLG) was tethered onto the membrane surface through the ring opening polymerization of N-carboxyanhydride (NCA) derived from γ-stearyl l-glutamate. Lipases from Candida rugosa were immobilized on these membranes by adsorption. Results on the basis of the enzyme adsorption capacity, activity and thermal stability were compared with those of the nascent PPMM. It was found that, as for the PAG-modified PPMM, the adsorption capacity and the activity retention of lipases were lower than those of the nascent ones, but the thermal stability was improved to some degree. On the other hand, tethering PSLG on the membrane surface increased the activity retention of lipases immobilized on the membrane from 57 to 72%, and the thermal stability was also improved.

Structural relationships between nascent apoA-I-containing particles that are extracellularly assembled in cell culture

Apolipoprotein A-I (apoA-I) incubated with CHO cells assembles three major nascent lipid complexes with diameters of 7.3, 9, and 11 nm. Previous studies suggested that the smaller nascent particles were precursors for the larger nascent ones. To test this hypothesis, the 7.3, 9, and 11 nm apoA-I-lipid complexes formed by incubating CHO cells with lipid-free apoA-I were isolated and subsequently each subpopulation was re-incubated with cells in the absence of other subpopulations. The physical-chemical characteristics of each subpopulation were examined before and after re-incubation in an effort to understand relationships. if any, between the different nascent complexes. The 7.3, 9, and 11 nm complexes were unique in that each of the particles had pre-alpha mobility on agarose gels: this rapid migration was not altered by re-incubation with cells. Protein crosslinking studies indicated that the 7.3, 9, and 11 nm complexes possessed 2, 3, and 4 apoA-I molecules per complex, respectively; it is unlikely that the size of the particle and number of apoA-I molecules per particle played a role in the increased negative charge of the particles. The present study shows that smaller particles did not give rise to larger ones upon re-incubation with cells. Rather, the 11 and 9 nm particles both generated smaller discs (the 11 nm giving rise primarily to 9 nm discs and the 9 nm complex giving rise to 7.3 nm discs) suggesting that, during incubation with cells, the complexes are destabilized and remodeled into smaller, not larger, complexes. Surprisingly, the 7.3 nm complexes during re-incubation with cells were extremely stable and did not undergo size alteration. When the 7.3 nm particles were incubated with additional small quantities of lipid-free apoA-I (1-2 microgram/ml), larger discoidal complexes were generated suggesting that the formation of larger particles may be driven by the availability of lipid-free apoA-I.

P17 and p17-ContaininggagPrecursors of Input Human Immunodeficiency Virus Are Transported into the Nuclei of Infected Cells

Subcellular localization of input human immunodeficiency virus type 1 (HIV-1) gag proteins was determined in infected H9 and Jurkat tat cells. Infected cells were fractionated at intervals, and the proteins in cell fraction were identified by immunoblotting using pooled sera from acquired immunodeficiency syndrome (AIDS) patients and monoclonal antibodies. Cycloheximide was added at 0 time to prove that the proteins detected were not nascent ones. Gag proteins p55, p41, p39 (in the most essential relative concentrations), and p17 were found in the cell nuclei for at least 4 h after infection. However, p24 was not found in the cell nuclei and was accumulated in the nuclear washing buffer. The data presented confirm the presence of karyotypic signal at the N terminus of p55 gag precursor. The potential role of nuclear localization of gag precursor is discussed.

Functional and ultrastructural evidence for intracellular formation of major histocompatibility complex class II-peptide complexes during antigen processing.

Antigen presentation requires intracellular processing of native antigens to produce immunogenic peptides that bind to major histocompatibility complex class II (MHC-II) molecules. In functional studies of antigen processing by elicited peritoneal macrophages, MHC-II-peptide complexes were formed intracellularly. Immunogenic peptides were not released to bind surface MHC-II molecules. Ultrastructural studies employing immunogold staining in ultrathin cryosections of these macrophages showed large amounts of MHC-II molecules in intracellular sac-like vacuoles in the peripheral cytoplasm; most of these were negative for the lamp 1 lysosomal/endosomal membrane protein and cathepsin D. MHC-II molecules were also present in endosomes containing cathepsin D and lamp 1 as well as previously internalized gold-transferrin. The intracellular pool of MHC-II molecules was only slightly decreased by treatment with cycloheximide for 3 hr, indicating that it consisted mainly of endocytosed, recycling molecules, as opposed to nascent ones. These ultrastructural studies support the notion that there is endocytosis of MHC-II molecules into endocytic compartments, consistent with our earlier biochemical data. Furthermore, we have defined the distinct endocytic compartments that must mediate important functions in antigen processing, including the formation of MHC-II-peptide complexes.