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关键词： Hydrological regimes   Diatom traits   Biofilm community functions   Metabolism   Nutrient uptake rates  

摘要： Despite increasing interest in hydrological effects on riverine ecosystems, few studies have documented the impact of hydrology on biofilm community functions, and those existing have typically focused on annual-based hydrological indices. In this study, we conducted monthly samplings during a year in five lowland streams with different flow regimes and investigated the impacts of hydrological conditions and physico-chemical variables on the trait composition of diatoms growing on artificial substrates, biomass (chlorophyll a and ash free dry weight), and biofilm community functions (biochemical processes, i.e., biofilm metabolism and nutrient uptake rates measured in the laboratory). Instead of the commonly used annual-based hydrological indices, we calculated indices for shorter periods (14 and similar to 28 days) of the hydrological regimes. Results of species-based variation partitioning showed that short-period hydrological indices (10.10 +/- 7.18%) contributed more to explain species distribution than physico-chemical variables (5.90 +/- 3.83%), indicating the dominant role of hydrology in structuring the diatom community. Specifically, we found different response patterns for different guilds and size lasses to the hydrological and physico-chemical variables, and our results demonstrated that species tolerating high disturbance may be more appropriate as indicators of environmental disturbance than low-tolerant species. We also found dominant effects of short-period hydrological events on biomass and biofilm community functions. Despite an overall negative effect of high flow events and flow variations on biomass and biofilm community functions, positive effects on function-biomass ratios were also observed, indicating that the effects of flow regimes on biofilm are complex. In conclusion, our study highlights the importance of including short-period hydrological conditions in studies on environmental factors shaping benthic algae. Based on our results, we re

关键词： Metallosurfactants   Mctallosomes   Cholesterol   Aftereffects   Rifampicin   MRSA  

摘要： The controlled stoichiometry of single-tailed surfactant cetylpyridinium chloride (CPC) in the presence of Cu ions led to a vesicular assembly known as 'metallosomes'. Unlike liposomes, their membrane properties such as microscopic dynamics, fluidity, and physicochemical variations, have not been explored. Therefore, metallosomes with a water-soluble metallosurfactant (bishexadecylpyridiniumcopper tetrachloride) with varying cholesterol concentrations were synthesized and explored for the induced effect of cholesterol on different membrane properties. Three different metallosomes were synthesized by varying the metallosurfactant to cholesterol molar ratio to 1:0, 1:0.5, and 1:1 and characterized with cryo-TEM, FESEM, DLS, and zeta-potential. For microscopic dynamics studies, quasielastic neutron scattering (QENS), for bilayer molecular arrangement XRD and SAXS, and for physicochemical properties, three fluorescent probes (ANS, Prodan, and Laurdan) were utilized. The Well Diffusion method was employed for exploring the antimicrobial behavior of empty as well as drug-loaded metallosomes. The spherical morphology of synthesized metallosomes was established with different studies and insertion of cholesterol has been found to lead to more stable and homogeneous suspensions. Also, more restricted, less fluid, and dehydration of membrane was observed with cholesterol. The antimicrobial activity as well as releasing profile was observed to be directly influenced in the presence of cholesterol. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Syringic acid   Cinnamic acid   R. ferruginea   antiradical Activity   Liposomes  

摘要： Syringic and cinnamic acids were previously identified as the major components on Rapanea ferruginea's leaf extract. In this work, these phenolic acids were investigated and correlated in two aspects. The first one was referred to their role against DPPH and hydroxyl radicals, considering the concentration detected in R. ferruginea extract. The second one considered their effects on the physico-chemical properties of soy asolectin liposomes, such as hydration degree, trans-gauche isomerization, vibrational, rotational and translational motions, state-of-phase, size and surface charge. The half-maximum inhibitory concentration (IC50) related to syringic acid in DPPH assays was detected as 7.36 x 10(-3) mM. At the cinnamic acid highest tested concentration (8.23 x 10(-3) mM), the activity against DPPH was around 4.6%. Regarding hydroxyl radical-induced lipid peroxidation, the IC50 detected for syringic acid free in solution (free-form) was equivalent to 0.082 x 10(-3) mM, a value 3.6 times lower than the detected for its liposome-loaded form. At the highest tested concentration (0.24 x 10(-3) mM), the free-form cinnamic acid inhibited lipid peroxidation by 4 times the observed to its liposome-loaded form. Results showed that hydrogen donation is not the preferential mechanism in which the tested phenolic acids inhibit hydroxyl radical-induced lipid peroxidation. Syringic acid showed higher antioxidant potential than cinnamic acid, probably having a primordial role in the properties related to R. ferruginea. Liposomes' physico-chemical data provided correlations between the phenolic acids' antioxidant potential and their influence in the mobility of specific lipid groups. The findings of this work will contribute to the design and development of phenolic acids-based and plant extract-based pharmacological systems. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Polymer nanoparticles   Nanoprecipitation   Physicochemical parameters   SANS   Colloidal stability   Nucleation-coalescence  

摘要： Polymer nanoparticles formed from polymers with biodegradable and biocompatible properties are promising candidates for biomedical applications. Herein, the role of different physicochemical parameters associated with the formation of hydrophobic iPoly(lactic-co-glycolic add) (PLGA) and Polycaprolactone (PCL)] and amphiphilic [Poly(ethylene glycol) methyl ether-block-poly(L-lactide-co-glycolide) (PEG-PLGA)] polymer nanopartides has been studied by Small-Angle Neutron Scattering (SANS). We show that the changes in size and the number density of hydrophobic polymer nanoparticles are associated with the polymer concentration or solvent-to-nonsolvent ratio or the synergetic effect of these parameters. These results support the formation of the hydrophobic PLGA nanoparticles as the nucleation of small molecules followed by the coalescence-induced growth process. PCL nanopartides follow a similar pathway as observed for PLGA nanopartides. Contrarily, any significant changes in the size and the number density of PEG-PLGA nanoparticles associated with the polymer concentration or solvent-to-nonsolvent ratio have not been observed. In amphiphilic PEG-PLGA nanoparticles, the PLGA cores follow the nucleation process while PEG molecules stay around the core with random conformation. The coalescence-induced growth, unlike hydrophobic polymer nanoparticles, is suppressed due to the hydrated steric barrier of PEG chains. This distinct difference in the formation mechanism of the hydrophobic and amphiphilic polymers could be utilized for applications associated with the different length scales of nanoparticles. (C) 2020 Elsevier B.V. All rights reserved.

关键词： DFT   Melatonin   Coronavirus   NLO   NBO  

摘要： Melatonin is a natural hormone from the pineal gland that regulates the sleep-wake cycle. We examined the structure and physico-chemical properties of melatonin using electronic structure methods and molecular-mechanics tools. Density functional theory (DFT) was used to optimise the ground-state geometry of the molecule from frontier molecular orbitals, which were analysed using the B3LYP functional. As its electrons interacted with electromagnetic radiation, electronic excitations between different energy levels were analysed in detail using time-dependent DFT with CAM-B3LYP orbitals. The results provide a wealth of information about melatonin's electronic properties, which will enable the prediction of its bioactivity. Molecular docking studies predict the biological activity of the molecules against the coronavirus2 protein. Excellent docking scores of -7.28, -7.20, and -7.06 kcal/mol indicate that melatonin can help to defend against the viral load in vulnerable populations. Hence it can be investigated as a candidate drug for the management of COVID. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Buclizine   Counter-ion stoichiometry   Hydration   Equilibrium solubility   Dissolution profile   Structure determination   Crystal engineering  

摘要： Buclizine (BCZ) is a chiral synthetic piperazine derivative which has antihistaminic, anti-muscarinic and antiemetic properties, and has been reintroduced as an appetite stimulant, especially for pediatric patients. Structural information about this drug, as well as other buclizine crystalline forms (solvates, salts and co-crystals) including the BCZ free-base (BCZ-FB), is non-existent. Here, we present for the first time the crystal structure of the monohydrochloride monohydrate salt of BCZ (BCZHCl center dot H2O), and of its anhydrous form, BCZHCl. Interestingly, BCZHCl center dot H2O was obtained by recrystallization from the raw material (BCZH(2)Cl(2)) in ethanol:water solution showing that BCZ anhydrous dihydrochloride salt changes easily to a monohydrochloride monohydrate salt modification, which raise concerns about formulation quality control. BCZHCl center dot H2O and BCZHCl crystallize in the orthorhombic space groups (Pna2(1) and Pca2(1)) belonging to the mm2 point group and are thus classified as non-centrosymmetric achiral structures (NA). Intuitively, we expect these salts to crystallize in a space group with a center of symmetry, since less than 5% of the known racemic compounds crystallize in the NA type. The crystal structures of BCZH(2)Cl(2) and BCZ-FB were not determined, but their existence was verified by other techniques (chloride ion analysis, PXRD, HPLC, FT-IR, DSC, TGA) and by comparison of the obtained results with those found for BCZHCl. Additionally, we have also performed an evaluation of the equilibrium solubility (at six different aqueous media) and the dissolution profile of the BCZHCl salt compared to the raw material and BCZ-FB. Different equilibrium solubility values were found comparing the three forms in acidic and neutral pH ranges and all of them were insoluble at pH > 7.0. Moreover, tablets prepared with BCZH(2)Cl(2), BCZHCl or BCZ-FB show significant differences in terms of dissolution profile.

关键词： Anaerobic digestion liquor   Wastewater pre-treatment   Biodegradability   Advanced oxidation processes   Hydrolysis   Ultrasound  

摘要： Centrifugation of anaerobically digested sewage sludge gives rise to a solid phase, which could be employed as a fertilizer, and a liquid fraction (ADL), which should be treated before being spilled out. This is not an easy task because this liquor is characterized for presenting high COD (similar to 16000 mg O-2/L), high ammonium content (similar to 4000 mg/L) and low biodegradability (BOD5/COD similar to 0.2). With the objective to pre-treat this aqueous waste before its treatment by means of more traditional aerobic processes, different physico-chemical methods (ultrasound, ozonation, hydrolysis and wet air oxidation) were assessed in this work. Ultrasound and thermal hydrolysis gave solubilizations around 47% and 68% respectively. The best results in terms of total COD removal were obtained when wet air oxidation (8 h, 160 C-200 degrees C and 6.0 MPa) and ozonation (8 h, 25 degrees C, 12 g/h O-3) techniques were employed achieving COD degradations of 71% and 38%, respectively. The pre-treatment of ADL with the four assayed techniques improved considerably the biodegradability (BOD5/COD) of the effluent, with values around 0.3-0.4, depending on the treatment. The experimental data were successfully fitted by kinetic models and the kinetic constants for the solubilization and degradation steps were obtained. Application of the proposed models can be of interest for the optimization and selection of the most suitable techniques and operational conditions, in each particular case.

关键词： Drugs   Micellization   Phase separation   Solubility   Thermodynamics   Organic solvent  

摘要： The physicochemical properties of drugs and drug-additive interactions have great importance to elucidate the pharmacological effect of the drug formulations. Plentiful pharmacologically active molecules are amphiphilic in nature. Knowledge about self-assembly, aggregate morphology as well as size and interfacial/micellar properties of such drugs in presence of pharmaceutical excipients (surfactants, electrolytes, polymers, hydrotropes, etc.) is vital from the fundamental and practical point of view. This article reviews the micellar properties and phase separation of drugs as well as drug-additive systems in aqueous and organic solvent-water mixed media. Results of several pharmaceutical excipients/surfactants assisted drug mixed systems have been analyzed through thermodynamic parameters which provide a comprehensive account on the physicochemical aspects of drug/drug-additives systems. Along with amphiphilic drugs, studies of a few non surface-active drugs have also been reviewed. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Hyaluronic acid   Hydrogel   NMR   Water   Relaxation   Diffusion  

摘要： Cross-linked hyaluronic acid (HA) hydrogels are used in many biomedical applications but their characterization in order to distinguish between physicochemical properties is challenging. Longitudinal (T-1) and transverse (T-2) relaxation times and diffusion coefficient (D) of water protons in diepoxide 1,4-butanediol diglycidyl ether (BDDE)-cross-linked HA hydrogels were analyzed by high-field NMR spectroscopy to distinguish between different physicochemical properties. Hydrogels of different degrees of modification and cross-linking, representing a range of gel content, swelling ability, elastic and viscous behavior were studied, as well as solutions of native HA of different molecular weights. T-1, T-2 and D were measured for several concentrations of HA and as a function of temperature. D and T-1 showed a weak concentration dependence, but did not differ between the hydrogels. T-2, dominated by chemical exchange between water protons and exchangeable protons of HA, varied significantly between the different hydrogels and the temperature profiles changed dramatically between different concentrations.

关键词： Fibrinolytic enzyme   Enzyme purification   Physiochemical properties   Statistical optimization   Fermentation  

摘要： Fibrinolytic enzymes are proteases responsible for cleavage of fibrin mesh in thrombus clots, which are the primary causative agents in cardiovascular diseases. Developing safe, effective and cheap thrombolytic agents are important for prevention and cure of thrombosis. Although a wide variety of sources have been discovered for fibrinolytic enzymes, only few of them have been employed in clinical and therapeutic applications due to the drawbacks such as high cost of production, low stability of enzyme or therapeutic side effects. However, the discovery of new fibrinolytic enzymes requires complex purification stages and characterization, which gives an insight into their diverse modes of action. Post-discovery, approaches such as a) statistical optimization for fermentative bioprocessing and b) genetic engineering are advantageous in providing economic viability by finding simple and cost-effective medium, strain development with sufficient nutrient supplements for stable and high-level production of recombinant enzyme. This review provides a comprehensive understanding of different sources, purification techniques, production through genetic engineering approaches and statistical optimization of fermentation parameters as proteases have a wide variety of industrial and biotechnological applications making 60% of total enzyme market worldwide. New strategies targeting increased enzyme yields, non-denaturing environments, improved stability, enzyme activity and strain improvement have been discussed. (C) 2020 Elsevier B.V. All rights reserved.