Influence of most reactive inorganic cation in the optical and biological activities of L-Lysine monohydrochloride crystal

Slow evaporation method was used to grow the pure and K⁺ ion doped L-Lysine monohydrochloride (L-LMHCL) crystals which has optical and antibiotic applications. The space group, structure and slight shifting of peaks are confirmed using single crystal XRD and the powder XRD. The FTIR analysis also shows that the K⁺ doped L-LMHCL has a slight shifting in the spectrum which indicates the functional group of L-LMHCL and the interaction between the K⁺ ions. The existence of K⁺ ion in the doped crystal is assured by the presence of potassium in the EDAX spectrum. The wide optical band gap was found for pure and K⁺ doped crystal using UV spectra and these are utilized in optoelectronic and nonlinear applications. The Kurtz Perry technique specified the NLO property of grown crystals. The dielectric property crystals was studied by varying the temperature. As a result, the highest dielectric constant is observed in doped crystal. An antibacterial activity against certain bacteria like E-coli, pseudomonas aeruginosa and staphylococcus aureus are provided by mm range for the grown crystals.     

Optimizing the crystal size and habit of β-sitosterol in suspension

The aim of this work was to survey how processing parameters affect the crystal growth of β-sitosterol in suspension. The process variables studied were the cooling temperature, stirring time and stirring rate during recrystallization. In addition, we investigated the effect a commonly used surfactant, polysorbate 80, has on crystal size distribution and the polymorphic form. This study describes the optimization of the crystallization process, with the object of preparing crystals as small as possible. Particle size distribution and habit were analyzed using optical microscopy, and the crystal structure was analyzed using X-ray diffractometry. The cooling temperature had a remarkable influence on the crystal size. Crystals with a median crystal length of ≈23 μm were achieved with a low cooling temperature (<10°C); however, a fairly large number of crystals over 50 μm appeared. Higher cooling temperatures (>30°C) caused notable crystal growth both in length and width. Rapid (250 rpm), continuous stirring until the suspensions had cooled to room temperature created small, less than 50 μm long (median <20 μm), needle-shaped crystals. The addition of surfactant slightly reduced the size of the initially large crystals. Both hemihydrate and monohydrate crystal forms occurred throughout, regardless of the processing parameters. By using an optimized process, it was possible to obtain a microcrystalline suspension, with a smooth texture.     

Purification, crystallization and preliminary crystallographic investigations of selenium-containing phycocyanin from selenium-rich algae ( Spirulina platensis )

The selenium-containing phycocyanin from the selenium-rich algae (Spirulina platensis) has been crystallized in two crystal forms by the hanging-drop vapor diffusion techniques. A chromatographic procedure of gel filtration and anion exchange was used for purification. Form I crystal with space group P2₁ and cell parameters a =108.0 ?, b= 117.0 ?, c = 184.0?, β= 90.2° and 12(αβ) units in the asymmetric unit was obtained by using (NH₄)₂SO₄ as precipitant. These crystals diffract up to 2.8 ?. Form II crystal obtained by using PEG4000 as precipitant belongs to space group P6₃ with unit cell constants a = 155.0 ?, c = 40.3 ?, γ =120.0° and one(αβ) unit in the asymmetric unit. The crystals diffract beyond 2.9 ?. The possible stacking forms of phycocyanin molecules in the first crystal form were discussed.     

Phenyltriazole-functionalized sulfamate inhibitors targeting tyrosyl- or isoleucyl-tRNA synthetase

Antimicrobial resistance is considered as one of the major threats for the near future as the lack of effective treatments for various infections would cause more deaths than cancer by 2050. The development of new antibacterial drugs is considered as one of the cornerstones to tackle this problem. Aminoacyl-tRNA synthetases (aaRSs) are regarded as good targets to establish new therapies. Apart from being essential for cell viability, they are clinically validated. Indeed, mupirocin, an isoleucyl-tRNA synthetase (IleRS) inhibitor, is already commercially available as a topical treatment for MRSA infections. Unfortunately, resistance developed soon after its introduction on the market, hampering its clinical use. Therefore, there is an urgent need for new cellular targets or improved therapies. Follow-up research by Cubist Pharmaceuticals led to a series of selective and in vivo active aminoacyl-sulfamoyl aryltetrazole inhibitors targeting IleRS (e.g. CB 168).Here, we describe the synthesis of new IleRS and TyrRS inhibitors based on the Cubist Pharmaceuticals compounds, whereby the central ribose was substituted for a tetrahydropyran ring. Various linkers were evaluated connecting the six-membered ring with the base-mimicking part of the synthesized analogues. Out of eight novel molecules, a three-atom spacer to the phenyltriazole moiety, which was established using azide-alkyne click chemistry, appeared to be the optimized linker to inhibit IleRS. However, 11 (K_i,app = 88 ± 5.3 nM) and 36a (K_i,app = 114 ± 13.5 nM) did not reach the same level of inhibitory activity as for the known high-affinity natural adenylate-intermediate analogue isoleucyl-sulfamoyl adenosine (IleSA, CB 138; K_i,app = 1.9 ± 4.0 nM) and CB 168, which exhibit a comparable inhibitory activity as the native ligand. Therefore, 11 was docked into the active site of IleRS using a known crystal structure of T. thermophilus in complex with mupirocin. Here, we observed the loss of the crucial 3′- and 4′- hydroxyl group interactions with the target enzyme compared to CB 168 and mupirocin, which we suggest to be the reason for the limited decrease in enzyme affinity. Despite the lack of antibacterial activity, we believe that structurally optimizing these novel analogues via a structure-based approach could ultimately result in aaRS inhibitors which would help to tackle the antibiotic resistance problem.     

Phytochemical profiling,antioxidant and antibacterial efficacy of a native Himalayan Fern: Woodwardia unigemmata (Makino) Nakai

Present work elucidates the antioxidant and antibacterial activity of Woodwardia unigemmata (Makino) Nakai along with chemical characterization using its aqueous (AEW), methanol (MEW), and hexane (HEW) extracts. Chemical profile of different extracts was illustrated by using Gas chromatography and mass spectrometry (GC-MS) analysis. Antioxidant activities were tested using DPPH and FRAP assays, total phenolic and flavonoid content by Folin-Ciocalteu and aluminum chloride method, respectively. Further, antibacterial activity against six plant and four animal pathogenic bacteria was analyzed by employing the disc diffusion assay. GC-MS analysis revealed the presence of catechol (21.96%), glycerol (20.22%), n-pentadecanoic acid (6.95%), glyceryl monoacetate (6.35 %), ethyl acetimidate (5.39 %) and 3-hydroxy-2,3-dihydromaltol (5.36%) in AEW; β-sitosterol (17.39%), pentadecanoic acid (9.81%), vitamin E (7.82%) and glycerol (7.05%) in MEW; γ-sitosterol (33.45%), vitamin E (10.04%) and campesterol (7.32%) in HEW as major constituents. Maximum phenolics (873 ± 6.01 mgGAE/g dry extract) as well as flavonoids (151 ± 11.44 mgQE/g dry extract) content was found in MEW, which also showed remarkable antioxidant potential (IC₅₀ 6.07 ± 1.4 µg/ml for DPPH and 768 ± 10.4 mg AAE/g dry extract for FRAP assay. In antibacterial activity, maximum inhibition (15 ± 0.9 mm) was observed for HEW against R. solanacearum, followed by AEW against A. tumefaciens and X. phaseoli (11 ± 0.3 mm each). MEW was found positive only against A. tumefaciens. Significant minimum inhibitory concentration (MIC) value observed for AEW against L. monocytogenes (10 mg/ml). Polar extracts had remarkable antioxidant potential, while non-polar extract did show significant antibacterial activity. Further, GC- MS reports indicated that this traditionally useful fern species can be an excellent source of biologically active compounds.     

Triboluminescence and crystal structure of the complex [Eu(NО3)3(HMPA)3]: role of cleavage planes

The atomic structure of crystals of the [Eu(NО₃)₃(HMPA)₃] [hexamethylphosphotriamide (HMPA)] complex characterized by an intensive luminescence and triboluminescence was determined using X‐ray structural analysis. Noncentrosymmetric crystals have a monoclinic syngony: a = 16.0686 (3), b = 11.0853 (2), c = 20.9655 Å (4), β = 93.232° (1), space group P2₁, Z = 4, ρ_calc = 1.560 g/cm³_. The crystal structure is represented by individual С₁₈Н₅₄EuN₁₂O₁₂P₃ complexes linked through van der Waals interactions with clearly expressed cleavage planes. The Eu(III) atom coordination polyhedron reflected the state of a distorted square antiprism. Structural aspects of the suggested model, including formation of triboluminescence properties, were considered and the role of the cleavage planes was discussed.     

Microbeam X-ray Diffraction Study of Granular Crystals Formed in Water-in-Oil Emulsion

Margarine and fat spread contain typical water-in-oil emulsions, including semi-solid fats, as continuous oil phases. The application of palm oil, one of the most promising trans-fat alternatives, for semi-solid fats is increasing. However, granular crystals often occur in palm-oil-based solid fats and cause deterioration. In this study, we carried out differential scanning calorimetry (DSC), optical microscopy, and X-ray diffraction (XRD) experiments on granular crystals in margarine. A conventional laboratory-scale technique was applied to examine thermal properties of high-melting fat fractions in granular crystals. In addition, microstructures of the granular crystal were precisely observed with a synchrotron radiation small-angle XRD (SR-μ-SAXD) technique by using a microbeam having a cross section of 5 × 5 μm². The following results were obtained. (1) DSC indicated that granular crystals are composed of high-melting fractions having a melting temperature of 23 °C. (2) Conventional XRD of granular crystals indicated that β-fat crystals of a triple chain length structure (β-3) melted below the melting of β′-fat of a double chain length structure (β′-2). (3) SR-μ-SAXD indicated that the fat crystals in normal margarine were β′-2. However, the fat crystals of the double and triple chain length structures were simultaneously observed at the center region of a granular crystal, whereas only the fat crystals of β-3 were observed at the outer region of a granular crystal. We analyzed the microstructures and formation processes of granular crystals in relation to the fractional crystallization of the β form of 1,3-dipalmitoyl-2-oleoyl-sn-glycerol promoted by crystallization and transformation of tripalmitin and tristearin fractions.     

Study on the flocculability of the Arthrobacter sp., an actinomycete resuscitated from the VBNC state

A bioflocculant with high flocculating activity, LC13-SF, produced by strain LC13^T which was in a viable but nonculturable (VBNC) state, and which was woken up by Rpf (resuscitation promoting factor), was systematically investigated with regard to its fermentation conditions and flocculating activity. The key parameters influencing the bioflocculant LC13-SF were investigated through measuring the optical density at 660 (OD₆₆₀) of the fermentation liquid and the optical density at 550 (OD₅₅₀) of the centrifugal supernatant. The flocculating efficiency and the Zeta potentials were chosen as the response variables for the study of the flocculating activity. The results showed that the optimal conditions for bioflocculant LC13-SF production were a fermentation time of 72 h, an initial pH of 7.0, a fermentation temperature of 30°C and a shaking speed of 150 r/min. The optimized flocculating process was as follows: a final volume percentage of bioflocculant LC13-SF and 0.5% (w/w) CaCl₂ were 1.5 and 5%, respectively in a 4 g/L Kaolin suspension, and the system pH was adjusted to 8.0. Under these conditions, the flocculating efficiency and the absolute value of the Zeta potential reached 94.83% and 4.37, respectively.     

Ailanthus altissima leaf extract mediated green production of zinc oxide (ZnO) nanoparticles for antibacterial and antioxidant activity

BackgroundFabricating zinc oxide nanoparticles (ZnO-NPs) from plant extracts is a cost-effective, safe, and environmentally friendly alternative to established chemical procedures. This study was aimed at the environmentally friendly fabrication of ZnO-NPs from plant extract. An additional objective was to investigate the antibacterial and antioxidant activity of these biosynthesized ZnO-NPs.MethodsZnO-NPs were fabricated using the leaf extract of Ailanthus altissima, as an eco-friendly approach. The physicochemical properties of ZnO-NPs were explored using UV–visible spectroscopy, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry. The bio-fabricated ZnO-NPs were examined for bactericidal activity against pathogenic bacteria (gram-negative and gram-positive) using the agar well diffusion technique. The antioxidant efficiency of ZnO-NPs was assessed using a DPPH assay.ResultsA surface Plasmon peak was recorded at 327 nm, showing the existence of ZnO-NPs in the reaction solution of plant extract and zinc sulfate hexahydrate salt. These nanoparticles were predominantly spherical and capped by different functional groups of biomolecules. Furthermore, ZnO-NPs showed a dose-dependent antibacterial and antioxidant activity. At 20 mg/mL ZnO-NPs, the maximum bactericidal potential of ZnO-NPs was reported against Staphylococcus aureus (201.2 mm). ZnO-NPs have an IC₅₀ value of 78.23 µg/mL, indicating that they are an effective antioxidant.ConclusionThis research presents an environmentally acceptable method for producing spherical ZnO-NPs with high antibacterial and antioxidant activities. These bio-fabricated ZnO-NPs could be a good option for applications in medicine and the healthcare industry.     

Antibacterial activity of ZnO nanoparticles prepared via non-hydrolytic solution route

The antibacterial activity of ZnO nanoparticles has been investigated and presented in this paper. Nanoparticles were prepared via non-hydrolytic solution process using zinc acetate di-hydrate (Zn(CH₃COO)₂·2H₂O) and aniline (C₆H₅NH₂) in 6 h refluxing at ∼65 °C. In the presence of four pathogens such as Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and Klebsiella pneumoniae, the antibacterial study of zinc oxide nanoparticles were observed. The antibacterial activity of ZnO nanoparticles (ZnO-NPs) were studied by spectroscopic method taking different concentrations (5–45 μg/ml) of ZnO-NPs. Our investigation reveals that the lowest concentration of ZnO-NPs solution inhibiting the growth of microbial strain is found to be 5 μg/ml for K. pneumoniae, whereas for E. coli, S. aureus, and S. typhimurium, it was calculated to be 15 μg/ml. The diameter of each ZnO-NPs lies between “20 and 30 nm” as observed from FESEM and transmission electron microscopy images. The composition of synthesized material was analyzed by the Fourier transform infrared spectroscopy, and it shows the band of ZnO at 441 cm⁻¹. Additionally, on the basis of morphological and chemical observations, the chemical reaction mechanism of ZnO-NPs was also proposed.     

Towards structural elucidation of eukaryotic photosystem II: Purification, crystallization and preliminary X-ray diffraction analysis of photosystem II from a red alga

Crystal structure of photosystem II (PSII) has been reported from prokaryotic cyanobacteria but not from any eukaryotes. In the present study, we improved the purification procedure of PSII dimers from an acidophilic, thermophilic red alga Cyanidium caldarium, and crystallized them in two forms under different crystallization conditions. One had a space group of P222₁ with unit cell constants of a = 146.8 Å, b = 176.9 Å, and c = 353.7 Å, and the other one had a space group of P2₁2₁2₁ with unit cell constants of a = 209.2 Å, b = 237.5 Å, and c = 299.8 Å. The unit cell constants of both crystals and the space group of the first-type crystals are different from those of cyanobacterial crystals, which may reflect the structural differences between the red algal and cyanobacterial PSII, as the former contains a fourth extrinsic protein of 20 kDa. X-ray diffraction data were collected and processed to a 3.8 Å resolution with the first type crystal. For the second type crystal, a post-crystallization treatment of dehydration was employed to improve the resolution, resulting in a diffraction data of 3.5 Å resolution. Analysis of this type of crystal revealed that there are 2 PSII dimers in each asymmetric unit, giving rise to 16 PSII monomers in each unit cell, which contrasts to 4 dimers per unit cell in cyanobacterial crystals. The molecular packing of PSII within the unit cell was constructed with the molecular replacement method and compared with that of the cyanobacterial crystals.     

Isolation of an Antibacterial Substance from Mahonia fortunei and its Biological Activity against Xanthomonas oryzae pv. oryzicola

This study aimed to isolate the antibacterial substance from Mahonia fortunei and determine its antibacterial activity against Xanthomonas oryzae pv. oryzicola (Xoc). Bacterial leaf streak of rice, caused by Xoc, is an important rice disease and difficult to control. During a screening of antibacterial plants against plant pathogenic bacteria at an early stage, the extract from M. fortunei was found to have a strong inhibitory effect on Xoc. In this study, the chemical components of M. fortunei stems were extracted using methanol solvent, the antibacterial substance was isolated and purified by liquid–liquid partition and silica gel column chromatography and its structure was identified by nuclear magnetic resonance. The effect and mode of action of the antibacterial substance on bacterial leaf streak of rice were also detected under greenhouse conditions. Two compounds were identified, berberine and jatrorrhizine, which had a strong inhibitory effect on Xoc. The antibacterial activity of berberine was stronger, with a half‐maximal inhibitory concentration (IC₅₀) of 2.9008 mg/l. At the concentration of 0.5 g/l, its control efficacy on bacterial leaf streak of rice was more than 84%. Additionally, berberine could be absorbed by rice leaves and be translocated up and down in the rice plant, and the effective period was long, but its capability of lateral translocation inside the blade was poor.     

Biochemical characterization and evaluation of potent inhibitors of the Pseudomonas aeruginosa PA01 acetohydroxyacid synthase

Microbes and plants synthesize essential branched-chain amino acids (BCAAs) such as valine, leucine, and isoleucine via a common biosynthetic pathway in which the first reaction is catalyzed by acetohydroxyacid synthase (AHAS, EC 4.1.3.18). Recently, AHAS was identified as a potential anti bacterial target. To help find an effective inhibitor that could act as an antibacterial compound, we cloned and characterized the catalytic subunit (CSU) of Pseudomonas aeruginosa AHAS, and found four potent inhibitors through chemical library screening. The ilvI gene of P. aeruginosa encodes a 65-kDa AHAS protein, consistent with the size of the purified enzyme on SDS-PAGE. Enzyme kinetics showed that the enzyme has a K_m of 14.2 mM and a specific activity of 0.12 U/mg. Enzyme activity was optimum at a temperature of 37 °C and a pH of 7.5. The K_d for thiamine diphosphate (ThDP) was 89.92 ± 17.9 μM, as determined by fluorescence quenching. The cofactor activation constants (K_s) for ThDP and (K_c) for Mg²⁺ were 0.6 ± 0.1 and 560.8 ± 7.4 μM, respectively. Further, we determined that AVS2087, AVS2093, AVS2236, and AVS2387 compounds are potent inhibitors of the catalytic subunit of P. aeruginosa AHAS. These compounds inhibit nearly 100% of AHAS activity, with IC₅₀ values of 1.19 μM, 5.0 nM, 25 nM, and 13 nM, respectively. Compound AVS2093 showed growth inhibition with a minimal inhibitory concentration (MIC) of 742.9 μg/ml against P. aeruginosa strain ATCC 9027. Furthermore, these findings were supported by molecular docking studies with the AVS compounds against P. aeruginosa AHAS in which AVS2093 showed minimum binding energy (−7.8 kJ/mol) by interacting with the receptor through a single hydrogen bond of 2.873 Å. Correlation of AVS2093 activity with P. aeruginosa AHAS cell growth inhibition suggested that AHAS might serve as a target protein for the development of novel antibacterial therapeutics. Results of the current study provide an impetus to further evaluate the potency of these inhibitors against pathogenic P. aeruginosa strains in vivo and to design more potent antibacterial agents based on these AVS inhibitors.     

Biological and docking studies of topoisomerase IV inhibition by thiosemicarbazides

4-Benzoyl-1-(4-methyl-imidazol-5-yl)-carbonylthiosemicarbazide (1) was synthesized, and its antibacterial and type IIA topoisomerase (DNA gyrase and topoisomerase IV) activity evaluated. (1) was found to have high therapeutic potential against opportunistic Gram-positive bacteria, and inhibitory activity against topoisomerase IV (IC₅₀ = 90 μM) but not against DNA gyrase. An increase in activity against topoisomerase IV (IC₅₀ = 14 μM) was observed when the imidazole moiety of (1) was replaced with the indole group in 4-benzoyl-1-(indol-2-yl)-carbonylthiosemicarbazide (2). However, (2) showed only weak antibacterial activity. Although the results of the bacterial type IIA topoisomerases inhibition study did not parallel antibacterial activities, our observations strongly imply that a 4-benzoylthiosemicarbazide scaffold can be developed into an efficient Gram-positive antibacterial targeting topoisomerase IV. The difference in activity against type IIA topoisomerases between (1) and (2) was further investigated by docking studies, which suggested that these compounds target the ATP binding pocket.     

Xanthone C-glycosides isomers purified from Dryopteris ramosa (Hope) C. Chr. with bactericidal and cytotoxic prospects

Xanthones C-glycosides are plants secondary metabolites with diverse biological activities. Among the C-glycoside xanthones, the mangiferin (MF) is of widespread occurrence in plants while isomangiferin (IsoMF) is not very common. For the present study mangiferin (MF) and isomangiferin (IsoMF) were isolated from Dryopteris ramosa. The antibacterial potential of MF and IsoMF was evaluated by using agar well diffusion method while cytotoxic properties of MF and IsoMF were assessed by brine shrimp lethality test (BSLT). The antibacterial potential of MF and IsoMF increases in dose dependent manner. The minimum inhibitory concentration (MIC) indicated strong antibacterial potential of MF against Salmonella setubal (125 µg/mL) and Bacillus subtilis (125 µg/mL) while MF showed weak antibacterial potential against Escherichia coli (500 µg/mL). On the other hand the IsoMF showed better antibacterial potential against all the tested strain including Escherichia coli (MIC = 250 µg/mL). The MF and IsoMF showed poor cytotoxicity towards Brine shrimp nauplii as indicated by their LD₅₀ (969.77 ± 0.67 and 768.92 ± 0.81 µg/mL respectively). The present study has highlighted the antibacterial potential of MF and IsoMF. Further evaluation of these two isomeric compounds may prove to be the future remedies for various bacterial infections and other human ailments.     

Antioxidant,antibacterial and cytotoxic potential of silver nanoparticles synthesized using terpenes rich extract of Lantana camara L. leaves

Several attempts have been made for green synthesis of silver nanoparticles (AgNPs) using different plant extracts. Present study revealed that, antioxidant, antibacterial and cytotoxic AgNPs were synthesized using terpenes-rich extract (TRE) of environmentally notorious Lantana camara L. leaves. AgNPs were characterized by advanced techniques like UV–Visible and Infra red spectroscopy; XRD, SEM techniques as terpenes coated sphere shaped NPs with average diameter 425 nm. Further, on evaluation, AgNPs were found to exhibit dose – dependent antioxidant potential, good to moderate antibacterial activity against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa; and toxicity on Brine shrimp (A. salinanauplii) with LD₅₀ value 514.50 µg/ml.     

High-resolution crystal structures of trimeric and rod phycocyanin

The phycobilisome light-harvesting antenna in cyanobacteria and red algae is assembled from two substructures: a central core composed of allophycocyanin surrounded by rods that always contain phycocyanin (PC). Unpigmented proteins called linkers are also found within the rods and core. We present here two new structures of PC from the thermophilic cyanobacterium Thermosynechococcus vulcanus. We have determined the structure of trimeric PC to 1.35 Å, the highest resolution reported to date for this protein. We also present a structure of PC isolated in its intact and functional rod form at 1.5 Å. Analysis of rod crystals showed that in addition to the α and β PC subunit, there were three linker proteins: the capping rod linker (L_R^8.7), the rod linker (L_R), and only one of three rod-core linkers (L_RC, CpcG4) with a stoichiometry of 12:12:1:1:1. This ratio indicates that the crystals contained rods composed of two hexamers. The crystallographic parameters of the rod crystals are nearly identical with that of the trimeric form, indicating that the linkers do not affect crystal packing and are completely embedded within the rod cavities. Absorption and fluorescence emission spectra were red-shifted, as expected for assembled rods, and this could be shown for the rod in solution as well as in crystal using confocal fluorescence microscopy. The crystal packing imparts superimposition of the three rod linkers, canceling out their electron density. However, analysis of B-factors and the conformations of residues facing the rod channel indicate the presence of linkers. Based on the experimental evidence presented here and a homology-based model of the L_R protein, we suggest that the linkers do not in fact link between rod hexamers but stabilize the hexameric assembly and modify rod energy absorption and transfer capabilities.     

Renal epithelial cell injury and its promoting role in formation of calcium oxalate monohydrate

The injurious effect of hydrogen peroxide (H₂O₂) on renal epithelial cells of the African green monkey (Vero cells) and the difference in the modulation of Vero cells on crystal growth of calcium oxalate (CaOxa) before and after injury were investigated. The degree of injury of Vero cells was proportional to the concentration and action time of H₂O₂. After the cells had been injured, the released amount of malonaldehyde in the culture medium increased, the superoxide dismutase activity decreased, the expression quantity of osteopontin on the surface of Vero cells increased significantly, the zeta potential became more negative, and the amount of CaOxa crystals adhering to cells increased. The CaOxa crystals induced by the cells in the control group were round and blunt; however, those induced by the injured cells had irregular shapes with sharp edges and corners. As the crystallization time increased from 6 to 24 h, the size of the crystals induced by the injured cells increased accordingly, whereas that of crystals induced by the control cells did not increase significantly. The injured cells could promote the growth of CaOxa crystals and their adhesion to the cells; thus, the formation of CaOxa stones was promoted. The cells in the control group could also be injured after being incubated with supersaturated CaOxa solution for a long time, which promoted the crystallization of CaOxa. The results suggest that the retention of supersaturated CaOxa solution or CaOxa crystals in the urinary tract for a long time is a risk factor for the formation of kidney stones.     

Lipase-catalyzed synthesis and antibacterial activity of N-vanillylnonanamide

N-vanillylnonanamide (VAN) was successfully synthesized from vanillylamine hydrochloride by enzymatic catalysis in supercritical carbon dioxide (SC–CO₂). Five commercial lipases, Novozyme 435, Lipozyme IM, Amano PS, Amano G and Sigma Candida cylindracea type VII, as biocatalysts for VAN synthesis were compared. Lipozyme IM exhibited best yields of tested lipases. Various parameters such as time, temperature, pressure and vanillylamine hydrochloride/nonanoic anhydride ratio that influenced the reaction were investigated. Nonanoic anhydride showed the best acyl donor of the employed substrates. An amidation yield of 40% was obtained when nonanoic anhydride and Lipozyme IM were used at 170 bar and 50 °C for 23 h in SC–CO₂. Besides, addition of 2 mM divalent salts (CuCl₂ and ZnCl₂) significantly increased 11–23% yield of the VAN. The enzyme operational stability suggested that Lipozyme IM maintained over 50 °C of the initial activity for the synthesis of VAN after reuse for 69 h. Furthermore, in vitro, VAN behaved as a potential antibacterial against Escherichia coli.