Dielectric behavior of DNA in water–organic co-solvent mixtures

The radiowave dielectric dispersions of DNA in different water–organic co-solvent mixtures have been measured in the frequency range from 100 kHz to 100 MHz, where the polarization mechanism is generally attributed to the confinement of counterions within some specific lengths, either along tangential or perpendicular to the polyion chain. The dielectric dispersions have been analyzed on the basis of two partially different dielectric models, a continuum counterion fluctuation model proposed by Mandel and a discrete charged site model, proposed by Minakata. The influence of the quality of the solvent on the dielectric parameters has been investigated in water–methanol and water–glycerol mixtures at different composition, by varying the permittivity ?_m and the viscosity η of the solvent phase. The analysis of the dielectric spectra in solvents where electrostatic and hydrodynamic interactions vary with the solvent composition suggests that both the two models are able, in principle, to account for the observed high-frequency dielectric behavior. However, while some certain assumptions are necessary about the polyion structure within the Mandel model, no structural prerequisite is needed within the Minakata model, where the polarization mechanism invoked considers a radial counterion exchange with the outer medium, which is largely independent of the local polyion conformation.     

A molecular dynamics simulation study of the effect of water–graphene interaction on the properties of confined water

The role of water in determining the structure and stability of biomacromolecules has been well studied. In this work, molecular dynamics simulations have been applied to investigate the effect of surface hydrophobicity on the structure and dynamics of water confined between graphene surfaces. In order to evaluate this effect, we apply various attractive/repulsive water–graphene interaction potentials (hydrophobicity). The properties of confined water are studied by applying a purely repulsive interaction potential between water–graphene (modelled as a repulsive r^?12 potential) and repulsive–attractive forces (modelled as an LJ(12-6) potential). Compared to the case of a purely repulsive graphene–water potential, the inclusion of repulsive–attractive forces leads to formation of sharp peaks for density and the number of hydrogen bonds. Also, it was found that repulsive–attractive graphene–water potential caused slower hydrogen bonds dynamics and restricted the diffusion coefficient of water. Consequently, it was found that hydrogen bond breakage and formation rate with the repulsive r^?12 potential model, will increase compared to the corresponding water confined with the LJ(12-6) potential.     

Yb-TCPP metal–organic framework as fluorescence sensor for detecting tetracycline in milk

Developing effective means for detecting contamination in milk during production, processing, and storage is both important and challenging. Tetracycline (TC), due to its use in treating animal infections, is among the most prevalent organic pollutants in milk, posing potential and significant threats to human health. However, efficient and in situ monitoring of TC remains lacking. Nevertheless, we have successfully developed a highly sensitive and selective fluorescence method for detecting TC in milk using a metal–organic framework material made from Yb-TCPP (ytterbium-tetra(4-carboxyphenyl)porphyrin). The calculated Stern–Volmer constant (K_SV) was 12,310.88 M⁻¹, and the detection limit was 2.44 × 10⁻⁶ M, surpassing previous reports. Crucially, Yb-TCPP fluoresces in the near-infrared region, promising its development into a specific fluorescence detection product for practical TC detection in milk, offering potential application value.     

A dual functional turn off florescence sensor using metal–organic framework for sensitive detection of aluminum(III) in aqueous solution

Aluminum, classified as one of the toxic heavy metals, has a recommended daily consumption limit of 3–10 mg, as specified by the World Health Organization (WHO). Herein, the selective and sensitive aluminum(III) fluorescence sensor based on TMU-16 metal–organic frameworks (MOFs) in aqueous medium, is reported. A sensing pathway was found via the cation exchange between aluminum(III) and zinc(II) ions, and caused selectivity and sensitivity detection of aluminum(III) with a 5–100 ppm linear range and 1.99 ppm limit of detection (LOD). This sensor offers the advantage of accurately determining the concentration range of aluminum(III) ions. At low concentrations, only fluorescence quenching was observed, while at higher concentrations, fluorescence emission not only undergoes quenching but also exhibits a blue shift in wavelength. Notably, the sensor demonstrates no interference from cation solutions of mercury(II), zinc(II), nickel(II), lead(II), cobalt(II), cadmium(II), silver(I), chromium(III), and iron(III). Another significant feature of this sensor is its selectivity toward copper(II) and aluminum(III) ions, due to quenching fluorescence in the presence of copper(II) ion. The results presented the sensor's selectivity toward copper(II) at low concentrations and aluminum(III) at high concentrations.     

A fluorescent terbium-metal–organic framework material for high-sensitivity detection of vomitoxin and oxytetracycline hydrochloride in water

A unique luminescent lanthanide metal–organic framework (LnMOF)–based fluorescence detection platform was utilized to achieve sensitive detection of vomitoxin (VT) and oxytetracycline hydrochloride (OTC-HCL) without the use of antibodies or biomolecular modifications. The sensor had a fluorescence quenching constant of 9.74 × 10⁶ M⁻¹ and a low detection limit of 0.68 nM for vomitoxin. Notably, this is the first example of a Tb-MOF sensor for fluorescence detection of vomitoxin. We further investigated its response to two mycotoxins, aflatoxin B1 and ochratoxin A, and found that their Stern–Volmer fluorescence quenching constants were lower than those of VT. In addition, the fluorescence sensor realized sensitive detection of OTC-HCL with a detection limit of 0.039 μM. In conclusion, the method has great potential as a sensitive and simple technique to detect VT and OTC-HCL in water.     

On the crystal structures and magnetism of some hybrid organic–inorganic metal organophosphonates

We review our recent work in the field of molecule-based magnets showing the structural and magnetic properties of a special class of hybrid organic–inorganic compounds, i.e. metal(II) organophosphonates. The synthesis, the crystal structures and, in particular, the magnetic studies of selected examples of compounds of formulas M(II)[(R–PO₃)(H₂O)], and M₂[(O₃P–R′–PO₃)(2H₂O)] M = Cr, Fe, Co; R = C_nH_2n+1, n = 1, 2, 3… and C₆H₅, R′ = (CH₂)₂ prepared in our laboratory are presented and discussed. Metal alkylphosphonates, except those of Co(II), are weak ferromagnets at low temperatures. The observed magnetic ordering temperature T_N varies from 4.2 to 25 K, depending on the transition metal ions and on crystal and molecular structure. Moreover, in the case of a bifunctional molecule like aminoethylphosphonic acid, NH₂(CH₂)₂PO₃H₂, or the carboxyethylphosphonic acid, HO₂C(CH₂)₂PO₃H₂, is used as a ligand, then a novel Cr(II) compound of formula Cr[NH₃(CH₂)₂PO₃(Cl)(H₂O)] and a microporous Fe(III) salt (NH₄)[Fe₂(OH){O₃P(CH₂)₂CO₂}₂] are isolated. The latter are both polar and, more interesting, Cr(II) ammoniumethylphosphonate chloride results to be a weak ferromagnet below T_N = 5.0 K.     

Fabrication of an organic–inorganic nanocomposite carrier for enzyme immobilization based on metal–organic coordination

An organic–inorganic nanocomposite which combined mesoporous silica SBA-15 and chitosan using a carboxyl functionalized ionic liquid as the bridging agent (SBA@CS) was successfully fabricated, and was used to immobilize porcine pancreas lipase (PPL) by physical adsorption, cross-linking and metal–organic coordination, respectively. The as-prepared carriers were characterized by scanning electron microscopy, Fourier transform infrared and energy-dispersive X-ray spectroscopy. Compared with immobilization onto the pure mesoporous silicon material SBA-15, all the batches of PPL immobilized onto organic–inorganic nanocomposites showed higher activity, improved stability and reusability as well as better resistance to pH and temperature changes. Among the immobilized PPLs, immobilization based on Co²⁺ coordination (SBA@CS-Co-PPL) produced the best enzymatic properties. The maximum immobilization efficiency and specific activity of 79.6% and 1975.8 U g⁻¹ were obtained with SBA@CS-Co, separately. More importantly, the activity of immobilized enzyme can still maintain 84.0% after 10 times of reuse. These results demonstrated that thus prepared organic–inorganic nanocomposite could be an ideal carrier for enzyme immobilization by metal–organic coordination.     

Hydration of serine–metal cation complexes: implication for the role of water in the origin of homochirality on the Earth

Amino Acids - It may be taken for granted that the processes that occurred in water were of crucial importance for the origin of life. Therefore, it is quite likely that water was also important...     

Gas adsorption and diffusion in a highly CO2 selective metal–organic framework: molecular simulations

Grand canonical Monte Carlo and equilibrium molecular dynamics simulations were used to assess the performance of an rht-type metal–organic framework (MOF), Cu-TDPAT, in adsorption-based and membrane-based separation of CH₄/H₂, CO₂/CH₄ and CO₂/H₂ mixtures. Adsorption isotherms and self-diffusivities of pure gases and binary gas mixtures in Cu-TDPAT were computed using detailed molecular simulations. Several properties of Cu-TDPAT such as adsorption selectivity, working capacity, diffusion selectivity, gas permeability and permeation selectivity were computed and compared with well-known zeolites and MOFs. Results showed that Cu-TDPAT is a very promising adsorbent and membrane material especially for separation of CO₂ and it can outperform traditional zeolites and MOFs such as DDR, MFI, CuBTC, IRMOF-1 in adsorption-based CO₂/CH₄ and CO₂/H₂ separations.     

Adaptation of the Morningness–Eveningness Stability Scale improved (MESSi) into Turkish

Morningness–eveningness is an individual difference that is related with various traits such as behavioral problems, personality, and health. The aim of the current study is to adopt the Morningness–Eveningness Stability Scale improved (MESSi) which is a novel assessment tool that consists of subscales of morning affect (MA), eveningness (EV), and distinctness (DI) into Turkish. Concurrent validity of the MESSi along with Big five inventory (BIG-5), Subjective alertness level, Pittsburg Sleep Quality Index (PSQI), Positive and Negative Affect Schedule (PANAS) were analyzed. The scale was administered to 1,076 high school and university students aged 14–47 years (M = 19.49, SD = 3.53). The explanatory factor analysis (EFA) and confirmatory factor analysis (CFA) revealed the three-factor structure of MESSi. According to the concurrent validity result of the MESSi with BIG-5, conscientiousness was found to correlate positively with MA and negatively with EV. Also, extraversion showed a negative correlation with DI and positive correlation with MA. Furthermore, the subjective alertness rating results showed that MA was positively related to alertness in the morning hours and negatively in the evening hours. Also, sleep quality-related results showed that EV and DI are positively related to total PSQI scores and negatively related to MA. In addition, concerning positive affect (PA) and negative affect (NA), MA was positively related with PA and negatively with NA, while DI was negatively related with PA and positively with NA. In overall, MESSi is a valid and reliable instrument and can be used in Turkish students.     

A box-model of metal flows through the Scheldt estuary (1981–1983 and 1992–1995)

The behaviour of Cu, Zn, Cd and Pb in the Scheldtestuary was investigated in the periods 1981 to 1983and 1995. The Hg behaviour was studied between 1992and 1994. A box model was used to establish therelationship between the trace metal inputs and thefate of these pollutants in the Scheldt estuary.Annual budgets were calculated for particulate anddissolved trace metals. For Hg, seasonal budgets ofthe various species (inorganic Hg, methylmercury,Hg °) could also be calculated. These budgetsallow an evaluation of the consistency of eachindividual flux or process, such as the inputs of thevarious metals into the North Sea, the sedimentationflux of particulate metals in the area of highturbidity, the evasional fluxes and the formationrates of Hg °, etc. in relation to the other ones. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chemical analysis of Lake Shira water (1997–2000)

The paper presents the results of chemical analysis of Shira during summer (July-August). The chemical composition of waters in the water body was found to be fairly homogeneous horizontally. However, the concentrations of most ions increased with depth. The near-bottom layers were characterised by higher total mineral content and ash content, higher concentration of sulphates, sulphites, sulphide, phosphorus, ammonium nitrogen, as compared to the layers above. Maximum concentration of oxygen was recorded in 6–8 m stratum, where the photosynthetic processes were most active. The anaerobic layer which lay below the 12 m depth contained high concentrations of sulphide and sulphite. The composition of the lake water could be characterised as sulphate-chloride-bicarbonate sodium-magnesium. The changes in the water quality due to any anthropogenic emissions were not marked.     

Effects of water content on the enantioselectivity of α-chymotrypsin catalysis in organic media

Summary The -chymotrypsin-catalyzed transesterification between N-trifluoroacetyl-DL-phenylalanine trifluoroethyl ester and 1-propanol was carried out in a variety of organic solvents. The addition of small quantities of water enhanced both the rate of reaction and enantioselectivity. A high enantioselectivity was achieved in ethyl acetate (E = 120), diethyl ether (86), or acetonitrile (60). The competing hydrolysis became significant at water content higher than 0.5% (w/w).     

Location-Dependent Local Field Enhancement Along the Surface of the Metal–Dielectric Core–Shell Nanostructure

A theoretical study based on quasi-static approximation is performed to investigate the location-dependent local field enhancement around the dielectric shell-coated gold nanosphere. Our calculation results show that the local field distribution near a gold nanoparticle can be altered greatly by coating with a dielectric shell. Because of the polarizability of the dielectric shell, increasing azimuth angle along the inner surface leads to the increase of the local field, which is opposite to that of the outer surface. Furthermore, the location-dependent local field enhancement and resonance frequency at both the inner and outer surfaces can also be modulated by varying the shell thickness and shell dielectric constant. These calculation results about the location-dependent local field enhancement show the potential of dielectric-coated metallic nanostructure for single-molecule detection based on surface-enhanced Raman scattering and surface enhanced fluorescence.     

Continuous fractional component Monte Carlo simulations of high-density adsorption in metal–organic frameworks

The continuous fractional component Monte Carlo method, which was designed to overcome difficulties with insertions and deletions of molecules, is modified to include configurational bias Monte Carlo methods and is further extended to binary systems. The modified method is shown to correctly predict adsorption of Ar in silicalite, Xe and Kr in HKUST-1, and enantiomers in a homochiral metal–organic framework. The modified method is also found to be approximately an order of magnitude more efficient in inserting and deleting molecules than traditional configurational bias grand canonical Monte Carlo simulations in dense systems.     

The impact of the Scheldt input on the trace metal distribution in the Belgian coastal area (results of 1981–1983 and 1995–1996)

Offshore fluxes of Cu, Zn, Cd, Pb and Hg were calculated based onresidual flow patterns and salinity gradients along the Belgian coast. Theresidual flow lines along the Belgian coast are more or less parallel to thecoast except in the area where the north-easterly flowing watermass comingfrom the Channel encounters the south-westerly-oriented Scheldt outflow,forming a residual hydrodynamical front. From the steady-state salinitypattern, diffusion coefficients perpendicular to the residual flow werededuced; they ranged from 21 to 108 m² s^-1. Offshore fluxes of dissolved and particulate trace metals based on diffusiveand mixing processes are calculated. The steady state profiles of dissolvedmetals show a dilution effect in the coastal waters, reaching an almostconstant concentration in the marine watermass in the 1981–1983dataset. The ratios of the Scheldt input of trace metals to the totaldissolved offshore flux vary from 38 to 55% (1981–1983),depending on the kind of metal, and from 55 to 91% (1995–1996).The ratio of the Scheldt input to the dissolved metal flow parallel to thecoast, is in both periods (1981–1983 and 1995–1996), smallerthan 1%. The steady-state concentration profiles of particular metalsversus salinity are fairly constant in the coastal-estuarine and marinewatermasses, but decrease very abruptly from the first to the secondwatermass. Assuming a conservative behaviour of the particular metals,offshore fluxes and the resulting concentration increases agree fairly wellwith the observed values. The ratios of the Scheldt input to the particulatetrace metal offshore flux vary between 30 to 46% (1981–1983)and 13 to 37% (1995–1996). The contribution of the Scheldtestuary to the flows parallel to the coast ranges from 1.6 to 2.9%(1981–1983) and from 0.6 to 1.6% (1995). This revised version was published online in July 2006 with corrections to the Cover Date.     

Oxidoreductases for the remediation of organic pollutants in water – a critical review

Water contamination by various recalcitrant organic aromatic compounds is an emerging environmental issue that is increasingly attracting the attention of environmental scientists. A great majority of these recalcitrant pollutants are industrial wastes, textile dyes, pharmaceuticals, hormones, and personal care products that are discharged into wastewater. Not surprisingly, various chemical, physical, and biological strategies have been proposed and developed to remove and/or degrade these pollutants from contaminated water bodies. Biological approaches, specifically using oxidoreductase enzymes (such as peroxidases and laccases) for pollutant degradation are a relatively new and a promising research area that has potential advantages over other methods due to their higher efficiency and the ease of handling. This review focuses on the application of different classes of oxidoreductase enzymes to degrade various classes of organic pollutants. In addition to classifying these enzymes based on structural differences, the major factors that can affect their remediation ability, such as the class of peroxidases employed, pH, molecular structure of the pollutant, temperature, and the presence of redox mediators are also examined and discussed. Interestingly, a literature survey combined with our unpublished data suggests that “peroxidases” are a very heterogeneous and diverse family of enzymes and have different pH profiles, temperature optima, thermal stabilities, requirements for redox mediators, and substrate specificities as well as varying detoxification abilities. Additionally, remediation of real-life polluted samples by oxidoreductases is also highlighted as well as a critical look at current challenges and future perspectives.     

Heterogeneity of the inland water–land palm ecotones (morichals) in the Orinoco lowlands,South America

We analyzed the distributional pattern of species and environmental gradients across inland water–land palm ecotones (morichals) of the Orinoco lowlands to increase comprehension of the nature of ecotone heterogeneity. A total of 91 species (53 genera and 45 families) with aboveground phytomass > 0.1 g dry mass were recorded. Detrented canonical correspondence analysis (DCCA) indicated that vegetation phytomass was related strongly to soil properties, including gradients of silt (14.5–4.7%), exchangeable Al (1.05–3.10 cmole kg⁻¹), K (0.03–0.30 cmole kg⁻¹), Na (0.01–0.08 cmole kg⁻¹), Mg (0.03–0.54 cmole kg⁻¹) concentrations, pH (3.7–5.0 units), and soil organic matter. Cluster analysis allowed the definition of four types of ecotones on the basis of hydrogeomorphic processes. The first major group (1) encompassing the sites from Venezuelan lowlands (i.e., 3V, 4V, 5V, 6V, and 7V) was related to less acidic soils with high organic matter content. The second group (II) from Eastern Colombian llanos (i.e., sites 8C, 9C, 11C, 12C, 13C, 14C, and 15C) was located in acidic soils (3.9–4.5 units) with high Mg concentration. The third group (III) (i.e., sites IV and 10C) was located in soils with high Na content, whereas the fourth group (IV) (i.e., site 2V) was characterized by species growing in soils with low exchangeable aluminum. The results evidenced the interactive role of valley constraint, landforms, hydrological regime, and soil feature in structuring the plant community. Biogeographic and floristic considerations were also taken into account to explain differences in species composition.     

Translocation of Oligonucleotide–Oligosaccharide Complexes into Cells of the Brain

Irradiation of a mixture of oligonucleotides with dextran resulted in the formation of a complex that is detected by a decelerated migration of an irradiated sample in electrophoretic gel compared to a non-irradiated one. When injected into the brain of neonatal rats, the formed complex penetrated into the cells 3 times easier compared to the original oligonucleotide, thus indicating that the use of radiation crosslinking of oligonucleotides with oligosaccharides is promising to enhance the efficiency of delivery of gene-targeted oligonucleotide drugs into cells.