Biosorption of Ni (II) by Schizosaccharomyces pombe: kinetic and thermodynamic studies

The potential of the dried yeast, wild-type Schizosaccharomyces pombe, to remove Ni(II) ion was investigated in batch mode under varying experimental conditions including pH, temperature, initial metal ion concentration and biosorbent dose. Optimum pH for biosorption was determined as 5.0. The highest equilibrium uptake of Ni(II) on S. pombe, q _e, was obtained at 25 °C as 33.8 mg g⁻¹. It decreased with increasing temperature within a range of 25–50 °C denoting an exothermic behaviour. Increasing initial Ni(II) concentration up to 400 mg L⁻¹ also elevated equilibrium uptake. No more adsorption took place beyond 400 mg L⁻¹. Equilibrium data fitted better to Langmuir model rather than Freundlich model. Sips, Redlich–Peterson, and Kahn isotherm equations modelled the investigated system with a performance not better than Langmuir. Kinetic model evaluations showed that Ni(II) biosorption process followed the pseudo-second order rate model while rate constants decreased with increasing temperature. Gibbs free energy changes (ΔG°) of the system at 25, 30, 35 and 50 °C were found as −1.47E + 4, −1.49E + 4, −1.51E + 4, and −1.58E + 4 J mol⁻¹, respectively. Enthalpy change (ΔH°) was determined as −2.57E + 3 J mol⁻¹ which also supports the observed exothermic behaviour of the biosorption process. Entropy change (ΔS°) had a positive value (40.75 J mol⁻¹ K⁻¹) indicating an increase in randomness during biosorption process. Consequently, S. pombe was found to be a potential low-cost agent for Ni(II) in slightly acidic aqueous medium. In parallel, it has been assumed to act as a separating agent for Ni(II) recovery from its aqueous solution.     

Mechanism of biochemical action of substituted 4-methylcoumarins. Part 11: Comparison of the specificities of acetoxy derivatives of 4-methylcoumarin and 4-phenylcoumarin to acetoxycoumarins: protein transacetylase

Our earlier observations led to the identification of a microsomal enzyme termed as acetoxy drug: protein transacetylase (TAase) catalyzing the transfer of acetyl groups from acetylated polyphenols to the receptor proteins. TAase was conveniently assayed by the irreversible inhibition of cytosolic glutathione S-transferase (GST) by the model acetoxycoumarin, 7,8-diacetoxy-4-methylcoumarin (1). The specificities of the acetoxy group on the benzenoid ring and position of the pyran carbonyl group of the coumarin with respect to oxygen heteroatom for the catalytic activity of TAase were also reported earlier. In this communication, we have demonstrated that the acetoxy coumarins and acetoxy dihydrocoumarins having a methyl group instead of a phenyl ring at the C-4, when used as the substrates, resulted in enhancement of TAase activity, while the saturation of double bond at C-3 and C-4 position had no effect on TAase activity. A comparison of the optimized structures of 1 and 7,8-diacetoxy-4-phenylcoumarin (2) suggested that the observed influence may be due to out of plane configuration of the phenyl ring at C-4. Further, the TAase-catalyzed activation of NADPH cytochrome c reductase and inhibition of aflatoxin B1 (AFB1)-DNA binding by acetoxy 4-phenylcoumarins and dihydrocoumarins were significantly lower as compared to those caused by acetoxy 4-methylcoumarins.     

Chm7 and Heh1 collaborate to link nuclear pore complex quality control with nuclear envelope sealing

The integrity of the nuclear envelope barrier relies on membrane remodeling by the ESCRTs, which seal nuclear envelope holes and contribute to the quality control of nuclear pore complexes (NPCs); whether these processes are mechanistically related remains poorly defined. Here, we show that the ESCRT‐II/III chimera, Chm7, is recruited to a nuclear envelope subdomain that expands upon inhibition of NPC assembly and is required for the formation of the storage of improperly assembled NPCs (SINC) compartment. Recruitment to sites of NPC assembly is mediated by its ESCRT‐II domain and the LAP2‐emerin‐MAN1 (LEM) family of integral inner nuclear membrane proteins, Heh1 and Heh2. We establish direct binding between Heh2 and the “open” forms of both Chm7 and the ESCRT‐III, Snf7, and between Chm7 and Snf7. Interestingly, Chm7 is required for the viability of yeast strains where double membrane seals have been observed over defective NPCs; deletion of CHM7 in these strains leads to a loss of nuclear compartmentalization suggesting that the sealing of defective NPCs and nuclear envelope ruptures could proceed through similar mechanisms.     

Monitoring microalgal growth of Chlorella minutissima with a new all solid-state contact nitrate selective sensor

As third generation feedstock, microalgae are microorganisms that can grow only in the optimum conditions. There are parameters including the concentration of macro and microelements in nutrient solution, pH, temperature and light intensity that have significant impact on microalgal growth. In recent years, various sensing devices have been developed for sensitive measurement of these parameters during microalgal growth. In this study, a new potentiometric nitrate selective sensor was developed to indicate the nitrate uptake of microalgae and the effect of nitrate nutrient on microalgal growth, specifically, and this sensor was successfully applied to determine nitrate concentration in medium during microalgal growth. Moreover, the effects of nitrate, carbonate and phosphate concentration in the growth medium on biomass production of Chlorella minutissima were investigated by using Box–Behnken design method, and optimum conditions were determined for the highest biomass production of microalgae. As a result of the experiments, it was seen that the highest C. minutissima production was achieved using the medium consist of 2.63 g/L NaNO₃, 0.35 g/L Na₂CO₃ and 0.4 g/L KH₂PO_4. Statistically, it was observed that there was a proportional relationship between the microalgae production and investigated parameters such as carbon, nitrogen and phosphate amounts of culture mediums. The electrode showed a wide linear range between 1.0 × 10⁻¹ and 5.0 × 10⁻⁵ M with a detection limit of the 5 × 10⁻⁶ M and the response time was found as 10 s. The results showed that developed nitrate selective sensor could be successfully applied for continuous measurement of nitrate in microalgal productions at reduced cost.     

Zipf’s Law: Balancing Signal Usage Cost and Communication Efficiency

We propose a model that explains the reliable emergence of power laws (e.g., Zipf’s law) during the development of different human languages. The model incorporates the principle of least effort in communications, minimizing a combination of the information-theoretic communication inefficiency and direct signal cost. We prove a general relationship, for all optimal languages, between the signal cost distribution and the resulting distribution of signals. Zipf’s law then emerges for logarithmic signal cost distributions, which is the cost distribution expected for words constructed from letters or phonemes.     

Protective role of intraperitoneally administered vitamins C and E and selenium on the levels of lipid peroxidation in the lens of rats made diabetic with streptozotocin

The aim of this work was to determine the protective effects of intraperitoneally administered vitamins C and E and selenium on the lipid peroxidation (MDA), glutathione peroxidase (GSH-Px), reduced glutathione (rGSH) activities in the lens of rats induced diabetic with streptozotocin (STZ). Lenses in the diabetic control group had a slightly higher mean level of MDA compared with lenses of the vitamin E and selenium groups, although the mean levels of MDA were significantly lower in control, combination, and vitamin C groups than in the diabetic control group (p < 0.05 andp < 0.01). However, MDA levels were significantly lower in vitamin C, vitamin E, and combination groups than in controls (p < 0.01). The GSH-Px activities of lenses were significantly higher in vitamin C-, vitamin E- and selenium-injected groups than that in the diabetic control group (p < 0.01), whereas, the activity of GSH-Px was significantly lower in the diabetic control group than in the control group. In addition, the rGSH content was seen to decrease only in the vitamin C group compared to both control and diabetic control groups (p < 0.05). In conclusion, the results from these experiments indicate that vitamins C and E and selenium can protect the lens against oxidative damage, but the effect of vitamin C appears to be much greater than that of vitamin E and selenium.     

An observation study of airborne pollen fall in Didim (SW Turkey): years 2004–2005

Pollen grains in the atmosphere of Didim, collected using a Durham sampler, were investigated in 2004 and 2005. Weekly pollen grains per square centimetre were calculated. Over a period of 2 years, 17,518 pollen grains/cm² belonging to 40 taxa and unidentified pollen grains were recorded. In 2004, 9,879 pollen grains were counted per cm², and in 2005 the value was 7,639 per cm². The majority of pollen grains investigated were Pinus spp. (45.58%), Cupressaceae/Taxaceae (13.49%), Olea spp. (9.19%), Platanus spp. (7.62%), Gramineae (6.33%), Pistacia spp. (4.34%), Morus spp. (3.81%), Quercus spp. (2.02%), Abies spp. (1.39%), and Plantago spp. (1.11%). During the month of April, 40.46% of total pollen grains were recorded. According to our results, pollen season durations for the dominated pollen grains in Didim were: the 7th–33rd weeks for Pinus spp., nearly the whole year except summer for Cupressaceae/Taxaceae, the 17th–29th weeks for Olea spp., the 10th–24th weeks for Platanus spp., the 8th–46th weeks for Gramineae, the 8th–20th weeks for Pistacia spp., the 11th–21st weeks for Morus spp., the 17th–21st weeks for Quercus spp., the 9th–27th weeks for Abies spp., and the 7th–26th weeks for Plantago spp.     

Element Status in Different Breeds of Dogs

The serum levels of copper, zinc, iron, manganese, nickel, cadmium, cobalt, sodium, potassium, calcium, and magnesium were determined in seven different breeds of dogs: Pointer, Poodle, Setter, Labrador Retriever, Golden Retriever, German Shepherd, and Mallinois. Only slight variations were found among the different breeds, and the results presented in this study can be used for laboratory studies in veterinary science.     

Nosocomial Infections and Obesity in Surgical Patients

Objective: There is an increased morbidity and mortality associated with surgery in the obese patient. This study was conducted to determine risk factors and compare the nosocomial infection rate in obese and nonobese surgical patients. Research Methods and Procedures: A total of 395 surgical patients were evaluated. BMI was calculated for each patient. Various conventional risk factors for nosocomial infections were recorded. Biochemical parameters with plasma total cholesterol and high‐density lipoprotein‐cholesterol levels were measured. The diagnosis of infection was made according to the Centers for Disease Control and Prevention criteria. Univariate and two‐step multivariate logistic regression methods were used for determination of nosocomial infection risk factors. Results: There were 117 nosocomial infections identified in 96 of 395 surgically operated patients. A significant increase in the total number of nosocomial infections was determined in obese patients compared with the normal‐weight patients (p < 0.05). High‐density lipoprotein‐cholesterol below the 10th percentile increased risk of surgical site infection. Discussion: Our results suggest that obesity is an important risk factor for postoperative nosocomial infection.