Synthesis,characterization, crystal structure and biological activity of the cobalt(IV) complex of 2,6-diacetylpyridine dioxime: [Co(dapdo)<Subscript>2</Subscript>]

The cobalt(IV) complex of 2,6-diacetylpyridine dioxime (dapdoH₂) was prepared and characterized by X-ray diffraction, elemental analysis and FT-IR. The titled complex was found to crystallize in the orthorhombic space group and was screened for antibacterial and antifungal activities by the disc diffusion and microtitter plate techniques using DMF as solvent. It has been found that the antimicrobial activity of the complex [Co(dapdo)₂] is slightly higher than the free ligand (dapdoH₂).     

Partial purification and characterization of protease enzyme from Bacillus subtilis megatherium

Bacteria of genus Bacillus are active producers of extracellular proteases, and characteristics of enzyme production by Bacillus species have been well studied. The aim of this experimental study is isolation and partial purification of protease enzyme from the Bacillus subtilis megatherium bacteria species. Protease enzyme is obtained by inducing spore genesis of bacteria from Bacillus species on suitable media. The partial purification was reali-zed by applying successively ammonium sulfate precipitation, dialysis, DEAE-cellulose ion exchange chromatography to the supernatant. In this study, the effect of substrate concentration, reaction time, the effect of inhibitor and activator on the optimum pH, optimum temperature, pH stability, and temperature stability was determined. Molecular weight of the obtained enzyme was investigated by SDS-PAGE. In this study, the specific activity of the supernatant, which was partially purified from Bacillus subtilis megatherium bacteria, was 10.4 U/mg, specific activity of supernatant was 13.5 U/mg after 80% ammonium sulfate fractionation. The final enzyme preparation was 1.1-fold purer than the crude homogenate. Molecular weight of the protease was determined, and it was found that the weight of enzyme was 45 kDa by using SDS-PAGE.     

Electrostatic effects on nanofiber formation of self-assembling peptide amphiphiles

Self-assembling peptide amphiphile molecules have been of interest to various tissue engineering studies. These molecules self-assemble into nanofibers which organize into three-dimensional networks to form hydrocolloid systems mimicking the extracellular matrix. The formation of nanofibers is affected by the electrostatic interactions among the peptides. In this work, we studied the effect of charged groups on the peptides on nanofiber formation. The self-assembly process was studied by pH and zeta potential measurements, FT-IR, circular dichroism, rheology, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. The aggregation of the peptides was triggered upon neutralization of the charged residues by pH change or addition of electrolyte or biomacromolecules. Understanding the controlled formation of the hydrocolloid gels composed of peptide amphiphile nanofibers can lead us to develop in situ gel forming bioactive collagen mimetic nanofibers for various tissue engineering studies including bioactive surface coatings.     

Optical CO<Subscript>2</Subscript> Sensing with Ionic Liquid Doped Electrospun Nanofibers

The first use of electrospun nanofibrous materials as highly responsive fluorescence quenching-based optical CO₂ sensors is reported. Poly(methyl methacrylate) and ethyl cellulose were used as polymeric materials. Sensing slides were fabricated by electrospinning technique. A fiber-optic bundle was used for the gas detection. CO₂ sensors based on the change in the fluorescence signal intensity of ion pair form of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). The sensor slides showed high sensitivities due to the high surface area-to-volume ratio of the nanofibrous membrane structures. The preliminary results of Stern-Volmer analysis show that the sensitivities of electrospun nanofibrous membranes to detect CO₂ are 24 to 120 fold higher than those of the thin film based sensors. The response times of the sensing reagents were short and the signal changes were fully reversible. The stability of ion pair form of HPTS in the employed matrix materials was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 7 months. Our stability tests are still in progress.     

γ-Robust facility relocation problem

In this paper, we consider relocating facilities, where we have demand changes in the network. Relocations are performed by closing some of the existing facilities from low demand areas and opening new ones in newly emerging areas. However, the actual changes of demand are not known in advance. Therefore, different scenarios with known probabilities are used to capture such demand changes. We develop a mixed integer programming model for facility relocation that minimizes the expected weighted distance while making sure that relative regret for each scenario is no greater than γ. We analyzed the problem structure and developed a Lagrangian Decomposition Algorithm (LDA) to expedite the solution process. Numerical experiments are carried out to show the performance of LDA against the exact solution method.     

Mathematical modelling of the container cranes under seismic loading and proving by shake table

This paper is concerned with modelling of the behaviour of container cranes under seismic loadings. For this purpose, physical and mathematical models are prepared. A six degrees-of-freedom non-linear mathematical model is developed in order to understand the dynamic behaviour of cranes under the seismic loadings. In order to determine the seismic behaviour of the container cranes against earthquakes, a 1/20 scaled crane model was designed and constructed. For the comparison of the models, the real earthquake records were used. The results are used to observe the destructive effects and compared with the period values of the most critical sections on the crane structure. When time and frequency domains are compared, it is seen that mathematical modelling of the container crane structure shows reasonable results under dynamic loadings. It will be available to take precautions and to increase seismic performance of cranes with the help of the developed dynamic model. Also, the developed mathematical model will be able to be used as a crane model in active vibration control studies in order to decrease the structural vibrations on container cranes.     

Investigation of Solvent Effects on Photophysical Properties of New Aminophthalimide Derivatives-Based on Methanesulfonate

Novel aminophthalimide derivatives were synthesized starting from (3aR,7aS)-2-(2-hydroxypropyl)-3a,4,7,7a–tetrahydro-1H-isoindole-1,3(2H)-dione (9) , and solvent effects on the photo-physical properties of these newly synthesized aminophthalimide derivatives (compounds 14 and 15) were investigated using UV-Vis absorption spectroscopy, steady-state and time-resolved fluorescence measurements. Both absorption and fluorescence spectra exhibited bathochromic shift with the increased polarity of the solvents for both molecules. Solute-solvent interactions were analyzed using the Lippert-Mataga and Bakhshiev polarity functions, and Kamlet-Taft and Catalan multiple linear regression approaches. The results revealed that these two molecules experienced specific interactions. Furthermore, photo-physical parameters were calculated for both molecules in all of the solvents, such as the fluorescence quantum yield, fluorescence lifetime, radiative (k_r) and non-radiative (k_nr) rate constant values. It was observed that the fluorescence quantum yield values decreased linearly with increasing solvent polarity. This study proved the new dyes including isopropyl methanesulfonate group displayed different behavior from previous studies of aminophthalimide derivatives in water. It was recommended that these new dyes having interesting properties by changing solvent can be used various applications such as environmentally sensitive fluorescent probes, labels in biology, laser industry.