Stabilization of bzip peptides through incorporation of fluorinated aliphatic residues

Two fluorinated amino acids, 5,5,5-trifluoroisoleucine (5TFI) and (2S,3R)-4,4,4-trifluorovaline (4TFV), which have been shown to serve as isoleucine surrogates in protein synthesis in Escherichia coli, have been incorporated in vivo into basic leucine zipper (bzip) peptides derived from GCN4. The extents of residue-specific incorporation of 5TFI and 4TFV were 90 and 88 %, respectively, of the encoded isoleucine residues, as evidenced by MALDI mass spectrometry and amino acid analysis. Both circular dichroism and equilibrium sedimentation studies of the fluorinated bzip peptides indicated preservation of secondary and higher-order protein structure. Thermal-denaturation experiments showed an increase of 27 degrees C in melting temperature when isoleucine was replaced by 5TFI. However, the T(m) of the peptide containing 4TFV was increased by only 4 degrees C over that of the peptide containing valine. Similar trends were observed in chemical denaturation studies in which DeltaDeltaG(unfold) in water was determined to be 2.1 or 0.3 kcal mol(-1) upon incorporation of 5TFI or 4TFV, respectively. When the fluorinated peptides were tested for DNA binding, both their affinity and specificity were similar to those of the respective hydrogenated peptides. These results suggest that fluorinated amino acids, even when introduced into the same positions, can have markedly different effects on the physical properties of proteins, while having little impact on secondary and higher-order structure.     

Two‐level multiscale enrichment methodology for modeling of heterogeneous plates

A new two‐level multiscale enrichment methodology for analysis of heterogeneous plates is presented. The enrichments are applied in the displacement and strain levels: the displacement field of a Reissner–Mindlin plate is enriched using the multiscale enrichment functions based on the partition of unity principle; the strain field is enriched using the mathematical homogenization theory. The proposed methodology is implemented for linear and failure analysis of brittle heterogeneous plates. The eigendeformation‐based model reduction approach is employed to efficiently evaluate the non‐linear processes in case of failure. The capabilities of the proposed methodology are verified against direct three‐dimensional finite element models with full resolution of the microstructure. Copyright © 2009 John Wiley & Sons, Ltd.     

Photovoltaic solar cell properties of CdxZn1−xO films prepared by sol–gel method

Cd_xZn_1−xO films have been deposited by sol–gel spin-coating method onto glass substrates. The Cd/Zn ratio in solution was changed from 0 to 1. Zinc acetate dehydrates, cadmium acetate dehydrates, 2-methoxyethanol and monoethanolamine were used as a starting material (zinc and cadmium), solvent and stabilizer, respectively. The crystal structure and orientation of the films were investigated by X-ray diffraction (XRD) patterns. XRD patterns show that the films are polycrystalline nature. As x varies from 0 to 1, it was observed that the crystal structure changed from wurtzite (ZnO) to cubic (CdO) structure. The optical properties of these films have been investigated by means of the optical transmittance and reflectance spectra. A significant change in optical absorption edge, optical band gap and optical constant with variation in composition was observed.     

Effect of heat treatment on physical properties of CdO films deposited by sol–gel method

CdO film has been deposited by sol–gel spin coating method on the glass substrate and then the film has been annealed at 400, 500, 600 °C for 1 h. Effect of annealing temperature on the structural and optical properties of the film has been investigated. The crystal structure and orientation of the as-grown and annealed CdO films have been investigated by X-ray diffraction method. Annealed CdO films are polycrystalline with (111) preferential orientation. The information on strain and grain size is obtained from the full width-at-half-maximum (FWHM) of the diffraction peaks. Texture coefficient and lattice constant have been calculated. The surface morphology of the films has been analyzed. The optical band gap value decreased with increasing the annealing temperatures.     

Synthesis and Photodiode Characterization of Novel Twisted Carbazole Derivatives with 1,3,5-Benzene Core

In this study, considering the information given in the literature the Ullman and Suzuki-Miyaura coupling reactions were carried out using carbazole, 1,3,5 tribromo benzene and aryl boronic acid. The synthesized novel carbazole derivative (CPF4) were characterized by 1H NMR and 13C NMR. The photophysical and thermal properties of the synthesized novel carbazole derivatives CPF4 were investigated Graphene oxide (GO) doped CPF4/p-Si photodiodes were fabricated. The electrical properties of these photodiodes were characterized by current–voltage (I?V) and capacitance–voltage (C?V) measurements. The photocurrent properties of the diode were studied under various illumination intensities. The photoresponse properties of the diodes increased with GO content. The results indicate that CPF4:GO/p-Si heterojunctions can be used as a photodetector for optoelectronic applications.     

Detection of microdroplet size and speed using capacitive sensors

Detection of the presence, size and speed of microdroplets in microfluidic devices is presented using commercially available capacitive sensors which make the droplet based microfluidic systems scalable and inexpensive. Cross-contamination between the droplets is eliminated by introducing a passivation layer between the sensing electrodes and droplets. A simple T-junction generator is used to generate droplets in microchannels. Coplanar electrodes are used to form a capacitance through the microfluidic channel. The change in capacitance due to the presence of a droplet in the sensing area is detected and used to determine the size and speed of the droplet. The design of a single pair of electrodes is used to detect the presence of a droplet and the interdigital finger design is used to detect the size and speed of the droplet. An analytical model is developed to predict the detection signal and guide the experimental optimization of the sensor geometry. The measured droplet information is displayed through a Labview interface in real-time. The use of capacitance sensors to monitor droplet sorting at a T-junction is also presented. The discussions in this paper can be generalized to any droplet detection application and can serve as a guideline in sensor selection.