Patterned growth and differentiation of neural cells on polymer derived carbon substrates with micro/nano structures in vitro

The growth of neuroblastoma (N2a) and Schwann cells has been explored on polymer derived carbon substrates of varying micro and nanoscale geometries: resorcinol-formaldehyde (RE) gel derived carbon films and electrospun nanofibrous (similar to 200 nm diameter) mat and SU-8 (a negative photoresist) derived carbon micro-patterns. MTT assay and complementary lactate dehydrogenase (LDH) assay established cytocompatibility of RE derived carbon films and fibers over a period of 6 days in culture. The role of length scale of surface patterns in eliciting lineage-specific adaptive response along, across and on the interspacing between adjacent micropatterns (i.e., ``on'', ``across'' and ``off'') has been assayed. Textural features were found to affect 3',5'-cyclic AMP sodium salt-induced neurite outgrowth, over a wide range of length scales: from similar to 200 nm (carbon fibers) to similar to 60 mu m (carbon patterns). Despite their innate randomness, carbon nanofibers promoted preferential differentiation of N2a cells into neuronal lineage, similar to ordered micro-patterns. Our results, for the first time, conclusively demonstrate the potential of RE-gel and SU-8 derived carbon substrates as nerve tissue engineering platforms for guided proliferation and differentiation of neural cells in vitro. (C) 2013 Elsevier Ltd. All rights reserved.

Metabolism of Plasmodium berghei. I. Krebs cycle

The free parasites of Plasmodium berghei, obtained from infected cells of rats using an antiserum method, were investigated to study the operation of Krebs cycle. P. berghei was found to respire only with succinate; pyruvate, and other substrates of the Krebs cycle were not oxidized. The presence of a succinate dehydrogenase and a functioning cytochrome oxidase system was demonstrated. Cell-free extracts of free parasites showed the presence of enzymes for the utilization of C4 dicarboxylic acids; other enzymes of the Krebs cycle could not be detected. P. berghei differs from other species of Plasmodium in this respect.

Beta-turns in nascent procollagen are sites of posttranslational enzymatic hydroxylation of proline

The selective hydroxylation of proline residues in nascent procollagen chains by prolyl hydroxylase (EC 1.14.11.2) can be understood in terms of the conformational feature of the -Pro-Gly-segments in linear peptides and globular proteins. The folded beta-turn conformation in such segments appears to be the conformational requirement for proline hydroxylation. The available data on the hydroxylation of native and synthetic substrates of prolyl hydroxylase are explained on the basis of the extent of beta-turn formation in them. Taken in conjunction with the conformational features of the hydroxyproline residue, our results bring out the conformational reason for the posttranslational proline hydroxylation which, it is proposed, leads to the "straightening" of the beta-turn segments into the linear triple-helical conformation.

Effect of peptide-based captopril analogues on angiotensin converting enzyme activity and peroxynitrite-mediated tyrosine nitration

Angiotensin converting enzyme (ACE) regulates the blood pressure by converting angiotensin I to angiotensin II and bradykinin to bradykinin 1-7. These two reactions elevate the blood pressure as angiotensin II and bradykinin are vasoconstrictory and vasodilatory hormones, respectively. Therefore, inhibition of ACE is an important strategy for the treatment of hypertension. The natural substrates of ACE, i.e., angiotensin II and bradykinin, contain a Pro-Phe motif near the site of hydrolysis. Therefore, there may be a Pro-Phe binding pocket at the active site of ACE, which may facilitate the substrate binding. In view of this, we have synthesized a series of thiol-and selenol-containing dipeptides and captopril analogues and studied their ACE inhibition activities. This study reveals that both the selenol or thiol moiety and proline residues are essential for ACE inhibition. Although the introduction of a Phe residue to captopril and its selenium analogue considerably reduces the inhibitory effect, there appears to be a Phe binding pocket at the active site of ACE.

Nanostructure Patterning on Flexible Substrates Using Electron Beam Lithography

Patterning nanostructures on flexible substrates plays a key role in the emerging flexible electronics technology. The flexible electronic devices are inexpensive and can be conformed to any shape. The potential applications for such devices are sensors, displays, solar cells, RFID, high-density biochips, optoelectronics etc. E-beam lithography is established as a powerful tool for nanoscale fabrication, but its applicability on insulating flexible substrates is often limited because of surface charging effects. This paper presents the fabrication of nanostructures on insulating flexible substrates using low energy E-beam lithography along with metallic layers for charge dissipation. Nano Structures are patterned on different substrates of materials such as acetate and PET foils. The fabrication process parameters such as the proximity gap of exposure, the exposure dosage and developing conditions have been optimized for each substrate.

Molecular dynamics studies on nucleoside 2',3'-cyclic phosphates

2',3'-cyclic nucleotides are intermediates and substrates of Ribonuclease (RNase)-catalysed reactions. The characterization of the equilibrium conformation as well as the flexibility inherent in these molecules helps in understanding the enzymatic action of RNases. The present study explores parameters like phase angle, glycosydic torsion angle and hydrogen bond to find possible interrelationship between them through Molecular Dynamics (MD) simulations on 3'-GMP, 3'-UMP, A>p, G>p, U>p, C>p, GpA>p and UpA>p. Interesting results of the effect of cyclisation and other constraints such as hydrogen bond between certain groups on the equilibrium ribose conformation have emerged from this study.

Structural and optical investigations of TiO2 films deposited on transparent substrates by sol-gel technique

An inexpensive and effective simple method for the preparation of nano-crystalline titanium oxide (anatase) thin films at room temperature on different transparent substrates is presented. This method is based on the use of peroxo-titanium complex, i.e. titanium isopropoxide as a single initiating organic precursor. Post-annealing treatment is necessary to convert the deposited amorphous film into titanium oxide (TiO2) crystalline (anatase) phase. These films have been characterized for X-ray diffraction (XRD) studies, atomic force microscopic (AFM) studies and optical measurements. The optical constants such as refractive index and extinction coefficient have been estimated by using envelope technique. Also, the energy gap values have been estimated using Tauc's formula for on glass and quartz substrates are found to be 3.35 eV and 3.39 eV, respectively.

Structural and optical investigations of TiO2 films deposited on transparent substrates by sol-gel technique

An inexpensive and effective simple method for the preparation of nano-crystalline titanium oxide (anatase) thin films at room temperature on different transparent substrates is presented. This method is based on the use of peroxo-titanium complex, i.e. titanium isopropoxide as a single initiating organic precursor. Post-annealing treatment is necessary to convert the deposited amorphous film into titanium oxide (TiO2) crystalline (anatase) phase. These films have been characterized for X-ray diffraction (XRD) studies, atomic force microscopic (AFM) studies and optical measurements. The optical constants such as refractive index and extinction coefficient have been estimated by using envelope technique. Also, the energy gap values have been estimated using Tauc's formula for on glass and quartz substrates are found to be 3.35 eV and 3.39 eV, respectively. (C) 2008 Elsevier B.V. All rights reserved.

On uniformity of film thickness on rotating substrates having a large source-to-substrate height

Abstract is not available.

Uniformity of film thickness on rotating planetary planar substrates

For the purposes of obtaining a number of components with nearly identical thickness distributions over the substrate area and of minimizing the inhomogeneities of the film, it is logical to presume that a substrate rotating on its own axis and revolving around another axis will give more uniformity in film thickness than a substrate only revolving around one axis. In relation to the practical applications, an investigation has been undertaken to study the refinement that can be achieved by using a planar planetary substrate holder. It is shown theoretically that the use of the planetary substrate holder under ideal conditions of source and geometry does not offer any further improvement in uniformity of thickness over the conventional rotary work-holder. It is also shown that the geometrical parameters alone have little influence over the uniformity achieved on a planetary substrate, because of the complex cyclidal motion of any point on it. However, for any given geometry, a non-integral speed ratio of the planetary substrate and the work-holder shows considerably less variation in thickness over the substrate area.

Synthesis of ZnO Nanoneedles on Flexible Polymer Substrates at Room Temperature by Activated Reactive Evaporation

ZnO nanoneedles were successfully deposited on flexible polymer substrates at room temperature by activated reactive evaporation. Neither a catalyst nor a template was employed in this synthesis. These synthesized needles measured 500 - 600 nm in length and its diameter varied from 30 - 15 nm from the base to the tip. The single-crystalline nature of the nanoneedle was observed by high-resolution transmission electron microscopy studies. The Raman studies on these nanoneedles had shown that they are oxygen deficient in nature. A possible growth mechanism has been proposed here, in which the nanoneedles nucleate and grow in the gas phase by vapor-solid mechanism.

Structural, ferroelectric and optical properties of Bi2VO5.5 thin films deposited on platinized silicon {(100) Pt/TiO2/SiO2/Si} substrates

Bismuth vanadate (Bi2VO5.5, BVO) thin films have been deposited by a pulsed laser ablation technique on platinized silicon substrates. The surface morphology of the BVO thin films has been studied by atomic force microscopy (AFM). The optical properties of the BVO thin films were investigated using spectroscopic ellipsometric measurements in the 300–820 nm wavelength range. The refractive index (n), extinction coefficient (k) and thickness of the BVO thin films have been obtained by fitting the ellipsometric experimental data in a four-phase model (air/BVOrough/BVO/Pt). The values of the optical constants n and k that were determined through multilayer analysis at 600 nm were 2.31 and 0.056, respectively. For fitting the ellipsometric data and to interpret the optical constants, the unknown dielectric function of the BVO films was constructed using a Lorentz model. The roughness of the films was modeled in the Brugmann effective medium approximation and the results were compared with the AFM observations.

Synthesis and characterization of Zn1-xMnxS nanocrystalline films prepared on glass substrates

Nanocrystalline Zn1-xMnxS films (x=0.04, 0.08 and 0.12) were deposited on glass substrates at 400 K using a simple resistive thermal evaporation technique. All the deposited films were characterized by chemical, structural, morphological, optical and magnetic properties. Scanning electron microscopy and atomic force microscopy studies showed that all the films investigated were in nanocrystalline form with the grain size lying in the range 10–20 nm. All the films exhibited cubic structure and the lattice parameters increase linearly with composition. The absorption edge shifted from the higher-wavelength region to lower wavelengths with increase in Mn concentration. The magnetization increased sharply with increase of the Mn content up to x=0.08 and then decreased with further increase of the Mn content. Particularly, Zn0.92Mn0.08S concentration samples show a weak ferromagnetic nature, which might be the optimum concentration for optoelectronic and spintronic device applications.

Sol-Gel Synthesis, characterization and optical properties of Tio2 thin films deposited on ITO/Glass substrates

TiO2 thin films have been deposited on glass and indium tin oxide (ITO) coated glass substrates by sol-gel technique. the influence of annealing temperature on the structural , morphological and optical properties has been examined. X-ray diffraction (XRD) results reveal the amorphous nature of the as-deposited film whereas the annealed films are found to be in the crystalline anatase phase. The surface morphology of the films at different annealing temperatures has been examined by atomic force microscopy (AFM). The in situ surface morphology of the as-deposited and annealed TiO2 films has also been examined by optical polaromicrograph (OPM). TiO2 films infatuated different structural and surface features with variation of annealing temperature. The optical studies on these films suggest their possible usage in sun-shielding applications.

Microwave irradiation-assisted method for the deposition of adherent oxide films on semiconducting and dielectric substrates

We report a method for the deposition of thin films and thick coatings of metal oxides through the liquid medium, involving the micro waveirradiation of a solution of a metal-organic complex in a suitable dielectric solvent. The process is a combination of sol-gel and dip-coating methods, wherein coatings can be obtained on nonconducting and semiconducting substrates, within a few minutes. Thin films of nanostructured ZnO (wurtzite) have been obtained on Si(100), glass and polymer substrates, the nanostructure determined by process parameters The coatings are strongly adherent and uniform over 15 mm x 15 mm, the growth rate similar to 0.25 mu m/min Coatings of nanocrystalline Fe2O3 and Ga2O3 have also been obtained The method is scalable to larger substrates, and is promising as a low temperature technique for coating dielectric substrates, including flexible polymers. (C) 2010 Elsevier B.V. All rights reserved.