In JoVE (1)

Other Publications (20)

Articles by Volkan Ötügen in JoVE

Other articles by Volkan Ötügen on PubMed

A Novel Sorbent Tube for Ambient Hydrogen Sulfide Determination

Talanta. Nov, 1998  |  Pubmed ID: 18967360

A novel tubular device has been developed for hydrogen sulfide determination in air. Several substrates such as commercial silica gel and alumina TLC plates, silica gel powder, alumina, CaSO(4), CaCO(3), BaSO(4), MgO, chalk, alpha-cellulose and ethyl cellulose were tested as solid substrates. 30-70-mesh silica gel was finally employed in glass tubes of 4.0 mm internal diameter. Silica gel is treated with 0.5 M aqueous CdCl(2) solution, dried, filled into the glass tube and sample gas is passed through the device using nitrogen as the carrier gas where 70% relative humidity is employed. The analyte reacts with the solid substrate to form a luminescent spot whose length in the tube is measured and correlated to concentration. The flow rate was 68 ml min(-1). The analytical system is linear in the range of 0.2-1.3 ppm H(2)S for the specified conditions. The prepared devices are stable at least for 3 months prior to sampling; and after sampling, the luminescing spot is stable also at least for 3 months.

Fiber Optic Sensors Using Novel Substrates for Hydrogen Sulfide Determination by Solid Surface Fluorescence

Talanta. Oct, 2000  |  Pubmed ID: 18968092

Two different fiber optic sensors were developed for the determination of hydrogen sulfide at ppb concentration levels; a probe-type fiber optic sensor coated with polyethylene oxide containing 0.5 M CdCl(2) and a fiber optic sensor utilizing 0.5 M CdCl(2)-pretreated filter paper as solid substrate. In the first type, CdCl(2)-polyethyleneoxide (PEO) mixture was coated onto the tip of a fiber optic probe and the probe was exposed to H(2)S. The methodology is based on the measurement of CdS fluorescence on the surface. Detection limit (3s) of the PEO-coated fiber optic system was 36.0 ppb for H(2)S and precision at the 0.552 ppm level was 29% R.S.D. For the fiber optic system utilizing CdCl(2)-pretreated filter paper, two different configurations were devised and evaluated; a bifurcated fiber optic sensor and a single fiber optic sensor. Similar figures were obtained with these two systems; the detection limit (3s) was 4.0 ppb for the bifurcated fiber optic sensor and 4.3 ppb for the single fiber optic sensor, and both sensors had linear responses in the range 0.032-1.0 ppm. Their precisions at 0.299 ppm level were also very similar, 10 and 11% R.S.D., respectively, for the bifurcated and single fiber systems. In addition to the fiber optic sensors developed, various surfactants (sodiumdodecylsulfate (SDS), Aerosol OT, Aerosol A102, Aerosol 501), some cellulosic substances (sodium carboxymethylcellulose (CMC), ethylcellulose, hydroxypropylmethylcellulose, ethylhydroxyethylcellulose, alpha-cellulose) and several water-soluble polymers (polyacrylicacid polyethleneoxide (PEO), polyvinylalcohol (PVA)) were dissolved in proper solvents and after mixing with 0.5 M CdCl(2), were spread over glass slides. These novel solid substrates were exposed to H(2)S and fluorescence signal on the surfaces of the glass slides was measured with a luminescence spectrometer. The new substrates were shown to be good alternatives to filter paper for the determination of H(2)S by room temperature solid surface fluorescence spectrometry.

Selective Pre-concentration of Selenite from Aqueous Samples Using Mercapto-silica

Talanta. Jul, 2003  |  Pubmed ID: 18969126

Silica gel modified with 3-mercaptopropyl-trimethoxysilane was used for the selective separation and pre-concentration of selenite (Se(IV)) from aqueous solutions containing Se(IV) and selenate (Se(VI)). Over a wide range of acidity, from 2 mol l(-1) HCl to pH 9.00, Se(IV) was taken up by the mercaptopropyl-silica with nearly 100% efficiency; Se(VI) however was unretained. Se(IV) content was determined by hydride generation atomic absorption spectrometry (HGAAS), following batch release of the selenium from the pre-concentration medium by acidic periodate. The overall pre-concentration efficiency, including both take-up and elution, in the range of 89-106%. The method was applied to spiked seawater samples containing as low as 800 ng l(-1) Se in selenite form. This solid-phase extraction system offers several major advantages over conventional solvent extraction procedures. It firstly exhibits high selectivity for Se(IV) over Se(VI). Using the solid-phase media, pre-concentration of Se(IV) in dilute water samples can be carried out in the field, stabilizing the selenite-selenium in a convenient form for transport and storage. In addition, selenium stored on silica is derived solely from Se(IV) overcoming problems of selenium redox speciation changes and loss during storage.

Preparation and Characterization of Ni-nitrilotriacetic Acid Bearing Poly(methacrylic Acid) Coated Superparamagnetic Magnetite Nanoparticles

Journal of Nanoscience and Nanotechnology. Feb, 2008  |  Pubmed ID: 18464394

Stable superparamagnetic magnetite (Fe3O4) nanoparticles were synthesized via co-precipitation in the presence of poly(methacrylic acid) (PMAA) in aqueous solution. The polymer coated Fe3O4 nanoparticles were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, thermal analysis, and vibrating sample magnetometry (VSM) techniques. These measurements reveal the presence of magnetite nanoparticles with a size of approximately 8 nm inside the PMAA matrix. The magnetization value of these superparamagnetic nanoparticles at room temperarure and 7 T was measured as about 40 emu/g. PMAA-coated Fe3O4 nanoparticles were further assembled with Ni-chelate through a reaction between a primary amine-bearing NTA (nitrilotriacetic acid) ligand and carboxy-functional groups of PMAA. NTA-PMAA-coated magnetite nanoparticles were then loaded with nickel ions and characterized using FTIR. The average amount of binded Ni on the surface of the NTA-modified PMAA coated Fe3O4 was calculated as 1.65 +/- 0.3 x 10(-6) mol nickel(II) ions per g of the magnetic particles from the inductively coupled plasma optical emission spectroscopy (ICP-OES) measurements.

Rapid Synthesis and Characterization of Maghemite Nanoparticles

Journal of Nanoscience and Nanotechnology. Feb, 2008  |  Pubmed ID: 18464419

Fe2O3-SiO2 nanocomposites were prepared by a sol-gel method using various evaporation surface to volume (S/V) ratios ranging from 0.03 to 0.2. The Fe2O3-SiO2 sols were gelated at various temperatures ranging from 50 degrees C to 70 degrees C, and subsequently they were calcined in air at 400 degrees C for 4 hours. The structure and the magnetic properties of the prepared Fe203-SiO2 nanocomposites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and vibrating sample magnetometer (VSM) measurements. The gelation temperature of the Fe2O3-SiO2 sols influenced strongly the particle size and crystallinity of the maghemite nanoparticles. It was observed that the particle size of maghemite nanoparticles increased with the increasing of the gelation temperature of the sols, which may be due to the agglomeration of the maghemite particles at elevated temperatures inside the microporosity of the silica matrix during the gelation process, and the subsequent calcination of these gels at 400 degrees C resulted in the formation of large size iron oxide particles. Magnetization studies at temperatures of 10, 195, and 300 K showed superparamagnetic behavior for all the nanocomposites prepared using the evaporation surface to volume ratio (S/V) of 0.1, 0.2, 0.09, and 0.08. The saturation magnetization, Ms, values measured at 10 K were 5.5, 8.5, and 9.5 emu/g, for the samples gelated at 50, 60, and 70 degrees C, respectively. At the gelation temperature of 70 degrees C, gamma-Fe2O3 crystalline superparamagnetic nanoparticles with the particle size of 9 +/- 2 nm were formed in 12 hours for the samples prepared at the S/V ratio of 0.2.

Silver Nanoparticle-doped Polyvinyl Alcohol Coating As a Medium for Surface-enhanced Raman Scattering Analysis

Journal of Nanoscience and Nanotechnology. Feb, 2008  |  Pubmed ID: 18464433

A simple polymer substrate for inducing Surface-Enhanced Raman Scattering (SERS) has been investigated. This SERS substrate consists of a solid support, such as a glass slide covered with polyvinyl alcohol (PVA) impregnated with fine silver nanoparticles. The preparation simply involves mixing aqueous PVA polymer with solid AgNO3 to produce a solution that can be easily spin coated on the glass substrate and dried to obtain a hard translucent coating. Aqueous solution of FeSO4.7H2O was used to reduce Ag+ ions to silver nanoparticles. The effects of various experimental conditions of sample preparation were investigated in order to improve the Raman enhancement efficiency of the substrate. The overall substrate performance was evaluated with the use of biologically important compounds: benzoic acid, p-amino benzoic acid, pyridine and dopamine. The spectral features of these compounds closely matched with those reported in literature. The use of the polymer matrix made the SERS substrate resistant to scratching, therefore, improving it to be more suitable for field applications. The hydrophilic nature of the polymer provides additional advantages for probing biological samples. The shelf-life of the dried, unreduced substrates is at least one month.

Pediatric Residents' Perceptions of Communication Competencies: Implications for Teaching

Medical Teacher. 2008  |  Pubmed ID: 18777421

Medical regulatory organizations worldwide require competency in communication skills. Pediatric communication competencies are unique, and little is known about pediatric residents' perceptions regarding these skills.

Laparoscopic Cholecystectomy in Elderly Patients

Bratislavské Lekárske Listy. 2008  |  Pubmed ID: 18792486

In this study, we hypothesize that LC is a safe procedure in a non-laparoscopic specialized general surgery unit in a teaching hospital.

Carboligation Reactions with Benzaldehyde Lyase Immobilized on Superparamagnetic Solid Support

Organic & Biomolecular Chemistry. Apr, 2009  |  Pubmed ID: 19343254

Histidine-tagged recombinant benzaldehyde lyase (BAL, EC was efficiently immobilized to surface-modified magnetic particles with affinity ligand binding. In addition to conventional benzoin condensation reactions, two important representative BAL-catalyzed carboligation reactions, were also performed with this magnetically responsive biocatalyst. The results obtained from the carboligation reactions that were performed with this simple and convenient heterogenous biocatalyst were comparable to that of free-enzyme-catalyzed reactions.

Results of Primary Ossiculoplasty and Prognostic Factors in Canal Wall-down Tympanoplasty

The Journal of Craniofacial Surgery. Mar, 2010  |  Pubmed ID: 20186074

The ideal goals of chronic middle ear surgery should be the permanent removal of disease and the preservation of good hearing function. The postoperative outcome of hearing and the status of middle ear after canal wall-down tympanoplasty with primary ossiculoplasty were studied in 192 ears with chronic middle ear disease. Cholesteatoma was present in 121 (63.0%) of 192 cases; in the remaining 71 cases (27.0%), there was middle ear mucosa disease without cholesteatoma. The stapes superstructure was present in 142 (73.9%) of 192 cases. The results of preoperative and postoperative pure-tone averages were 55.12 (SD, 4.92) and 35.81 (SD, 4.84) dB, respectively. The preoperative and postoperative air-bone gaps in 192 cases were 32.70 (SD, 5.18) and 21.16 (SD, 5.09) dB, respectively. The mean hearing gain of the 192 ears was 19.17 (SD, 6.09) dB. The presence of stapes superstructure positively affects hearing status. Also, better hearing results were obtained in cholesteatoma cases presented. Recurrences of disease were seen rarely compared with literature. It was revealed that the postoperative outcome of primary canal wall-down tympanoplasty with ossicular chain reconstruction is suitable for safe ear and hearing ear.

Germanium Determination by Flame Atomic Absorption Spectrometry: an Increased Vapor Pressure-chloride Generation System

Talanta. Mar, 2011  |  Pubmed ID: 21315908

A new chloride generation system was designed for the direct, sensitive, rapid and accurate determination of the total germanium in complex matrices. It was aimed to improve the detection limit of chloride generation technique by increasing the vapor pressure of germanium tetrachloride (GeCl(4)). In order to do so, a novel joint vapor production and gas-liquid separation unit equipped with a home-made oven was incorporated to an ordinary nitrous oxide-acetylene flame atomic absorption spectrometer. Several variables such as reaction time, temperature and acid concentration have been investigated. The linear range for germanium determination was 0.1-10 ng mL(-1) for 1 mL sampling volume with a detection limit (3s) of 0.01 ng mL(-1). The relative standard deviation (RSD) was 2.4% for nine replicates of a 1 ng mL(-1) germanium solution. The method was validated by the analysis of one non-certified and two certified geochemical reference materials, respectively, CRM GSJ-JR-2 (Rhyolite), and GSJ-JR-1 (Rhyolite), and GBW 07107 (Chinese Rock). Selectivity of the method was investigated for Cd(2+), Co(2+), Cu(2+), Fe(3+), Ga(3+), Hg(2+), Ni(2+), Pb(2+), Sn(2+), and Zn(2+) ions and ionic species of As(III), Sb(III), Te(IV), and Se(IV).

Crystal Structure of the FimD Usher Bound to Its Cognate FimC-FimH Substrate

Nature. Jun, 2011  |  Pubmed ID: 21637253

Type 1 pili are the archetypal representative of a widespread class of adhesive multisubunit fibres in Gram-negative bacteria. During pilus assembly, subunits dock as chaperone-bound complexes to an usher, which catalyses their polymerization and mediates pilus translocation across the outer membrane. Here we report the crystal structure of the full-length FimD usher bound to the FimC-FimH chaperone-adhesin complex and that of the unbound form of the FimD translocation domain. The FimD-FimC-FimH structure shows FimH inserted inside the FimD 24-stranded β-barrel translocation channel. FimC-FimH is held in place through interactions with the two carboxy-terminal periplasmic domains of FimD, a binding mode confirmed in solution by electron paramagnetic resonance spectroscopy. To accommodate FimH, the usher plug domain is displaced from the barrel lumen to the periplasm, concomitant with a marked conformational change in the β-barrel. The amino-terminal domain of FimD is observed in an ideal position to catalyse incorporation of a newly recruited chaperone-subunit complex. The FimD-FimC-FimH structure provides unique insights into the pilus subunit incorporation cycle, and captures the first view of a protein transporter in the act of secreting its cognate substrate.

Large-scale Voter Behavior

International Journal of Group Psychotherapy. Jan, 2012  |  Pubmed ID: 22229371

First Successful Preimplantation Genetic Diagnosis of Epidermolysis Bullosa with Pyloric Atresia: Case Study of a Novel C.4505-4508insACTC Mutation

Journal of Assisted Reproduction and Genetics. Apr, 2012  |  Pubmed ID: 22354727

Domain Activities of PapC Usher Reveal the Mechanism of Action of an Escherichia Coli Molecular Machine

Proceedings of the National Academy of Sciences of the United States of America. Jun, 2012  |  Pubmed ID: 22645361

P pili are prototypical chaperone-usher pathway-assembled pili used by Gram-negative bacteria to adhere to host tissues. The PapC usher contains five functional domains: a transmembrane β-barrel, a β-sandwich Plug, an N-terminal (periplasmic) domain (NTD), and two C-terminal (periplasmic) domains, CTD1 and CTD2. Here, we delineated usher domain interactions between themselves and with chaperone-subunit complexes and showed that overexpression of individual usher domains inhibits pilus assembly. Prior work revealed that the Plug domain occludes the pore of the transmembrane domain of a solitary usher, but the chaperone-adhesin-bound usher has its Plug displaced from the pore, adjacent to the NTD. We demonstrate an interaction between the NTD and Plug domains that suggests a biophysical basis for usher gating. Furthermore, we found that the NTD exhibits high-affinity binding to the chaperone-adhesin (PapDG) complex and low-affinity binding to the major tip subunit PapE (PapDE). We also demonstrate that CTD2 binds with lower affinity to all tested chaperone-subunit complexes except for the chaperone-terminator subunit (PapDH) and has a catalytic role in dissociating the NTD-PapDG complex, suggesting an interplay between recruitment to the NTD and transfer to CTD2 during pilus initiation. The Plug domain and the NTD-Plug complex bound all of the chaperone-subunit complexes tested including PapDH, suggesting that the Plug actively recruits chaperone-subunit complexes to the usher and is the sole recruiter of PapDH. Overall, our studies reveal the cooperative, active roles played by periplasmic domains of the usher to initiate, grow, and terminate a prototypical chaperone-usher pathway pilus.

Effects of Maternal Left Lateral Position and Rest on Amniotic Fluid Index: a Prospective Clinical Study

The Journal of Reproductive Medicine. May-Jun, 2012  |  Pubmed ID: 22696825

To compare the effect of both maternal rest and activity on the amniotic fluid index (AFI).

Copper(0) Nanoparticles Supported on Silica-coated Cobalt Ferrite Magnetic Particles: Cost Effective Catalyst in the Hydrolysis of Ammonia-borane with an Exceptional Reusability Performance

ACS Applied Materials & Interfaces. Aug, 2012  |  Pubmed ID: 22856878

Herein we report the development of a new and cost-effective nanocomposite catalyst for the hydrolysis of ammonia-borane (NH(3)BH(3)), which is considered to be one of the most promising solid hydrogen carriers because of its high gravimetric hydrogen storage capacity (19.6% wt) and low molecular weight. The new catalyst system consisting of copper nanoparticles supported on magnetic SiO(2)/CoFe(2)O(4) particles was reproducibly prepared by wet-impregnation of Cu(II) ions on SiO(2)/CoFe(2)O(4) followed by in situ reduction of the Cu(II) ions on the surface of magnetic support during the hydrolysis of NH(3)BH(3) and characterized by ICP-MS, XRD, XPS, TEM, HR-TEM and N(2) adsorption-desorption technique. Copper nanoparticles supported on silica coated cobalt(II) ferrite SiO(2)/CoFe(2)O(4) (CuNPs@SCF) act as highly active catalyst in the hydrolysis of ammonia-borane, providing an initial turnover frequency of TOF = 2400 h(-1) at room temperature, which is not only higher than all the non-noble metal catalysts but also higher than the majority of the noble metal based homogeneous and heterogeneous catalysts employed in the same reaction. More importantly, they were easily recovered by using a permanent magnet in the reactor wall and reused for up to 10 recycles without losing their inherent catalytic activity significantly, which demonstrates the exceptional reusability of the CuNPs@SCF catalyst.

New Approach for the Surface Enhanced Resonance Raman Scattering (SERRS) Detection of Dopamine at Picomolar (pM) Levels in the Presence of Ascorbic Acid

Analytical Chemistry. Sep, 2012  |  Pubmed ID: 22881404

The development of a novel surface-enhanced resonance Raman scattering (SERRS) platform that allows fast and sensitive detection of dopamine (DA) has been reported. The iron-nitrilotriacetic acid attached silver nanoparticle (Ag-Fe(NTA)) substrate provides remarkable sensitivity and reliable repeatability. The advantages of both the surface functionalization for specific analytes and the SERRS are integrated into a single functional unit. While the silver core gives the necessary enhancing properties, the Fe-NTA receptors can trap DA adjacent the silver core and the NTA-Fe-DA complex formed provides resonance enhancement with a 632.8 nm laser. DA could be detected in pM level without any pretreatment with a reliable discrimination against AA, by utilizing low laser power (10 mW) and short data acquisition time (10 s). The high sensitivity along with the improved selectivity of this sensing approach is a significant step toward molecular diagnosis of Parkinson's disease.

The Structure of the PapD-PapGII Pilin Complex Reveals an Open and Flexible P5 Pocket

Journal of Bacteriology. Dec, 2012  |  Pubmed ID: 23002225

P pili are hairlike polymeric structures that mediate binding of uropathogenic Escherichia coli to the surface of the kidney via the PapG adhesin at their tips. PapG is composed of two domains: a lectin domain at the tip of the pilus followed by a pilin domain that comprises the initial polymerizing subunit of the 1,000-plus-subunit heteropolymeric pilus fiber. Prior to assembly, periplasmic pilin domains bind to a chaperone, PapD. PapD mediates donor strand complementation, in which a beta strand of PapD temporarily completes the pilin domain's fold, preventing premature, nonproductive interactions with other pilin subunits and facilitating subunit folding. Chaperone-subunit complexes are delivered to the outer membrane usher where donor strand exchange (DSE) replaces PapD's donated beta strand with an amino-terminal extension on the next incoming pilin subunit. This occurs via a zip-in-zip-out mechanism that initiates at a relatively accessible hydrophobic space termed the P5 pocket on the terminally incorporated pilus subunit. Here, we solve the structure of PapD in complex with the pilin domain of isoform II of PapG (PapGIIp). Our data revealed that PapGIIp adopts an immunoglobulin fold with a missing seventh strand, complemented in parallel by the G1 PapD strand, typical of pilin subunits. Comparisons with other chaperone-pilin complexes indicated that the interactive surfaces are highly conserved. Interestingly, the PapGIIp P5 pocket was in an open conformation, which, as molecular dynamics simulations revealed, switches between an open and a closed conformation due to the flexibility of the surrounding loops. Our study reveals the structural details of the DSE mechanism.

Evaluation of a National Bright Futures Oral Health Curriculum for Pediatric Residents

Academic Pediatrics. Dec, 2012  |  Pubmed ID: 23257667

OBJECTIVE: Training in Bright Futures and oral health concepts is critical for delivery of high-quality primary care and preventive health services by residents, our future pediatric workforce. The goal of this study was to evaluate the effectiveness of an online health promotion curriculum on pediatric residents' confidence, knowledge, and clinical performance in Bright Futures and oral health practice. METHODS: Residents from sites that had been stratified by size and randomized were assigned to the Bright Futures Oral Health curriculum (intervention group) or an active control group. Confidence and knowledge were measured by self-report and multiple-choice questions, respectively. Clinical performance was measured with structured clinical observations, performed by trained faculty, of Bright Futures and oral health performance before and after intervention. Mean scores between intervention and control groups were compared using a 2-tailed, repeated-measures F test. RESULTS: A total of 143 pediatric residents from 27 Continuity Research Network (CORNET) sites participated in the study. At a median of 3 months after intervention, the intervention group demonstrated significant improvement in general Bright Futures confidence (n = 128, F = 6.564, P = .012) and knowledge (n = 102, F = 5.296, P = .023), oral health confidence (n = 123, F = 15.220, P < .001), and clinical performance skills in oral health (n = 96, F = 11.315, P = .001) compared with the control group. CONCLUSIONS: The Bright Futures Oral Health curriculum promoted an increase in confidence and knowledge in Bright Futures concepts and in confidence and clinical performance in oral health concepts among pediatric residents. This online curriculum demonstrated a positive impact on documented resident behavior, maintained for 3 months after intervention, and provides a replicable national training model to advance important elements of primary care pediatrics.

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