Ruthenium(II)/(III) complexes of 4-hydroxy-pyridine-2,6-dicarboxylic acid with PPh₃/AsPh₃ as co-ligand: Impact of oxidation state and co-ligands on anticancer activity <i>in vitro</i>

Kamatchi, Thangavel Sathiya,Chitrapriya, Nataraj,Lee, Hyosun,Fronczek, Chris F.,Fronczek, Frank R.,Natarajan, Karuppannan The Royal Society of Chemistry 2012 Dalton transactions Vol.41 No.7

<P>With the aim to develop more efficient, less toxic, target specific metal drugs and evaluate their anticancer properties in terms of oxidation state and co-ligand sphere, a sequence of Ru<SUP>II</SUP>, Ru<SUP>III</SUP> complexes bearing 4-hydroxy-pyridine-2,6-dicarboxylic acid and PPh<SUB>3</SUB>/AsPh<SUB>3</SUB> were synthesized and structurally characterized. Biological studies such as DNA binding, antioxidant assays and cytotoxic activity were carried out and their anticancer activities were evaluated. Interactions of the complexes with calf thymus DNA revealed that the triphenylphosphine complexes could bind more strongly than the triphenylarsine complexes. The free radical scavenging ability, assessed by a series of <I>in vitro</I> antioxidant assays involving DPPH radical, hydroxyl radical, nitric oxide radical, superoxide anion radical, hydrogen peroxide and metal chelating assay, showed that the Ru<SUP>III</SUP> complexes possess excellent radical scavenging properties compared to those of Ru<SUP>II</SUP>. Cytotoxicity studies using three cancer lines <I>viz</I> HeLa, HepG2, HEp-2 and a normal cell line NIH 3T3 showed that Ru<SUP>II</SUP> complexes exhibited substantial cytotoxic specificity towards cancer cells. Furthermore, the Ru<SUP>II</SUP> complexes were found to be superior to Ru<SUP>III</SUP> complexes in inhibiting the growth of cancer cells.</P> <P>Graphic Abstract</P><P>We investigate the effects of oxidation states of ruthenium and the size of the ligands present in the complexes on DNA binding, antioxidant activity and cytotoxicity. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1dt11273b'> </P>

Self-organized multi-layered graphene-boron-doped diamond hybrid nanowalls for high-performance electron emission devices

Sankaran, Kamatchi Jothiramalingam,Ficek, Mateusz,Kunuku, Srinivasu,Panda, Kalpataru,Yeh, Chien-Jui,Park, Jeong Young,Sawczak, Miroslaw,Michałowski, Paweł Piotr,Leou, Keh-Chyang,Bogdanowicz, Robert,Li The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.3

<P>Carbon nanomaterials such as nanotubes, nanoflakes/nanowalls, and graphene have been used as electron sources due to their superior field electron emission (FEE) characteristics. However, these materials show poor stability and short lifetimes, which prevent their use in practical device applications. The aim of this study was to find an innovative nanomaterial possessing both high robustness and reliable FEE behavior. Herein, a hybrid structure of self-organized multi-layered graphene (MLG)-boron doped diamond (BDD) nanowall materials with superior FEE characteristics was successfully synthesized using a microwave plasma enhanced chemical vapor deposition process. Transmission electron microscopy reveals that the as-prepared carbon clusters have a uniform, dense, and sharp nanowall morphology with sp<SUP>3</SUP> diamond cores encased by an sp<SUP>2</SUP> MLG shell. Detailed nanoscale investigations conducted using peak force-controlled tunneling atomic force microscopy show that each of the core-shell structured carbon cluster fields emits electrons equally well. The MLG-BDD nanowall materials show a low turn-on field of 2.4 V μm<SUP>−1</SUP>, a high emission current density of 4.2 mA cm<SUP>−2</SUP> at an applied field of 4.0 V μm<SUP>−1</SUP>, a large field enhancement factor of 4500, and prominently high lifetime stability (lasting for 700 min), which demonstrate the superiority of these materials over other hybrid nanostructured materials. The potential of these MLG-BDD hybrid nanowall materials in practical device applications was further illustrated by the plasma illumination behavior of a microplasma device with these materials as the cathode, where a low threshold voltage of 330 V (low threshold field of 330 V mm<SUP>−1</SUP>) and long plasma stability of 358 min were demonstrated. The fabrication of these hybrid nanowalls is straight forward and thereby opens up a pathway for the advancement of next-generation cathode materials for high brightness electron emission and microplasma-based display devices.</P>

Embargo Nature of CuO-PANI Composite Against Corrosion of Mild Steel in Low pH Medium

Selvaraj, P. Kamatchi,Sivakumar, S.,Selvaraj, S. The Korean Electrochemical Society 2019 Journal of electrochemical science and technology Vol.10 No.2

Incorporation of CuO nanoparticles during the polymerization of aniline in the presence of ammonium peroxydisulphate as an oxidizing agent and sodium salt of dodecylbenzene sulphonic acid as dopant as well as surfactant yielded water soluble CuO-PANI composite. Comparison of recorded spectra like FTIR, XRD and SEM with reported one confirm the formation of the composite. Analysis by gravimetric method exposes that the synthesized composite is having resistivity against corrosion, with slight variation in efficiency on extending the time duration up to eight hours in strong acidic condition. OCP measurement, potentiodynamic polarization and EIS studies also confirms the suppression ability of composite against corrosion. Riskless working environment could be provided by the synthesized composite during industrial cleaning process.

Microwave cavity perturbation of nitrogen doped nano-crystalline diamond films

Cuenca, Jerome A.,Sankaran, Kamatchi Jothiramalingam,Pobedinskas, Paulius,Panda, Kalpataru,Lin, I-Nan,Porch, Adrian,Haenen, Ken,Williams, Oliver A. Elsevier 2019 Carbon Vol.145 No.-

<P><B>Abstract</B></P> <P>Non-contact and non-destructive electrical conductivity measurements of nitrogen doped nano-crystalline diamond films have been demonstrated using a microwave cavity perturbation system. The conductivity of the films was controlled by simply varying the CH<SUB>4</SUB> gas concentration during microwave plasma assisted chemical vapour deposition, thereby promoting the formation of sp<SUP>2</SUP> carbon at the grain boundaries. The presence of sp<SUP>2</SUP> carbon is verified through Raman spectroscopy, x-ray photoelectron spectroscopy and electron energy loss spectroscopy, while scanning electron microscopy confirms an increasing surface area for sp<SUP>2</SUP> to form. The microwave cavity perturbation results show that the measured cavity quality factor varies with CH<SUB>4</SUB> concentration. The extraction of conductivity is achieved through a depolarisation model, which must be considered when the sample is smaller than the cavity and through both electric and magnetic field perturbations. The microwave measurements are comparable to contacting and damaging measurements when the film conductivity is greater than the substrate, thus demonstrating an invaluable method for determining conductivity without the need for depositing any electrodes on the film.</P>

Methodologies for numerical modelling of prestressed concrete box-girder for long term deflection

M.C. Lalanthi,P. Kamatchi,K. Balaji Rao,S. Saibabu 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.3

In this paper, two methods M1 and M2 to determine long-term deflection through finite element analyses including the effect of creep and relaxation are proposed and demonstrated for a PSC box-girder. In both the methods, the effect of creep is accounted by different models from international standards viz., ACI-209R-92, CEB MC 90-99, B3 and GL2000. In M1, prestress losses due to creep and relaxation and age adjusted effective modulus are estimated through different models and have been used in finite element (FE) analyses for individual time steps. In M2, effects of creep and relaxation are implemented through the features of FE program and the time dependent analyses are carried out in single step. Variations in time-dependent strains, prestress losses, stresses and deflections of the PSC box-girder bridge through M1 and M2 are studied. For the PSC girder camber obtained from both M1 and M2 are lesser than simple bending theory based calculations, this shows that the camber is overestimated by simple bending theory which may lead to non-conservative design. It is also observed that stresses obtained from FEM for bottom fibre are lesser than the stresses obtained from bending theory at transfer for the PSC girder which may lead to non-conservative estimates.

Tribological Properties of Ultrananocrystalline Diamond Films in Inert and Reactive Tribo-Atmospheres: XPS Depth-Resolved Chemical Analysis

Rani, Revati,Panda, Kalpataru,Kumar, Niranjan,Sankaran, Kamatchi Jothiramalingam,Ganesan, K.,Lin, I-Nan American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.15

<P>Tribological properties of diamond films are sensitive to the chemically reactive and inert tribo-atmospheric media, and therefore, it is difficult to understand the underlying tribological mechanisms. In the present work, tribological properties of surface-modified ultrananocrystalline diamond (UNCD) thin films were investigated in four distinct tribo-environmental conditions of ambient humid-atmosphere, nitrogen (N<SUB>2</SUB>), argon (Ar), and methane (CH<SUB>4</SUB>) gases. The in situ depth-resolved X-ray photoelectron spectroscopy (XPS) showed the desorption of oxygen and oxy-functional additives and sputtering of weakly bonded amorphous carbon species from the UNCD film surface after the Ar<SUP>+</SUP>-ion sputtering process. After desorption of these chemical entities, friction and wear were decreased and run-in regime cycles became shorter in UNCD films. Friction in the ambient humid-atmosphere was higher compared to other tribo-environmental conditions, and it was explained by the oxidation mechanism of the sliding interfaces and the formation of the oxidized carbon transferfilm. However, low friction and wear in the N<SUB>2</SUB> atmosphere was associated with the adsorption of N<SUB>2</SUB> species, forming nitrogen-terminated carbon bonds at the sliding interfaces. This was directly investigated by XPS and energy dispersive X-ray spectroscopy techniques. Furthermore, low friction in the Ar atmosphere was explained by the physical adsorption of Ar gaseous species, which tend to avoid the covalent carbon bond formation across the sliding interfaces. Moreover, ultralow friction in the CH<SUB>4</SUB> atmosphere was governed by the passivation of dangling carbon bonds by dissociative CH<SUB>4</SUB> complexes, which creates hydrogen-terminated repulsive sliding interfaces. More importantly, a shorter run-in regime with low friction and wear in Ar<SUP>+</SUP>-ion-sputtered UNCD films were explained by desorption of the oxygen and oxy-functional groups, which are inherently present in the UNCD films.</P> [FIG OMISSION]</BR>

Dynamic friction behavior of ultrananocrystalline diamond films: A depth-resolved chemical phase analysis

Panda, Kalpataru,Rani, Revati,Kumar, Niranjan,Sankaran, Kamatchi Jothiramalingam,Park, Jeong Young,Ganesan, K.,Lin, I-Nan Elsevier 2019 Ceramics international Vol.45 No.17

<P><B>Abstract</B></P> <P>Investigation of dynamic changes in friction behavior of ultrananocrystalline diamond (UNCD) films is a complex mainly because of the rapid change in chemical composition at the sliding interfaces. To address this issue, for the first time, we report chemical phase analysis of transferfilm using the depth-resolved X-ray photoelectron spectroscopy (XPS) technique. The friction coefficient of the UNCD films was high during the initial run-in regime, but it gradually decreased to an ultralow value after longer sliding cycles at the ambient atmospheric tribo-condition. Depth-resolved XPS analysis showed a higher sp<SUP>3</SUP>/sp<SUP>2</SUP> carbon ratio during the initial run-in regime. This ratio decreased with increasing sliding cycles and consequently the friction coefficient decreased. However, a higher value of the friction coefficient throughout the run-in regime persisted at the high-vacuum tribo-condition. In this case, the sp<SUP>3</SUP>/sp<SUP>2</SUP> carbon ratio inside the transferfilm was quite high and no considerable changes were observed in the depth-resolved XPS analysis. This investigation confirmed that the dynamic friction behavior in UNCD films was manipulated by the sp<SUP>3</SUP>/sp<SUP>2</SUP> carbon ratio inside the transferfilm which showed tribo-atmospheric dependence.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Triboenvironment Dependent Chemical Modification of Sliding Interfaces in Ultrananocrystalline Diamond Nanowall Film: Correlation with Friction and Wear

Rani, Revati,Panda, Kalpataru,Kumar, Niranjan,Sankaran, Kamatchi Jothiramalingam,Pandian, Ramanathaswamy,Ficek, Mateusz,Bogdanowicz, Robert,Haenen, Ken,Lin, I-Nan American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.1

<P>Tribological properties of ultrananocrystalline diamond nanowall (UNCD NW) films were investigated quantitatively in three different and controlled triboenvironmental conditions, proposing the passivation and graphitization mechanisms. However, these mechanisms are rather complicated and possibly can be understood in well-controlled tribological conditions. It was shown that the friction and wear of these films were high in high-vacuum and room temperature (HV–RT) tribo conditions where the passivation of carbon dangling bonds were restricted and frictional shear-induced transformation of sp<SUP>3</SUP> carbon into amorphous carbon (a-C) and tetrahedral amorphous carbon (t-aC) were noticed. However, the friction coefficients were reduced to the ultralow value in ambient atmospheric and room temperature (AA–RT) tribo conditions. Here, both passivation of dangling bonds through atmospheric water vapor and graphitization of the contact interfaces were energetically favorable mechanisms. Furthermore, the conversion of diamond sp<SUP>3</SUP> into hydrogenated–graphitized phase was the dominating mechanism for the observed superlow friction coefficient and ultrahigh wear resistance of films in high-vacuum and high temperature (HV–HT) tribo conditions. These mechanisms were comprehensively investigated by micro-Raman and X-ray photoelectron spectroscopy analyses of the sliding interfaces.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2018/jpccck.2018.122.issue-1/acs.jpcc.7b10992/production/images/medium/jp-2017-10992p_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp7b10992'>ACS Electronic Supporting Info</A></P>

Regulation of Protein Structural Changes by Incorporation of a Small-Molecule Linker

Kim, Youngmin,Yang, Cheolhee,Kim, Tae Wu,Thamilselvan, Kamatchi,Kim, Yonggwan,Ihee, Hyotcherl MDPI 2018 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.19 No.12

<P>Proteins have the potential to serve as nanomachines with well-controlled structural movements, and artificial control of their conformational changes is highly desirable for successful applications exploiting their dynamic structural characteristics. Here, we demonstrate an experimental approach for regulating the degree of conformational change in proteins by incorporating a small-molecule linker into a well-known photosensitive protein, photoactive yellow protein (PYP), which is sensitized by blue light and undergoes a photo-induced N-terminal protrusion coupled with chromophore-isomerization-triggered conformational changes. Specifically, we introduced thiol groups into specific sites of PYP through site-directed mutagenesis and then covalently conjugated a small-molecule linker into these sites, with the expectation that the linker is likely to constrain the structural changes associated with the attached positions. To investigate the structural dynamics of PYP incorporated with the small-molecule linker (SML-PYP), we employed the combination of small-angle X-ray scattering (SAXS), transient absorption (TA) spectroscopy and experiment-restrained rigid-body molecular dynamics (MD) simulation. Our results show that SML-PYP exhibits much reduced structural changes during photo-induced signaling as compared to wild-type PYP. This demonstrates that incorporating an external molecular linker can limit photo-induced structural dynamics of the protein and may be used as a strategy for fine control of protein structural dynamics in nanomachines.</P>

Chromophore-Removal-Induced Conformational Change in Photoactive Yellow Protein Determined through Spectroscopic and X-ray Solution Scattering Studies

Kim, Youngmin,Ganesan, Prabhakar,Jo, Junbeom,Kim, Seong Ok,Thamilselvan, Kamatchi,Ihee, Hyotcherl American Chemical Society 2018 The journal of physical chemistry. B, Condensed ma Vol.122 No.16

<P>Photoactive yellow protein (PYP) induces negative phototaxis in <I>Halorhodospira halophila</I> via photoactivation triggered by light-mediated chromophore isomerization. Chromophore isomerization proceeds via a volume-conserving isomerization mechanism due to the hydrogen-bond network and steric constraints inside the protein, and causes significant conformational changes accompanied by N-terminal protrusion. However, it is unclear how the structural change of the chromophore affects the remote N-terminal domain. To understand photocycle-related structural changes, we investigated the structural aspect of chromophore removal in PYP because it possesses a disrupted hydrogen-bond network similar to that in photocycle intermediates. A comparison of the structural aspects with those observed in the photocycle would give a clue related to the structural change mechanism in the photocycle<SUB>.</SUB> Chromophore removal effects were assessed via UV-vis spectroscopy, circular dichroism, and X-ray solution scattering. Molecular shape reconstruction and an experiment-restrained rigid-body molecular dynamics simulation based on the scattering data were performed to determine protein shape, size, and conformational changes upon PYP bleaching. Data show that chromophore removal disrupted the holo-PYP structure, resulting in a small N-terminal protrusion, but the extent of conformational changes was markedly less than those in the photocycle. This indicates that disruption of the hydrogen-bond network alone in bleached PYP does not induce the large conformational change observed in the photocycle, which thus must result from the organized structural transition around the chromophore triggered by chromophore photoisomerization along with disruption of the hydrogen-bond network between the chromophore and the PYP core.</P> [FIG OMISSION]</BR>