Search

The antibacterial efficacy of a Cu(II) complex of $$\hbox {2-hydroxyphenyl-azo-2}^{\prime }\hbox {-naphthol}$$ (HPAN) was studied on gram-positive Bacillus subtilis and gram-negative Escherichia coli. In vitro antimicrobial activity was determined by an agar-well diffusion assay and minimum inhibitory concentration. $$\hbox {Cu}^{\mathrm{II}}(\hbox {HPAN})_{2}$$ was found to be better than HPAN in antibacterial activity. Although both bacterial strains succumbed to high concentrations of each compound, at low concentrations only $$\hbox {Cu}^{\mathrm{II}}(\hbox {HPAN})_{2}$$ was active on B. subtilis. To explain the observations, reductive cleavage of the azo-bond to aromatic amines was followed by an in vitro enzyme assay using cell extracts of E. coli containing azo-reductase. Interaction of $$\hbox {Cu}^{\mathrm{II}}(\hbox {HPAN})_{2}$$ with calf thymus DNA was compared with HPAN for correlation with antibacterial activity. Enzyme-assay on the reductive degradation of azo bond and DNA interaction do not individually explain trends observed in antibacterial activity. Comparable binding of $$\hbox {Cu}^{\mathrm{II}}(\hbox {HPAN})_{2}$$ and HPAN with calf thymus DNA was attributed to the presence of anionic species of the complex in solution. Significant activity of the complex was probably due to effective cellular uptake of it by bacterial cells as shown by a fluorescence study. The activity of the complex resembled some established antimicrobial agents. Since the complex has a moiety, not common to most antibacterial agents, resistance towards it should be significantly less, hence an advantage. Synopsis: $$\hbox {2-Hydroxyphenyl-azo-2}^{\prime }\hbox {-naphthol}$$ (HPAN) and its $$\hbox {Cu}^{\mathrm{II}}$$ complex were screened for antibacterial activity by agar-well diffusion assay and minimum inhibitory concentration. Studies on azo bond cleavage by enzyme assay and DNA binding of the compounds were done to explain the antibacterial activity. The pronounced activity of $$\hbox {Cu}^{\mathrm{(II)}}$$ -HPAN is attributed to an effective cellular uptake by bacterial cells.

Wetting of rough surfaces involves time-dependent effects, such as surface deformations, nonuniform filling of surface pores within or outside the contact area, and surface chemistries, but the detailed impact of these phenomena on wetting is not entirely clear. Understanding these effects is crucial for designing coatings for a wide range of applications, such as membrane-based oil-water separation and desalination, waterproof linings/windows for automobiles, aircrafts, and naval vessels, and antibiofouling. Herein, we report on time-dependent contact angles of water droplets on a rough polydimethylsiloxane (PDMS) surface that cannot be completely described by the conventional Cassie-Baxter or Wenzel models or the recently proposed Cassie-impregnated model. Shells of sand dollars (Dendraster excentricus) were used as lithography-free, robust templates to produce rough PDMS surfaces with hierarchical, periodic features ranging from 1 × 10(-7) to 1 × 10(-4) m. Under saturated vapor conditions, we found that in the short term (1 min), the contact angle of a sessile water droplet on the templated PDMS, θ(SDT) = 140 ± 3°, was accurately described by the Cassie-Baxter model (predicted θ(SDT) = 137°); however, after 90 min, θ(SDT) fell to 110°. Fluorescent confocal microscopy confirmed that the initial reduction in θ(SDT) to 110° (the Wenzel limit) was primarily a Cassie-Baxter to Wenzel transition during which pores within the contact area filled gradually, and more rapidly for ethanol-water mixtures. After 90 min, the contact line of the water droplet became pinned, perhaps caused by viscoelastic deformation of the PDMS around the contact line, and a significant volume of water began to flow from the droplet to pores outside the contact region, causing θ(SDT) to decrease to 65° over 48 h on the rough surface. The system we present here to explore the concept of contact angle time dependence (dynamics) and modeling of natural surfaces provides insights into the design and development of long- and short-lived coatings.

The formation of reactive oxygen species (ROS) by anthracycline anticancer drugs is essential for their antitumor activity but they also make these drugs cardiotoxic. When complexed with metal ions there is a decrease in ROS formation and therefore in cardiotoxicity. Interestingly, in spite of producing fewer ROS, some of the complexes are effective antitumor agents, often better than the parent anthracycline. Purpurin (LH3), a hydroxy-9,10-anthraquinone, resembles doxorubicin at the core. An MnII complex of LH3 [MnII(LH2)2] was synthesized to see the extent to which the complex resembles metal–anthracyclines with regard to structure and function. The crystal structure was determined by Rietveld refinement of PXRD data using an appropriate structural model developed on the basis of spectroscopic information. This is only the second report on the crystal structure of a hydroxy-9,10-anthraquinone with a 3d-transition metal ion. Bond lengths and bond angles were obtained by structural refinement. The structure is supported by DFT calculations. DNA binding of the complex is slightly better than for purpurin but more importantly unlike purpurin, the binding constant values remained constant even with an increase in the pH of the medium. The NADH dehydrogenase assay and the DCFDA-ROS generation assay showed that generation of superoxide in the former and ROS in general in the latter were significantly less for the complex than for purpurin. Even with decreased ROS formation, the complex is able to maintain the biological activity of purpurin.

Reductive cleavage of azo bond in a CoIIcomplex of HPIA decreased significantly implying less toxicity. On human colon carcinoma HCT116, ALL MOLT-4 & MCF-7 breast cancer cells complex was more effective than HPIA but less toxic towards normal cells.

A priori estimation of delays with error variance of atmospheric radio wave propagation is important for precise position estimation and integrity of the system like Global Positioning System (GPS). Tropospheric effects are less severe than the ionospheric counterpart, but behave in a complex manner, making it difficult to isolate them. In this present paper, a ground based radiometer has been utilized to study the characteristics of tropospheric delay and compared it with the MODIS satellite observations over Kolkata (22.57°N, 88.37°E). Results indicate a good agreement between radiometer and MODIS data except the monsoon months. A climatology of spatial and temporal variation of dry and wet tropospheric delay over the Indian subcontinent have also been estimated using MODIS data and NCEP–NCAR reanalysis data for 2008–2012. The spatial variations of dry delay over Indian region are observed to be in the range of 120–250 cm with limited seasonal variability. However, the wet delay varies from 20 cm in winter months to 45 cm during monsoon period in the coastal and central Indian region. Further analysis reveals that the contribution of wet delays in total delay is significant only along the Indo-Gangetic plain. This indicates that extra precaution is needed in handling tropospheric delay for this region due to fast varying nature of water vapor.

© 2015 American Chemical Society. Numerous attempts have been made to translate mussel adhesion to diverse synthetic platforms. However, the translation remains largely limited to the Dopa (3,4-dihydroxyphenylalanine) or catechol functionality, which continues to raise concerns about Dopa's inherent susceptibility to oxidation. Mussels have evolved adaptations to stabilize Dopa against oxidation. For example, in mussel foot protein 3 slow (mfp-3s, one of two electrophoretically distinct interfacial adhesive proteins in mussel plaques), the high proportion of hydrophobic amino acid residues in the flanking sequence around Dopa increases Dopa's oxidation potential. In this study, copolyampholytes, which combine the catechol functionality with amphiphilic and ionic features of mfp-3s, were synthesized and formulated as coacervates for adhesive deposition on surfaces. The ratio of hydrophilic/hydrophobic as well as cationic/anionic units was varied in order to enhance coacervate formation and wet adhesion properties. Aqueous solutions of two of the four mfp-3s-inspired copolymers showed coacervate-like spherical microdroplets ( ≈ 1-5 μm at pH ∼4 (salt concentration ∼15 mM). The mfp-3s-mimetic copolymer was stable to oxidation, formed coacervates that spread evenly over mica, and strongly bonded to mica surfaces (pull-off strength: ∼17.0 mJ/m2). Increasing pH to 7 after coacervate deposition at pH 4 doubled the bonding strength to ∼32.9 mJ/m2without oxidative cross-linking and is about 9 times higher than native mfp-3s cohesion. This study expands the scope of translating mussel adhesion from simple Dopa-functionalization to mimicking the context of the local environment around Dopa. (Figure Presented).

India though being the birthplace of the ancient science of sex, it is really a matter of shame that the post British India, considers it a taboo, to talk and discuss it in the public. Like many other ancient scriptures and technologies that were all initiated by India, but are now used and further developed by the western world, India, in this case too only boasts itself of having just invented this, but, with little implications in their modern life. Like the Vedas, Upansihadas, Ayurveda, Yoga, Mathematics, Kamasutra or the science of sex, had also developed in this part of the world first, but, is considered obscene in present day India. What is even more insane is that there are numerous, monuments, buildings of the ancient and medieval history still present in this country, which openly depicts sex in the form of sculptures and paintings, and are popular tourist destinations, but watching the same over electronic media has been labelled illicit.

An acetate-bridged binuclear Cu((II)) complex of the antiparasitic drug ornidazole was synthesized and characterized by different techniques. Single crystal X-ray diffraction revealed that the complex had a paddle wheel structure. Enzymatic assay experiments performed under anaerobic conditions on ornidazole and its Cu((II))-complex using xanthine oxidase as a model nitro-reductase showed that complex formation is able to cause a significant decrease in the reduction of the nitro group on the imidazole ring. Reduction products of 5-nitroimidazoles interact with DNA, causing destruction of the double helical structure and strands, leading to the inhibition of protein synthesis. Although not directly coordinated to the metal center, such a decrease in the generation of nitro radical anion through complex formation would result in decreased cytotoxicity of the complex, which could be a disadvantage from the standpoint of drug efficacy. For this reason, other aspects associated with the drug action of 5-nitroimidazoles, such as DNA binding, were studied. Experiments using cyclic voltammetry revealed that the binding of the complex was almost comparable to ornidazole. Bactericidal activity of ornidazole and the complex was studied on two separate bacterial strains, showing that the complex was comparable to ornidazole. Nitro radical anions are known to adversely affect the central nervous system, and this study showed that the Cu((II)) complex has the ability to decrease the generation of NO2˙(-) to an extent that struck the correct balance for beneficial activity, as cytotoxicity due to ornidazole was not affected.

THA, a structural analogue of the family of anthracycline anticancer drugs, was used to understand how environmental changes affect its biophysical interactions with DNA. A variation of the ionic strength of the medium was attempted at a constant pH. Under such varying conditions, the binding constant and the site size of interaction were evaluated. Owing to the close structural similarity with anthracyclines and the fact that the quinone moiety in these drugs control the chemical reactions, the effect of the ionic strength on the physicochemical and biophysical attributes of hydroxy-9,10-anthraquinones is important. With an increase in ionic strength, the dissociation of the first proton of THA is affected to a greater extent compared to the second proton. Since the pKa1 is connected to the generation of the mono-anion of THA, an increase in its value implies that there would be less anion in the medium leading to improved DNA binding. Increased NaCl concentration neutralizes the negative charges on the DNA backbone manifesting in an overall increase in the binding constant for THA. This fact might be exploited for the use of such molecules in cancer patients. However, in the case of a CuII complex of THA and the formation of anions being almost negligible, there is a marked improvement in DNA binding. The cytotoxic action of THA (LH3) and its CuII complex [CuII(LH2)2] was also studied on three breast carcinoma cell lines and a primary human dermal fibroblast cell line. The complex was seen to perform better than THA. The results could be explained with the help of the comet assay, the γH2AX foci assay, and DAPI staining followed by western blotting with an apoptotic protein marker. The findings of THA and its CuII complex were compared to anthracycline doxorubicin.

pK

India though being the birthplace of the ancient science of sex, it is really a matter of shame that the post British India, considers it a taboo, to talk and discuss it in the public. Like many other ancient scriptures and technologies that were all initiated by India, but are now used and further developed by the western world, India, in this case too only boasts itself of having just invented this, but, with little implications in their modern life. Like the Vedas, Upansihadas, Ayurveda, Yoga, Mathematics, Kamasutra or the science of sex, had also developed in this part of the world first, but, is considered obscene in present day India. What is even more insane is that there are numerous, monuments, buildings of the ancient and medieval history still present in this country, which openly depicts sex in the form of sculptures and paintings, and are popular tourist destinations, but watching the same over electronic media has been labelled illicit.

A major drawback of azo compounds is their associated toxicity, often carcinogenic, which is related to the reduction of the azo bond. This study intends to re-investigate this behavior by studying 5-amino-2-((3-hydroxy-4-((3-hydroxyphenyl) phenyl) diazenyl) phenol (AHPD), a compound containing two azo bonds. Interaction of AHPD and its dimeric Cu(II) complex with bacterial strains Escherichia coli and Staphylococcus aureus revealed the complex was less toxic. Reductive cleavage of the azo bond in AHPD and the complex followed using cytochrome c reductase (a model azo-reductase) as well as azo-reductase enzymes obtained from bacterial cell extracts. Degradation of the azo bond was less in the complex allowing us to correlate the observed cytotoxicity. Cyclic voltammetry on AHPD and the complex support observations of enzyme assay experiments. These were particularly useful in realizing the formation of amines as an outcome of the reductive cleavage of azo bonds in AHPD that could not be identified through an enzyme assay. Results suggest that complex formation of azo compounds could be a means to control the formation of amines responsible for cytotoxicity. Studies carried out on bacterial cells for mere simplicity bear significance for multicellular organisms and could be important for human beings involved with the preparation and utilization of azo dyes.

Precipitable water vapour (PWV) is an important input for numerical weather prediction model, meteorology and high-precision navigational applications. Conventional methods for the determination of PWV using radiosonde are not sufficient owing to poor temporal resolution, whereas radiometer-derived PWV is reliable only in fair weather conditions. Global positioning system (GPS) is a very useful and cost-effective tool to determine PWV continuously in all weather conditions. The processing of GPS data to extract the PWV information is, however, very complicated due to very small effect of the PWV (~0.5% of total delay) on GPS frequencies than other sources of delay and errors and requires a network of GPS in differential configuration for such purpose. The authors show how the problem can be handled in a standalone dual-frequency GPS receiver in a relatively less complicated manner with reasonable accuracy. The performances of different dry tropospheric delay models are also investigated. The methodology is tested with GPS measurements at Kolkata (22.57°N, 88.37°E) and Bangalore (13.01°N, 77.5°E). The results indicate that the proposed methodology can be implemented for PWV estimation using single GPS receiver with satisfactory performance.

Two new copper(II) complexes, [Cu(L)(OCN)] ( 1 ) and [CuL(dca)] n ( 2) , where HL = 2-(-(2-(diethylamino)ethylimino)methyl)naphthalen-1-ol, dca = N(CN) 2 − , have been synthesized and characterized by elemental analysis, IR, UV–VIS spectroscopy and single crystal X-ray diffraction studies. Complex 1 has square planar and complex 2 square pyramidal geometries in solid state around metal centre. Interactions of the complexes with calf thymus DNA (CT DNA) were studied by UV–VIS spectroscopy. Binding constant and site size of interaction were determined. Binding site size and intrinsic binding constant K revealed complex 1 interacted with calf thymus DNA better than complex 2.

Propagation effects on Ku-band over an earth-space path is carried out at Kolkata, India, a tropical location, by receiving a Ku-band signal with horizontal plane polarization transmitted from the geostationary satellite NSS-6 (at 95°E). The amplitude of co-polar attenuation has been monitored along with the measurements of rain rate, rain drop size distribution and height profile of rain rate. The cross-polar enhancement of the signal is also monitored by receiving the same signal in orthogonal direction with another identical receiver. The experimental observations are used to study the effect of melting layer on both co-polar attenuation and cross-polar enhancement for the rain events observed during 2012–2013. Melting layer is indicated by the bright band signature in vertical profile of rain rate. The ground based drop size measurements indicate that the stratiform rain has more number of small drops whereas convective rain composed of large rain drops. The results indicate that the depolarization due to melting layer is more dominant compared to that due to the drop deformation mechanism at low rain rates.

Summary Nowcasting of heavy rain events using microwave radiometer has been carried out at Kolkata (22.65°N, 88.45°E), a tropical location. Microwave radiometer can produce the temperature and humidity profiles of the atmosphere with fairly good accuracy. Definite changes are observed in temperature and humidity profiles before and at the onset of heavy rain events. Concurrent changes in the brightness temperatures (BT) at 22 GHz and 58 GHz are found to be suitable to nowcast rain. The time derivatives of brightness temperatures at 22 GHz and 58 GHz are used as inputs to the proposed nowcasting model. In addition, the standard deviation of the product of these time derivatives is also considered. The model has been developed using the data of 2011 and validated for rain events of 2012–2013 showing a prediction efficiency of about 90% with alarm generated about 25 min in advance.

Alizarin (DHA), a simple analogue of the anthracycline core was used to form a complex with MnII to see if the complex matches the efficacy of anthracyclines. It was characterized by spectroscopic techniques, mass spectrometry and TGA. In the absence of a single crystal, the structure was obtained by computational techniques. Interaction of the complex with DNA at different ionic strength and pH was compared with anthracyclines to see if it addresses some of the shortcomings of hydroxy-9,10-anthraqunones in general and DHA in particular when compared to anthracyclines. Increased affinity of the complex towards DNA and that its binding constant values do not decrease with increase in pH or decrease in ionic strength of the medium are positive attributes of complex formation. This is significant since cancer patients often experience fluctuation of pH and ionic strength in body fluids during treatment that affect efficacy of drugs. The complex decreases the flow of electrons from NADH to molecular oxygen owing to decreased semiquinone formation; a fact important for controlling cardiotoxicity. Experiments on ROS depletion in HeLa, Hep G2 and WI 38 lung fibroblast cells by the H2DCFDA assay suggests a shift in mechanism for the complex from that of DHA. Loss in efficacy due to decrease in semiquinone formation by the complex is made up by other attributes of complex formation that eventually promote cytotoxicity. Compounds were tried on HeLa, Hep G2 and WI 38 lung fibroblast cells. An effort was made to correlate aspects of semiquinone formation, ROS generation and interaction with DNA with results obtained on two cancer cell lines and a normal cell line.

Interaction of metal ions with biologically active molecules like 5-nitroimidazoles modulates their electronic environment and therefore influences their biological function. In the present work, an antiparasitic drug tinidazole (tnz) was selected and a Cu(II) complex of tnz [Cu2(OAc)4(tnz)2] was prepared. A dinuclear paddle-wheel [Cu2(OAc)4(tnz)2] was obtained by single-crystal XRD and further characterized by spectroscopic techniques and cyclic voltammetry. To understand the biological implications of complex formation, interaction of tnz and its complex was studied with calf thymus DNA, bacterial and fungal cell lines. Results of calf thymus DNA interaction using cyclic voltammetry indicate the overall binding constant (K*) of Cu2(OAc)4(tnz)2 [(59 ± 6) × 104 M−1] is ~17 times greater than that of tnz [(3.3 ± 0.4) × 104 M−1]. Minimum inhibitory concentration values suggest that [Cu2(OAc)4(tnz)2] possesses better antibacterial activity than tnz on both bacterial strains, while the activity on a fungal strain was comparable.

The effect of the earth's atmosphere on radio waves propagating over an earth-space path is a major concern in the design and performance of satellite communications systems. Some characteristics of cloud and its effect on signal propagation has been studied using multi-wavelength radiometer at a tropical location of Kolkata, India. The liquid water content profile shows high values at higher altitude during pre-monsoon season indicating the presence of cloud above zero degree isotherm. Significant change in attenuation value is observed for same liquid water content due to change in temperature and accordingly a suitable relationship is obtained for the present location. The measurements indicate that ~4 dB and ~12 dB attenuation is caused due to cloud at 0.01% outage probability at the Ka and V band, respectively. ITU-R model is found to be overestimating the cloud attenuation over this location and indicate the need for more experimental measurement from tropical region.

Geckos are highly efficient climbers and can run over any kind of surface with impeccable dexterity due to the typical design of their hierarchical foot structure. We have fabricated tilted, i.e., asymmetric, poly(dimethylsiloxane) (PDMS) microflaps of two different densities that mimic the function of the micrometer sized setae on the gecko foot pad. The adhesive properties of these microflaps were investigated in a modified surface forces apparatus; both for normal pure loading and unloading (detachment), as well as unloading after the surfaces were sheared, both along and against the tilt direction. The tilted microflaps showed directional, i.e., anisotropic adhesive behavior when sheared against an optically smooth (RMS roughness ≈ 10 ± 8 nm) SiO2surface. Enhanced adhesion was measured after shearing the flaps along the tilted (gripping) direction and low adhesion when sheared against the tilted (releasing) direction. A Johnson-Kendall-Roberts (JKR) theory using an effective surface energy and modulus of rigidity (stiffness) quantitatively described the contact mechanics of the tilted microflaps against the SiO2surface. We also find an increasing adhesion and stick-slip of the surfaces during detachment which we explain qualitatively in terms of the density of flaps, considering it to increase from 0% (no flaps, smooth surface) to 100% (close-packed flaps, effectively smooth surface). Large energy dissipation at the PDMS-silica interface caused by the viscoelastic behavior of the polymer results in stick-slip peeling and hence an enhanced adhesion energy is observed during the separation of the microflaps surface from the smooth SiO2surface after shearing of the surfaces. For structured multiple contact surfaces, hysteresis as manifested by different loading and unloading paths can be due entirely to the elastic JKR micro-contacts. These results have important implications in the design of biomimetic adhesives. © 2013 American Chemical Society.

We have synthesized model hydrophobic silicone thin films on gold surfaces by a two-step covalent grafting procedure. An amino-functionalized gold surface reacts with monoepoxy-terminated polydimethylsiloxane (PDMS) via a click reaction, resulting in a covalently attached nanoscale thin film of PDMS, and the click chemistry synthesis route provides great selectivity, reproducibility, and stability in the resulting model hydrophobic silicone thin films. The asymmetric interaction forces between the PDMS thin films and mica surfaces were measured with the surface forces apparatus in aqueous sodium chloride solutions. At an acidic pH of 3, attractive interactions are measured, resulting in instabilities during both approach (jump-in) and separation (jump-out from adhesive contact). Quantitative analysis of the results indicates that the Derjaguin-Landau-Verwey-Overbeek theory alone, i.e., the combination of electrostatic repulsion and van der Waals attraction, cannot fully describe the measured forces and that the additional measured adhesion is likely due to hydrophobic interactions. The surface interactions are highly pH-dependent, and a basic pH of 10 results in fully repulsive interactions at all distances, due to repulsive electrostatic and steric-hydration interactions, indicating that the PDMS is negatively charged at high pH. We describe an interaction potential with a parameter, known as the Hydra parameter, that can account for the extra attraction (low pH) due to hydrophobicity as well as the extra repulsion (high pH) due to hydrophilic (steric-hydration) interactions. The interaction potential is general and provides a quantitative measure of interfacial hydrophobicity/hydrophilicity for any set of interacting surfaces in aqueous solution. © 2013 American Chemical Society.

Mytilus foot protein type 6 (mfp-6) is crucial for maintaining the reducing conditions needed for optimal wet adhesion in marine mussels. In this report, we describe the expression and production of a recombinant Mytilus californianus foot protein type 6 variant 1 (rmfp-6.1) fused with a hexahistidine affinity tag in Escherichia coli and its purification by affinity chromatography. Recombinant mfp-6 showed high purification yields of 5-6 mg L(-1) cell culture and excellent solubility in low pH buffers that retard oxidation of its many thiol groups. Purified rmfp-6.1 protein showed high 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity when compared with vitamin C. Using the highly sensitive surface forces apparatus (SFA) technique to measure interfacial surface forces in the nano-Newton range, we show that rmfp-6.1 is also able to rescue the oxidation-dependent adhesion loss of mussel foot protein 3 (mfp-3) at pH 3. The adhesion rescue is related to a reduction of dopaquinone back to 3,4-dihydroxyphenyl-l-alanine in mfp-3, which is the reverse reaction observed during the detrimental enzymatic browning process in fruits and vegetables. Broadly viewed, rmfp-6.1 has potential as a versatile antioxidant for applications ranging from personal products to antispoilants for perishable foods during processing and storage. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1587-1593, 2013.

Radiation-induced double-strand modification of DNA was studied in the absence and presence of sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulfonate (NaQSH 2 ) and its metal (Cu 2+ and Ni 2+ ) complexes in aerated, de-aerated (Argon saturated) and N 2 O saturated aqueous media at pH 7.4. Ethidium bromide, an established DNA intercalator was used to estimate DNA remaining after interaction with γ-radiation, by measuring loss of fluorescence of the ethidium bromide–DNA adduct. In de-aerated (Argon saturated) and N 2 O saturated aqueous media radiation-induced double-strand modification of calf thymus DNA was comparatively less in presence of NaQSH 2 and its Ni(II) complex than standard control indicating the compounds behaved as radio-protectors. However, in presence of the Cu(II) complex radiation-induced double-strand modification increased significantly. In N 2 O saturated medium, double-strand modification of DNA was almost double in all cases than that observed in de-aerated (Argon saturated) medium indicating OH radicals played a major role in modifying DNA. That OH radicals were important was verified by repeating experiments using tertiary-butanol that showed significant decrease in DNA modification. Another important observation was in aerated medium NaQSH 2 , Ni(II)–NaQSH 2 did not show radioprotection while Cu(II)–NaQSH 2 was an almost equally effective radiosensitizer as that observed in N 2 O saturated medium. Role of molecular oxygen as radiosensitizer was thus realized.

Currently, global positioning system (GPS) satellites transmit the Klobuchar coefficients to estimate ionospheric delay for the single-frequency users. These coefficients are broadcast to the users on the basis of seasonal ionospheric variations and average solar flux. In low-latitude Indian region, prediction of the delay using these coefficient is not accurate because of complex behaviour of the ionospheric. In this study, new Klobuchar-like cofficients are generated using regional total electron content data collected from the 18 stations in Indian. Using these coefficients, a novel approach for near-real-time prediction of the ionospheric delay (for every 5 min) is proposed. This approach provides the opportunity to generate the Klobuchar-like coefficients using shorter data sets (1 day) rather than using long-term statistics of several years, as done in the generation of GPS broadcast Klobuchar coefficients. Performance of the prediction is evaluated for the geomagnetic quiet (Ap index 300) days of 2005 and 2007. Prediction accuracy is significantly improved using the single-frequency users of the Regional Navigational Satellite Systems, such as the proposed Indian Regional Navigation Satellite System.

This paper investigates the variability of raindrop size distribution (DSD) and particularly, the role of specific drop sizes in rain integral parameters at a tropical location. Rain DSDs for the years 2006–2007 at Ahmedabad (23°04′ N, 72°38′ E) have been measured using a Disdrometer. Variability of DSD is evaluated and its effect on the integral rain parameters like radar reflectivity, rainfall intensity and attenuation are examined. It is observed that drops with diameter around 4 mm contribute maximum to the radar reflectivity while drops having diameter 3 mm contribute maximum to the rainfall intensity for the present location. Further, a strong effect due to variability of critical drop diameter is observed on rain rate and rain attenuation but the effect is found to be less pronounced on radar reflectivity.

Anthracyclines are broad-spectrum antibiotics that are used against several human cancers. Hydroxy-9,10-anthraquinone compounds closely resemble anthracycline antibiotics from a structural and functional viewpoint. High cost and aspects of toxicity introduce limitations on its use. On complex formation the toxicities of anthracyclines decrease. A close analogue is sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (AS), which is a comparatively cheaper molecule and resembles a good number of anthracycline derivatives. It forms a complex with CuII, [Cu(AS)2]. The complex interacts with calf thymus DNA that was studied by UV/Vis spectroscopy and cyclic voltammetry. The experimental data obtained from the two techniques was analyzed for binding constant and size of the binding site. These results not only corroborate each other but also justify earlier data obtained using fluorescence spectroscopy. An important aspect to this study was that nonlinear curve fitting, which is usually applied for analyzing DNA interaction using fluorescence and absorption spectroscopy, was used for the first time to analyze the interaction of the complex with DNA using cyclic voltammetry by monitoring the change in the reduction peak current (Ip). The DNA binding data provides an insight into a probable mode of action of the hydroxy-9,10-anthraquinones within cells as modification of DNA that leads to cell death is an important aspect in cancer research.

The anthracycline drug adriamycin and its metal complexes are efficient in treating several forms of human cancers with recognized antineoplastic activity attributed to strong interactions with DNA within the target cells. The hydroxy-9,10-anthraquinone unit present in the molecule controls and regulates drug action. Metal ions when linked to adriamycin help to reduce the generation of radicals responsible for toxic side effects. A complex of adriamycin with Ni(II) was prepared and its physicochemical characteristics and DNA-binding ability were compared to a Ni(II) complex of sodium-1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (NaLH2), an analog of adriamycin. Interactions with calf thymus DNA of both complexes were studied by UV-Vis and fluorescence spectroscopy. Binding parameters determined for both complexes agree with each other. Binding of the Ni(II)-adriamycin complex to DNA was five to eight times stronger than for the Ni(II) complex of the hydroxy-9,10-anthraquinone analog, Na2[Ni(NaLH)2Cl2] · ...

Hydroxy-9,10-anthraquinones are cheaper alternatives to anthracycline drugs. They closely resemble anthracycline drugs both from a structural and functional viewpoint. Electrochemical behavior of the Ni(II) complex (Na2[Ni(NaLH)2Cl2]⋅2H2O) of sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (NaLH2), analogue of the core unit of anthracycline anticancer drugs, was studied at physiological pH using cyclic voltammetry. The Ni(II) complex of sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate undergoes diffusion-controlled one-electron reduction that enables performing an electrochemical study on the interaction of the complex with calf thymus DNA. The complex was titrated with increasing concentrations of DNA, and the reduction peak for the unbound complex helped in evaluating binding parameters. Analysis of binding data using nonlinear curve fit in a cyclic voltammetry experiment is the first such attempt. The paper evaluates site size of interaction that also serves as a means to determine stoichiometry of complex formation, between a metal ion and ligand from a DNA interaction study, probably a first of its kind.

Hydroxy-9,10-anthraquinones resemble anthracycline-based anticancer drugs. By varying the pH of the solution, the proton dissociation constants of 1,2,5,8-tetrahydroxy-9,10-anthraquinone (THAQ) were determined. Interaction of THAQ with calf thymus DNA (ct DNA) was studied by UV–Vis spectroscopy to determine the overall binding constant and site size of interaction. The binding constant values (~104) for THAQ interacting with ct DNA at different pH were an order less than that known for anthracyclines. From knowledge of the overall binding constants at different pH values and the first pK of THAQ, the contribution of each form (neutral and monoanionic) towards overall binding with ct DNA could be obtained under physiological conditions. Hence, knowing the contributions of the neutral and monoanionic forms, it now becomes possible to know the overall binding constant for an interaction of THAQ with ct DNA at any pH. The calculated parameters help in understanding the role of the negative charge on the monoanionic form during interaction and suggests suitable chemical modifications that could prevent the development of such negative charges. This could lead to an increase in binding of THAQ to ct DNA. The study also helps to recognize the importance of sugar units in anthracycline anticancer drugs in DNA interaction. Copyright © 2011 John Wiley & Sons, Ltd.

Melting layer height, which is normally assumed to be the limits of rain region, is an important parameter to consider the performance of earth space communication link above 10 GHz. In this paper, the variation of melting layer observed by a vertically looking Micro Rain Radar (MRR) for 3 years has been presented for two different climatic locations in Indian tropical region — Shillong (25°34′ N, 91°53′ E, 1050 m) and Trivandrum (8°29′ N, 76°57′ E, 4 m). The analyses show that the variation is quite significant for different months in Shillong but not for Trivandrum. The height of melting layer shows a strong correlation with ground temperature of these locations. The results agree well with the long term Tropical Rainfall Measuring Mission (TRMM) measurements of melting layer indicating suitability of using TRMM data for such study. A comparison of MRR with the nearest Radiosonde measurement indicates that MRR can have potential application in the study of zero degree isotherm height in rainy conditions. Results also clearly indicate that the assumption of constant rain height is not a valid one for all tropical locations.

Most geckos can rapidly attach and detach from almost any kind of surface. This ability is attributed to the hierarchical structure of their feet (involving toe pads, setal arrays, and spatulae), and how they are moved (articulated) to generate strong adhesion and friction forces on gripping that rapidly relax on releasing. Inspired by the gecko's bioadhesive system, various structured surfaces have been fabricated suitable for robotic applications. In this study, x–y–z asymmetric, micrometer-sized rectangular flaps composed of polydimethylsiloxane (PDMS) were fabricated using massively parallel micro-electromechanical systems (MEMS) techniques with the intention of creating directionally responsive, high-to-low frictional-adhesion toe pads exhibiting properties similar to those found in geckos. Using a surface forces apparatus (SFA), the friction and adhesion forces of both vertical (symmetric) and angled/tilted (x–y–z asymmetric) microflaps under various loading, unloading and shearing conditIons were investigated. It was found that the anisotropic structure of tilted microflaps gives very different adhesion and tribological forces when articulated along different x–y–z directions: high friction and adhesion forces when articulated in the y–z plane along the tilt (+y) direction, which is also the direction of motion, and weak friction and adhesion forces when articulated against the tilt (–y) direction. These results demonstrate that asymmetric angled structures, as occur in geckos, are required to enable the gecko to optimize the requirements of high friction and adhesion on gripping, and low frictional-adhesion on releasing. These properties are intimately coupled to a (also optimum) articulation mechanism. We discuss how both of these features can be simultaneously optimized in the design of robotic systems that can mimic the gecko adhesive system.

The anthracycline drugs adriamycin and daunorubicin, efficient in the treatment of various human cancers, form strong intercalation complexes with DNA. The therapeutic efficacy and toxicity of such anticancer drugs are governed by biochemical reactions of the core dihydroxy-9,10-anthraquinone unit. The high cost and toxic side effects of anthracycline drugs limit their use in cancer therapy. For a few decades, efforts have been made to find cheap, less toxic yet efficient analogues of anthracyclines. This work on 1,4-dihydroxy-9,10-anthraquinone (QH2), a simple analogue of the anthracyclines, was carried out to compare its biochemical properties with anthracyclines. UV-Vis and fluorescence spectroscopic methods were used to analyze interaction of the compound with calf thymus DNA. The data were used to evaluate the binding constant and site size.

Cytotoxic studies using an azo compound HPAN and its Co(II) complex were carried out on non-small lung epithelium carcinoma (A549) cells and peripheral blood mononuclear (PBM) cells. The results obtained suggest that the Co(II) complex is much less toxic toward both cell lines and the decreased toxicity due to the complex was more pronounced with carcinoma A549 cells. An attempt was made to correlate the findings related to cytotoxicity with the interaction of the compounds with DNA using calf thymus DNA as the target. The study was able to conclude that the complex was a relatively weak binder to calf thymus DNA. This information was used to explain the interaction of azo compounds with DNA in peripheral blood mononuclear cells and A549 lung carcinoma cells. It was concluded that the Co(II) complex interacts with DNA to a much lesser extent than HPAN alone. Cyclic voltammetry experiments carried out with HPAN and the Co(II) complex further showed that the presence of the metal ion in the complex prevents reduction of the azo group to such species that are responsible for inducing cytotoxicity. The overall finding was that complex formation with azo compounds might serve as a possible route to curb their toxicities.

Anthracycline drugs show anticancer activity, an ability to inhibit DNA replication and RNA transcription but are costly. This study attempts to see if cheaper hydroxy-9,10-anthraquinones (1,2,4-trihydroxy-9,10-anthraquinone) that structurally resemble anthracyclines mimic its biological interactions and whether it can be a suitable substitute. Proton dissociation at 298 K for THA, pK1 = 4.82 ± 0.05 (phenolic OH at C2) and particularly pK2 = 9.22 ± 0.05 (phenolic OH at C1 and C4) closely resemble those of the anthracyclines. THA undergoes a single step two-electron reduction in aqueous media (pH 7.36) having E1/2 = −0.69 V and two successive single-electron reduction in DMF having E1/2 values −0.70 V and −1.06 V, respectively. CV data showed quasi-reversible nature of THA in aqueous media. E1/2 values of THA were comparable to anthracycline drugs suggesting similarity in redox behavior. Binding studies of THA to ct DNA using UV–Vis and fluorescence spectroscopy were analyzed. Intrinsic binding constant and site size of interaction were (4.80 ± 0.2) × 104 M−1 and (5.96 ± 0.3) bases, respectively. THA, approximately three to five times weaker in binding ct DNA than anthracycline anticancer drugs suggests a role for sugar moieties present in anthracyclines. Anti-leukemic activity studies of THA on cultured MOLT-4 cell lines were performed and apoptosis measured by MTT assay. Result indicates THA to be a potent inducer of apoptosis in MOLT-4 cell line having an IC50 value of 33.8 µM. THA therefore possesses anti-leukemic activity that is comparable to anthracyclines on P388 leukemia and the study reveals that 1,2,4-trihydroxy-9,10-anthraquinone to be a suitable substitute to the costlier anthracyclines. Copyright © 2011 John Wiley & Sons, Ltd.

The electron transfer reactions involving quinones, hydroquinones, and catechols are very important in many areas of chemistry, especially in biological systems. The therapeutic efficiency as well as toxicity of anthracycline anticancer drugs, a class of anthraquinones, is governed by their electrochemical properties. Other quinones serve as important functional moiety in various biological systems like electron-proton carriers in the respiratory chain and their involvement in photosynthetic electron flow systems. The present paper summarizes literatures on the reduction of quinones in different solvents under various conditions using different electrochemical methods. The influence of different reaction conditions including pH of the media, nature of supporting electrolytes, nature of other additives, intramolecular or intermolecular hydrogen bonding, ion pair formation, polarity of the solvents, stabilization of the semiquinone and quinone dianion, catalytic property, and adsorption at the electrode surface, are discussed and relationships between reaction conditions and products formed have been presented.

Rain attenuation is an important aspect of signal propagation above 10GHz frequency. The attenuation time series generation from point rain rate measurement is crucial due to unavailability of actual signal measurements. In this paper, a simple and realistic approach has been demonstrated for better estimation of rain attenuation using Ku-band signal propagation data and ground rain rate measurements at Kolkata, India. The ITU-R model of rain attenuation has been modifled by incorporating an efiective slant path model. The efiective slant path has been estimated and modelled in terms of a power-law relationship of rain rate data of 2007{2008. The methodology has been validated with the measured data of 2006. Comparison with ITU-R and SAM clearly demonstrates the improved predictability of the proposed model at the present tropical location.

Large area Cathode Pad Chambers (CPC) with inner and outer radii of 23.7 cm and 117 cm respectively have been fabricated and tested for 2nd Tracking station of Muon Spectrometer of ALICE.

Two terdentate NNO donor Schiff base ligands CH 3 C(OH) CHC(CH 3 ) NCH 2 C 5 H 4 N [ HL 1 ] and C 6 H 5 C(OH) CHC(CH 3 ) NCH 2 C 5 H 4 N [ HL 2 ] were used to synthesize two mononuclear square planar copper(II) complexes, [Cu L 1 (CF 3 COO)] ( 1 ) and [Cu L 2 (CF 3 COO)] ( 2 ). The complexes were characterized by elemental analyses, FT-IR, UV–vis spectral methods and their structures were established by single crystal X-ray diffraction study. The biochemical activity of the complexes towards DNA binding were performed using absorbance and fluorescence titration methods and their mode of binding with calf thymus DNA has been established by viscosity measurement technique.

Satellite Based Augmentation Systems (SBAS) for navigational services rely heavily on the accu- rate estimation of the Total Electron Content (TEC) along the slant ray path. The Wide Area Augmentation Sys- tem (WAAS) estimates and transmits the delay corrections by assuming a 5x5 degree ionospheric grid (in lati- tude and longitude) at 350 km altitude using a single shell model. The user interpolates these delay values at hislher position using bilinear interpolation. In this paper, the effect of the variation of grid size on the interpo- lation of the TEC is analyzed using TEC data from the year 2005. It is observed that the reduction of grid size from 5x5 to I xl degree and the choice of Kriging technique to interpolate the TEC both at the IGP as well as at the user side result in more accurate estimation of the delay for the GPS Aided Geo Augmented Navigation (GAGAN) system over the Indian region.

The microstructure of rain has been studied with observations using a vertical looking Micro Rain Radar (MRR) at Ahmedabad (23.06°N, 72.62°E), a tropical location in the Indian region. The rain height, derived from the bright band signature of melting layer of radar reflectivity profile, is found to be variable between the heights 4600 m and 5200 m. The change in the nature of rain, classified on the basis of radar reflectivity, is also observed through the MRR. It has been found that there are three types of rain, namely, convective, mixed and stratiform rain, prevailing with different vertical rain microstructures, such as, Drop Size Distribution (DSD), mean drop size, rain rate, liquid water content and average fall speed of the drops at different heights. It is observed that the vertical DSD profile is more inhomogeneous for mixed and stratiform type rain than for convective type rain. It is also found that the large number of drops of size

Rain drop size distributions (DSD) are measured with disdrometers at flve difierent climatic locations in the Indian tropical region. The distribution of drop size is assumed to be lognormal to model the rain attenuation in the frequency range of 10{100GHz. The rain attenuation is estimated assuming single scattering of spherical rain drops. Difierent attenuation characteristics are observed for difierent regions due to the dependency of DSD on climatic conditions. A comparison shows that signiflcant difierences between ITU-R model and DSD derived values occur at high frequency and at high rain rates for difierent regions. At frequencies below 30GHz, the ITU-R model matches well with the DSD generated values up to 30mm/h rain rate but difier above that. The results will be helpful in understanding the pattern of rain attenuation variation and designing the systems at EHF bands in the tropical region.

Copper(II) forms a complex with sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (sodium quinizarin-2-sulphonate, NaQSH(2)), an analogue of the core unit of anthracycline antibiotics used in the treatment of cancer. The 1:2 metal-ligand complex is formed in aqueous solution at neutral and acidic pH while in alkaline pH both 1:1 and 1:2 species are formed. The effective stability constant of the 1:2 metal-ligand complex is 9.64x10(16) while that of the 1:1 metal-ligand complex is 9.4x10(9). The 1:2 complex Cu(NaQSH)(2)(H(2)O)(2) was synthesized and characterized by different techniques in solid state and in solution. The complex Cu(NaQSH)(2)(H(2)O)(2) interacts with calf thymus DNA which was studied by fluorescence spectroscopy. The binding constant and site size for the interaction with DNA were determined.

The anthracycline drugs, adriamycin and daunorubicin, efficient in the treatment of various human cancers, form strong intercalation complexes with DNA. The therapeutic efficiency and toxic properties of the drugs are associated with electron transfer processes, which correlate well with the redox behaviour of the compounds. Sodium 1,4-dihydroxy 9,10-anthraquinone-2-sulphonate (sodium quinizarin-2-sulphonate, NaLH2) (Na-Qz-2S) is a molecule that resembles anthracycline drugs and has a simpler structure in comparison to these drugs. Two electrons in the course of chemical action reduce this molecule like the anthracyclines. Electrochemical methods were used to identify this process. UV-Vis and fluorescence spectroscopy were used to analyse binding of the compound to calf thymus DNA. The binding constant and site size were evaluated for Na-Qz-2S and the same compared to that of the anthracyclines. Such comparisons are essential in order to understand whether the simpler hydroxy-anthraquinones can be a substitute for anthracycline drugs in cancer chemotherapy. Copyright © 2009 John Wiley & Sons, Ltd.

Ionizing radiation when allowed to fall upon cells or DNA, the radicals produced modify the base-pair region of the double strands. Radiation-induced double-strand modifications in calf thymus DNA were detected using Ni(II) and Fe(III) complexes of 1,2 dihydroxy 9,10 anthraquinone (DHA). 60 Co was used as the source for γ -radiation and ethidium bromide (EB) as the fluorescent dye for detecting double-strand modifications caused in DNA. Results show that the Fe(III)–DHA complex is more efficient in modifying the base-pair region in double-stranded DNA in comparison to DHA or the Ni(II)–DHA complex.

Future Satellite Based Navigation Systems based on GPS, like US Wide Area Augmentation Sysytem (WAAS), are of global interest to the scientific community. Precise estimation of ionospheric delay is most crucial for successful implementation of the systems. Due to the complex ionospheric structure and large variation of Total Electron Content (TEC) in low latitudes, it is necessary to compare and validate the efficiency of the existing algorithms in this region. In this study, performances of the various interpolation algorithms for TEC calculation at ionospheric grid point (IGP) and user position for gridbased Single Shell Model have been tested for 72 test days of 2005. Based on the results obtained from this analysis, it has been found that, for the Indian region, it would be more suitable to use Ordinary Kriging in place of Planar Fit to estimate delay at an IGP (as used by US WAAS). It has also been found that Ordinary Kriging performs better than the Bilinear Interpolation technique at the user end.

The active fraction and/or compounds of Calendula officinalis responsible for wound healing are not known yet. In this work we studied the molecular target of C. officinalis hydroethanol extract (CEE) and its active fraction (water fraction of hydroethanol extract, WCEE) on primary human dermal fibroblasts (HDF). In vivo, CEE or WCEE were topically applied on excisional wounds of BALB/c mice and the rate of wound contraction and immunohistological studies were carried out. We found that CEE and only its WCEE significantly stimulated the proliferation as well as the migration of HDF cells. Also they up-regulate the expression of connective tissue growth factor (CTGF) and α-smooth muscle actin (α-SMA) in vitro. In vivo, CEE or WCEE treated mice groups showed faster wound healing and increased expression of CTGF and α-SMA compared to placebo control group. The increased expression of both the proteins during granulation phase of wound repair demonstrated the potential role of C. officinalis in wound healing. In addition, HPLC-ESI MS analysis of the active water fraction revealed the presence of two major compounds, rutin and quercetin-3-O-glucoside. Thus, our results showed that C. officinalis potentiated wound healing by stimulating the expression of CTGF and α-SMA and further we identified active compounds. Copyright © 2016 John WileySons, Ltd.

Variation of pyridyl based receptors around a Cu(II) center results in structural diversity allowing redox triggered Cu(II)/Cu(I) fluorescence switch for intracellular Cu(I) imaging. Single crystal X-ray structures of 2-hydroxy-6-methylnicotinic acid (L1), its mono nuclear Cu(II) complex, viz. [Cu(L1)(2)(H2O)(SO4)]center dot 2H(2)O (C1a), polymeric Cu(II) complex (C1b) and a dinuclear Cu(II) complex of 2-(naphthalen-2-ylmethylsulfanyl)nicotinic acid (L4), viz. [Cu-2(L4)(4)(H2O)(2)]center dot 1.12H(2)O (C4) with a Cu-Cu distance of 2.6028(7) angstrom are reported. Moreover, C1a interacts with calf thymus DNA, which is useful for disruption of normal DNA activity with plausible applications in biology (binding constant, K' = 1.56 x 10(4)). Chemical or electrochemical reduction of C1a generates a fluorescent Cu(I) complex. The lowest detection limit of L1 for Cu(I) is 50 mu M. The association constant of L1 for Cu+ is 7.09 x 10(2). Quenching constants of Cu(II) for L1, L2, L3 and L4 are 4 x 10(5), 4.2 x 10(6), 8.9 x 10(5) and 4.4 x 10(6), respectively. The magnetic behavior of C1b indicates a ferromagnetic one-dimensional solid.