Laser spectroscopic studies of Tb3+-doped oxyfluoroborate glass

Tb3+-doped oxyfluoroborate glasses have been prepared for different concentrations of Tb. The absorption, fluorescence and photoacoustic spectra of these have been recorded and studied. It is marked that the fluorescence intensity of different fluorescence transitions decreases with the increase of Tb ion concentration in the glass. This quenching at higher concentration is due to the energy transfer among the excited and nearest neighbor unexcited Tb ions in the glass. The lifetime measurement confirms it, as the lifetime of a particular state was found to decrease with the increase of Tb ion concentration in the glass. The mechanism of the energy transfer process was determined to involve quadrupole quadrupole interaction. We have also studied the energy transfer from Tb3+-->Pr3+ when both the rare earths are doped together in the glass. A decrease in the lifetime of the 5D4 level of Tb3+ with the increase of Pr3+ concentration confirms this.     

Deterministic inhomogeneous inertia ratchets

We study the deterministic dynamics of a periodically driven particle in the underdamped case in a spatially symmetric periodic potential. The system is subjected to a space-dependent friction coefficient, which is similarly periodic as the potential but with a phase difference. We observe that frictional inhomogeneity in a symmetric periodic potential mimics most of the qualitative features of deterministic dynamics in a homogeneous system with an asymmetric periodic potential. We point out the need of averaging over the initial phase of the external drive at small frictional inhomogeneity parameter values or analogously low potential asymmetry regimes in obtaining ratchet current. We also show that at low amplitudes of the drive, where ratchet current is not possible in the deterministic case, noise plays a significant role in realizing ratchet current.     

Recognition of Hg(2+) using diametrically disubstituted cyclam unit

A newly synthesized 1,4,8,11-tetraazacyclotetradecane derivative (L), functionalized with a diazo moiety as the reporter functionality, is found to bind specifically to Hg(2+) with an associated change in color that could be visually detected. With biologically benign β-CD, it forms an inclusion complex (L·2β-CD), which shows a much higher solubility in water, and this helps in developing a more intense color on binding to Hg(2+) in a CH(3)CN-HEPES buffer medium. The nontoxic nature of L was checked with the living cells of a Gram negative bacterium, Pseudomonas putida . Further, experiments revealed that these two reagents could be used as staining agents for the detection of Hg(2+) present in this microorganism.     

FAIR@Germany

The proposed international Facility for Antiproton and Ion Research (FAIR) at GSI-Darmstadt, will be a source of exotic radionuclidic beam and is expected to be operational in 2016. The facility will deliver 2 GeV/u to 45 GeV/u beam covering the entire range of the periodic table with the intensities three orders of magnitude higher than that available anywhere in the world today. This facility will serve all areas of fundamental sciences including nuclear physics, physics at extreme density conditions like neutron stars, plasma and laser physics, hadron physics and applied areas in chemistry, biology and material sciences. In this article, we discuss briefly the FAIR facility, with special emphasis on Indian participation.     

Zn(II)-cyclam based chromogenic sensors for recognition of ATP in aqueous solution under physiological conditions and their application as viable staining agents for microorganism

Two chromogenic complexes, L.Zn (where L is (E)-4-((4-(1,4,8,11-tetraazacyclotetradecan-1-ylsulfonyl)phenyl)diazenyl)-N,N-dimethylaniline) and its [2]pseudorotaxane form (α-CD.L.Zn), were found to bind preferentially to adenosine triphosphate (ATP), among all other common anions and biologically important phosphate (AMP, ADP, pyrophosphate, and phosphate) ions in aqueous HEPES buffer medium of pH 7.2. Studies with live cell cultures of prokaryotic microbes revealed that binding of these two reagents to intercellular ATP, produced in situ, could be used in delineating the gram-positive and the gram-negative bacteria. More importantly, these dyes were found to be nontoxic to living microbes (eukaryotes and prokaryotes) and could be used for studying the cell growth dynamics. Binding to these two viable staining agents to intercellular ATP was also confirmed by spectroscopic studies on cell growth in the presence of different respiratory inhibitors that influence the intercellular ATP generation.     

An expedient, fast and competent synthesis of organic dithiocarbamates over nanocrystalline MgO in water at room temperature

A new, expeditious, efficient and eco-friendly method for the synthesis of organic dithiocarbamates has been achieved at room temperature using basic nanocrystalline MgO catalyst in aqueous condition. The method has been applied for the synthesis of a range of compounds with variable functionalities in excellent yield and selectivity.     

Study of silver nanoparticle-hemoglobin interaction and composite formation

Nanoscience is now an expanding field of research and finds potential application in biomedical area, but it is limited due to lack of comprehensive knowledge of the interactions operating in nano-bio system. Here, we report the studies on the interaction and formation of nano-bio complex between silver nanoparticle (AgNP) and human blood protein hemoglobin (Hb). We have employed several spectroscopic (absorption, emission, Raman, FTIR, CD, etc.) and electron diffraction techniques (FE-SEM and HR-TEM) to characterize the Hb-AgNP complex system. Our results show the Hb-AgNP interaction is concentration and time dependent. The AgNP particle can attach/come closer to heme, tryptophan, and amide as well aromatic amine residues. As a result, the Hb undergoes conformational change and becomes unfolded through the increment of β-sheet structure. The AgNP-Hb can form charge-transfers (CT) complex where the Hb-heme along with the AgNP involved in the electron transfer mechanism and form Hb-AgNP assembled structure. The electron transfer mechanism has been found to be dependent on the size of silver particle. The overall study is important in understanding the nano-bio system and in predicting the avenues to design and synthesis of novel nano-biocomposite materials in material science and biomedical area.     

Interaction of glucose with hemoglobin: a study in aqueous solution and at the air-water interface using the Langmuir-Blodgett technique

Here, we report the glycosylation of human adult hemoglobin (Hb) studied in aqueous solution and at the air-water interface by the Langmuir-Blodgett (LB) technique. Pressure-area (π-A) and pressure-time (π-t) measurements show that the concentration of glucose (GLC) and interaction time have an effect on Hb molecular area as well as on surface activity. Solution studies by UV-vis absorption and emission spectroscopy show that the GLC can alter the local conformation of Hb to some extent at the tryptophan and heme residues. CD spectroscopic studies in solution indicate that the α-helix content increases in the presence of GLC at the secondary structure level, which may be the cause of an increased adsorption rate of Hb. Also, secondary structure calculation using FTIR technique in the LB film follows the decrease in α-helix and increase in β-sheet structure as well as the formation of intermolecular aggregates. AFM images of Hb in the LB film indicate the transition from globular to an ellipsoid-like structure of Hb in the presence of GLC. FTIR studies of the LB film support the AFM imaging and the analysis of π-t kinetics. The molecular docking study revealed that Val 1 and Lys 132 are the most favorable docked sites along with some other sites such as Hem 147, Trp 37, Asp 94, Tyr 145, Leu 91, His 143, Glu 43 etc. The overall study may predict the processes of interactions with the increased concentration of GLC on Hb as well as on other long lived proteins.     

Novel Sensing Assembly Comprising Engineered Gold Dendrites and MWCNT‐AuNPs Nanohybrid for Acetaminophen Detection in Human Urine

A layered nanohybrid comprising of multi walled carbon nanotubes(MWCNT)‐gold nanoparticles (AuNPs) has been designed as a matrix for the development of Au dendritic nanostructures (AuDN) with enhanced catalytic activity. The developed sensor matrix was thoroughly characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), and energy dispersive X‐ray spectroscopy (EDX). The developed sensor probe MWCNT‐AuNPs/AuDN over glassy carbon electrode (GCE) was used for the label free detection of acetaminophen (AP), a commonly used drug associated with hepatotoxicity when overdosed, as a model molecule. The final sensor probe was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV). The sensor shows excellent analytical performances with a linear dynamic range (LDR) of 100 to 7500 nM, and a low limit of detection (LOD) of 2.12 (±0.03) nM, which is better than recently reported AP sensors. The practical application / clinical possibilities of the final sensor were evaluated by real sample analysis in human urine by spike and recovery method, where the AP recoveries were found in between 92 % to 96 %. The sensor probe shows negligible response towards co‐existing interfering molecules like glucose, urea, uric acid and various amino acids, which are commonly found in real samples (p<0.001, n=3). The shelf life of the sensor probe was evaluated and found to be stable for 8 weeks. The fabricated sensor probe using MWCNT‐AuNPs/AuDN is easy to fabricate, simple, robust, and able to detect AP in urine with high recoveries shows its possibilities to be used in clinical settings.