Orchestration of Haemophilus influenzae RecJ Exonuclease by Interaction with Single-Stranded DNA-Binding Protein

RecJ exonuclease plays crucial roles in several DNA repair and recombination pathways, and its ubiquity in bacterial species points to its ancient origin and vital cellular function. RecJ exonuclease from Haemophilus influenzae is a 575-amino-acid protein that harbors the characteristic motifs conserved among RecJ homologs. The purified protein exhibits a process 5'-3' single-stranded-DNA-specific exonuclease activity. The exonuclease activity of H. influenzae RecJ (HiRecJ) was supported by Mg2+ or Mn2+ and inhibited by Cd2+ suggesting a different mode of metal binding in HiRecJ as compared to Escherichia coli RecJ (EcoRecJ). Site-directed mutagenesis of highly conserved residues in HiRecJ abolished enzymatic activity. Interestingly, substitution of alanine for aspartate 77 resulted in a catalytically inactive enzyme that bound to DNA with a significantly higher affinity as compared to the wild-type enzyme. Noticeably, steady-state kinetic studies showed that H. influenzae single-stranded DNA-binding protein (HiSSB) increased the affinity of HiRecJ for single-stranded DNA and stimulated its exonuclease activity. HiSSB, whose C-terminal tail had been deleted, failed to enhance RecJ exonuclease activity. More importantly, HiRecJ was found to directly associate with its cognate single-stranded DNA-binding protein (SSB), as demonstrated by various in vitro assays, Interaction studies carried out with the truncated variants of HiRecJ and HiSSB revealed that the two proteins interact via the C-terminus of SSB protein and the core-catalytic domain of RecJ. Taken together, these results emphasize direct interactio between RecJ and SSB, which confers functional cooperativity to these two proteins. In addition, these results implicate SSB as being involved in the recruitment of RecJ to DNA and provide insights into the interplay between these proteins in repair and recombination pathways.

Melanopsin mediated post-illumination pupil response in early age-related macular degeneration

Purpose To determine whether melanopsin expressing intrinsically photosensitive Retinal Ganglion Cell (ipRGC) inputs to the pupil light reflex (PLR) are affected in early age-related macular degeneration (AMD). Methods The PLR was measured in 40 participants (20 early AMD and 20 age-matched controls) using a custom-built Maxwellian-view pupillometer. Sinusoidal stimuli (0.5 Hz, 11.9 s duration, 35.6° diameter) were presented to the study eye and the consensual pupil response was measured for stimuli with high melanopsin excitation (464nm; blue) and with low melanopsin excitation (638 nm; red) that biased activation to the outer retina. Two melanopsin PLR metrics were quantified: the Phase Amplitude Percentage (PAP) during the sinusoidal stimulus presentation and the Post-Illumination Pupil Response (PIPR). The PLR during stimulus presentation was analyzed using latency to constriction, transient pupil response and maximum pupil constriction metrics. Diagnostic accuracy was evaluated using receiver operating characteristic (ROC) curves. Results The blue PIPR was significantly less sustained in the early AMD group (p<0.001). The red PIPR was not significantly different between groups (p>0.05). The PAP and blue stimulus constriction amplitude were significantly lower in the early AMD group (p < 0.05). There was no significant difference between groups in the latency or transient amplitude for both stimuli (p>0.05). ROC analysis showed excellent diagnostic accuracy for the blue PIPR metrics (AUC>0.9). Conclusions This is the initial report that the melanopsin controlled PIPR is dysfunctional in early AMD. The non-invasive, objective measurement of the ipRGC controlled PIPR has excellent diagnostic accuracy for early AMD.

Structure and Rheology of Cationic Molecular Hydrogels of Quinuclidine Grafted Bile Salts. Influence of the Ionic Strength and Counter-Ion type

Quinuclidine grafted cationic bile salts are forming salted hydrogels. An extensive investigation of the effect of the electrolyte and counterions on the gelation has been envisaged. The special interest of the quinuclidine grafted bile salt is due to its broader experimental range of gelation to study the effect of electrolyte. Rheological features of the hydrogels are typical of enthalpic networks exhibiting a scaling law of the elastic shear modulus with the concentration (scaling exponent 2.2) modeling cellular solids in which the bending modulus is the dominant parameter. The addition of monovalent salt (NaCl) favors the formation of gels in a first range (0.00117 g cm-3 (0.02 M) < TNaCl < 0.04675 g cm-3 (0.8 M)). At larger salt concentrations, the gels become more heterogeneous with nodal zones in the micron scale. Small-angle neutron scattering experiments have been used to characterize the rigid fibers ( ≈ 68 Å) and the nodal zones. Stress sweep and creeprecovery measurements are used to relate the lack of linear viscoelastic domain to a mechanism of disentanglement of the fibers from their associations into fagots. The electrostatic interactions can be screened by addition of salt to induce a progressive evolution toward flocculation. SEM, UV absorbance, and SAXS study of the Bragg peak at large Q-values complete the investigation.

Charge transport in transparent conductors: A comparison

A comparative investigation of charge transport properties is presented, for polymeric [poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)], single-wall carbon nanotube (SWNT) and inorganic (indium tin oxide, ITO), transparent conducting electrodes. The polymeric and nanotube systems show hopping transport at low temperatures, in contrast with the disordered-metal transport in ITO. The low temperature magnetotransport (up to 11 T) and high electric-field transport (up to 500 V/cm) indicate the significant role of nanoscopic scale disorder for charge transport in polymer and nanotube based systems. The results show that characteristic length scales like localization length correlates with the nanomorphology in these systems. Further, the high frequency conductivity measurements (up to 30 MHz) in PEDOT:PSS and SWNT follow the extended pair approximation model [σ(ω)=σ(0)[1+(ω/ω0)s].

Metal chelates in vinyl polymerization: Bulk polymerization of acrylonitrile initiated by Cu(II)-imine complexes

This article deals with the kinetics and mechanism of acrylonitrile (AN) polymerization initiated by Cu(II)-4-anilino 3-pentene 2-one[Cu(II)ANIPO], Cu(II)-4-p-toluedeno 3-pentene 2-one [Cu(II)TPO], and Cu(II)-4-p-nitroanilino 3-pentene 2-one [Cu(II)NAPO] in bulk at 60°C. The polymerization is free radical in nature. The exponent of initiator(I) is 0.5. The initiation step is a complex formation between the chelate and monomer and subsequent decomposition of the intermediate complex giving rise to free radical and Cu(I). This is substantiated by ultraviolet (UV) and electron spin resonance (ESR) studies. The activation energies and kinetic and chain transfer constants have also been evaluated.

Architecture Optimization of Aerospace Computing Systems

Simultaneous consideration of both performance and reliability issues is important in the choice of computer architectures for real-time aerospace applications. One of the requirements for such a fault-tolerant computer system is the characteristic of graceful degradation. A shared and replicated resources computing system represents such an architecture. In this paper, a combinatorial model is used for the evaluation of the instruction execution rate of a degradable, replicated resources computing system such as a modular multiprocessor system. Next, a method is presented to evaluate the computation reliability of such a system utilizing a reliability graph model and the instruction execution rate. Finally, this computation reliability measure, which simultaneously describes both performance and reliability, is applied as a constraint in an architecture optimization model for such computing systems. Index Terms-Architecture optimization, computation

Structure and interactions of aspirin-like drugs

A pre-requisite for the elucidation of the mechanism of action of aspirin-like drugs, which are believed to exert their pharmacological effects through the inhibition of prostaglandin biosynthesis, is an understanding of their molecular geometry, the non-covalent interactions they are likely to be involved in, and the geometrical and the electronic consequences of such interactions. This has been sought to be achieved through the x-ray analysis of these drug molecules and their crystalline complexes with other suitable molecules. The results obtained from such studies have been discussed in terms of specific typical examples. For instance, antipyrine can form metal and hydrogen-bonded complexes; phenylbutazone can form ionic complexes with basic molecules. Complex formation is accompanied by characteristic changes in the molecular geometry and the electronic structure in both the cases. The results obtained so far appear to indicate that the important common invariant structural features of the fenamates, deduced from crystal structures, are retained even when complexation takes place.

Cholinergic Muscarinic Receptors in Human Fetal Brain: Ontogeny of [3H]Quinuclidinyl Benzilate Binding Sites in Corpus Striatum, Brainstem, and Cerebellum

The ontogeny of muscarinic receptors was studied in human fetal striatum, brainstem, and cerebellum to investigate general principles of synaptogenesis as well as the physiological balance between various chemical synapses during development in a given region of the brain. [3H]Quinuclidinyl benzilate ([-'H]QNB) binding was assayed in total particulate fraction (TPF) from various parts of brain. In the corpus striatum, QNB binding sites are present at 16 weeks of gestation (average concentration 180 fmol/mg protein of TPF), slowly increase up to 24 weeks (average concentration 217 fmol/mg protein), and rapidly increase during the third trimester to 480 fmol/mg protein of TPF. In contrast, dopaminergic receptors exist as two subpopulations. one with low affinity and the other with high affinity up to the 24th week of gestation; all of them acquire the highaffinity characteristic during the third trimester. In brainstem, the muscarinic receptors show maximum concentration by 16 weeks of age (360 fmolimg protein of TPF). Subsequently the muscarinic receptor concentration shows a gradual decline in the brainstem. In cerebellum, except for a slight increase at 24 weeks (average concentration 90 fmol/mg protein of TPF), the receptor concentration remained nearly constant at about 60-70 fmolimg protein of TPF throughout fetal life. This study demonstrates that the ontogeny of muscarinic receptors varies among the different regions, and the patterns observed suggest that receptor formation occurs principally in the third trimester. Also noteworthy is the finding that the QNB binding sites decreased in all regions of the human brain during adult life. Key Words: Cholinergic muscarinic receptors-Quinuclidinyl benzilate-Corpus striaturn-Brainstem-Cerebellum. Ravikumar B. V. and Sastry P. S. Cholinergic muscarinic receptors in human fetal brain: Ontogeny of [3H]quinuclidinyl benzilate binding sites in corpus striatum, brainstem, and cerebellum. J. Neurochem. 45, 1948- 1950 (1985).

Influence of time step in the simulation modelling of evapotranspiration

Three simulations of evapotranspiration were done with two values of time step,viz 10 min and one day. Inputs to the model were weather data, including directly measured upward and downward radiation, and soil characteristics. Three soils were used for each simulation. Analysis of the results shows that the time step has a direct influence on the prediction of potential evapotranspiration, but a complex interaction of this effect with the soil moisture characteristic, rate of increase of ground cover and bare soil evaporation determines the actual transpiration predicted. The results indicate that as small a time step as possible should be used in the simulation.

LIII absorption edge studies of mixed valent cerium intermetallics and related systems

LIII absorption edge measurements clearly delineate 3+ and 4+ states of Ce. Absorption edges of 3+ compounds show a single peak, while those of 4+ compounds show two peaks, both appearing at higher energies than the characteristic peaks of 3+ compounds. In systems where there is interconfigurational fluctuation, features due to both 3+ and 4+ states are distinctly seen.

Thermal conductivity of a new carbon nanotube analog: The diamond nanothread

Based on the non-equilibrium molecular dynamics simulations, we have studied the thermal conductivities of a novel ultra-thin one-dimensional carbon nanomaterial - diamond nanothread (DNT). Unlike single-wall carbon nanotube (CNT), the existence of the Stone-Wales transformations in DNT endows it with richer thermal transport characteristics. There is a transition from wave-dominated to particle-dominated transport region, which depends on the length of poly-benzene rings. However, independent of the transport region, strong length dependence in thermal conductivity is observed in DNTs with different lengths of poly-benzene ring. The distinctive SW characteristic in DNT provides more degrees of freedom to tune the thermal conductivity not found in the homogeneous structure of CNT. Therefore, DNT is an ideal platform to investigate various thermal transport mechanisms at the nanoscale. Its high tunability raises the potential to design DNTs for different applications, such as thermal connection and temperature management.

A pattern adaptive thinning algorithm

A simple sequential thinning algorithm for peeling off pixels along contours is described. An adaptive algorithm obtained by incorporating shape adaptivity into this sequential process is also given. The distortions in the skeleton at the right-angle and acute-angle corners are minimized in the adaptive algorithm. The asymmetry of the skeleton, which is a characteristic of sequential algorithm, and is due to the presence of T-corners in some of the even-thickness pattern is eliminated. The performance (in terms of time requirements and shape preservation) is compared with that of a modern thinning algorithm.

Phase relations and dielectric properties of BaTi03 ceramics heavily substituted with neodymium

Investigations on the phase relations and dielectric properties of (1 -x)BaTiO3 + xNd2/3TiO 3 (BNT) ceramics sintered in air below 1650 K have been carried out. X-ray powder diffraction studies indicate apparent phase singularity for compositions with x < 0.3. Nd2Ti207 is detected at higher neodymium concentrations. The unit cell parameter changes continuously with neodymium content, and BaTiO3 is completely cubic at room temperature with x -- 0.0525, whereas electron diffraction studies indicate that the air-sintered BNT ceramics with x > 0.08 contain additional phases that are partly amorphous even to an electron beam. SEM observations reveal that BaTiO3 grains are mostly covered by a molten intergranular phase, and show the presence of randomly distributed Nd2Ti207 grains. Energy dispersive X-ray analysis shows the Ba-Nd-Ti ternary composition of the intergranular phase. Differential thermal analysis studies support the formation of a partial melt involving dissolution-precipitation of boundary layers of BaTiO3 grains. These complex phase relations are accounted for in terms of the phase instability of BaTiO3 with large cation-vacancy concentration as a result of heavy Nd 3+ substitution. The absence of structural intergrowth in (1 - x)BaTiO3 + xNd2/3TiO3 under oxidative conditions leads to a separation of phases wherein the new phases undergo melting and remain X-ray amorphous. BNT ceramics with 0.1 < x < 0.3 have ~eff >~ 104 with tan 6 < 0.1 and nearly flat temperature capacitance characteristics. The grain-size dependence of ee,, variations of ~eff and tan 6 with the measuring frequency, the non-ohmic resistivities, and the non-linear leakage currents at higher field-strengths which are accompanied by the decrease in eeff and rise in tan 3, are explained on the basis of an intergranular (internal boundary layer) dielectric characteristic of these ceramics.

Expansivity of liquid (cyclohexane + acetic anhydride) near its critical solution point

A simple volume dilatometer is described for the precise measurements of volume changes as a function of temperature in liquid mixtures. The expansivity of (cyclohexane + acetic anhydride) in the critical region was measured. The critical solution temperature Tc was approached to within 9 mK. For T > (Tc + 0.3 K), the results results follow both a logarithmic and a power-law behaviour with an exponent ≈ 1/8. But for T < (Tc + 0.3 K), the results seem to be affected possibly by gravity or temperature gradients. In this region, the expected expansivity anomaly is rounded off to a cusp. The expansivity shows a reduced anomaly for off-critical compositions. A discussion of the local extremum and a correlation between negative expansivity and the resistivity anomaly are also given.

Effect of a magnetic field on the flow and blood oxygenation in channels of variable cross-section

The effect of a magnetic field on the flow and oxygenation of an incompressible Newtonian conducting fluid in channels with irregular boundaries has been investigated. The geometric parameter δ, which is a ratio of the mean half width of the channel d to the characteristic length λ along the channel over which the significant changes in the flow quantities occur, has been used for perturbing the governing equations. Closed form solutions of the various order equations are presented for the stream function. The equations for oxygen partial pressure remain nonlinear even after perturbation, therefore a numerical solution is presented. The expressions for shear stress at a wall and pressure distributions are derived. Here the separation in the flow occurs at a higher Reynolds number than the corresponding non-magnetic case. It is found that the magnetic field has an effect on local oxygen concentration but has a little effect on the saturation length.