Inhibition of Tyrosine Phosphorylation of Sperm Flagellar Proteins, Outer Dense Fiber Protein-2 and Tektin-2, Is Associated With Impaired Motility During Capacitation of Hamster Spermatozoa

In mammals, acquisition of fertilization competence of spermatozoa is dependent on the phenomenon of sperm capacitation. One of the critical molecular events of sperm capacitation is protein tyrosine phosphorylation. In a previous study, we demonstrated that a specific epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor, tyrphostin-A47, inhibited hamster sperm capacitation, accompanied by a reduced sperm protein tyrosine phosphorylation. Interestingly, a high percentage of tyrphostin-A47-treated spermatozoa exhibited circular motility, which was associated with a distinct hypo-tyrosine phosphorylation of flagellar proteins, predominantly of Mr 45,000-60,000. In this study, we provide evidence on the localization of capacitation-associated tyrosine-phosphorylated proteins to the nonmembranous, structural components of the sperm flagellum. Consistent with this, we show their ultrastructural localization in the outer dense fiber, axoneme, and fibrous sheath of spermatozoa. Among hypo-tyrosine phosphorylated major proteins of tyrphostin-A47-treated spermatozoa, we identified the 45 kDa protein as outer dense fiber protein-2 and the 51 kDa protein as tektin-2, components of the sperm outer dense fiber and axoneme, respectively. This study shows functional association of hypo-tyrosine-phosphorylation status of outer dense fiber protein-2 and tektin-2 with impaired flagellar bending of spermatozoa, following inhibition of EGFR-tyrosine kinase, thereby showing the critical importance of flagellar protein tyrosine phosphorylation during capacitation and hyperactivation of hamster spermatozoa.

Design of a Non-glycosylated Outer Domain-derived HIV-1 gp120 Immunogen That Binds to CD4 and Induces Neutralizing Antibodies

The outer domain (OD) of the HIV-1 envelope glycoprotein gp120 is an important target for vaccine design as it contains a number of conserved epitopes, including a large fraction of the CD4 binding site.Attempts to design OD-based immunogens in the past have met with little success. We report the design and characterization of an Escherichia coli-expressed OD-based immunogen (ODEC), based on the sequence of the HxBc2 strain. The ODEC-designed immunogen lacks the variable loops V1V2 and V3 and incorporates 11 designed mutations at the interface of the inner and the outer domains of gp120. Biophysical studies showed that ODEC is folded and protease-resistant, whereas ODEC lacking the designed mutations is highly aggregation-prone. In contrast to previously characterized OD constructs, ODEC bound CD4 and the broadly neutralizing antibody b12 but not the non-neutralizing antibodies b6 and F105. Upon immunization in rabbits, ODEC was highly immunogenic,and the sera showed measurable neutralization for four subtype B and one subtype C virus including two b12-resistant viruses. In contrast,sera from rabbits immunized with gp120 did not neutralize any of the viruses. ODEC is the first example of a gp120 fragment-based immunogen that yields significant neutralizing antibodies.

Effects of Ultrafast Solvation on the Rate of Adiabatic Outer-Sphere Electron Transfer Reactions

Recent studies have demonstrated that solvation dynamics in many common dipolar liquids contain an initial, ultrafast Gaussian component which may contribute even more than 60% to the total solvation energy. It is also known that adiabatic electron transfer reactions often probe the high-frequency components of the relevant solvent friction (Hynes, J. T. J. Phys. Chem. 1986, 90, 3701). In this paper, we present a theoretical study of the effects of the ultrafast solvent polar modes on the adiabatic electron transfer reactions by using the formalism of Hynes. Calculations have been carried out for a model system and also for water and acetonitrile. It is found that, in general, the ultrafast modes can greatly enhance the rate of electron transfer, even by more than an order of magnitude, over the rate obtained by using only the slow overdamped modes usually considered. For water, this acceleration of the rate can be attributed to the high-frequency intermolecular vibrational and librational modes. For a weakly adiabatic reaction, the rate is virtually indistinguishable from the rate predicted by the Marcus transition state theory. Another important result is that even in this case of ultrafast underdamped solvation, energy diffusion appears to be efficient so that electron transfer reaction in water is controlled essentially by the barrier crossing dynamics. This is because the reactant well frequency is-directly proportional to the rate of the initial Gaussian decay of the solvation time correlation function. As a result, the value of the friction at the reactant well frequency rarely falls below the value required for the Kramers turnover except when the polarizability of the water molecules may be neglected. On the other hand, in acetonitrile, the rate of electron transfer reaction is found to be controlled by the energy diffusion dynamics, although a significant contribution to the rate comes also from the barrier crossing rate. Therefore, the present study calls for a need to understand the relaxation of the high-frequency modes in dipolar liquids.

Progressively More Prolate Dark Matter Halo In the Outer Galaxy As Traced by Flaring Hi gas

A galactic disk in a spiral galaxy is generally believed to be embedded in an extended dark matter halo, which dominates its dynamics in the outer parts. However, the shape of the halo is not clearly understood. Here we show that the dark matter halo in the Milky Way is prolate in shape. Further, it is increasingly more prolate at larger radii, with the vertical-to-planar axis ratio monotonically increasing to 2.0 at 24 kpc. This is obtained by modeling the observed steeply flaring atomic hydrogen gas layer in the outer Galactic disk, where the gas is supported by pressure against the net gravitational field of the disk and the halo. The resulting prolate-shaped halo can explain several long-standing puzzles in galactic dynamics, for example, it permits long-lived warps thus explaining their ubiquitous nature.

Enhanced efficiency of tri-layered dye solar cells with hydrothermally synthesized titania nanotubes as light scattering outer layer

In the present study dye sensitized solar cells (DSSCs) have been fabricated with a tri-layer photo anode consisting of hydrothermally prepared titania nano tubes (TNT) having a diameter of 9-10 nm and length of several micrometers as outer layer, P25 TiO2 powder as transparent light absorbing middle layer and a compact TiO2 inner layer to improve the adhesion of different layers on a transparent conducting oxide coated substrate. In comparison to cells fabricated using TNTs or P25 alone, the tri-layer DSSCs exhibit an enhanced efficiency of 7.15% with a current density of 17.12 mA cm(-2) under AM 1.5 illumination. The enhancement is attributed to the light scattering generated by TNTs aggregates, reduction in electron transport resistance at the TiO2/dye/electrolyte interface and an improvement in electron life-time. (c) 2012 Elsevier B.V. All rights reserved.

Role of outer membrane exopolymers of Acidithiobacillus ferrooxidans in adsorption of cells onto pyrite and chalcopyrite

Bacterial surface polymers play a major role in the adhesion of bacterial cells to solid surfaces. Lipopolysaccharides (LPS) are essential constituents of the cell walls of almost all Gram-negative bacteria. This paper reports the results of the investigations on the role of outer membrane exopolymers (LPS) of the chemolithotroph, Acidithiobacillus ferrooxidans, in adsorption of the cells onto pyrite and chalcopyrite. Optimization of EDTA treatment for removal of LPS from cell surface and the surface characterization of EDTA-treated cells are outlined. There was no change in cell morphology or loss in cell motility upon treatment with upto 0.04 mM EDTA for 1 h. Partial removal of LPS by EDTA treatment resulted in reduced adsorption of the cells on both pyrite and chalcopyrite. The protein profile of the EDTA-extractable fraction showed presence of certain outer membrane proteins indicating that EDTA treatment results in temporary gaps in the outer membrane. Also, specificity towards pyrite compared to chalcopyrite that was exhibited by untreated cells was lost when their exopolymer layers were stripped off, which could be attributed to the role of outer membrane proteins in the mineral-specificity exhibited by the bacteria. (C) 2013 Elsevier B.V. All rights reserved.

Formation of annular austenitic ring between outer ferrite layer and solid globule in a semi-solid processed SS 304L

The microstructure of an austenitic SS 304L rapidly quenched from its semi-solid state shows a unique annular austenitic ring in between the core of each globule and its ferritic outer layer. On the basis of experimental results and microstructural analysis, it is proposed that the ring is formed as a result of preferential austenitic phase nucleation in a small quantity of liquid entrapped between adjacent solid globules during rapid quenching, in spite of the fact that ferrite is the thermodynamically stable phase for the alloy. (C) 2014 Elsevier B.V. All rights reserved.

An Improved Outer Bound on the Storage-Repair-Bandwidth Tradeoff of Exact-Repair Regenerating Codes

While the tradeoff between the amount of data stored and the repair bandwidth of an (n, k, d) regenerating code has been characterized under functional repair (FR), the case of exact repair (ER) remains unresolved. It is known that there do not exist ER codes which lie on the FR tradeoff at most of the points. The question as to whether one can asymptotically approach the FR tradeoff was settled recently by Tian who showed that in the (4, 3, 3) case, the ER region is bounded away from the FR region. The FR tradeoff serves as a trivial outer bound on the ER tradeoff. In this paper, we extend Tian's results by establishing an improved outer bound on the ER tradeoff which shows that the ER region is bounded away from the FR region, for any (n; k; d). Our approach is analytical and builds upon the framework introduced earlier by Shah et. al. Interestingly, a recently-constructed, layered regenerating code is shown to achieve a point on this outer bound for the (5, 4, 4) case. This represents the first-known instance of an optimal ER code that does not correspond to a point on the FR tradeoff.

Outer Bounds on the Secrecy Rate of the 2-User Symmetric Deterministic Interference Channel with Transmitter Cooperation

This paper derives outer bounds for the 2-user symmetric linear deterministic interference channel (SLDIC) with limited-rate transmitter cooperation and perfect secrecy constraints at the receivers. Five outer bounds are derived, under different assumptions of providing side information to receivers and partitioning the encoded message/output depending on the relative strength of the signal and the interference. The usefulness of these outer bounds is shown by comparing the bounds with the inner bound on the achievable secrecy rate derived by the authors in a previous work. Also, the outer bounds help to establish that sharing random bits through the cooperative link can achieve the optimal rate in the very high interference regime.

Outer Bounds on the Sum Rate of the K-User MIMO Gaussian Interference Channel

This paper derives outer bounds on the sum rate of the K-user MIMO Gaussian interference channel (GIC). Three outer bounds are derived, under different assumptions of cooperation and providing side information to receivers. The novelty in the derivation lies in the careful selection of side information, which results in the cancellation of the negative differential entropy terms containing signal components, leading to a tractable outer bound. The overall outer bound is obtained by taking the minimum of the three outer bounds. The derived bounds are simplified for the MIMO Gaussian symmetric IC to obtain outer bounds on the generalized degrees of freedom (GDOF). The relative performance of the bounds yields insight into the performance limits of multiuser MIMO GICs and the relative merits of different schemes for interference management. These insights are confirmed by establishing the optimality of the bounds in specific cases using an inner bound on the GDOF derived by the authors in a previous work. It is also shown that many of the existing results on the GDOF of the GIC can be obtained as special cases of the bounds, e. g., by setting K = 2 or the number of antennas at each user to 1.

Dynamos driven by weak thermal convection and heterogeneous outer boundary heat flux

We use numerical dynamo models with heterogeneous core-mantle boundary (CMB) heat flux to show that lower mantle lateral thermal variability may help support a dynamo under weak thermal convection. In our reference models with homogeneous CMB heat flux, convection is either marginally supercritical or absent, always below the threshold for dynamo onset. We find that lateral CMB heat flux variations organize the flow in the core into patterns that favour the growth of an early magnetic field. Heat flux patterns symmetric about the equator produce non-reversing magnetic fields, whereas anti-symmetric patterns produce polarity reversals. Our results may explain the existence of the geodynamo prior to inner core nucleation under a tight energy budget. Furthermore, in order to sustain a strong geomagnetic field, the lower mantle thermal distribution was likely dominantly symmetric about the equator. (C) 2015 Elsevier B.V. All rights reserved.

Diffraction Of Elastic Waves By Two Parallel Rigid Strips Embedded In An Infinite Orthotropic Medium

The elastodynamic response of a pair of parallel rigid strips embedded in an infinite orthotropic medium due to elastic waves incident normally on the strips has been investigated. The mixed boundary value problem has been solved by the Integral Equation method. The normal stress and the vertical displacement have been derived in closed form. Numerical values of stress intensity factors at inner and outer edges of the strips and vertical displacement at points in the plane of the strips for several orthotropic materials have been calculated and plotted graphically to show the effect of material orthotropy.

Investigation of the Internal Heterostructure of Highly Luminescent Quantum Dot-Quantum Well Nanocrystals

In this paper, we report on the growth and characterization of quantum dot−quantum well nanostructures with photoluminescence (PL) that is tunable over the visible range. The material exhibits a PL efficiency as high as 60% and is prepared by reacting ZnS nanocrystals in turn with precursors for CdSe and ZnS in an attempt to form a simple “ZnS/CdSe/ZnS quantum-well structure”. Through the use of synchrotron radiation-based photoelectron spectroscopy in conjunction with detailed overall compositional analysis and correlation with the size of the final composite nanostructure, the internal structure of the composite nanocrystals is shown to consist of a graded alloy core whose composition gradually changes from ZnS at the very center to CdSe at the onset of a CdSe layer. The outer shell is ZnS with a sharp interface, probably reflecting the relative thermodynamic stabilities of the parent binary phases. These contrasting aspects of the internal structure are discussed in terms of the various reactivities and are shown to be crucial for understanding the optical properties of such complex heterostructured nanomaterials.