Simulations of Two-Dimensional Unbiased Polymer Translocation Using the Bond Fluctuation Model

We use the Bond Fluctuation Model (BFM) to study the pore-blockade times of a translocating polymer of length $N$ in two dimensions, in the absence of external forces on the polymer (i.e., unbiased translocation) and hydrodynamic interactions (i.e., the polymer is a Rouse polymer), through a narrow pore. Earlier studies using the BFM concluded that the pore-blockade time scales with polymer length as $\tau_d \sim N^\beta$, with $\beta=1+2\nu$, whereas some recent studies with different polymer models produce results consistent with $\beta=2+\nu$, originally predicted by us. Here $\nu$ is the Flory exponent of the polymer; $\nu=0.75$ in 2D. In this paper we show that for the BFM if the simulations are extended to longer polymers, the purported scaling $\tau_d \sim N^{1+2\nu}$ ceases to hold. We characterize the finite-size effects, and study the mobility of individual monomers in the BFM. In particular, we find that in the BFM, in the vicinity of the pore the individual monomeric mobilities are heavily suppressed in the direction perpendicular to the membrane. After a modification of the BFM which counters this suppression (but possibly introduces other artifacts in the dynamics), the apparent exponent $\beta$ increases significantly. Our conclusion is that BFM simulations do not rule out our theoretical prediction for unbiased translocation, namely $\beta=2+\nu$.Comment: minor proofreading corrections, 23 pages (double spacing), 7 figures, published versio

Conformational change of L7/L12 stalk in the different functional states of 50S ribosomes

Conformational change of 50S ribosomes takes place during protein synthesis. The primary change is most likely in the secondary or tertiary structure of rRNA in the L7/L12 stalk region. In order to throw further light on this conformational change, the change in fluorescence of tight couple 50S ribosomes on conversion to loose couple 50S ribosomes containing 5-(iodoacetamido ethyl)-aminonaphthalene-l-sulphonic acid-labelled L7/L12, following the treatment with elongation factor-G and 5'-guanylyl methylene diphosphate was measured. It was enhanced in agreement with the results reported earlier. Further, the quenching of fluorescence of 50S ribosomes containing 5-(iodoacetamido ethyl)-aminonaphthalene-1-sulphonic acid-labelled L7/L12 by acrylamide was studied. The quenching is more in case of loose couples. On conversion of loose couple 50S ribosomes to tight couple ones the quenching becomes less whereas the reverse happens on conversion of tight couple 70S ribosomes to loose couples. These results indicate the conformational change of L7/L12 stalk in the different functional states of 50S ribosomes

A comparative study of the conduction velocity of motor and sensory fibres of ulnar and median nerves among leprosy patients and normal subjects

Background: Leprosy and the associated scourge have affected humanity for thousands of years. One of the most debilitating consequences of leprosy is peripheral neuropathy. Nerve Conduction Velocity study provides us with a non-invasive modality to assess peripheral nerve involvement in leprosy.Methods: With this in mind, a cross-sectional observational study was conducted including 30 leprosy patients as "Cases" and 30 age-matched healthy subjects, not suffering from any kind of neurological disorders, as "Controls". Using a digital electromyography machine, the Latency, Amplitude and Conduction Velocities of Motor and Sensory fibres of Ulnar and Median nerves were recorded. The results were compared among controls and cases using suitable statistical tests (descriptive statistics and significance testing using unpaired t-test).Results: In this study, with regard to Sensory Nerve conduction Velocity (SNCV), statistically very significant difference was noted in case of right (p 0.0011) and left (p 0.0037) ulnar nerves among controls and cases. The difference in the amplitude of Motor Action potential (MAP) with regard to right median nerve, among cases and controls, was also statistically significant (p 0.0127). Further the amplitude of Sensory Nerve Action Potential (SNAP) values were higher among cases compared to controls.Conclusions: As such, the findings of this study (and which is also corroborated by many previous studies) lead us to the conclusion that NCV studies can detect lepromatous neuropathy much before the emergence of frank clinical signs and this type of neuropathy is predominantly demyelinating in nature with occasional axonal loss

Escape from noisy intermittent repellers

Intermittent or marginally-stable repellers are commonly associated with a power law decay in the survival fraction. We show here that the presence of weak additive noise alters the spectrum of the Perron - Frobenius operator significantly giving rise to exponential decays even in systems that are otherwise regular. Implications for ballistic transport in marginally stable miscrostructures are briefly discussed.Comment: 3 ps figures include

Evaluation of the optical switching characteristics of erbium-doped fibres for the development of a fibre Bragg grating sensor interrogator

A polling topology that employs optical switching based on the properties of erbium-doped fibres (EDFs) is used to interrogate an array of FBGs. The properties of the EDF are investigated in its pumped and un-pumped states and the EDFs’ switching properties are evaluated by comparing them with a high performance electronically controlled MEM optical switch. Potential advantages of the proposed technique are discussed. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Regulatory role of proteasome in determination of platelet life span

Limit of platelet life span (8-10 days) is determined by the activity of a putative "internal clock" composed of Bcl-2 family proteins, while role of other molecular players in this process remains obscure. Here, we sought to establish a central role of proteasome in platelet life span regulation. Administration of mice with inhibitors of proteasome peptidase activity induced significant thrombocytopenia. This was associated with enhanced clearance of biotin-labeled platelets from circulation and reduction in average platelet half life from 66 to 37 h. Cells pretreated in vitro with proteasome inhibitors exhibited augmented annexin V binding and drop in mitochondrial transmembrane potential indicative of apoptotic cell death and decreased platelet life span. These cells were preferentially phagocytosed by monocyte-derived macrophages, thus linking proteasome activity with platelet survival. Decisive role of proteasome in this process was underscored from enhanced expression of conformationally active Bax in platelets with attenuated proteasome activity, which was consistent with pro-apoptotic phenotype of these cells. The present study establishes a critical role of proteasome in delimiting platelet life span ostensibly through constitutive elimination of the conformationally active Bax. These findings bear potential implications in clinical settings where proteasome peptidase activities are therapeutically targeted

Energy Efficient UAV-Assisted Emergency Communication with Reliable Connectivity and Collision Avoidance

Emergency communication is vital for search and rescue operations following natural disasters. Unmanned Aerial Vehicles (UAVs) can significantly assist emergency communication by agile positioning, maintaining connectivity during rapid motion, and relaying critical disaster-related information to Ground Control Stations (GCS). Designing effective routing protocols for relaying crucial data in UAV networks is challenging due to dynamic topology, rapid mobility, and limited UAV resources. This paper presents a novel energy-constrained routing mechanism that ensures connectivity, inter-UAV collision avoidance, and network restoration post-UAV fragmentation while adapting without a predefined UAV path. The proposed method employs improved Q learning to optimize the next-hop node selection. Considering these factors, the paper proposes a novel, Improved Q-learning-based Multi-hop Routing (IQMR) protocol. Simulation results validate IQMRs adaptability to changing system conditions and superiority over QMR, QTAR, and QFANET in energy efficiency and data throughput. IQMR achieves energy consumption efficiency improvements of 32.27%, 36.35%, and 36.35% over QMR, Q-FANET, and QTAR, along with significantly higher data throughput enhancements of 53.3%, 80.35%, and 93.36% over Q-FANET, QMR, and QTAR.Comment: 13 page

Palladium-catalyzed coupling of functionalized primary and secondary amines with aryl and heteroaryl halides: two ligands suffice in most cases

We report our studies on the use of two catalyst systems, based on the ligands BrettPhos and RuPhos, which provide the widest scope for Pd-catalyzed C–N cross-coupling reactions to date. Often low catalyst loadings and short reaction times can be used with functionalized aryl and heteroaryl coupling partners. The reactions are highly robust and can be set up and performed without the use of a glovebox. These catalysts should find wide application in the synthesis of complex molecules including pharmaceuticals, natural products and functional materials.Amgen Inc.National Institutes of Health (U.S.) (Grant GM-58160)American Chemical SocietyBoehringer IngelheimNational Science Foundation (U.S.) (CHE 9808061)National Science Foundation (U.S.) (DBI 9729592