From Molecular to Supramolecular: An Exploration into the Modes of Self-assembly in Conformationally Locked Polycyclitols

This brief account highlights the notable findings of our investigation into the supramolecular chemistry of conformationally locked polycyclitols in the solid state. The study was aimed at analyzing the crystal packing and unraveling the modalities of non-covalent interactions (particularly, intramolecular vis-a-vis intermolecular OH center dot center dot center dot O hydrogen bonds) in polyols. The know-how obtained thereof, was successfully utilized to engineer self-assemblies of designer polycyclitols, having hydrogen bond donors and acceptors fettered onto a trans-decalin scaffold. The results seek to draw particular attention to the intrinsic attribute of this rigid carbocyclic framework to lock functional groups into spatially invariant positions and bring potential intramolecular hydrogen bonding partners into favorable interaction geometry to engender predictability in the self-assembly patterns.

Molecular Marriage through Partner Preferences in Covalent Cage Formation and Cage-to-Cage Transformation

Unprecedented self-sorting of three-dimensional purely organic cages driven by dynamic covalent bonds is described. Four different cages were first synthesized by condensation of two triamines and two dialdehydes separately. When a mixture of all the components was allowed to react, only two cages were formed, which suggests a high-fidelity self-recognition. The issue of the preference of one triamine for a particular dialdehyde was further probed by transforming a non-preferred combination to either of the two preferred combinations by reacting it with the appropriate triamine or dialdehyde.

Force Biased Molecular Dynamics Simulation Study of Effect of Dendrimer Generation on Interaction with DNA

We have studied the effect of dendrimer generation on the interaction between dsDNA and the PAMAM dendrimer using force biased simulation of dsDNA with three generations of dendrimer: G3, G4, and G5. Our results for the potential of mean force (PMF) and the dendrimer asphericity along the binding pathway, combined with visualization of the simulations, demonstrate that dendrimer generation has a pronounced impact on the interaction. The PMF increases linearly with increasing generation of the dendrimer. While, in agreement with previous results, we see an increase in the extent to which the dendrimer bends the dsDNA with increasing dendrimer generation, we also see that the deformation of the dendrimer is greater with smaller generation of the dendrimer. The larger dendrimer forces the dsDNA to conform to its structure, while the smaller dendrimer is forced to conform to the structure of the dsDNA. Monitoring the number of bound cations at different values of force bias distance shows the expected effect of ions being expelled when the dendrimer binds dsDNA.

Medium Voltage Drive for Induction Motors Using Multilevel Octadecagonal Voltage Space Vectors

Multilevel inverters with hexagonal and dodecagonal voltage space vector structures have improved harmonic profile compared to two-level inverters. Further improvement in the quality of the waveform is possible using multilevel octadecagonal (18-sided polygon) voltage space vectors. This paper proposes an inverter circuit topology capable of generating multilevel octadecagonal voltage space vectors, by cascading two asymmetric three-level inverters. By the proper selection of dc-link voltages and the resultant switching states for the inverters, voltage space vectors, whose tips lie on three concentric octadecagons, are obtained. The advantages of octadecagonal voltage space vector-based pulsewidth modulation (PWM) techniques are the complete elimination of fifth, seventh, eleventh, and thirteenth harmonics in phase voltages and the extension of linear modulation range. In this paper, a simple PWM timing calculation method is also proposed. Experimental results have been presented in this paper to validate the proposed concept.

Revision of the scolopendrid centipede digitipes Attems, 1930, from India (Chilopoda: Scolopendromorpha): reconciling molecular and morphological estimates of species diversity

Recent work on molecular phylogenetics of Scolopendridae from the Western Ghats, Peninsular India, has suggested the presence of six cryptic species of the otostigmine Digitipes Attems, 1930, together with three species described in previous taxonomic work by Jangi and Dass (1984). Digitipes is the correct generic attribution for a monophyletic group of Indian species, these being united with three species from tropical Africa (including the type) that share a distomedial process on the ultimate leg femur of males that is otherwise unknown in Otostigminae. Second maxillary characters previously used in the diagnosis of Digitipes are dismissed because Indian species do not possess the putatively diagnostic character states. Two new species from the Western Ghats that correspond to groupings identified based on monophyly, sequence divergence and coalescent analysis using molecular data are diagnosed based on distinct morphological characters. They are D. jangii and D. periyarensis n. spp. Three species named by Jangi and Dass (Digitipes barnabasi, D. coonoorensis and D. indicus) are revised based on new collections; D. indicus is a junior subjective synonym of Arthrorhabdus jonesii Verhoeff, 1938, the combination becoming Digitipes jonesii (Verhoeff, 1938) n. comb. The presence of Arthrorhabdus in India is accordingly refuted. Three putative species delimited by molecular and ecological data remain cryptic from the perspective of diagnostic morphological characters and are presently retained in D. barnabasi, D. jangii and D. jonesii. A molecularly-delimited species that resolved as sister group to a well-supported clade of Indian Digitipes is identified as Otostigmus ruficeps Pocock, 1890, originally described from a single specimen and revised herein. One Indian species originally assigned to Digitipes, D. gravelyi, deviates from confidently-assigned Digitipes with respect to several characters and is reassigned to Otostigmus, as O. gravelyi (Jangi and Dass, 1984) n. comb.

Nanoindentation in Crystal Engineering: Quantifying Mechanical Properties of Molecular Crystals

Nanoindentation is a technique for measuring the elastic modulus and hardness of small amounts of materials. This method, which has been used extensively for characterizing metallic and inorganic solids, is now being applied to organic and metalorganic crystals, and has also become relevant to the subject of crystal engineering, which is concerned with the design of molecular solids with desired properties and functions. Through nanoindentation it is possible to correlate molecular-level properties such as crystal packing, interaction characteristics, and the inherent anisotropy with micro/macroscopic events such as desolvation, domain coexistence, layer migration, polymorphism, and solid-state reactivity. Recent developments and exciting opportunities in this area are highlighted in this Minireview.

Molecular Design of Synthetic Benzimidazoles for the Switchover of the Duplex to G-quadruplex DNA Recognition

Benzimidazole derivatives are well known for their antibacterial, antiviral, anticonvulsant, antihistaminic, anthelmintic and antidepressant activities. Benzimidazole's unique base-selective DNA recognition property has been studied widely. However, most of the early benzimidazole systems have been targeted towards the binding of duplex DNA. Here we have shown the evolution and progress of the design and synthesis of new benzimidazole systems towards selective recognition of the double-stranded DNA first. Then in order to achieve selective recognition of the G-quadruplex DNA and utilize their potential as future anti-cancer drug candidates, we have demonstrated their selective cytotoxicity towards the cancer cells and potent telomerase inhibition ability.

Diffusion of pentane isomers in faujasite-type zeolites : NMR and molecular dynamics study

Diffusion of pentane isomers in zeolites NaX has been investigated using pulsed field gradient nuclear magnetic resonance (PFG-NMR) and molecular dynamics (MD) techniques respectively. Temperature and concentration dependence of diffusivities have been studied. The diffusivities obtained from NMR are roughly an order of magnitude smaller than those obtained from MD. The dependence of diffusivity on loading at high temperatures exhibits a type I behavior according to the classification of Karger and Pfeifer 1]. NMR diffusivities of the isomers exhibit the order D(n-pentane) > D(isopentane) > D(neopentane). The results from MD suggest that the diffusivities of the isomers follow the order D(n-pentane) < D(isopentane) < D(neopentane). The activation energies from NMR show E-a(n-pentane) < E-a(isopentane) < E-a(neopentane) whereas those from MD suggest the order E-a(n-pentane) > (isopentane) > E-a(neopentane). The latter follows the predictions of levitation effect whereas those of NMR appears to be due to the presence of defects in the zeolite crystals. The differences between diffusivities estimated by NMR and MD are attributed to the longer time and length scales sampled by the NMR technique, as compared to MD. (C) 2012 Elsevier Inc. All rights reserved.

Molecular cloning, overexpression, and characterization of autophosphorylation in calcium-dependent protein kinase 1 (CDPK1) from Cicer arietinum

In plants, calcium-dependent protein kinases (CDPKs) are key intermediates in calcium-mediated signaling that couple changes in Ca2+ levels to a specific response. In the present study, we report the high-level soluble expression of calcium-dependent protein kinase1 from Cicer arietinum (CaCDPK1) in Escherichia coli. The expression of soluble CaCDPK1 was temperature dependent with a yield of 3-4 mg/l of bacterial culture. CaCDPK1 expressed as histidine-tag fusion protein was purified using Ni-NTA affinity chromatography till homogeneity. The recombinant CaCDPK1 protein exhibited both calcium-dependent autophosphorylation and substrate phosphorylation activities with a V (max) and K (m) value of 13.2 nmol/min/mg and 34.3 mu M, respectively, for histone III-S as substrate. Maximum autophosphorylation was seen only in the presence of calcium. Optimum temperature for autophosphorylation was found to be 37 A degrees C. The recombinant protein showed optimum pH range of 6-9. The role of autophosphorylation in substrate phosphorylation was investigated using histone III-S as exogenous substrate. Our results show that autophosphorylation happens before substrate phosphorylation and it happens via intra-molecular mechanism as the activity linearly depends on enzyme concentrations. Autophosphorylation enhances the kinase activity and reduces the lag phase of activation, and CaCDPK1 can utilize both ATP and GTP as phosphodonor but ATP is preferred than GTP.

Molecular beam epitaxial growth of (11-22) GaN on m-plane sapphire

The structural and optical properties of semipolar (1 1 -2 2) GaN grown on m-plane (1 0 -1 0) sapphire substrates by molecular beam epitaxy were investigated. An in-plane orientation relationship was found to be 1 -1 0 0] GaN parallel to 1 2-1 0] sapphire and -1 -1 2 3] GaN parallel to 0 0 0 1] sapphire for semipolar GaN on m-plane sapphire substrates. The near band emission (NBE) was found at 3.432 eV, which is slightly blue shifted compared to the bulk GaN. The Raman E-2 (high) peak position observed at 569.1 cm(-1), which indicates that film is compressively strained. Schottky barrier height (phi(b)) and the ideality factor (eta) for the Au/semipolar GaN Schottky diode found to be 0.55 eV and 2.11, respectively obtained from the TE model.

Multicomponent self-sorting of a Pd-7 molecular boat and its use in catalytic Knoevenagel condensation

Unique three-component self-assembly of a cis-blocked 90 degrees Pd(II) acceptor with amixture of tri- and tetra-imidazole donors led to the self-sorting of a Pd-7 molecular boat with an internal nanocavity, which catalyses the Knoevenagel condensation of a series of aromatic aldehydes with 1,3-dimethylbarbituric acid and Meldrum's acid in aqueous media.

Hybrid organogels and aerogels from co-assembly of structurally different low molecular weight gelators

The blending of perfluorinated bile ester derivatives with the gelator 2,3-didecyloxyanthracene (DDOA) yields a new class of hybrid organo- and aerogels displaying a combination of optical and mechanical properties that differ from those of pure gels. Indeed, the nanofibers constituting the hybrid organogels emit polarized blue light and display dichroic near-UV absorption via the achiral DDOA molecules, thanks to their association with a chiral bile ester. Moreover, the thermal stability and the mechanical yield stress of the mixed organogels in DMSO are enhanced for blends of DDOA with the deoxycholic gelator (DC11) having a C-11 chain, as compared to the pure components' gels. When the chain length of the ester is increased to C-13 (DC13) a novel compound for aerogel formation directly in scCO(2) is obtained under the studied conditions. A mixture of this compound with DDOA is also able to gelate scCO(2) leading to novel composite aerogel materials. As revealed by SAXS measurements, the hybrid and the pure DDOA and DC13 aerogels display cell parameters that are very similar. These SAXS experiments suggest that crystallographic conditions are very favorable for the growth of hybrid molecular arrangements in which DDOA and DC13 units could be interchanged. Specific molecular interactions between two components are not always a pre-requisite condition for the formation of a hybrid nanostructured material in which the components mutually induce properties.

Structure, molecular dynamics, and stress in a linear polymer

We present a study correlating uniaxial stress in a polymer with its underlying structure when it is strained. The uniaxial stress is significantly influenced by the mean-square bond length and mean bond angle. In contrast, the size and shape of the polymer, typically represented by the end-to-end length, mass ratio, and radius of gyration, contribute negligibly. Among externally set control variables, density and polymer chain length play a critical role in influencing the anisotropic uniaxial stress. Short chain polymers more or less behave like rigid molecules. Temperature and rate of loading, in the range considered, have a very mild effect on the uniaxial stress.

Position control of DC motors with experience mapping based prediction controller

The paper presents a new controller inspired by the human experience based, voluntary body action control (dubbed motor control) learning mechanism. The controller is called Experience Mapping based Prediction Controller (EMPC). EMPC is designed with auto-learning features without the need for the plant model. The core of the controller is formed around the motor action prediction-control mechanism of humans based on past experiential learning with the ability to adapt to environmental changes intelligently. EMPC is utilized for high precision position control of DC motors. The simulation results are presented to show that accurate position control is achieved using EMPC for step and dynamic demands. The performance of EMPC is compared with conventional PD controller and MRAC based position controller under different system conditions. Position Control using EMPC is practically implemented and the results are presented.