Polyaniline Langmuir-Blodgett film based cholesterol biosensor

Cholesterol oxidase (ChOx) has been covalently linked to Langmuir-Blodgett (LB) monolayers of polyaniline (PANI)-stearic acid (SA) prepared onto indium-tin-oxide (ITO) coated glass plates via glutaraldehyde (Glu) chemistry. These ChOx/Glu/PANI-SA LB film/ITO electrodes have been characterized by FT-IR, cyclic voltammetry, and scanning electron microscopy, respectively. The results of response measurements carried out on these bioelectrodes using linear sweep voltammetry (LSV) reveal linearity from 25 to 400 mg/dL of cholesterol concentration with sensitivity of 88.9 nA mg(-1) dL. The linear regression analysis of bioelectrode reveals standard deviation and correlation coefficient of 0.737 microA and 0.9988, respectively. The low value of the Michaelis-Menten constant of these bioelectrodes obtained as 1.21 mM for the immobilized enzyme indicates increased interaction between ChOx and cholesterol in the PANI-SA LB film.     

Premonitory effects near critical transition temperature in ordering systems – a Monte Carlo simulation

Premonitory effects manifest themselves in an ordering transition of the first kind (order) in the form of anomalously high short-range order (SRO) intensity at temperatures marginally above T _c, the critical transition temperature. This intensity located at the superlattice positions of the long-range ordered (LRO) phase is often attributed to the formation of ‘heterophase fluctuations’ resembling clusters of the LRO phase. Monte Carlo simulations in a hypothetical system showing FCC-to-L1₂ ordering transition have been carried out here to shed some light on this phenomenon and to look into the atomic configurations that make up these fluctuations.     

Ab initio study on the formation of chemically ordered Zr2Al phase by coupled replacive–displacive transformation

We performed plane wave-based first principles calculations using the projector augmented wave (PAW) potential under the generalized gradient approximation (GGA) within the density functional theory to study the formation of ordered omega (B8₂-structured) Zr₂Al phase in β-Zr₃Al alloy. The transformation involves both replacive and displacive processes. We investigated two possible paths for the transformation where steps involving replacive (diffusive) and displacive processes occur in succession with their sequence of occurrence being different in the two paths. From this study, it was possible to show that the initial chemical ordering facilitates the displacive process leading to the transformation. It was also possible to correlate instability with respect to omega-type displacements in Zr₂Al alloy with the number of Zr–Al bonds present in the unit cell. Electronic structure analysis indicated that stronger Zr–Al bonding plays an important role in the formation of chemically ordered omega phase.     

Structure and binding of the H4 histone tail and the effects of lysine 16 acetylation

The H4 histone tail plays a critical role in chromatin folding and regulation--it mediates strong interactions with the acidic patch of proximal nucleosomes and its acetylation at lysine 16 (K16) leads to partial unfolding of chromatin. The molecular mechanism associated with the H4 tail/acidic patch interactions and its modulation via K16 acetylation remains unknown. Here we employ a combination of molecular dynamics simulations, molecular docking calculations, and free energy computations to investigate the structure of the H4 tail in solution, the binding of the H4 tail with the acidic patch, and the effects of K16 acetylation. The H4 tail exhibits a disordered configuration except in the region Ala15-Lys20, where it exhibits a strong propensity for an α-helical structure. This α-helical region is found to dock very favorably into the acidic patch groove of a nucleosome with a binding free energy of approximately -7 kcal mol(-1). We have identified the specific interactions that stabilize this binding as well as the associated energetics. The acetylation of K16 is found to reduce the α-helix forming propensity of the H4 tail and K16's accessibility for mediating external interactions. More importantly, K16 acetylation destabilizes the binding of the H4 tail at the acidic patch by mitigating specific salt bridges and longer-ranged electrostatic interactions mediated by K16. Our study thus provides new microscopic insights into the compaction of chromatin and its regulation via posttranslational modifications of histone tails, which could be of interest to chromatin biology, cancer, epigenetics, and drug design.     

Natural product DNA major groove binders

Covering: 1980 to 2011. Major groove recognition of DNA by proteins utilizes the variation in hydrogen bond donor/acceptor content that makes DNA base-pairs distinguishable from one another. Specific ligand-DNA interactions in the major groove are necessary to develop approaches for inhibition of DNA-protein interactions. As opposed to minor groove binders, little research has been achieved in recognition of the DNA major groove. This review summarizes the progress in identification of natural products that bind to the major groove of DNA. We first review the natural products, pluramycins, aflatoxins, azinomycins, leinamycin, neocarzinostatin, and ditercalinium, that are known to possess major groove interacting elements. These compounds, however, interact primarily with DNA by intercalation between base-pair steps. Some of these compounds utilize non-covalent interactions in order to position themselves to alkylate DNA at the nucleophilic N7 positions on nearby purine bases. Finally, recent reports of non-covalent major groove binding with carbohydrates, aminoglycosides in particular, have revealed them as promising leads for DNA major groove binding probes or drugs.     

Accessing a small library of pluripotent 1,4,5-trisubstituted 1H-1,2,3-triazoles via diversity-oriented synthesis

Diversity-oriented synthesis of structurally different, novel and small drug like molecules based on 1,4,5-trisubstituted 1,2,3-triazoles is developed in a streamlined sequence of different sets of reactions. The method involves the use of simple, readily available and highly economical substrates and reagents. The molecules developed herein have potential to be exploited either as chemotherapeutic agents or as scaffolds for other biologically active compounds.     

High pressure behavior of alkaline earth tellurides

We have predicted high pressure structural behavior and elastic properties of alkaline earth tellurides (AETe; AE = Ca, Sr, Ba) by using two body interionic potential approach with modified ionic charge (Z _m e). This method has been found quite satisfactory in case of the rare earth compounds. The equation of state curve, structural phase transition pressure from NaCl (B1) to CsCl (B2) phase and associated volume collapse at transition pressure of alkaline earth tellurides (AETe) obtained from this approach, so have been compared with experimentally measured data reveal good agreement. We have also investigated bulk modulus, second and third order elastic constants and pressure derivatives of second order elastic constants at ambient pressure which shows predominantly ionic nature of these compounds. First time, we have calculated the Poisson ratio, Young and Shear modulus of these compounds.      

High Energy Density Supercapacitors: An Overview of Efficient Electrode Materials,Electrolytes, Design,and Fabrication

Supercapacitors (SCs) are potentially trustworthy energy storage devices, therefore getting huge attention from researchers. However, due to limited capacitance and low energy density, there is still scope for improvement. The race to develop novel methods for enhancing their electrochemical characteristics is still going strong, where the goal of improving their energy density to match that of batteries by increasing their specific capacitance and raising their working voltage while maintaining high power capability and cutting the cost of production. In this light, this paper offers a succinct summary of current developments and fresh insights into the construction of SCs with high energy density which might help new researchers in the field of supercapacitor research. From electrolytes, electrodes, and device modification perspectives, novel applicable methodologies were emphasized and explored. When compared to conventional SCs, the special combination of electrode material/composites and electrolytes along with their fabrication design considerably enhances the electrochemical performance and energy density of the SCs. Emphasis is placed on the dynamic and mechanical variables connected to SCs′ energy storage process. To point the way toward a positive future for the design of high-energy SCs, the potential and difficulties are finally highlighted. Further, we explore a few important topics for enhancing the energy densities of supercapacitors, as well as some links between major impacting factors. The review also covers the obstacles and prospects in this fascinating subject. This gives a fundamental understanding of supercapacitors as well as a crucial design principle for the next generation of improved supercapacitors being developed for commercial and consumer use.     

Accounting for boundary effects in nearest-neighbor searching

Givenn data points ind-dimensional space, nearest-neighbor searching involves determining the nearest of these data points to a given query point. Most averagecase analyses of nearest-neighbor searching algorithms are made under the simplifying assumption thatd is fixed and thatn is so large relative tod thatboundary effects can be ignored. This means that for any query point the statistical distribution of the data points surrounding it is independent of the location of the query point. However, in many applications of nearest-neighbor searching (such as data compression by vector quantization) this assumption is not met, since the number of data pointsn grows roughly as 2 ^d .Largely for this reason, the actual performances of many nearest-neighbor algorithms tend to be much better than their theoretical analyses would suggest. We present evidence of why this is the case. We provide an accurate analysis of the number of cells visited in nearest-neighbor searching by the bucketing andk-d tree algorithms. We assumem ^dpoints uniformly distributed in dimensiond, wherem is a fixed integer ≥2. Further, we assume that distances are measured in theL _∞ metric. Our analysis is tight in the limit asd approaches infinity. Empirical evidence is presented showing that the analysis applies even in low dimensions. A preliminary version of this paper appeared in theProceedings of the 11th Annual ACM Symposium on Computational Geometry, 1995, pp. 336–344. Part of this research was conducted while the first author was visiting the Max-Planck-Institut für Informatik, Saarbrücken, Germany. The first author was supported by the ESPRIT Basic Research Actions Program, under Contract No. 7141 (project ALCOM II). The support of the National Science Foundation under Grant CCR-9310705 is gratefully acknowledged by the second author. The third author was supported in part by AT&T Bell Laboratories and the Society of Fellows at Harvard University.