Cytotoxic agents for KB and SiHa cells from n-hexane fraction of Cissampelos pareira and its chemical composition

Eleven constituents were characterised by gas chromatography–mass spectrometry analysis, and five molecules were isolated using column chromatography. The in vitro study of the extract and isolated molecules against KB and SiHa cell lines revealed oleanolic acid (1) and oleic acid (2) as potent cytotoxic molecules with potential anticancer activity. The IC₅₀ values of n-hexane extract (CPHF), oleanolic acid (1) and oleic acid (2) were >300, 56.08 and 70.7 μg/mL (μM), respectively, against KB cell lines and >300, 47.24 and 80.2 μg/mL (μM), respectively, against SiHa cell lines.     

How does a hydrocarbon staple affect peptide hydrophobicity?

Water is essential for the proper folding of proteins and the assembly of protein–protein/ligand complexes. How water regulates complex formation depends on the chemical and topological details of the interface. The dynamics of water in the interdomain region between an E3 ubiquitin ligase (MDM2) and three different peptides derived from the tumor suppressor protein p53 are studied using molecular dynamics. The peptides show bimodal distributions of interdomain water densities across a range of distances. The addition of a hydrocarbon chain to rigidify the peptides (in a process known as stapling) results in an increase in average hydrophobicity of the peptide–protein interface. Additionally, the hydrophobic staple shields a network of water molecules, kinetically stabilizing a water chain hydrogen‐bonded between the peptide and MDM2. These properties could result in a decrease in the energy barrier associated with dehydrating the peptide–protein interface, thereby regulating the kinetics of peptide binding. © 2015 Wiley Periodicals, Inc.     

Hydromagnetic flow due to torsional oscillations of an infinite disk about a steady non-zero mean

The present investigation is the study of the laminar hydromagnetic flow due to torsional oscillations of an infinite disk about a steady non-zero mean in an electrically conducting fluid. Separate solutions have been obtained for the limiting cases of low and high frequency oscillations. The low frequency solution is obtained by expressing the flow functions in powers (ik) while for high frequencies, the flow functions are expressed in powers of $\text{(ik)}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$, where $\text{k =}\text{ω}\text{Ω}$ being the ratio of the frequency of oscillations ω to the mean disk-angular velocity Ω and i² = ?1. It is found that the oscillating part of the transverse shearing stress has a phase-lead while that of the radial shearing stress has a phase lag behind the disk oscillations. The phase-lead in the former case and phase-lag in the latter case decrease with the increase in the strength of the applied magnetic field.     

Detection of fluctuating density gradient flow field in shock wave boundary layer interactions using laser Schlieren system

This paper demonstrates the feasibility of laser Schlieren system in studying unsteady shock motion in important flow phenomena such as shock wave/boundary layer interactions. Time-dependent voltage signals from multichannel measurements reveal important aspects of flow behavior such as amplitude and velocity of shock motion, frequency content, and cross-correlation functions in a very straightforward way. Tests were performed on a Halis axisymmetric configuration in a hypersonic flow with air and CO₂. Received: 8 August 2001 / Accepted: 8 November 2001     

Clionasterol Glucoside and Acylated Clionasterol Glucosides from Oplismenus burmannii

A new clionasterol glucoside, clionasterol‐[(1'→3α)‐O‐β‐D]‐glucopyranoside ( 1 ), a new acylated clionasterol glucoside, clionasterol‐[6'‐O‐acyl‐(1'→3β)‐O‐b‐D]‐glucopyranoside ( 2 ) and clionasterol ( 3 ) were isolated from the aerial parts of Oplismenus burmannii. The nature and length of fatty acid acyl chains in 2 was identified by alkaline methanolysis of compound 2 . The aglycone fraction on GC‐MS analysis showed three peaks in GC at t_R 49.86 (82.1%), 51.13 (13.3%) and 56.53 (4.6%) min, which were characterized as arachidic acid methyl ester ( a ) oleic acid methyl ester ( b ) and 12‐methyltetradecanoic acid methyl ester ( c ) respectively. Thus 2 was characterized as a mixture of three new compounds, clionasterol‐[6'‐O‐eicosanoyl‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2a ), clionasterol‐[6'‐O‐(8Z)‐octa‐deca‐9‐enoyl‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2b ) and clionasterol‐[6'‐O‐(12‐methyltetradecanoyl)‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2c ).     

An Improved Protocol for DNA Extraction from Alkaline Soil and Sediment Samples for Constructing Metagenomic Libraries

An improved single-step protocol has been developed for extracting pure community humic substance-free DNA from alkaline soils and sediments. The method is based on direct cell lysis in the presence of powdered activated charcoal and polyvinylpolypyrrolidone followed by precipitation with polyethyleneglycol and isopropanol. The strategy allows simultaneous isolation and purification of DNA while minimizing the loss of DNA with respect to other available protocols for metagenomic DNA extraction. Moreover, the purity levels are significant, which are difficult to attain with any of the methods reported in the literature for DNA extraction from soils. The DNA thus extracted was free from humic substances and, therefore, could be processed for restriction digestion, PCR amplification as well as for the construction of metagenomic libraries.     

Carbon nanotube-nucleobase hybrids: nanorings from uracil-modified single-walled carbon nanotubes

Single‐walled carbon nanotubes (SWCNTs) have been covalently functionalized with uracil nucleobase. The hybrids have been characterized by using complementary spectroscopic and microscopic techniques including solid‐state NMR spectroscopy. The uracil‐functionalized SWCNTs are able to self‐assemble into regular nanorings with a diameter of 50–70 nm, as observed by AFM and TEM. AFM shows that the rings do not have a consistent height and thickness, which indicates that they may be formed by separate bundles of CNTs. The simplest model for the nanoring formation likely involves two bundles of CNTs interacting with each other via uracil–uracil base‐pairing at both CNT ends. These nanorings can be envisaged for the development of advanced electronic circuits.     

Exciton-coupled charge-transfer dynamics in a porphyrin J-aggregate/TiO(2) complex

Exciton-coupled charge-transfer (CT) dynamics in TiO(2) nanoparticles (NP) sensitized with porphyrin J-aggregates has been studied by femtosecond time-resolved transient absorption spectroscopy. J-aggregates of 5,10,15-triphenyl-20-(3,4-dihydroxyphenyl) porphyrin (TPPcat) form CT complexes on TiO(2) NP surfaces. Catechol-mediated strong CT coupling between J-aggregate and TiO(2) NP facilitates interfacial exciton dissociation for electron injection into the conduction band of the TiO(2) nanoparticle in pulse width limited time (<80 fs). Here, the electron-transfer (<80 fs) process dominates over the intrinsic exciton-relaxation process (J-aggregates: ca. 200 fs) on account of exciton-coupled CT interaction. The parent hole on J-aggregates is delocalized through J-aggregate excitonic coherence. As a result, holes immobilized on J-aggregates are spatially less accessible to electrons injected into TiO(2) , and thus the back electron transfer (BET) process is slower than that of the monomer/TiO(2) system. The J-aggregate/porphyrin system shows exciton spectral and temporal properties for better charge separation in strongly coupled composite systems.