Mechanisms and roles of the RNA-based gene silencing

RNA silencing is a remarkable type of gene regulation. This process has been found to occur in many different organisms such as plants (co-suppression), fungi (quelling), and animals (RNA interference; RNAi). Double-stranded RNA (dsRNA) is a potent trigger in RNA silencing mechanisms operating in a wide range of organisms. This mechanism recognizes dsRNA and processes them into small 21-25nt RNAs (smRNAs). Small RNAs can guide post-transcriptional degradation of complementary messenger RNAs and in plants, transcriptional gene silencing is occurred by methylation of homologous DNA sequences. In plants, it serves as an antiviral defense, and many plant viruses encode suppressors of silencing such as helper component-proteinase of potyviruses (HC-Pro) and the p25 protein encoded by potato virus X (PVX). HC-Pro acts by preventing accumulation of smRNAs that provide specificity determinant for homologous RNA degradation, but p25 viral protein acts by targeting the mobile silencing signal. The encouraging view is that RNA silencing is part of a sophisticated network of interconnected pathways for cellular defense and development and that it may become a powerful tool to manipulate gene expression experimentally

REVIEW ARTICLE - Mechanisms and roles of the RNA-based gene silencing

RNA silencing is a remarkable type of gene regulation. This process has been found to occur in many different organisms such as plants (co-suppression), fungi (quelling), and animals (RNA interference; RNAi). Double-stranded RNA (dsRNA) is a potent trigger in RNA silencing mechanisms operating in a wide range of organisms. This mechanism recognizes dsRNA and processes them into small 21-25nt RNAs (smRNAs). Small RNAs can guide post-transcriptional degradation of complementary messenger RNAs and in plants, transcriptional gene silencing is occurred by methylation of homologous DNA sequences. In plants, it serves as an antiviral defense, and many plant viruses encode suppressors of silencing such as helper component-proteinase of potyviruses (HC-Pro) and the p25 protein encoded by potato virus X (PVX). HC-Pro acts by preventing accumulation of smRNAs that provide specificity determinant for homologous RNA degradation, but p25 viral protein acts by targeting the mobile silencing signal. The encouraging view is that RNA silencing is part of a sophisticated network of interconnected pathways for cellular defense and development and that it may become a powerful tool to manipulate gene expression experimentally

Effect of ultraviolet and pulsed light treatments on ascorbic acid content in fruit juices-A review of the degradation mechanism

Ascorbic acid (AA) is a highly sensitive nutrient, which degrades at high temperatures (>60 °C), in the presence of metal ions and oxygen. There is a dearth of studies on the effect of pasteurization on AA in juices. This review attempts to propose a mechanism for the degradation of AA during ultraviolet (UV) and pulsed light (PL) treatments. While photodegradation and aerobic degradation contribute to AA degradation during UV and PL treatments, the anaerobic degradation is the most significant mechanism post UV and PL treatments during storage. The photodegradation of AA results in the formation of ascorbyl radicals, which get converted to dehydroascorbic acid (DHAA). These radicals generated during the UV and PL treatment can induce a cascade of reactions, which can prolong the degradation of AA during storage. The factors influencing AA degradation during UV and PL treatment include extrinsic factors, which majorly include process variables such as fluence, voltage, and temperature of UV and PL processing. The intrinsic factors of the juice such as pH, dissolved oxygen, enzymes, peroxides, sugars, polyphenols, and metal ions significantly affect the AA content in juices. Since the major objective of UV and PL pasteurization is ensuring microbial safety and enzymatic stability, a careful optimization of the process conditions is necessary to achieve maximal retention of bioactives, such as AA. It can be concluded that photodegradation, aerobic oxidation and anaerobic degradation are the major mechanisms governing the degradation of AA in juices

Pressure effects on diffusion in liquid ammonia: a simulation study using a combination of isobaric-isothermal and microcanonical molecular dynamics

The effects of pressure on translational and rotational diffusion in liquid ammonia are investigated by means of molecular dynamics simulations. Calculations are done at two different temperatures and at many different pressures by using a two-part protocol involving molecular dynamics in isobaric-isothermal ensemble in the first part and in microcanonical ensemble in the second part. Our results are analyzed in terms of pressure-induced changes in structural properties such as packing and hydrogen bond properties. Also, the present results of liquid ammonia are compared with corresponding results for other hydrogen bonded liquids that were reported in recent years

Asymmetry and oscillation of the fluid flow pattern in a continuous casting mould: A water model study

The fluid flow pattern inside the continuous casting mould is mostly asymmetrical about the central plane and oscillating. Present work studies the frequency of flow oscillation for different mould dimensions, SEN position and its configuration, fluid inlet condition into the mould etc. A time average symmetry has been observed in the prevailing flow pattern inside the mould. However, this symmetry is disturbed when the SEN is displaced from its symmetrical position by more than four percent of the mould width. An upward SEN port angle and increase of flow rate increase the frequency of flow oscillation significantly. The use of a buffer over the continuous casting mould does not reduce the frequency of flow oscillation

Synthesis of a novel glucose capped gold nanoparticle as a better theranostic candidate.

Gold nanoparticles are predominantly used in diagnostics, therapeutics and biomedical applications. The present study has been designed to synthesize differently capped gold nanoparticles (AuNps) by a simple, one-step, room temperature procedure and to evaluate the potential of these AuNps for biomedical applications. The AuNps are capped with glucose, 2-deoxy-D-glucose (2DG) and citrate using different reducing agents. This is the first report of synthesis of 2DG-AuNp by the simple room temperature method. The synthesized gold nanoparticles are characterized with UV-Visible Spectroscopy, Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and selected area electron diffraction (SAED), Dynamic light scattering (DLS), and Energy-dispersive X-ray spectroscopy (SEM-EDS). Surface-enhanced Raman scattering (SERS) study of the synthesized AuNps shows increase in Raman signals up to 50 times using 2DG. 3-(4, 5-dimethylthiozol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay has been performed using all the three differently capped AuNps in different cell lines to assess cytotoxcity if any, of the nanoparticles. The study shows that 2DG-AuNps is a better candidate for theranostic application

Chemical equation.

<p>The reduction reaction equation for the formation of Au nanoparticles.</p

UV-visible absorption spectrum of AuNPs.

<p><b>A</b> UV-visible absorption spectrum of glucose-AuNps showing SPR peak at 540 nm; <b>B</b> Citrate-AuNps showing SPR peak at 520 nm; <b>C</b> 2DG-AuNps showing SPR peak at 525 nm.</p