scholarly journals Tuning G-Quadruplex Nanostructures with Lipids. Towards Designing Hybrid Scaffolds for Oligonucleotide Delivery

2020 ◽  
Vol 22 (1) ◽  
pp. 121
Author(s):  
Santiago Grijalvo ◽  
Anna Clua ◽  
Marc Eres ◽  
Raimundo Gargallo ◽  
Ramon Eritja
Keyword(s):  
Solid Phase ◽  
Renilla Luciferase ◽  
Terminal Position ◽  
Alkyl Chains ◽  
G Quadruplex ◽  
Biophysical Studies ◽  
The Stability ◽  
Oligonucleotide Delivery ◽  
Oligonucleotide Conjugates ◽  
Hybrid Scaffolds

Two G-quadruplex forming oligonucleotides [d(TG4T)4 and d(TG6T)4] were selected as two tetramolecular quadruplex nanostructures because of their demonstrated ability to be modified with hydrophobic molecules. This allowed us to synthesize two series of G-quadruplex conjugates that differed in the number of G-tetrads, as well as in the terminal position of the lipid modification. Both solution and solid-phase syntheses were carried out to yield the corresponding lipid oligonucleotide conjugates modified at their 3′- and 5′-termini, respectively. Biophysical studies confirmed that the presence of saturated alkyl chains with different lengths did not affect the G-quadruplex integrity, but increased the stability. Next, the G-quadruplex domain was added to an 18-mer antisense oligonucleotide. Gene silencing studies confirmed the ability of such G-rich oligonucleotides to facilitate the inhibition of target Renilla luciferase without showing signs of toxicity in tumor cell lines.

TEM characterization of Au/Polysilicon interactions

1990 ◽  
Vol 48 (4) ◽  
pp. 650-651
Author(s):  
N. David Theodore ◽  
Leslie H. Allen ◽  
C. Barry Carter ◽  
James W. Mayer
Keyword(s):  
Solid Phase ◽  
Single Crystal Silicon ◽  
Chemical Vapor ◽  
Electrical Contacts ◽  
Silicon Substrates ◽  
Crystal Silicon ◽  
Transmission Electron ◽  
Polysilicon Films ◽  
The Stability

Metal/polysilicon investigations contribute to an understanding of issues relevant to the stability of electrical contacts in semiconductor devices. These investigations also contribute to an understanding of Si lateral solid-phase epitactic growth. Metals such as Au, Al and Ag form eutectics with Si. reactions in these metal/polysilicon systems lead to the formation of large-grain silicon. Of these systems, the Al/polysilicon system has been most extensively studied. In this study, the behavior upon thermal annealing of Au/polysilicon bilayers is investigated using cross-section transmission electron microscopy (XTEM). The unique feature of this system is that silicon grain-growth occurs at particularly low temperatures ∽300°C).Gold/polysilicon bilayers were fabricated on thermally oxidized single-crystal silicon substrates. Lowpressure chemical vapor deposition (LPCVD) at 620°C was used to obtain 100 to 400 nm polysilicon films. The surface of the polysilicon was cleaned with a buffered hydrofluoric acid solution. Gold was then thermally evaporated onto the samples.

The influence of the Stokes and Archimedes forces on the stability of a two-phase flow

2003 ◽  
Vol 3 ◽  
pp. 266-270
Author(s):  
B.H. Khudjuyerov ◽  
I.A. Chuliev
Keyword(s):  
Spectral Method ◽  
Stability Region ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Solid Phase ◽  
Stability Characteristic ◽  
Phase Flow ◽  
Two Phase ◽  
The Stability

The problem of the stability of a two-phase flow is considered. The solution of the stability equations is performed by the spectral method using polynomials of Chebyshev. A decrease in the stability region gas flow with the addition of particles of the solid phase. The analysis influence on the stability characteristic of Stokes and Archimedes forces.

An in Silico Investigation of Binding Modes and Pathway of APTO-253 on c-KIT G-Quadruplex DNA

2020 ◽  
Author(s):  
Saikat Pal ◽  
Sandip Paul
Keyword(s):  
Cancer Therapy ◽  
In Silico ◽  
Binding Modes ◽  
Quadruplex Dna ◽  
G Quadruplex ◽  
The Stability

The stability of c-KIT G-quadruplex DNA by ligands has been a significant concern in the growing field of cancer therapy. Thus, it is very important to understand the mechanism behind...

scholarly journals Telomeric G-Quadruplexes: From Human to Tetrahymena Repeats

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Erika Demkovičová ◽  
Ľuboš Bauer ◽  
Petra Krafčíková ◽  
Katarína Tlučková ◽  
Petra Tóthova ◽  
...  
Keyword(s):  
Life Cycle ◽  
Base Substitution ◽  
Telomeric Dna ◽  
Purine Base ◽  
Telomeric Sequences ◽  
G Quadruplex ◽  
The Stability ◽  
Scientific Value ◽  
The Relationship ◽  
Adenine Base

The human telomeric and protozoal telomeric sequences differ only in one purine base in their repeats; TTAGGG in telomeric sequences; and TTGGGG in protozoal sequences. In this study, the relationship between G-quadruplexes formed from these repeats and their derivatives is analyzed and compared. The human telomeric DNA sequence G3(T2AG3)3 and related sequences in which each adenine base has been systematically replaced by a guanine were investigated; the result is Tetrahymena repeats. The substitution does not affect the formation of G-quadruplexes but may cause differences in topology. The results also show that the stability of the substituted derivatives increased in sequences with greater number of substitutions. In addition, most of the sequences containing imperfections in repeats which were analyzed in this study also occur in human and Tetrahymena genomes. Generally, the presence of G-quadruplex structures in any organism is a source of limitations during the life cycle. Therefore, a fuller understanding of the influence of base substitution on the structural variability of G-quadruplexes would be of considerable scientific value.

scholarly journals The influence of the nature and textural properties of different supports on the thermal behavior of Keggin type heteropolyacids

2006 ◽  
Vol 71 (3) ◽  
pp. 235-249 ◽  
Author(s):  
Alexandru Popa ◽  
Viorel Sasca ◽  
Mircea Stefanescu ◽  
Erne Kis ◽  
Radmila Marinkovic-Neducin
Keyword(s):  
Thermal Stability ◽  
Thermal Decomposition ◽  
Thermal Behavior ◽  
Solid Phase ◽  
Textural Properties ◽  
Nitrogen Adsorption ◽  
Active Phase ◽  
Support Surface ◽  
Sem Images ◽  
The Stability

In order to obtain highly dispersed heteropolyacids (HPAs) species, H3PMo12O40 and H4PVMo11O40 were supported on various supports: silica (Aerosil - Degussa and Romsil types) and TiO2. The structure and thermal decomposition of supported and unsupported HPAs were followed by different techniques (TGA-DTA, FTIR, XRD, low temperature nitrogen adsorption, scanning electron microscopy). All the supported HPAs were prepared by impregnation using the incipient wetness technique with a 1:1 mixture of water-ethanol. Samples were prepared with different concentrations to examine the effect of loading on the thermal behavior of the supported acid catalysts. The thermal stability was evaluated with reference to the bulk solid acids and mechanical mixtures. After deposition on silica types supports, an important decrease in thermal stability was observed on the Romsil types and a small decrease on the Aerosil type. The stability of the heteropolyacids supported on titania increased due to an anion-support interaction, as the thermal decomposition proceeded in two steps. The structure of the HPAs was not totally destroyed at 450 ?C as some IR bands were still preserved. A relatively uniform distribution of HPAs on the support surface was observed for all compositions of the active phase. No separate crystallites of solid phase HPAs were found in the SEM images.

scholarly journals Phase Transformation of Cr(VI)-Adsorbed Ferrihydrite at Different pH in The Presence of Mn(II): Fate of Mn(II) and Cr(VI)

2021 ◽  
Author(s):  
Zecong Ding ◽  
Fenglian Fu ◽  
Guangzhao Sun ◽  
Chujia Ye
Keyword(s):  
Phase Transformation ◽  
Heavy Metal Ions ◽  
Solid Phase ◽  
Transformation Products ◽  
Transformation Process ◽  
Toxic Heavy Metal ◽  
Chromium Vi ◽  
Initial Ph ◽  
The Stability ◽  
Mn Concentration

Abstract Ferrihydrite is an important sink for the toxic heavy metal ions, such as chromium(VI). As ferrihydrite is thermodynamically unstable and gradually transforms into hematite and goethite, the stability of Cr(VI)-adsorbed ferrihydrite is environmentally significant. This study investigated the phase transformation of Cr(VI)-adsorbed ferrihydrite at different pH in the presence of aqueous Mn(II), as well as the fate of Mn(II) and Cr(VI) in the transformation process of ferrihydrite. Among the ferrihydrite transformation products, hematite was dominant, and goethite was minor. The pre-adsorbed Cr(VI) inhibited the conversion of ferrihydrite to goethite at initial pH 3.0, whereas little amount of adsorbed Mn(II) favored the formation of goethite at initial pH 7.0. After the aging process, Cr species in solid phase existed primarily as Cr(III) in the presence of Mn(II) at initial pH 7.0 and 11.0. The aqueous Mn concentration was predominantly unchanged at initial pH 3.0, whereas the aqueous Mn(II) was adsorbed onto ferrihydrite or form Mn(OH)2 precipitates at initial pH 7.0 and 11.0, promoting the immobilization of Cr(VI). Moreover, the oxidation of Mn(II) occurred at initial pH 7.0 and 11.0, forming Mn(III/IV) (hydr)oxides.

scholarly journals The effect of hairpin loop on the structure and gene expression activity of the long-loop G-quadruplex

2021 ◽  
Author(s):  
Subramaniyam Ravichandran ◽  
Maria Razzaq ◽  
Nazia Parveen ◽  
Ambarnil Ghosh ◽  
Kyeong Kyu Kim
Keyword(s):  
Gene Expression ◽  
Rna Structure ◽  
Biological Significance ◽  
Cellular Functions ◽  
Hairpin Loops ◽  
G Quadruplex ◽  
Reporter Assays ◽  
Expression Activity ◽  
The Stability ◽  
And Function

Abstract G-quadruplex (G4), a four-stranded DNA or RNA structure containing stacks of guanine tetrads, plays regulatory roles in many cellular functions. So far, conventional G4s containing loops of 1–7 nucleotides have been widely studied. Increasing experimental evidence suggests that unconventional G4s, such as G4s containing long loops (long-loop G4s), play a regulatory role in the genome by forming a stable structure. Other secondary structures such as hairpins in the loop might thus contribute to the stability of long-loop G4s. Therefore, investigation of the effect of the hairpin-loops on the structure and function of G4s is required. In this study, we performed a systematic biochemical investigation of model G4s containing long loops with various sizes and structures. We found that the long-loop G4s are less stable than conventional G4s, but their stability increased when the loop forms a hairpin (hairpin-G4). We also verified the biological significance of hairpin-G4s by showing that hairpin-G4s present in the genome also form stable G4s and regulate gene expression as confirmed by in cellulo reporter assays. This study contributes to expanding the scope and diversity of G4s, thus facilitating future studies on the role of G4s in the human genome.

A New Electrically Reversible Depassivation/Passivation Mechanism in Polycrystalline Silicon

1996 ◽  
Vol 424 ◽  
Author(s):  
Vyshnavi Suntharalingam ◽  
Stephen J. Fonash
Keyword(s):  
Electric Fields ◽  
Polycrystalline Silicon ◽  
Solid Phase ◽  
Hydrogen Release ◽  
Temperature Bias ◽  
Polysilicon Films ◽  
The Stability ◽  
Quartz Substrates ◽  
Hydrogenated Amorphous ◽  
Positively Charged

AbstractAn electrically reversible depassivation/passivation phenomenon, recently found for hydrogen passivated polysilicon [1] is further explored in this report. This reversible effect is seen in both ECR and RE hydrogen passivated n-channel thin film transistors (TFTs) but is not seen in the corresponding hydrogen passivated pchannel TFrs, nor is it seen in either n- or p-channel TETs before hydrogenation. This phenomenon has been observed when room temperature bias stressing TFTs fabricated on solid phase or laser crystallized polysilicon films on quartz substrates [1]. A model involving hydrogen release or capture at defects, positively charged hydrogen motion in device electric fields, and subsequent hydrogen capture at other defects has been proposed. This phenomenon has significant implications for polycrystalline silicon TFT’ design and operation. By extension, it also offers significant insight into the stability problems of hydrogenated amorphous silicon.

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