scholarly journals Structural Characterization and Anti-Proliferation Activities Against Tumor Cells of an Arabinogalactan from Juniperus convallium

Molecules ◽  
2019 ◽  
Vol 24 (10) ◽  
pp. 1850 ◽  
Author(s):  
Beibei Li ◽  
Mengxue Dong ◽  
Ji De ◽  
Li Ye ◽  
Daofeng Chen ◽  
...  
Keyword(s):  
Public Health ◽  
Therapeutic Agent ◽  
Average Molecular Weight ◽  
2D Nmr ◽  
Filamentous Structure ◽  
Nmr Analysis ◽  
Force Microscopy ◽  
Atomic Force ◽  
Ic50 Values ◽  
Public Health Challenge

As a hyperproliferative disorder, cancer has continued to be a major public health challenge. In the present study, a polysaccharide JC-PS1 was isolated and purified from Juniperus convallium. JC-PS1 is a heteropolysaccharide composed of Ara, Gal, GalA and Rha with the average molecular weight of 280 kDa. Based on the methylation and 2D NMR analysis, JC-PS1 was elucidated as a backbone of →5)-α-Araf-(1→ and →3,5)-α-Araf-(1→, and three kinds of branches attached to the O-3 position of →3,5)-α-Araf-(1→, including β-GalpA-(1→3)-β-Galp-(1→, α-Araf-(1→3)-α-Rhap-(1→ and α-Araf-(1→3)-β-Galp-(1→. Accordingly, the atomic force microscopy of JC-PS1 showed a linear filamentous structure with small proportion of branches. Furthermore, JC-PS1 exhibited significant anti-proliferation activities against PANC-1, A431, MDA-MB-231, U118MG and H1975 cells with the IC50 values of 296.8, 477.9, 657.4, 686.7 and 862.1 μg/mL, respectively. This indicated that JC-PS1 could be a potential therapeutic agent for the treatment of cancer.

scholarly journals The Morphology and Performance of Poly(Vinyl Chloride) Containing Melamine Schiff Bases against Ultraviolet Light

Molecules ◽  
2019 ◽  
Vol 24 (4) ◽  
pp. 803 ◽  
Author(s):  
Gamal El-Hiti ◽  
Mohammad Alotaibi ◽  
Ahmed Ahmed ◽  
Basheer Hamad ◽  
Dina Ahmed ◽  
...  
Keyword(s):  
Ultraviolet Light ◽  
Vinyl Chloride ◽  
Schiff Bases ◽  
Average Molecular Weight ◽  
Hydroxyl Group ◽  
Force Microscopy ◽  
Polymeric Surface ◽  
Atomic Force ◽  
Poly Vinyl Chloride ◽  
And Performance

Five Schiff bases derived from melamine have been used as efficient additives to reduce the process of photodegradation of poly(vinyl chloride) films. The performance of Schiff bases has been investigated using various techniques. Poly(vinyl chloride) films containing Schiff bases were irradiated with ultraviolet light and any changes in their infrared spectra, weight, and the viscosity of their average molecular weight were investigated. In addition, the surface morphology of the films was inspected using a light microscope, atomic force microscopy, and a scanning electron micrograph. The additives enhanced the films resistance against irradiation and the polymeric surface was much smoother in the presence of the Schiff bases compared with the blank film. Schiff bases containing an ortho-hydroxyl group on the aryl rings showed the greatest photostabilization effect, which may possibly have been due to the direct absorption of ultraviolet light. This phenomenon seems to involve the transfer of a proton as well as several intersystem crossing processes.

scholarly journals Reverse Transcription Mechanically Initiates HIV-1 Capsid Disassembly

2017 ◽  
Vol 91 (12) ◽  
Author(s):  
Sanela Rankovic ◽  
Janani Varadarajan ◽  
Ruben Ramalho ◽  
Christopher Aiken ◽  
Itay Rousso
Keyword(s):  
Atomic Force Microscopy ◽  
Reverse Transcription ◽  
Target Cells ◽  
Filamentous Structure ◽  
Force Microscopy ◽  
The Core ◽  
Atomic Force ◽  
Capsid Shell ◽  
Hiv 1 ◽  
Capsid Disassembly

ABSTRACT The HIV-1 core consists of the viral genomic RNA and several viral proteins encased within a conical capsid. After cell entry, the core disassembles in a process termed uncoating. Although HIV-1 uncoating has been linked to reverse transcription of the viral genome in target cells, the mechanism by which uncoating is initiated is unknown. Using time-lapse atomic force microscopy, we analyzed the morphology and physical properties of isolated HIV-1 cores during the course of reverse transcription in vitro. We found that, during an early stage of reverse transcription the pressure inside the capsid increases, reaching a maximum after 7 h. High-resolution mechanical mapping reveals the formation of a stiff coiled filamentous structure underneath the capsid surface. Subsequently, this coiled structure disappears, the stiffness of the capsid drops precipitously to a value below that of a pre-reverse transcription core, and the capsid undergoes partial or complete rupture near the narrow end of the conical structure. We propose that the transcription of the relatively flexible single-stranded RNA into a more rigid filamentous structure elevates the pressure within the core, which triggers the initiation of capsid disassembly. IMPORTANCE For successful infection, the HIV-1 genome, which is in the form of a single-stranded RNA enclosed inside a capsid shell, must be reverse transcribed into double-stranded DNA and released from the capsid (in a process known as uncoating) before it can be integrated into the target cell genome. The mechanism that triggers uncoating is a pivotal question of long standing. By using atomic force microscopy, we found that during reverse transcription the pressure inside the capsid increases until the internal stress exceeds the strength of the capsid structure and the capsid breaks open. The application of AFM technologies to study purified HIV-1 cores represents a new experimental platform for elucidating additional aspects of capsid disassembly and HIV-1 uncoating.

Cryogenic atomic force microscopy

1991 ◽  
Vol 49 ◽  
pp. 54-55
Author(s):  
K. A. Fisher ◽  
M. G. L. Gustafsson ◽  
M. B. Shattuck ◽  
J. Clarke
Keyword(s):  
Room Temperature ◽  
Rapid Freezing ◽  
Cryogenic Temperatures ◽  
Soft Or ◽  
Electrically Conductive ◽  
Force Microscopy ◽  
Flexible Molecules ◽  
Advantages And Disadvantages ◽  
Atomic Force ◽  
Chemical Perturbation

The atomic force microscope (AFM) is capable of imaging electrically conductive and non-conductive surfaces at atomic resolution. When used to image biological samples, however, lateral resolution is often limited to nanometer levels, due primarily to AFM tip/sample interactions. Several approaches to immobilize and stabilize soft or flexible molecules for AFM have been examined, notably, tethering coating, and freezing. Although each approach has its advantages and disadvantages, rapid freezing techniques have the special advantage of avoiding chemical perturbation, and minimizing physical disruption of the sample. Scanning with an AFM at cryogenic temperatures has the potential to image frozen biomolecules at high resolution. We have constructed a force microscope capable of operating immersed in liquid n-pentane and have tested its performance at room temperature with carbon and metal-coated samples, and at 143° K with uncoated ferritin and purple membrane (PM).

AFM study of the dynamics of α-alumina surface faceting during high-temperature processing

1995 ◽  
Vol 53 ◽  
pp. 334-335 ◽  
Author(s):  
Michael W. Bench ◽  
Jason R. Heffelfinger ◽  
C. Barry Carter
Keyword(s):  
High Temperature ◽  
Thin Foil ◽  
Sem Analysis ◽  
Conductive Coatings ◽  
Force Microscopy ◽  
Minimal Sample ◽  
Atomic Force ◽  
Formation And Evolution ◽  
High Temperature Processing ◽  
Nominal Surface

To gain a better understanding of the surface faceting that occurs in α-alumina during high temperature processing, atomic force microscopy (AFM) studies have been performed to follow the formation and evolution of the facets. AFM was chosen because it allows for analysis of topographical details down to the atomic level with minimal sample preparation. This is in contrast to SEM analysis, which typically requires the application of conductive coatings that can alter the surface between subsequent heat treatments. Similar experiments have been performed in the TEM; however, due to thin foil and hole edge effects the results may not be representative of the behavior of bulk surfaces.The AFM studies were performed on a Digital Instruments Nanoscope III using microfabricated Si3N4 cantilevers. All images were recorded in air with a nominal applied force of 10-15 nN. The alumina samples were prepared from pre-polished single crystals with (0001), , and nominal surface orientations.

Scanning tunneling microscopy and atomic force microscopy: New tools for biology

1989 ◽  
Vol 47 ◽  
pp. 778-779
Author(s):  
CE Bracker ◽  
P. K. Hansma
Keyword(s):  
Physical Property ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Small Scale ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
New Family ◽  
Small Probe ◽  
Atomic Force ◽  
Transmission Electron

A new family of scanning probe microscopes has emerged that is opening new horizons for investigating the fine structure of matter. The earliest and best known of these instruments is the scanning tunneling microscope (STM). First published in 1982, the STM earned the 1986 Nobel Prize in Physics for two of its inventors, G. Binnig and H. Rohrer. They shared the prize with E. Ruska for his work that had led to the development of the transmission electron microscope half a century earlier. It seems appropriate that the award embodied this particular blend of the old and the new because it demonstrated to the world a long overdue respect for the enormous contributions electron microscopy has made to the understanding of matter, and at the same time it signalled the dawn of a new age in microscopy. What we are seeing is a revolution in microscopy and a redefinition of the concept of a microscope.Several kinds of scanning probe microscopes now exist, and the number is increasing. What they share in common is a small probe that is scanned over the surface of a specimen and measures a physical property on a very small scale, at or near the surface. Scanning probes can measure temperature, magnetic fields, tunneling currents, voltage, force, and ion currents, among others.

Morphology and development of flow-pattern defect with extended nonagitated Secco etching

1994 ◽  
Vol 52 ◽  
pp. 868-869
Author(s):  
Y. Pan
Keyword(s):  
Flow Pattern ◽  
Silicon Crystal ◽  
Gate Oxide ◽  
Crystal Growth Rate ◽  
Etch Depth ◽  
Force Microscopy ◽  
Etch Pit ◽  
Float Zone ◽  
Atomic Force ◽  
Multiple Step

The D defect, which causes the degradation of gate oxide integrities (GOI), can be revealed by Secco etching as flow pattern defect (FPD) in both float zone (FZ) and Czochralski (Cz) silicon crystal or as crystal originated particles (COP) by a multiple-step SC-1 cleaning process. By decreasing the crystal growth rate or high temperature annealing, the FPD density can be reduced, while the D defectsize increased. During the etching, the FPD surface density and etch pit size (FPD #1) increased withthe etch depth, while the wedge shaped contours do not change their positions and curvatures (FIG.l).In this paper, with atomic force microscopy (AFM), a simple model for FPD morphology by non-crystallographic preferential etching, such as Secco etching, was established.One sample wafer (FPD #2) was Secco etched with surface removed by 4 μm (FIG.2). The cross section view shows the FPD has a circular saucer pit and the wedge contours are actually the side surfaces of a terrace structure with very small slopes. Note that the scale in z direction is purposely enhanced in the AFM images. The pit dimensions are listed in TABLE 1.

Surface roughness measurements of vanadium-contaminated fluidized cracking catalysts by atomic force microscopy

1996 ◽  
Vol 54 ◽  
pp. 866-867
Author(s):  
H. Kinney ◽  
M.L. Occelli ◽  
S.A.C. Gould
Keyword(s):  
Surface Roughness ◽  
Zeolite Y ◽  
Atomic Level ◽  
Microporous Structure ◽  
Contact Mode ◽  
Force Microscopy ◽  
Atomic Force ◽  
Before And After ◽  
Roughness Measurements ◽  
Cracking Catalysts

For this study we have used a contact mode atomic force microscope (AFM) to study to topography of fluidized cracking catalysts (FCC), before and after contamination with 5% vanadium. We selected the AFM because of its ability to well characterize the surface roughness of materials down to the atomic level. It is believed that the cracking in the FCCs occurs mainly on the catalysts top 10-15 μm suggesting that the surface corrugation could play a key role in the FCCs microactivity properties. To test this hypothesis, we chose vanadium as a contaminate because this metal is capable of irreversibly destroying the FCC crystallinity as well as it microporous structure. In addition, we wanted to examine the extent to which steaming affects the vanadium contaminated FCC. Using the AFM, we measured the surface roughness of FCCs, before and after contamination and after steaming.We obtained our FCC (GRZ-1) from Davison. The FCC is generated so that it contains and estimated 35% rare earth exchaged zeolite Y, 50% kaolin and 15% binder.

Development of the UHV-STM

1990 ◽  
Vol 48 (1) ◽  
pp. 322-323
Author(s):  
M. Iwatsuki ◽  
S. Kitamura ◽  
A. Mogami
Keyword(s):  
Surface Science ◽  
Real Space ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Great Promise ◽  
Force Microscopy ◽  
Atomic Force ◽  
Stm Image ◽  
Surface Construction ◽  
Very High

Since Binnig, Rohrer and associates observed real-space topographic images of Si(111)-7×7 and invented the scanning tunneling microscope (STM),1) the STM has been accepted as a powerful surface science instrument.Recently, many application areas for the STM have been opened up, such as atomic force microscopy (AFM), magnetic force microscopy (MFM) and others. So, the STM technology holds a great promise for the future.The great advantages of the STM are its high spatial resolution in the lateral and vertical directions on the atomic scale. However, the STM has difficulty in identifying atomic images in a desired area because it uses piezoelectric (PZT) elements as a scanner.On the other hand, the demand to observe specimens under UHV condition has grown, along with the advent of the STM technology. The requirment of UHV-STM is especially very high in to study of surface construction of semiconductors and superconducting materials on the atomic scale. In order to improve the STM image quality by keeping the specimen and tip surfaces clean, we have built a new UHV-STM (JSTM-4000XV) system which is provided with other surface analysis capability.

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