Atomic Force and Electron Microscopy of High Molecular Weight Circular DNA Complexes with Synthetic Oligopeptide Trivaline

2000 ◽  
Vol 17 (4) ◽  
pp. 687-695 ◽  
Author(s):  
Larissa P. Martinkina ◽  
Dmitry V. Klinov ◽  
Alexander A. Kolesnikov ◽  
Vyacheslav Yu. Yurchenko ◽  
Sergey A. Streltsov ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Dna Complexes ◽  
Circular Dna ◽  
Atomic Force

Stereocomplex electrospun fibers from high molecular weight of poly(L-lactic acid) and poly(D-lactic acid)

2020 ◽  
Vol 40 (2) ◽  
pp. 136-142 ◽  
Author(s):  
Homa Maleki ◽  
Hossein Barani
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Thermal Properties ◽  
High Molecular Weight ◽  
Chemical Properties ◽  
Electrospun Fibers ◽  
Scanning Calorimetry ◽  
Force Microscopy ◽  
Atomic Force ◽  
Electrospinning Method

AbstractThe stereocomplex formation is a promising method to improve the properties of poly(lactide) (PLA)-based products due to the strong interaction of the side-by-side arrangement of the molecular chains. Recently, electrospinning method has been applied to prepare PLA stereocomplex, which is more convenient. The objective of the current study is to make stereocomplexed PLA nanofibers using electrospinning method and compare their properties and structures with pure poly(l-lactide) (PLLA) fibers. The stereocomplexed fibers were electrospun from a blend solution of high molecular weight PLLA and poly(d-lactide) (1:1 ratio). The morphology of the obtained electrospun fibers was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Differential scanning calorimetry was applied to study their thermal properties and crystallinity. Fourier transform infrared spectroscopy (FTIR) test was conducted on the samples to characterize their chemical properties. The SEM and AFM images indicated that smooth uniform fibers with a cylindrical structure were produced. Besides, the FTIR results and thermal properties confirmed that only stereocomplex crystallites formed in the resulting fibers via the electrospinning method.

Synthesis of polystyrene-grafted carbon nanocapsules

2007 ◽  
Vol 22 (1) ◽  
pp. 132-140 ◽  
Author(s):  
Hsuan-Ming Huang ◽  
Hung-Chieh Tsai ◽  
I-Chun Liu ◽  
Raymond Chien-Chao Tsiang
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Polymeric Composite ◽  
Decomposition Temperature ◽  
Polymeric Composite Material ◽  
Scanning Calorimetry ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Carbon Nanocapsules

A novel polymeric composite material, polystyrene (PS)-grafted carbon nanocapsules (CNCs), has been prepared. sec-butyllithium was first used to introduce negative charges on CNCs, and these CNC carbanions acted then as initiators for anionic polymerization of styrene. Based on a weight loss at the decomposition temperature of the butyl groups, the quantity of the butyls attached to the CNC surface was determined as 1.18 wt%, corresponding to 0.25 mol% initiator per mol of carbon atom on the CNC surface. Furthermore, the decomposition temperature of butylated CNCs was lower than that of the pristine CNCs by nearly 200 °C. The polystyrene content in our PS-grafted CNC sample was approximately 20%, and the molecular weight of the grafted PS on the surface of CNCs was calculated as 1200 gmol−1. Compared with the molecular weight of the ungrafted PS, the molecular weight of grafted PS was lower, thus indicating rates of initiation and/or propagation for CNC-bound carbanions lower than those of the free sec-butyllithium. The PS-grafted CNCs had good dispersion in toluene, tetrahydrofuran, cyclohexane, and other common organic solvents in which polystyrene was dissolvable and thus indicated good compatibility when further blended with other styrenic polymers. The PS-grafted CNCs were characterized and examined by Fourier transform infrared, thermogravimetric analysis, atomic force microscopy, differential scanning calorimetry, ultraviolet-visible spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The electron microscopy images indicated that the PS-grafted CNCs were homogeneous composites containing uniform polymer/CNC ratios.

scholarly journals The deoxyribonucleic acid of Micrococcus radiodurans

1966 ◽  
Vol 101 (3) ◽  
pp. 647-650 ◽  
Author(s):  
AH Schein
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Deoxyribonucleic Acid ◽  
High Molecular Weight Dna ◽  
Caesium Chloride

The DNA of Micrococcus radiodurans was prepared by three methods. Although the recovery of DNA varied considerably, the percentage molar base ratios of the DNA from the three preparations were essentially the same: guanine, 33+/-2; adenine, 18+/-1; cytosine, 33+/-2; thymine, 17+/-1. Base compositions calculated from T(m) values and from density in caesium chloride gradients also yielded guanine+cytosine contents of 66 and 68% of total bases respectively. No unusual bases were observed. The S(20,w) values were characteristic of high-molecular-weight DNA. Electron microscopy showed the purified DNA in long strands; occasionally these were coiled.

scholarly journals The cercarial glycocalyx of Schistosoma mansoni.

1985 ◽  
Vol 100 (5) ◽  
pp. 1423-1434 ◽  
Author(s):  
J C Samuelson ◽  
J P Caulfield
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Schistosoma Mansoni ◽  
High Molecular Weight ◽  
Membrane Surface ◽  
Periodate Oxidation ◽  
Apparent Molecular Weight ◽  
Ruthenium Red ◽  
Unit Membrane

Cercariae, the freshwater stage of Schistosoma mansoni infectious to man, are covered by a single unit membrane and an immunogenic glycocalyx. When cercariae penetrate the host skin, they transform to schistosomula by shedding tails, secreting mucous and enzymes, and forming microvilli over their surface. Here the loss of the glycocalyx from cercariae transforming in vitro was studied morphologically and biochemically. By scanning electron microscopy, the glycocalyx was a dense mesh composed of 15-30 nm fibrils that obscured spines on the cercarial surface. The glycocalyx was absent on organisms fixed without osmium and was partially lost when parasites aggregated in their own secretions before fixation. By transmission electron microscopy, a 1-2 microns thick mesh of 8-15-nm fibrils was seen on parasites incubated with anti-schistosomal antibodies or fixed in aldehydes containing tannic acid or ruthenium red. Cercariae transformed to schistosomula when tails were removed mechanically and parasites were incubated in saline. Within 5 min of transformation, organisms synchronously formed microvilli which elongated to 3-5 microns by 20 min and then were shed. However, considerable fibrillar material remained adherent to the double unit membrane surface of schistosomula. For biochemical labeling, parasites were treated with eserine sulfate, which blocked cercarial swimming, secretion, infectivity, and transformation to schistosomula. Material labeled by periodate oxidation and NaB3H4 was on the surface as shown by autoradiography and had an apparent molecular weight of greater than 10(6) by chromatography. Periodate-NaB3H4 glycocalyx had an isoelectric point of 5.0 +/- 0.4 and was precipitable with anti-schistosomal antibodies. More than 60% of the radiolabeled glycocalyx was released into the medium by transforming parasites in 3 h and was recovered as high molecular weight material. Parasites labeled with periodate and fluorescein-thiosemicarbazide and then transformed had a corona of fluorescence containing microvilli, much of which was shed onto the slide. Material on cercariae labeled by lodogen-catalyzed iodination was also of high molecular weight and was antigenic. In conclusion, the cercarial glycocalyx appears to be composed of acidic high molecular weight fibrils which are antigenic and incompletely cleared during transformation.

scholarly journals Low and high molecular weight poly(l-lysine)s/poly(l-lysine)-DNA complexes initiate mitochondrial-mediated apoptosis differently

FEBS Letters ◽  
2005 ◽  
Vol 579 (27) ◽  
pp. 6191-6198 ◽  
Author(s):  
Peter Symonds ◽  
J. Clifford Murray ◽  
A. Christy Hunter ◽  
Grazyna Debska ◽  
Adam Szewczyk ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Dna Complexes ◽  
High Molecular Weight Poly

Tribotechnical properties of ultra-high molecular weight polyethylene filled with sulfur, diphenylguanidine and 2-mercaptobenzothiazole

2020 ◽  
pp. 91-98
Author(s):  
S. N. Danilova ◽  
A. A. Dyakonov ◽  
A. P. Vasiliev ◽  
Y. S. Gerasimova ◽  
A. A. Okhlopkova ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Wear Resistance ◽  
Surface Layer ◽  
Ir Spectroscopy ◽  
High Molecular Weight ◽  
High Wear Resistance ◽  
Carbonyl Groups ◽  
Tribotechnical Properties ◽  
Ultra High Molecular Weight

The paper studies tribotechnical properties, hardness and density of composites based on ultra-high molecular weight polyethylene (UHMWPE) filled with sulfur, diphenylguanidine (DFG) and 2-mercaptobenzothiazole (MBT) and their mixtures. It has been established that the introduction of selected fillers has practically no effect on hardness and density of the composites, but leads to a significant (by 2–3 times) increase in the wear resistance of materials. Using electron microscopy, it has been established that secondary structures are formed in composites containing MBT that protect the surface layer of the material from wear. Using IR spectroscopy, it was established that tribochemical reactions occur during the wear of composites with the formation of hydroxyl and carbonyl groups. The developed materials UHMWPE / MBT and UHMWPE / FGD / MBT have high wear resistance and can be used as materials for tribological purposes.

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