scholarly journals Birefringence and DNA Condensation of Liquid Crystalline Chromosomes

2010 ◽  
Vol 9 (10) ◽  
pp. 1577-1587 ◽  
Author(s):  
Man H. Chow ◽  
Kosmo T. H. Yan ◽  
Michael J. Bennett ◽  
Joseph T. Y. Wong
Keyword(s):  
Liquid Crystalline ◽  
Nanostructural Material ◽  
Low Protein ◽  
Transmission Electron ◽  
Liquid Crystalline Phases ◽  
Multiple Orders ◽  
High Concentrations ◽  
Positive Correlations ◽  
Packaging Strategy

ABSTRACT DNA can self-assemble in vitro into several liquid crystalline phases at high concentrations. The largest known genomes are encoded by the cholesteric liquid crystalline chromosomes (LCCs) of the dinoflagellates, a diverse group of protists related to the malarial parasites. Very little is known about how the liquid crystalline packaging strategy is employed to organize these genomes, the largest among living eukaryotes—up to 80 times the size of the human genome. Comparative measurements using a semiautomatic polarizing microscope demonstrated that there is a large variation in the birefringence, an optical property of anisotropic materials, of the chromosomes from different dinoflagellate species, despite their apparently similar ultrastructural patterns of bands and arches. There is a large variation in the chromosomal arrangements in the nuclei and individual karyotypes. Our data suggest that both macroscopic and ultrastructural arrangements affect the apparent birefringence of the liquid crystalline chromosomes. Positive correlations are demonstrated for the first time between the level of absolute retardance and both the DNA content and the observed helical pitch measured from transmission electron microscopy (TEM) photomicrographs. Experiments that induced disassembly of the chromosomes revealed multiple orders of organization in the dinoflagellate chromosomes. With the low protein-to-DNA ratio, we propose that a highly regulated use of entropy-driven force must be involved in the assembly of these LCCs. Knowledge of the mechanism of packaging and arranging these largest known DNAs into different shapes and different formats in the nuclei would be of great value in the use of DNA as nanostructural material.

Use of light microscopy in the qualitative and quantitative study of liquid crystalline order

1992 ◽  
Vol 50 (1) ◽  
pp. 264-265
Author(s):  
Christopher Viney
Keyword(s):  
Light Microscopy ◽  
Liquid Crystalline ◽  
Structural Characteristics ◽  
Molecular Order ◽  
Liquid Crystalline Phases ◽  
Convenient Technique ◽  
Liquid Crystalline Materials ◽  
Transparent Windows

Light microscopy is a convenient technique for characterizing molecular order in fluid liquid crystalline materials. Microstructures can usually be observed under the actual conditions that promote the formation of liquid crystalline phases, whether or not a solvent is required, and at temperatures that can range from the boiling point of nitrogen to 600°C. It is relatively easy to produce specimens that are sufficiently thin and flat, simply by confining a droplet between glass cover slides. Specimens do not need to be conducting, and they do not have to be maintained in a vacuum. Drybox or other controlled environmental conditions can be maintained in a sealed chamber equipped with transparent windows; some heating/ freezing stages can be used for this purpose. It is relatively easy to construct a modified stage so that the generation and relaxation of global molecular order can be observed while specimens are being sheared, simulating flow conditions that exist during processing. Also, light only rarely affects the chemical composition or molecular weight distribution of the sample. Because little or no processing is required after collecting the sample, one can be confident that biologically derived materials will reveal many of their in vivo structural characteristics, even though microscopy is performed in vitro.

Liquid crystalline phases of monoolein and water for topical delivery of cyclosporin A: Characterization and study of in vitro and in vivo delivery

2006 ◽  
Vol 63 (2) ◽  
pp. 146-155 ◽  
Author(s):  
Luciana B. Lopes ◽  
João L.C. Lopes ◽  
Dionéia C.R. Oliveira ◽  
José A. Thomazini ◽  
M. Tereza J. Garcia ◽  
...  
Keyword(s):  
Cyclosporin A ◽  
Liquid Crystalline ◽  
Topical Delivery ◽  
Crystalline Phases ◽  
Liquid Crystalline Phases ◽  
In Vivo Delivery

Effects of diets high in refined carbohydrates on renal ammonium excretion in rats

1986 ◽  
Vol 250 (2) ◽  
pp. E156-E163 ◽  
Author(s):  
H. G. Preuss ◽  
R. Fournier ◽  
J. Areas ◽  
D. Slemmer
Keyword(s):  
Protein Intake ◽  
Complex Form ◽  
Ammonium Excretion ◽  
Spontaneously Hypertensive ◽  
Low Protein ◽  
Positive Correlations ◽  
Refined Carbohydrates ◽  
High Sucrose

Ammonium excretion was investigated in spontaneously hypertensive rats (SHR) and normotensive control rats (WKY) ingesting different diets. SHR and WKY on low protein-high sucrose diets surprisingly showed the same ammonium excretion as rats ingesting a higher protein-lower sucrose diet. This was unexpected, because ammonium excretion correlates positively with protein intake. The relatively high ammonium excretion despite low protein intake (approximately 40% of control) was not associated with acidosis, hypokalemia, hypocalcemia, and/or hypomagnesemia. In a follow-up study, where diets were high in refined carbohydrates (sucrose, glucose, and starch) but more equal in protein content compared with a diet high in carbohydrates of a more complex form (grains), ammonium excretion increased significantly. When we examined the factors known to influence ammonium excretion, the only significant positive correlations found were between norepinephrine, epinephrine, dopamine, and ammonium excretion. These correlations still remained significant when only the data from the rats on the diets high in refined carbohydrates, i.e., rats on the same dietary intake of minerals and proteins, were compared. In vitro, we corroborated that catecholamines significantly increased ammoniagenesis from kidney slices. Our data show that diets high in refined carbohydrates augment both ammonium and catecholamine excretion and suggest that these two events may be interrelated.

Self-assembly of surfactant-silicate nanophases

1995 ◽  
Vol 53 ◽  
pp. 180-181
Author(s):  
S. A. Walker ◽  
J. A. Zasadzinski
Keyword(s):  
Self Assembly ◽  
Liquid Crystalline ◽  
Freeze Fracture ◽  
Initial Step ◽  
New Variety ◽  
Transmission Electron ◽  
Liquid Crystalline Phases ◽  
Trimethyl Benzene ◽  
Organic Surfactant

Nanostructured zeolites are ubiquitous throughout chemistry as catalysts and sorption media' A new variety of zeolites, constructed by templating inorganic silica on surfactant liquid crystalline phases, consist of ordered arrays of cylindrical pores with diameters ranging from 20 Å to greater than 500 Å. The nanostructure of these materials can be tailored to a variety of applications, each of which makes use of the zeolite network's large surface area and prescribed microstructure. Recent studies indicate that the initial step in the nanophase formation is a cooperative self-assembly of inorganic silicate species and organic surfactant species, dictated by ionic interaction between silicate anions and cationic surfactants. Freeze-fracture transmission electron microscopy (FF-TEM) is the only technique that can visualize this self-assembly process in situ to determine phase boundaries and examine the formation mechanism.The nanophases form on mixing aqueous cetyl trimethylammonium bromide (CTAB) with silicate (SiO2; prepared from CAB-O-SIL M-5, tetramethylammonium hydroxide (TMA-OH), trimethyl benzene (TMB), methanol (CH3OH), and water).

Invite Article: The Liquid-Crystalline Phases of Double-Stranded Nucleic Acids in Vitro and in Vivo

1988 ◽  
Vol 3 (11) ◽  
pp. 1443-1459 ◽  
Author(s):  
Yu M. Yevdokimov ◽  
S. G. Skuridin ◽  
V. I. Salyanov
Keyword(s):  
Nucleic Acids ◽  
Liquid Crystalline ◽  
Crystalline Phases ◽  
Liquid Crystalline Phases

scholarly journals Vancomycin Loaded Glycerol Monooleate Liquid Crystalline Phases Modified with Surfactants

Pharmaceutics ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 521
Author(s):  
Spomenka Milak ◽  
Angela Chemelli ◽  
Otto Glatter ◽  
Andreas Zimmer
Keyword(s):  
Liquid Crystalline ◽  
Hexagonal Phase ◽  
In Vitro Release ◽  
Polarized Light ◽  
Polyglycerol Ester ◽  
Liquid Crystalline Phases ◽  
Release Data ◽  
The Impact ◽  
Glycerol Monooleate

The influence of two tuning agents, polyglycerol ester (PE) and triblock copolymer (TC), on the properties of glycerol monooleate (MO) liquid crystalline phase (LCP) was investigated to achieve the therapeutic concentration of vancomycin hydrochloride (VHCl) into the eye, topically during 60 min (1 h) and intravitreally during 2880 min (48 h). Different techniques were used to elucidate the impact of surfactants on the structure of the LCP: polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), and in vitro release tests I and II (simulating local and intravitreal application in the eye). The structure analysis by SAXS depicts that the inclusion of PE into the MO LCP provided partial transition of a hexagonal phase into a lamellar phase, and TC induced a partial transition of a hexagonal phase into an LCP which identification was difficult. The LCP modulated with PE and TC demonstrated different VHCl’s release patterns and were evaluated by comparing our release data with the literature data. The comparison indicated that the LCP modulated with 30% w/w PE could be a promising VHCl delivery system intravitreally during 2880 min.

scholarly journals Interactions of Plutonium with Pseudomonas sp. Strain EPS-1W and Its Extracellular Polymeric Substances

2016 ◽  
Vol 82 (24) ◽  
pp. 7093-7101 ◽  
Author(s):  
Mark A. Boggs ◽  
Yongqin Jiao ◽  
Zurong Dai ◽  
Mavrik Zavarin ◽  
Annie B. Kersting
Keyword(s):  
Extracellular Polymeric Substances ◽  
The United States ◽  
Aerobic Bacterium ◽  
Rapid Reduction ◽  
Content Type ◽  
Transmission Electron ◽  
Redox Active ◽  
High Concentrations ◽  
Literature Highlight

ABSTRACTSafe and effective nuclear waste disposal, as well as accidental radionuclide releases, necessitates our understanding of the fate of radionuclides in the environment, including their interaction with microorganisms. We examined the sorption of Pu(IV) and Pu(V) toPseudomonassp. strain EPS-1W, an aerobic bacterium isolated from plutonium (Pu)-contaminated groundwater collected in the United States at the Nevada National Security Site (NNSS) in Nevada. We compared Pu sorption to cells with and without bound extracellular polymeric substances (EPS). Wild-type cells with intact EPS sorbed Pu(V) more effectively than cells with EPS removed. In contrast, cells with and without EPS showed the same sorption affinity for Pu(IV).In vitroexperiments with extracted EPS revealed rapid reduction of Pu(V) to Pu(IV). Transmission electron microscopy indicated that 2- to 3-nm nanocrystalline Pu(IV)O2formed on cells equilibrated with high concentrations of Pu(IV) but not Pu(V). Thus, EPS, while facilitating Pu(V) reduction, inhibit the formation of nanocrystalline Pu(IV) precipitates.IMPORTANCEOur results indicate that EPS are an effective reductant for Pu(V) and sorbent for Pu(IV) and may impact Pu redox cycling and mobility in the environment. Additionally, the resulting Pu morphology associated with EPS will depend on the concentration and initial Pu oxidation state. While our results are not directly applicable to the Pu transport situation at the NNSS, the results suggest that, in general, stationary microorganisms and biofilms will tend to limit the migration of Pu and provide an important Pu retardation mechanism in the environment. In a broader sense, our results, along with a growing body of literature, highlight the important role of microorganisms as producers of redox-active organic ligands and therefore as modulators of radionuclide redox transformations and complexation in the subsurface.

Molecular Order in Silk Secretions

1991 ◽  
Vol 248 ◽  
Author(s):  
Christopher Viney ◽  
Keven Kerkam ◽  
Lisa Gilliland ◽  
David Kaplan ◽  
Stephen Fossey
Keyword(s):  
Liquid Crystalline ◽  
Polarized Light ◽  
Amino Acid Sequences ◽  
Silk Proteins ◽  
Secondary Structure Analysis ◽  
Liquid Crystalline Phases ◽  
Strength And Stiffness ◽  
Supramolecular Aggregates

AbstractTransmitted polarized light microscopy of various natural silk secretions reveals their ability to form nematic liquid crystalline phases. Observations of microstructure, together with a simple secondary structure analysis of known amino acid sequences in silk proteins, suggest that the rodlike structures forming the nematic phase are supramolecular aggregates, rather than individual rigid molecular segments. The optical birefringence of dragline fiber produced by controlled silking depends on the linear haul-off velocity, and can exceed the birefringence of naturally spun fibers; this suggests the possibility of in-vitro spinning of silk to obtain values of strength and stiffness even greater than those achieved in vivo.

Sign in / Sign up

Export Citation Format

Share Document