Classical study of atomic bound state dynamics in circularly polarized ultrastrong fields

2014 ◽  
Vol 47 (13) ◽  
pp. 135601 ◽  
Author(s):  
S S Luo ◽  
P D Grugan ◽  
B C Walker
Keyword(s):  
Bound State ◽  
Circularly Polarized ◽  
Classical Study

Differential polarization imaging of sickled cells

1988 ◽  
Vol 46 ◽  
pp. 62-63
Author(s):  
Marcos F. Maestre
Keyword(s):  
Optical Properties ◽  
Theoretical Approach ◽  
Polarized Light ◽  
Polarization Microscopy ◽  
Spectroscopic Techniques ◽  
Polarization Imaging ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
Microscopic Scale ◽  
Chiral Structures

Recently we have developed a form of polarization microscopy that forms images using optical properties that have previously been limited to macroscopic samples. This has given us a new window into the distribution of structure on a microscopic scale. We have coined the name differential polarization microscopy to identify the images obtained that are due to certain polarization dependent effects. Differential polarization microscopy has its origins in various spectroscopic techniques that have been used to study longer range structures in solution as well as solids. The differential scattering of circularly polarized light has been shown to be dependent on the long range chiral order, both theoretically and experimentally. The same theoretical approach was used to show that images due to differential scattering of circularly polarized light will give images dependent on chiral structures. With large helices (greater than the wavelength of light) the pitch and radius of the helix could be measured directly from these images.

CRYO-Electron Microscopy of the Acto-Myosin-ATP Complex

1990 ◽  
Vol 48 (1) ◽  
pp. 248-249
Author(s):  
John Trinickt ◽  
Howard White
Keyword(s):  
Electron Microscopy ◽  
Atp Hydrolysis ◽  
Myosin Head ◽  
Bound State ◽  
Cross Linking ◽  
Weakly Bound ◽  
Cryo Electron Microscopy ◽  
Myosin Subfragment 1 ◽  
Attached State ◽  
High Fraction

The primary force of muscle contraction is thought to involve a change in the myosin head whilst attached to actin, the energy coming from ATP hydrolysis. This change in attached state could either be a conformational change in the head or an alteration in the binding angle made with actin. A considerable amount is known about one bound state, the so-called strongly attached state, which occurs in the presence of ADP or in the absence of nucleotide. In this state, which probably corresponds to the last attached state of the force-producing cycle, the angle between the long axis myosin head and the actin filament is roughly 45°. Details of other attached states before and during power production have been difficult to obtain because, even at very high protein concentration, the complex is almost completely dissociated by ATP. Electron micrographs of the complex in the presence of ATP have therefore been obtained only after chemically cross-linking myosin subfragment-1 (S1) to actin filaments to prevent dissociation. But it is unclear then whether the variability in attachment angle observed is due merely to the cross-link acting as a hinge.We have recently found low ionic-strength conditions under which, without resorting to cross-linking, a high fraction of S1 is bound to actin during steady state ATP hydrolysis. The structure of this complex is being studied by cryo-electron microscopy of hydrated specimens. Most advantages of frozen specimens over ambient temperature methods such as negative staining have already been documented. These include improved preservation and fixation rates and the ability to observe protein directly rather than a surrounding stain envelope. In the present experiments, hydrated specimens have the additional benefit that it is feasible to use protein concentrations roughly two orders of magnitude higher than in conventional specimens, thereby reducing dissociation of weakly bound complexes.

Binding Mechanism and Structural Insights into the Identified Protein Target of Covid-19 with In-Vitro Effective Drug Ivermectin

2020 ◽  
Author(s):  
Parth Sarthi Sen Gupta ◽  
Satyaranjan Biswal ◽  
Saroj Kumar Panda ◽  
Abhik Kumar Ray ◽  
Malay Kumar Rana
Keyword(s):  
Ternary Complex ◽  
Bound State ◽  
Molecular Target ◽  
Cooperative Interaction ◽  
Effective Drug ◽  
Rna Dependent Rna Polymerase ◽  
Protein Target ◽  
Ternary Complex Formation ◽  
Structural Insights

<p>While an FDA approved drug Ivermectin was reported to dramatically reduce the cell line of SARS-CoV-2 by ~5000 folds within 48 hours, the precise mechanism of action and the COVID-19 molecular target involved in interaction with this in-vitro effective drug are unknown yet. Among 12 different COVID-19 targets studied here, the RNA dependent RNA polymerase (RdRp) with RNA and Helicase NCB site show the strongest affinity to Ivermectin amounting -10.4 kcal/mol and -9.6 kcal/mol, respectively. Molecular dynamics of corresponding protein-drug complexes reveals that the drug bound state of RdRp with RNA has better structural stability than the Helicase NCB site, with MM/PBSA free energy of -135.2 kJ/mol, almost twice that of Helicase (-76.6 kJ/mol). The selectivity of Ivermectin to RdRp is triggered by a cooperative interaction of RNA-RdRp by ternary complex formation. Identification of the target and its interaction profile with Ivermectin can lead to more powerful drug designs for COVID-19 and experimental exploration. </p>

Correlation of Phraseological Semantic Fields in Russian Study of Aphorisms

2020 ◽  
pp. 60-71
Author(s):  
Anshelika Korolkova
Keyword(s):  
Negative Correlation ◽  
Semantic Field ◽  
Positive Correlation ◽  
Classical Study ◽  
Semantic Fields ◽  
Zero Correlation ◽  
Russian Study

The article deals with the interconnection and interdependence of phraseological semantic fields of Russian study of aphorisms in synchronic and in diachronic approaches. The correlation of phraseological semantic fields of Russian study of aphorisms is considered as their interdependence due to various factors (linguistic and extra-linguistic ones). The correlation of the phraseological semantic fields of Russian study of aphorisms is manifested in the existence of many antinomies. The natural linguistic antinomies of life / death / immortality or war / peace, or good / evil, or friend / enemy, or villainy / nobility are reflected in Russian aphorisms and have entered the corresponding phraseological semantic fields. The corpus of Russian study of aphorisms containsnot only antinomic aphorisms, but also antinomic relations that extend to the level of language and speech. Therefore, in Russian study of aphorisms there are phraseological semantic fields that implement these antinomies. In addition to the antinomic phraseological semantic fields in the corpus of classical Russian study of aphorisms there are other types of correlations. The keywords (concepts) of many phraseological semantic fields are closely thematically connected. When the number of units from one field is changed, the number of units in another phraseological semantic field also changes. Most phraseological semantic fields of Russian study of aphorisms do not show a zero correlation in either synchronic or diachronic approaches. This is due to, first of all, the universality of the aphoristic theme, with all the ideological and thematic uniqueness of the sayings used by Russian writers. However, a few phraseological and semantic fields of aphorisms by Russian writers may show a negative correlation, which is due to the diversity of the thematic groups that comprise them. A positive correlation of phraseological semantic fields, the most significant in the number of their constituent components, shows deep internal linguistic systemic connections in Russian classical study of aphorisms.

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