Pinocytotic-Like Forms of Mitochondria From Rat Anterior Pituitary

1968 ◽  
Vol 26 ◽  
pp. 146-147
Author(s):  
Burton B. Silver
Keyword(s):  
Electron Micrographs ◽  
Conformational Changes ◽  
Anterior Pituitary ◽  
Dynamic State ◽  
Surrounding Cell ◽  
The Matrix ◽  
The Moment ◽  
Cell Medium ◽  
Sectioned Tissue ◽  
State Of Activity

Sectioned tissue rarely indicates evidence of what is probably a highly dynamic state of activity in mitochondria which have been reported to undergo a variety of movements such as streaming, divisions and coalescence. Recently, mitochondria from the rat anterior pituitary have been fixed in a variety of configurations which suggest that conformational changes were occurring at the moment of fixation. Pinocytotic-like vacuoles which may be taking in or expelling materials from the surrounding cell medium, appear to be forming in some of the mitochondria. In some cases, pores extend into the matrix of the mitochondria. In other forms, the remains of what seems to be pinched off vacuoles are evident in the mitochondrial interior. Dense materials, resembling secretory droplets, appear at the junction of the pores and the cytoplasm. The droplets are similar to the secretory materials commonly identified in electron micrographs of the anterior pituitary.

A Biological System Producing a Self-Assembling Cholesteric Protein Liquid Crystal

1971 ◽  
Vol 8 (1) ◽  
pp. 93-109
Author(s):  
A. C. NEVILLE ◽  
B. M. LUKE
Keyword(s):  
Liquid Crystal ◽  
Electron Density ◽  
Electron Micrographs ◽  
Self Assembly ◽  
Liquid Crystalline ◽  
Density Variation ◽  
Self Assembling ◽  
The Matrix ◽  
Electron Density Variation ◽  
Helicoidal Structure

The protein in the oothecal glands of praying mantids (Sphodromantis tenuidentata, Miomantis monacha) exists in the form of lamellar liquid crystalline spherulites, which coalesce as they flow out of a punctured gland tubule. Electron micrographs of sections of these spherulites after fixation show parabolic patterns of an electron-light component, set in a continuous matrix of protein. Such patterns arise in helicoidal systems (e.g. arthropod cuticle) and microdensitometric scans of the matrix show a rhythmical electron-density variation consistent with helicoidal structure. Double spiral patterns identical to those seen in liquid crystal spherulites are illustrated. These properties resemble those of cholesteric liquid crystals. The constructional units appear to be molecular rather than fibrillar as described by previous authors. The helicoidal architecture arises by self-assembly in the gland lumen. Lamellar surface structures self-assembled spontaneously on glass coverslips when the protein was left to stand for several days. When heated to 55 °C, the birefringent liquid crystalline protein abruptly changes to an isotropic gel, with associated loss of parabolic patterning in electron micrographs and of the rhythmical electron-density variation on microdensitometric scans. This behaviour is compared to the formation of gelatin from collagen, in terms of the randomization of an originally ordered secondary structure.

ROTATIONS AND VIBRATIONS OF FULLERENES IN THE MOLECULAR COMPLEX C20@C80

2021 ◽  
pp. 35-48
Author(s):  
M.A. Bubenchikov ◽  
◽  
A.M. Bubenchikov ◽  
D.V. Mamontov ◽  
◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Classical Mechanics ◽  
Rotation Frequency ◽  
Dynamic State ◽  
Large Molecules ◽  
Rotational Degrees Of Freedom ◽  
Rotational Motions ◽  
Centers Of Mass ◽  
The Moment

The aim of this work is to apply classical mechanics to a description of the dynamic state of C20@C80 diamond complex. Endohedral rotations of fullerenes are of great interest due to the ability of the materials created on the basis of onion complexes to accumulate energy at rotational degrees of freedom. For such systems, a concept of temperature is not specified. In this paper, a closed description of the rotation of large molecules arranged in diamond shells is obtained in the framework of the classical approach. This description is used for C20@C80 diamond complex. Two different problems of molecular dynamics, distinguished by a fixing method for an outer shell of the considered bimolecular complex, are solved. In all the cases, the fullerene rotation frequency is calculated. Since a class of possible motions for a single carbon body (molecule) consists of rotations and translational displacements, the paper presents the equations determining each of these groups of motions. Dynamic equations for rotational motions of molecules are obtained employing the moment of momentum theorem for relative motions of the system near the fullerenes’ centers of mass. These equations specify the operation of the complex as a molecular pendulum. The equations of motion of the fullerenes’ centers of mass determine vibrations in the system, i.e. the operation of the complex as a molecular oscillator.

scholarly journals D-Optimal Slope Design for Second Degree Kronecker Model Mixture Experiment With Three Ingredients

2020 ◽  
Vol 9 (2) ◽  
pp. 30
Author(s):  
Ngigi Peter Kung’u ◽  
J. K. Arap Koske ◽  
Josphat K. Kinyanjui
Keyword(s):  
Information Matrix ◽  
Coefficient Matrix ◽  
Three Dimensions ◽  
Matrix Means ◽  
The Matrix ◽  
Optimal Values ◽  
The Moment ◽  
Product Algebra ◽  
Slope Design ◽  
Second Degree

This study presents an investigation of an optimal slope design in the second degree Kronecker model for mixture experiments in three dimensions. The study is restricted to weighted centroid designs, with the second degree Kronecker model. A well-defined coefficient matrix is used to select a maximal parameter subsystem for the model since its full parameter space is inestimable. The information matrix of the design is obtained using a linear function of the moment matrices for the centroids and directly linked to the slope matrix. The discussion is based on Kronecker product algebra which clearly reflects the symmetries of the simplex experimental region. Eventually the matrix means are used in determining optimal values of the efficient developed design.

scholarly journals The Dynamic Life of Virus Capsids

Viruses ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 618
Author(s):  
Michael B. Sherman ◽  
Hong Q. Smith ◽  
Thomas J. Smith
Keyword(s):  
Immune System ◽  
Small Molecules ◽  
Conformational Changes ◽  
Environmental Cues ◽  
Virus Capsids ◽  
P Domain ◽  
Single Polypeptide ◽  
Dynamic Structures ◽  
The Moment ◽  
The Right

Protein-shelled viruses have been thought as “tin cans” that merely carry the genomic cargo from cell to cell. However, through the years, it has become clear that viruses such as rhinoviruses and caliciviruses are active and dynamic structures waiting for the right environmental cues to deliver their genomic payload to the host cell. In the case of human rhinoviruses, the capsid has empty cavities that decrease the energy required to cause conformational changes, resulting in the capsids “breathing”, waiting for the moment when the receptor binds for it to release its genome. Most strikingly, the buried N-termini of VP1 and VP4 are transiently exposed during this process. A more recent example of a “living” protein capsid is mouse norovirus (MNV). This family of viruses have a large protruding (P) domain that is loosely attached to the shell via a single-polypeptide tether. Small molecules found in the gut, such as bile salts, cause the P domains to rotate and collapse onto the shell surface. Concomitantly, bile alters the conformation of the P domain itself from one that binds antibodies to one that recognizes receptors. In this way, MNV appears to use capsid flexibility to present one face to the immune system and a completely different one to attack the host tissue. Therefore, it appears that even protein-shelled viruses have developed an impressive array of tricks to dodge our immune system and efficiently attack the host.

Effect of Deep Cryogenic Process on the Microstructure and Hardness and Wear Resistance of High Carbon Tool Steel

2018 ◽  
Vol 934 ◽  
pp. 100-104
Author(s):  
Yuan Ching Lin ◽  
Ji Wei Gong
Keyword(s):  
Wear Resistance ◽  
Tool Steel ◽  
Cryogenic Treatment ◽  
Wear Test ◽  
High Carbon ◽  
Deep Cryogenic Treatment ◽  
Treatment Conditions ◽  
The Matrix ◽  
Cryogenic Process ◽  
The Moment

In this investigation, the effects of different heat treatment conditions on the mechanical properties of high carbon tool steel (SK2) were explored. Experimental results indicated that immediately doing deep cryogenic treatment can effectively reduce retained austenite after quenching. The moment of the holding time for the cryogenic treatment was extended can promote the fine carbides precipitated, and thus increased its hardness. The results of X-ray diffraction showed that the carbides in the matrix included Fe3C and Fe7C3.The wear test results demonstrated that the specimen with Q-T1hr-C24hr-T1hr treatment has the highest wear resistance than the others, which was caused by the effect of several tempering processes to improve toughness of the matrix and to precipitate considerable quantities of the fine carbides.

scholarly journals Influence of the addition sequence of PVA-fibers and water on mixing and rheological behavior of mortars

2016 ◽  
Vol 9 (2) ◽  
pp. 226-243 ◽  
Author(s):  
M. S. de França ◽  
F. A. Cardoso ◽  
R. G. Pileggi
Keyword(s):  
Rheological Behavior ◽  
Mechanical Performance ◽  
Mixing Time ◽  
Mix Design ◽  
Mixing Process ◽  
Water Addition ◽  
Test Parameters ◽  
The Matrix ◽  
Mixing Sequences ◽  
The Moment

ABSTRACT The mixing process of fiber-containing cementitious suspensions is a crucial factor to obtaining a good dispersion of fibers and guarantee adequate mechanical performance of the hardened products. The addition of fibers into the suspension causes reduction of the fluidity of the system due to factors inherent to the fibers, the matrix and their interaction. During mixing, these interactions make dispersion and homogenization processes more difficult due to the formation of fibers - particles agglomerates. Conventional techniques to assess workability of mortars are inadequate to evaluate the rheological behavior of fiber-reinforced systems, in which parameters like viscosity and yield stress are not completely taken into account. Therefore, this work employs rotational rheometry to evaluate the influence of fiber and water addition sequences on mixing and rheological behavior of mortars containing Polyvinyl Alcohol (PVA) fibers. Constant test parameters were: mixing time of 317s; impeller velocity 126.5 rpm; water flow 128g/s. A constant mix design was used with a water content of 16%wt, and a 0.2%vol of fibers were added to the reference composition. Four mixing sequences were studied: S1 and S2 are based on the addition of fibers at different stages of the mixing process; while in S3 and S4 not only the fibers are added at different stages, but also the water addition is performed in two steps (25% first and 75% latter).Results showed that it is possible to optimize the mixing step of fiber-containing systems by changing the moment of fiber addition into the mixture. The introduction of fibers after mixing the dry mortar with water, when it already had achieved its fluidity point, demanded a lower mixing effort and produced a more flowable material.

scholarly journals Structural Mechanism of Transport of Mitochondrial Carriers

2021 ◽  
Vol 90 (1) ◽  
Author(s):  
J. J. Ruprecht ◽  
E.R.S. Kunji
Keyword(s):  
Binding Site ◽  
Conformational Changes ◽  
Substrate Binding ◽  
Ion Homeostasis ◽  
Annual Review ◽  
Publication Date ◽  
Intermembrane Space ◽  
Substrate Binding Site ◽  
Mitochondrial Carriers ◽  
The Matrix

Members of the mitochondrial carrier family [solute carrier family 25 (SLC25)] transport nucleotides, amino acids, carboxylic acids, fatty acids, inorganic ions, and vitamins across the mitochondrial inner membrane. They are important for many cellular processes, such as oxidative phosphorylation of lipids and sugars, amino acid metabolism, macromolecular synthesis, ion homeostasis, cellular regulation, and differentiation. Here, we describe the functional elements of the transport mechanism of mitochondrial carriers, consisting of one central substrate-binding site and two gates with salt-bridge networks on either side of the carrier. Binding of the substrate during import causes three gate elements to rotate inward, forming the cytoplasmic network and closing access to the substrate-binding site from the intermembrane space. Simultaneously, three core elements rock outward, disrupting the matrix network and opening the substrate-binding site to the matrix side of the membrane. During export, substrate binding triggers conformational changes involving the same elements but operating in reverse. Expected final online publication date for the Annual Review of Biochemistry, Volume 90 is June 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Probabilistic representations of matrix variate skew normal models

2015 ◽  
Vol 23 (1) ◽  
Author(s):  
Wei Ning
Keyword(s):  
Normal Distribution ◽  
Random Variable ◽  
Moment Generating Function ◽  
Normal Random Variable ◽  
Skew Normal Distribution ◽  
Probabilistic Representation ◽  
The Matrix ◽  
Distribution Family ◽  
The Moment ◽  
Skew Normal

AbstractAzzalini [Scand. J. Stat. 12 (1985), 171–178] first introduced the skew normal distribution family with a shape parameter λ, and then extended this family by adding an additional shape parameters ξ. Basic properties of these two families were studied. Henze [Scand. J. Stat. 13 (1986), 271–275] gave the probabilistic representations for these two families by interpreting it as the linear combination of a normal random variable with another normal random variable truncated at the origin and several properties were illustrated. Chen and Gupta [Statistics 39 (2005), no. 3, 247–253] extended the skew normal distribution family to the matrix variate and proposed the moment generating function and the quadratic form of the matrix variate skew normal models. Motivated by these results, we first study the probabilistic representation for the matrix variate skew normal models and several properties. Then we define the extended skew normal model of the matrix variate, and give the probabilistic representation for this family and its extension.

New methods to simultaneously localize proteoglycan by LM and EM

1978 ◽  
Vol 36 (2) ◽  
pp. 672-673
Author(s):  
Nona Shepard
Keyword(s):  
Articular Cartilage ◽  
Electron Micrographs ◽  
Toluidine Blue ◽  
Chemical Interaction ◽  
Ruthenium Red ◽  
Cationic Dyes ◽  
Keratan Sulphate ◽  
New Methods ◽  
Pathological Conditions ◽  
Sectioned Tissue

Proteoglycan is a major component ofa cartilage and up to 70% can be lost during routine processing unless special measures are taken. With this in mind and the fact that proteoglycan loss and or alteration is primary in most pathological conditions of articular cartilage, full retention is, therefore, essential to validate the interpreting of electron micrographs.The cationic dyes, Safranin 0 and Toluidine Blue 0, seemed like likely candidates as their chemical interaction with proteoglycan has been well documented by Rosenberg. Both dyes bind stoichlometrically to polyanions; one molecule of dye to each negatively charged chondroitin 6 - sulfate or keratan sulphate molecule. Szirmal has reported that cationic dyes bind proteoglycan of fresh sectioned tissue. Therefore, following Insitu fixation with Safaranin 0 or Toluidinz Blue 0, thz resulting Image would be a quantitative example of proteoglycan localization and if present in sufficent mass would scatter electrons. Ruthenium red is widely used for E. M., but we found it of little value as an L. M. stain

scholarly journals THE MORPHOLOGY OF THE SWELLING PROCESS IN RAT LIVER MITOCHONDRIA

1971 ◽  
Vol 48 (2) ◽  
pp. 291-302 ◽  
Author(s):  
D. R. Myron ◽  
J. L. Connelly
Keyword(s):  
Electron Microscope ◽  
Outer Membrane ◽  
Rat Liver ◽  
Conformational Changes ◽  
Large Amplitude ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
The Matrix

Through the use of combined spectrophotometric and electron microscope techniques, large amplitude swelling of rat liver mitochondria has been described as an ordered sequence of ultrastructural transitions. Prior to the actual swelling, mitochondria undergo two major conformational changes: condensed to twisted form and twisted to orthodox form. This sequence is independent of (a) the nature of swelling agents and (b) the time of onset of swelling. Agents that delay the onset of swelling act to increase the duration of the twisted conformation. Agents that prevent extensive swelling hold mitochondria in intermediate conformations. Gross swelling, immediately preceded by a decrease in electron opacity of the matrix, involves the rupture of the outer membrane and expansion of the inner compartment of the mitochondrion.

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