Kinetics of Aggregation and Crystallization of Polyaspartic Acid Stabilized Calcium Phosphate Particles at High Concentrations

2015 ◽  
Vol 16 (5) ◽  
pp. 1550-1555 ◽  
Author(s):  
Daniel V. Krogstad ◽  
Dongbo Wang ◽  
Sheng Lin-Gibson
Keyword(s):  
Calcium Phosphate ◽  
Polyaspartic Acid ◽  
Calcium Phosphate Particles ◽  
High Concentrations ◽  
Kinetics Of

scholarly journals Desensitization Contributes to the Synaptic Response of Gain-of-Function Mutants of the Muscle Nicotinic Receptor

2006 ◽  
Vol 128 (5) ◽  
pp. 615-627 ◽  
Author(s):  
Sergio Elenes ◽  
Ying Ni ◽  
Gisela D. Cymes ◽  
Claudio Grosman
Keyword(s):  
Nicotinic Receptor ◽  
Dissociation Rate ◽  
Gain Of Function ◽  
Naturally Occurring ◽  
Channel Opening ◽  
Speed Up ◽  
High Concentrations ◽  
Dissociation Rate Constants ◽  
Kinetics Of ◽  
Peak Value

Although the muscle nicotinic receptor (AChR) desensitizes almost completely in the steady presence of high concentrations of acetylcholine (ACh), it is well established that AChRs do not accumulate in desensitized states under normal physiological conditions of neurotransmitter release and clearance. Quantitative considerations in the framework of plausible kinetic schemes, however, lead us to predict that mutations that speed up channel opening, slow down channel closure, and/or slow down the dissociation of neurotransmitter (i.e., gain-of-function mutations) increase the extent to which AChRs desensitize upon ACh removal. In this paper, we confirm this prediction by applying high-frequency trains of brief (∼1 ms) ACh pulses to outside-out membrane patches expressing either lab-engineered or naturally occurring (disease-causing) gain-of-function mutants. Entry into desensitization was evident in our experiments as a frequency-dependent depression in the peak value of succesive macroscopic current responses, in a manner that is remarkably consistent with the theoretical expectation. We conclude that the comparatively small depression of the macroscopic currents observed upon repetitive stimulation of the wild-type AChR is due, not to desensitization being exceedingly slow but, rather, to the particular balance between gating, entry into desensitization, and ACh dissociation rate constants. Disruption of this fine balance by, for example, mutations can lead to enhanced desensitization even if the kinetics of entry into, and recovery from, desensitization themselves are not affected. It follows that accounting for the (usually overlooked) desensitization phenomenon is essential for the correct interpretation of mutagenesis-driven structure–function relationships and for the understanding of pathological synaptic transmission at the vertebrate neuromuscular junction.

scholarly journals Evaluation of the kinetics of oxidation and removal of organic matter in the self-purification of a mountain river

DYNA ◽  
2015 ◽  
Vol 82 (191) ◽  
pp. 183-193 ◽  
Author(s):  
Jorge Virgilio Rivera Gutiérrez
Keyword(s):  
Water Quality ◽  
Water System ◽  
The Self ◽  
Organic Load ◽  
Mountain River ◽  
Kinetics Of Oxidation ◽  
Kinetic Rates ◽  
High Concentrations ◽  
Kinetics Of

The study is based on the determination of the kinetic rates and assessment of self-purification of the Frio River, due to the uptake of organic load. The kinetic rates were calculated by applying differential and logarithmic methods on concentrations of water quality determinants present in each of the (7) reach of the river. The water system easily recovers the amount of oxygen, k<sub>d</sub>= 0.4, k<sub>a</sub> 3.2 d<sup>-1</sup>, only receives 27.7 Ton. d<sup>-1</sup>, the organic load, making high concentrations of carbon, ammonium and remain sediment. The length Influence of discharges, LIV- BOD yielded a mean per tranche of 10 km, compared to 3 km each way, means that the river can´t self- purification that need more length of travel. The study illustrates the modeling of the determinants of quality, developed by the QUAL2K, using the calculated rates.

scholarly journals The study of the microstructure of cheese before and after vacuum drying

2020 ◽  
Vol 10 (4) ◽  
pp. 6007-6014
Keyword(s):  
Calcium Phosphate ◽  
Surface Shape ◽  
Vacuum Drying ◽  
Protein Matrix ◽  
Fat Globules ◽  
Before And After ◽  
Calcium Phosphate Particles ◽  
Structure State ◽  
Cheese Microstructure ◽  
Scanning Electron

Scanning electron microscope allowed us to get screens of different cheese microstructure that form a base for further investigation of a cheese structure state before and after the process of drying and for their comparison. Any cheese structure presents a matrix of proteins penetrated with moisture capillaries; fat globules are located both inside the protein matrix and on a cheese surface. Shape of capillaries is either round or oval. Capillaries vary in size and number that has an impact on the cheese pattern which is described by hole and void shapes and order. Electron microscopy was also used for detecting deposition of calcium phosphate. Particles of calcium phosphate changed in size, before drying they were 10–12 µm, and after drying they reached 20–30 µ. These particles concentrate in the dried cheese and agglomerate into larger particles. The most concentrated calcium phosphate proportion was found in pores and micro-voids of the dry cheese. As for mature cheese samples, calcium lactate was established as well.

scholarly journals Sedimentation Study of Biphasic Calcium Phosphate Particles

2007 ◽  
pp. 365-368
Author(s):  
Ahmed Fatimi ◽  
Jean Francois Tassin ◽  
Monique Aselo V. Axelos ◽  
Pierre Weiss
Keyword(s):  
Calcium Phosphate ◽  
Biphasic Calcium Phosphate ◽  
Calcium Phosphate Particles

Impact of the Kinetics of Salt Crystallization on Stone Damage During Rewetting/Drying and Humidity Cycling

2013 ◽  
Vol 80 (2) ◽  
Author(s):  
Julie Desarnaud ◽  
François Bertrand ◽  
Noushine Shahidzadeh-Bonn
Keyword(s):  
Sodium Sulfate ◽  
Phase Contrast ◽  
Sulfate Solution ◽  
Salt Crystallization ◽  
Severe Damage ◽  
Contrast Microscopy ◽  
Salt Crystals ◽  
High Concentrations ◽  
The Impact ◽  
Kinetics Of

In this study, we show that the key to understand why the same salt can cause damage in some conditions and not in others is the kinetics of crystallization. We present experiments assessing the impact of the recrystallization dynamics of sodium sulfate on damage observed in sandstone after repeated cycles of rewetting/drying and humidification/drying. Macroscopic and microscopic scale experiments using magnetic resonance imaging and phase contrast microscopy demonstrate that sodium sulfate that has both hydrated and anhydrous phases can lead to severe damage in sandstone during rewetting/drying cycles, but not during humidity cycling. During rewetting (a rapid process) in regions (pores) that are highly concentrated in salt, anhydrous microcrystals dissolve only partially, giving rise to a heterogeneous salt solution that is supersaturated with respect to the hydrated phase. The remaining anhydrous crystals then act as seeds for the formation of large amounts of hydrated crystals, creating grape-like structures that expand rapidly. These clusters can generate stresses larger than the tensile strength of the stone, leading to damage. On the other hand, with humidification (a slow process) and after complete deliquescence of salt crystals, the homogeneous sodium sulfate solution can reach high concentrations during evaporation without any nucleation, favoring the formation of isolated anhydrous crystals (thenardite). The crystallization of the anhydrous salt generates only very small stresses compared to the hydrated clusters and therefore causes hardly any damage to the stone.

Microfiltration performance: physicochemical aspects of whey pretreatment

1995 ◽  
Vol 62 (2) ◽  
pp. 269-279 ◽  
Author(s):  
Genevieve Gesan ◽  
Georges Daufin ◽  
Uzi Merin ◽  
Jean-Pierre Labbe ◽  
Auguste Quemerais
Keyword(s):  
Calcium Phosphate ◽  
Membrane Surface ◽  
Physicochemical Process ◽  
High Shear ◽  
Lower Content ◽  
Phosphate Ions ◽  
Complex Lipid ◽  
Ionic Calcium ◽  
Calcium Phosphate Particles ◽  
Soluble Calcium

SUMMARYClarification of whey by microfiltration (MF) can be achieved after appropriate pretreatment of the feed. A control pretreatment consists of a physicochemical process comprising increased ionic calcium and pH accompanied by heat (50 °C, 15 min) to cause aggregation of complex lipid–calcium phosphate particles, which are then separated by MF. This pretreatment process was modified by increasing the temperature to 55 °C and by maintaining the pH constant during heat treatment. This modification resulted in larger calcium phosphate particles and a lower content of soluble calcium and phosphate ions. As a consequence, a longer period of MF operation, better whey clarification and lower calcium and phosphate content of the filtrate were achieved. This suggests that a loosely structured deposit was formed on the membrane surface which was less resistant to filtration than that resulting from the control pretreatment. During MF, it was necessary to avoid zones of high shear in the retentate compartment that might cause physical alteration of the aggregates.

scholarly journals Determinants in 3Dpol Modulate the Rate of Growth of Hepatitis A Virus

2010 ◽  
Vol 84 (16) ◽  
pp. 8342-8347 ◽  
Author(s):  
Krishnamurthy Konduru ◽  
Gerardo G. Kaplan
Keyword(s):  
Hepatitis A ◽  
Hepatitis A Virus ◽  
Rna Replication ◽  
Virus Genome ◽  
Nucleotide Sequence Analysis ◽  
Reverse Genetic ◽  
Genetic Studies ◽  
High Concentrations ◽  
Kinetics Of ◽  
Atypical Member

ABSTRACT Hepatitis A virus (HAV), an atypical member of the Picornaviridae, grows poorly in cell culture. To define determinants of HAV growth, we introduced a blasticidin (Bsd) resistance gene into the virus genome and selected variants that grew at high concentrations of Bsd. The mutants grew fast and had increased rates of RNA replication and translation but did not produce significantly higher virus yields. Nucleotide sequence analysis and reverse genetic studies revealed that a T6069G change resulting in a F42L amino acid substitution in the viral polymerase (3Dpol) was required for growth at high Bsd concentrations whereas a silent C7027T mutation enhanced the growth rate. Here, we identified a novel determinant(s) in 3Dpol that controls the kinetics of HAV growth.

Kinetics of the cellular intake of a gene expression inducer at high concentrations

2015 ◽  
Vol 11 (9) ◽  
pp. 2579-2587 ◽  
Author(s):  
Huy Tran ◽  
Samuel M. D. Oliveira ◽  
Nadia Goncalves ◽  
Andre S. Ribeiro
Keyword(s):  
Gene Expression ◽  
Single Event ◽  
Transcription Activity ◽  
High Concentrations ◽  
Kinetics Of

Characterization of the cellular intake kinetics of a lactose analogue fromin vivosingle-event measurements of transcription activity.

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