Half-Time Heat Map Reveals Ultrasonic Effects on Morphology and Kinetics of Amyloidogenic Aggregation Reaction

2021 ◽  
Author(s):  
Kichitaro Nakajima ◽  
Hajime Toda ◽  
Keiichi Yamaguchi ◽  
Masatomo So ◽  
Kensuke Ikenaka ◽  
...  
Keyword(s):  
Half Time ◽  
Heat Map ◽  
Kinetics Of

scholarly journals Fast-Scanning Chip-Calorimetry Measurement of Crystallization Kinetics of Poly(Glycolic Acid)

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 891
Author(s):  
Yongxuan Chen ◽  
Kefeng Xie ◽  
Yucheng He ◽  
Wenbing Hu
Keyword(s):  
Crystallization Kinetics ◽  
Temperature Region ◽  
Glycolic Acid ◽  
Crystal Nucleation ◽  
Side Group ◽  
Half Time ◽  
Temperature Range ◽  
Chip Calorimetry ◽  
Kinetics Of ◽  
Fast Scanning Chip Calorimetry

We report fast-scanning chip-calorimetry measurement of isothermal crystallization kinetics of poly(glycolic acid) (PGA) in a broad temperature range. We observed that PGA crystallization could be suppressed by cooling rates beyond -100 K s−1 and, after fast cooling, by heating rates beyond 50 K s-1. In addition, the parabolic curve of crystallization half-time versus crystallization temperature shows that PGA crystallizes the fastest at 130 °C with the minimum crystallization half-time of 4.28 s. We compared our results to those of poly(L-lactic acid) (PLLA) with nearby molecular weights previously reported by Androsch et al. We found that PGA crystallizes generally more quickly than PLLA. In comparison to PLLA, PGA has a much smaller hydrogen side group than the methyl side group in PLLA; therefore, crystal nucleation is favored by the higher molecular mobility of PGA in the low temperature region as well as by the denser molecular packing of PGA in the high temperature region, and the two factors together decide the higher crystallization rates of PGA in the whole temperature range.

scholarly journals Melt Crystallization Behavior and Crystalline Morphology of Polylactide/Poly(ε-caprolactone) Blends Compatibilized by Lactide-Caprolactone Copolymer

Polymers ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1181 ◽  
Author(s):  
Chunmei Zhang ◽  
Qiaofeng Lan ◽  
Tianliang Zhai ◽  
Shengqiang Nie ◽  
Jun Luo ◽  
...  
Keyword(s):  
Crystallization Behavior ◽  
Crystallization Time ◽  
Half Time ◽  
Melt Crystallization ◽  
Crystalline Morphology ◽  
Casting Method ◽  
Three Samples ◽  
Significant Difference ◽  
Compatibilization Effect ◽  
Kinetics Of

Lactide-Caprolactone copolymer (LACL) was added to a Polylactide/Poly(ε-caprolactone) (PLA/PCL) blend as a compatibilizer through solution mixing and the casting method. The melt crystallization behavior and crystalline morphology of PLA, PLA/PCL, and PLA/PCL/LACL were investigated using differential scanning calorimeter (DSC) and polarized optical microscopy (POM), respectively. The temperature of the shortest crystallization time for the samples was observed at 105 °C. The overall isothermal melt crystallization kinetics of the three samples were further studied using the Avrami theory. Neat PLA showed a higher half-time of crystallization than that of the PLA/PCL and PLA/PCL/LACL blends, whereas the half-time of crystallization of PLA/PCL and PLA/PCL/LACL showed no significant difference. The addition of PCL decreased the spherulite size of crystallized PLA, and the nuclei density in the PLA/PCL/LACL blend was much higher than that of the PLA and PLA/PCL samples, indicating that LACL had a compatibilization effect on the immiscible PLA/PCL blend, thereby promoting the nucleation of PLA. The spherulites in the PLA/PCL and PLA/PCL/LACL blend exhibited a smeared and rough morphology, which can be attributed to the fact that PCL molecules migrated to the PLA spherulitic surface during the crystallization of PLA.

scholarly journals Physical Properties and Non-Isothermal Crystallisation Kinetics of Primary Mechanically Recycled Poly(l-lactic acid) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3396
Author(s):  
Luboš Běhálek ◽  
Jan Novák ◽  
Pavel Brdlík ◽  
Martin Borůvka ◽  
Jiří Habr ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Physical Properties ◽  
Structural Changes ◽  
The Other ◽  
Half Time ◽  
Crystallisation Kinetics ◽  
Isothermal Crystallisation ◽  
Melt Crystallisation ◽  
Kinetics Of ◽  
Crystallisation Rate

The physical properties and non-isothermal melt- and cold-crystallisation kinetics of poly (l-lactic acid) (PLLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biobased polymers reprocessed by mechanical milling of moulded specimens and followed injection moulding with up to seven recycling cycles are investigated. Non-isothermal crystallisation kinetics are evaluated by the half-time of crystallisation and a procedure based on the mathematical treatment of DSC cumulative crystallisation curves at their inflection point (Kratochvil-Kelnar method). Thermomechanical recycling of PLLA raised structural changes that resulted in an increase in melt flow properties by up to six times, a decrease in the thermal stability by up to 80 °C, a reduction in the melt half-time crystallisation by up to about 40%, an increase in the melt crystallisation start temperature, and an increase in the maximum melt crystallisation rate (up to 2.7 times). Furthermore, reprocessing after the first recycling cycle caused the elimination of cold crystallisation when cooling at a slow rate. These structural changes also lowered the cold crystallisation temperature without impacting the maximum cold crystallisation rate. The structural changes of reprocessed PHBV had no significant effect on the non-isothermal crystallisation kinetics of this material. Additionally, the thermomechanical behaviour of reprocessed PHBV indicates that the technological waste of this biopolymer is suitable for recycling as a reusable additive to the virgin polymer matrix. In the case of reprocessed PLLA, on the other hand, a significant decrease in tensile and flexural strength (by 22% and 46%, respectively) was detected, which reflected changes within the biobased polymer structure. Apart from the elastic modulus, all the other thermomechanical properties of PLLA dropped down with an increasing level of recycling.

The Kinetics of Hydroxyl-Radical-Induced Strand Breakage of Hyaluronic Acid. A Pulse Radiolysis Study Using Conductometry and Laser-Light-Scattering

1990 ◽  
Vol 45 (9-10) ◽  
pp. 1031-1043 ◽  
Author(s):  
David J. Deeble ◽  
Eberhard Bothe ◽  
Heinz-Peter Schuchmann ◽  
Barry J. Parsons ◽  
Glyn O. Phillips ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
Free Radical ◽  
Light Scattering ◽  
Dose Rate ◽  
Hydroxyl Radicals ◽  
Laser Light ◽  
Laser Light Scattering ◽  
Half Time ◽  
Strand Breakage ◽  
Kinetics Of

Abstract Hydroxyl radicals were generated radiolytically in N2O -and N2O / O2(4: 1)-saturated aqueous solutions of hyaluronic acid. The hydroxyl radicals react rapidly with hyaluronic acid mainly by abstracting carbon-bound H atom s. As a consequence of subsequent free-radical reactions, chain breakage occurs the kinetics of which has been followed using the pulse radio­ lysis technique. In the absence of oxygen, strand breakage was followed by the change in conductivity in­ duced by the release of cationic counterions condensed at the surface of hyaluronic acid which is a polyanion consisting of subunits of glucuronic acid alternating with N-acetyl-glucosamine. It appears that strand breakage is not due to one single first-order process, however, the con ­ tributions of the different com ponents cannot be adequately resolved. At pH7 the overall half-life is 1.4 ms, in both acid and basic solutions the rate of free-radical induced strand breakage is accelerated (at pH 4.8, t1/2 = 0.6 ms; at pH 10, t1/2 = 0.18 ms). In the absence of oxygen there is no effect of dose rate on the kinetics of strand breakage. In the presence of oxygen in addition to conductom etric detection, strand breakage was also followed by changes in low-angle laser light-scattering. These two techniques are complementary in that in this system the conductometry requires high doses per pulse while the light-scat­ tering technique is best operated in the low -dose range. In the presence of oxygen a pro­ nounced dose-rate effect is observed, e.g. at pH 9.7 after a dose of 9.4 Gy the overall half-time is approx. 0.5 s, while after a dose of 6.6 Gy the half-time is approx. 0.23 s. Both the yield and the rate of strand breakage increase with increasing pH, e.g. at pH 7 G(strand breaks) = 0.7 × 10-7 mol J-1 and at pH 10.4, 4.8 × 10-7 mol J-7. The radiolytic yields of CO2, H2O2, organic hydroperoxides, O2·- and oxygen consum ption have been determined in y-irradiated N2O/ 0 2(4: 1)-saturated solutions of both hyaluronic acid and β-cyclodextrin.

Peripheral muscle ergoreceptors and ventilatory response during exercise recovery in heart failure

1999 ◽  
Vol 276 (3) ◽  
pp. H913-H917 ◽  
Author(s):  
Noelle Francis ◽  
Alain Cohen-Solal ◽  
Damien Logeart
Keyword(s):  
Heart Failure ◽  
Chronic Heart Failure ◽  
Ventilatory Response ◽  
Normal Subjects ◽  
Exercise Recovery ◽  
Cuff Inflation ◽  
Half Time ◽  
Peripheral Muscle ◽  
Patients With Heart Failure ◽  
Kinetics Of

Recent studies have suggested that the increased ventilatory response during exercise in patients with chronic heart failure was related to the activation of muscle metaboreceptors. To address this issue, 23 patients with heart failure and 7 normal subjects performed arm and leg bicycle exercises with and without cuff inflation around the arms or the thighs during recovery. Obstruction slightly reduced ventilation and gas exchange variables at recovery but did not change the kinetics of recovery of these parameters compared with nonobstructed recovery: half-time of ventilation recovery was 175 ± 54 to 176 ± 40 s in patients and 155 ± 66 to 127 ± 13 s in controls ( P < 0.05, patients vs. controls, not significant within each group from baseline to obstructed recovery). We conclude that muscle metaboreceptor activation does not seem to play a role in the exertion hyperventilation of patients with heart failure.

scholarly journals Kinetics of the inhibition of human factor Xa by full-length and truncated recombinant tissue factor pathway inhibitor

1994 ◽  
Vol 297 (1) ◽  
pp. 131-136 ◽  
Author(s):  
T Lindhout ◽  
G Willems ◽  
R Blezer ◽  
H C Hemker
Keyword(s):  
Tissue Factor ◽  
Tissue Factor Pathway Inhibitor ◽  
Factor Xa ◽  
Product Formation ◽  
Dissociation Rate ◽  
Full Length ◽  
Inhibition Constant ◽  
Half Time ◽  
Tissue Factor Pathway ◽  
Kinetics Of

The inhibition equilibrium and kinetics of association and dissociation of the binding of three types of recombinant tissue factor pathway inhibitor (TFPI), namely full-length TFPI, C-terminal-truncated TFPI, and TFPI without the third Kunitz domain (TFPI1-161), to factor Xa have been measured. Formation and dissociation of the complexes were monitored by continuous measurement of the changes in the rate of hydrolysis of a peptidyl-p-nitroanilide substrate. Progress curves of product formation were fitted to a set of equations describing a one-step bimolecular inhibitory reaction in the presence of a competing substrate. For full-length TFPI the rate constants of association (kon) and dissociation (koff) were (5.1 +/- 0.7) x 10(6) M-1.s-1 and (2.6 +/- 0.9) x 10(-4)s-1 respectively. Thus, although the inhibition constant (50 pM) is far below the plasma concentration (2.5 nM) of TFPI, the half-time for transition to equilibrium in plasma is rather long (66s). The truncated forms of TFPI differ in that they have a 4-fold lower kon value but a similar dissociation rate constant. Therefore the inhibition constant, Ki, is 4-fold higher (0.2 nM) and the half-time to achieve equilibrium is prolonged to 250 s. The kon values of full-length and C-terminal-truncated TFPI, but not that of TFPI1-161, were found to decrease with increasing ionic strength.

scholarly journals Development of a Radioimmunoassay for Plasma C-Peptide in Sheep: Kinetics of C-Peptide and Effects of Exogenous Growth Hormone and Glucose on Insulin and C-Peptide

1988 ◽  
Vol 41 (4) ◽  
pp. 517 ◽  
Author(s):  
D Leenanuruksa ◽  
GH McDowell
Keyword(s):  
Growth Hormone ◽  
Plasma Insulin ◽  
Bovine Growth Hormone ◽  
Half Time ◽  
C Peptide ◽  
Exogenous Growth ◽  
Before And After ◽  
Glucose Challenge ◽  
Insulin Secretion Rate ◽  
Kinetics Of

An antiserum to purified bovine C-peptide was used to develop a sensitive radioimmunoassay for C-peptide in sheep. The assay was used to measure kinetics of C-peptide and insulin in non-pregnant and non-lactating sheep. Injected, purified C-peptide was distributed in pools comprising c. 11�4% of liveweight, the half time of C-peptide was estimated as 13�7 min and its clearance rate was c. 5 ml kg-I min-I. In lactating ewes exogenous recombinant bovine growth hormone (rebGH) increased both plasma insulin and C-peptide as did glucose challenge given before and during administration of rebGH. Estimates of insulin secretion rate in lactating ewes were c. 7 X 10-3 and 8�5 x 10-3 nmol kg-I min-I before and after glucose challenge prior to injections of rebGH. After 4 days of injection of rebGH, corresponding values were c. 8 x 10- 3 and 10 x 10-3 nmol min-I kg-I.

Kinetics of Methylation of Methyl 5-Deoxy-α/β-D-xylofuranosides

2004 ◽  
Vol 69 (10) ◽  
pp. 1877-1888
Author(s):  
Mária Oščendová ◽  
Jitka Moravcová
Keyword(s):  
Sodium Hydroxide ◽  
Methyl Iodide ◽  
Rate Constants ◽  
Reaction Rate ◽  
Steric Effect ◽  
Order Reaction ◽  
Half Time ◽  
First Order ◽  
Consecutive Reactions ◽  
Kinetics Of

The kinetics of methylation of methyl 5-deoxy-α-D-xylofuranoside (1), methyl 5-deoxy-β-D-xylofuranoside (2) and their partly methylated derivatives with methyl iodide in the presence of sodium hydroxide in acetonitrile was studied. The reaction rate was independent of the base concentration during the first half-time only and the methylation proceeded as a first-order reaction. The rate constants of all side and consecutive reactions were calculated and the influence of both polar and steric effect is discussed. The methylation of 1 was highly regioselective giving almost exclusively 5-deoxy-2-O-methyl-α-D-xylofuranoside.

Release of Arsenic from Model Wastewater Treatment Solids: A Mechanism Based on Surface Ligand Exchange

1994 ◽  
Vol 29 (4) ◽  
pp. 507-544 ◽  
Author(s):  
C.R. Paige ◽  
W.J. Snodgrass ◽  
Ronald V. Nicholson ◽  
J.M. Sharer
Keyword(s):  
Activation Energy ◽  
Wastewater Treatment ◽  
Exchange Reaction ◽  
Ligand Exchange ◽  
Half Time ◽  
Surface Exchange ◽  
Surface Ligand ◽  
Crystalline Nature ◽  
Kinetics Of ◽  
Surface Ligand Exchange

Abstract The loss of arsenic from model wastewater treatment solids has been studied by neutron activation analysis. The data show that the loss of arsenic from unstirred solids is controlled by a surface exchange reaction and also clearly demonstrate that arsenic is not retained in a solid solution. This is in contrast to metal ions which are retained in crystalline solids as solid solutions. The activation energy Eafor the exchange reaction is calculated to be 40 kJ/mol. Data were retrieved for the half-time of arsenic exchanging from these solids. The presence of arsenic, either in the solid or in the aqueous phase contacting the solid, altered the kinetics of transformation to and the crystalline nature of the final products. These data have implications for the disposal of wastes to landfill.

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