Structure and aggregation kinetics of vinyltriethoxysilane-derived organic/silica hybrids

The aggregation kinetics of solutions of vinyltriethoxysilane-derived organic/silica hybrid species were studied by small-angle X-ray scattering (SAXS) in a strongly basic medium. The SAXS intensity was analysed by a modified Sharp–Bloomfield (SB) global function and its evolution was found to be compatible with the growth, coiling and branching of the polymeric macromolecules in solution. A form factor valid for randomly and nonrandomly branched polycondensates and for polydisperse coils of linear chains was used in the modified SB model, instead of the Debye function valid for monodisperse coils of linear chains. The aggregation kinetics are accelerated with increasing base concentration in the studied range, but all the kinetics curves can be matched to a unique curve using an appropriate time scaling factor. The aggregation kinetics suggest that physical forces (hydrothermal forces) associated with phase coarsening could be active in the aggregation process, together with diffusion mechanisms.

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Dynamical scaling in fractal structures in the aggregation of tetraethoxysilane-derived sonogels

Journal of Applied Crystallography ◽

10.1107/s0021889810025161 ◽

2010 ◽

Vol 43 (5) ◽

pp. 949-954 ◽

Cited By ~ 8

Author(s):

Dimas R. Vollet ◽

Dario A. Donatti ◽

Alberto Ibañez Ruiz ◽

Fabio S. de Vicente

Keyword(s):

Factor Model ◽

Fractal Structures ◽

Saxs Data ◽

Scaling Properties ◽

Dynamical Scaling ◽

X Ray Scattering ◽

Linear Chains ◽

Saxs Intensity ◽

Scattering Factor ◽

Kinetics Of

Dynamical scaling properties in fractal structures were investigated from small-angle X-ray scattering (SAXS) data of the kinetics of aggregation in silica-based gelling systems. For lack of a maximum in the SAXS intensity curves, a characteristic correlation distance ξ was evaluated by fitting a particle scattering factor model valid for polydisperse coils of linear chains andf-functional branched polycondensates in solution, so the intensity atq= ξ−1,I(ξ−1,t), was considered to probe dynamical scaling properties. The following properties have been found: (i) the SAXS intensities corresponding to different timest,I(q,t), are given by a time-independent functionF(qξ) =I(q,t)ξ−D/Q, where the scattering invariantQhas been found to be time-independent; (ii) ξ exhibited a power-law behavior with time as ξ ≃tα, the exponent α being close to 1 but diminishing with temperature; (iii)I(ξ−1,t) exhibited a time dependence given byI(ξ−1,t) ≃tβ, with the exponent β found to be around 2 but diminishing with temperature, following the same behavior as the exponent α. In all cases, β/α was quite close to the fractal dimensionDat the end of the studied process. This set of findings is in notable agreement with the dynamical scaling properties.

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Functional Fractionation of Platelets: Aggregation Kinetics and Glycoprotein Labeling of Differing Platelet Populations

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657259 ◽

1982 ◽

Vol 48 (02) ◽

pp. 211-216 ◽

Cited By ~ 12

Author(s):

V M Haver ◽

A R L Gear

Keyword(s):

Galactose Oxidase ◽

Aggregation Kinetics ◽

Maximal Rate ◽

Membrane Glycoproteins ◽

Whole Cells ◽

Reversible Aggregation ◽

Significant Difference ◽

Small Doses ◽

Major Loss ◽

Kinetics Of

SummaryPlatelet heterogeneity has been studied with a technique called functional fractionation which employs gentle centrifugation to yield subpopulations (“reactive” and “less-reactive” platelets) after exposure to small doses of aggregating agent. Aggregation kinetics of the different platelet populations were investigated by quenched-flow aggregometry. The large, “reactive” platelets were more sensitive to ADP (Ka = 1.74 μM) than the smaller “less-reactive” platelets (Ka = 4.08 μM). However, their maximal rate of aggregation (Vmax, % of platelets aggregating per sec) of 23.3 was significantly lower than the “less-reactive” platelets (Vmax = 34.7). The “reactive” platelets had a 2.2 fold higher level of cyclic AMP.Platelet glycoproteins were labeled using the neuraminidase-galactose oxidase – [H3]-NaBH4 technique. When platelets were labeled after reversible aggregation, the “reactive” platelets showed a two-fold decrease in labeling efficiency (versus control platelets). However, examination of whole cells or membrane preparations from reversibly aggregated platelets revealed no significant difference in Coomassie or PAS (Schiff) staining.These results suggest that the large, “reactive” platelets are more sensitive to ADP but are not hyperaggregable in a kinetic sense. Reversible aggregation may cause a re-orientation of membrane glycoproteins that is apparently not characterized by a major loss of glycoprotein material.

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In situ Time-Resolved Small-Angle X-ray Scattering Reveals the Formation Kinetics of Polyelectrolyte Complex Micelles

10.26434/chemrxiv.9876395.v1 ◽

2019 ◽

Author(s):

Hao Wu ◽

Jeffrey Ting ◽

Siqi Meng ◽

Matthew Tirrell

Keyword(s):

Small Angle ◽

Self Assembly ◽

Electrostatic Interactions ◽

Polyelectrolyte Complex ◽

Time Resolved ◽

X Ray ◽

X Ray Scattering ◽

Kinetics Of ◽

Ray Scattering

We have directly observed the <i>in situ</i> self-assembly kinetics of polyelectrolyte complex (PEC) micelles by synchrotron time-resolved small-angle X-ray scattering, equipped with a stopped-flow device that provides millisecond temporal resolution. This work has elucidated one general kinetic pathway for the process of PEC micelle formation, which provides useful physical insights for increasing our fundamental understanding of complexation and self-assembly dynamics driven by electrostatic interactions that occur on ultrafast timescales.

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Kinetics of Network Formation and Heterogeneous Dynamics of an Egg White Gel Revealed by Coherent X-Ray Scattering

Physical Review Letters ◽

10.1103/physrevlett.126.098001 ◽

2021 ◽

Vol 126 (9) ◽

Author(s):

Nafisa Begam ◽

Anastasia Ragulskaya ◽

Anita Girelli ◽

Hendrik Rahmann ◽

Sivasurender Chandran ◽

...

Keyword(s):

Network Formation ◽

Egg White ◽

X Ray ◽

X Ray Scattering ◽

Heterogeneous Dynamics ◽

Kinetics Of ◽

Ray Scattering

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Shear-induced reaction-limited aggregation kinetics of Brownian particles at arbitrary concentrations

The Journal of Chemical Physics ◽

10.1063/1.3361665 ◽

2010 ◽

Vol 132 (13) ◽

pp. 134903 ◽

Cited By ~ 33

Author(s):

Alessio Zaccone ◽

Daniele Gentili ◽

Massimo Morbidelli

Keyword(s):

Aggregation Kinetics ◽

Brownian Particles ◽

Kinetics Of ◽

Induced Reaction

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Controlling the Kinetics of an Enzymatic Reaction through Enzyme or Substrate Confinement into Lipid Mesophases with Tunable Structural Parameters

International Journal of Molecular Sciences ◽

10.3390/ijms21145116 ◽

2020 ◽

Vol 21 (14) ◽

pp. 5116

Author(s):

Marco Mendozza ◽

Arianna Balestri ◽

Costanza Montis ◽

Debora Berti

Keyword(s):

Reaction Kinetics ◽

Self Assembly ◽

Liquid Crystalline ◽

Structural Parameters ◽

Enzymatic Reaction ◽

X Ray Scattering ◽

Nitrophenyl Phosphate ◽

Vis Spectroscopy ◽

Kinetics Of ◽

Enzyme Alkaline Phosphatase

Lipid liquid crystalline mesophases, resulting from the self-assembly of polymorphic lipids in water, have been widely explored as biocompatible drug delivery systems. In this respect, non-lamellar structures are particularly attractive: they are characterized by complex 3D architectures, with the coexistence of hydrophobic and hydrophilic regions that can conveniently host drugs of different polarities. The fine tunability of the structural parameters is nontrivial, but of paramount relevance, in order to control the diffusive properties of encapsulated active principles and, ultimately, their pharmacokinetics and release. In this work, we investigate the reaction kinetics of p-nitrophenyl phosphate conversion into p-nitrophenol, catalysed by the enzyme Alkaline Phosphatase, upon alternative confinement of the substrate and of the enzyme into liquid crystalline mesophases of phytantriol/H2O containing variable amounts of an additive, sucrose stearate, able to swell the mesophase. A structural investigation through Small-Angle X-ray Scattering, revealed the possibility to finely control the structure/size of the mesophases with the amount of the included additive. A UV–vis spectroscopy study highlighted that the enzymatic reaction kinetics could be controlled by tuning the structural parameters of the mesophase, opening new perspectives for the exploitation of non-lamellar mesophases for confinement and controlled release of therapeutics.

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