Theory and experiment of chain length effects on the adsorption of polyelectrolytes onto spherical particles: the long and the short of it

2021 ◽  
Vol 23 (1) ◽  
pp. 300-310
Author(s):  
Sperydon Koumarianos ◽  
Rohith Kaiyum ◽  
Christopher J. Barrett ◽  
Neal Madras ◽  
Ozzy Mermut
Keyword(s):  
Simple Model ◽  
Chain Length ◽  
Competitive Adsorption ◽  
Spherical Particles ◽  
Polyelectrolyte Chain ◽  
Repeat Units ◽  
Spherical Silica ◽  
Spherical Silica Particles ◽  
Theory And Experiment

We study here the role of polyelectrolyte chain length, that is number of repeat units (mers), in the competitive adsorption of a simple model polyanion onto 85 nm spherical silica particles capped with a model polycation.

Preparation of Spherical Silica with Controllable Size

2018 ◽  
Vol 281 ◽  
pp. 65-70
Author(s):  
Shu Lin Wang ◽  
Zhao Wang ◽  
Bing Hao Li ◽  
Man Xu
Keyword(s):  
Particle Size ◽  
Silica Particle ◽  
Sol Gel ◽  
Silica Particles ◽  
Spherical Particles ◽  
Alkali Content ◽  
Spherical Silica ◽  
Hydrolysis Temperature ◽  
Spherical Silica Particles ◽  
Size And Morphology

The spherical silica particles were prepared by sol-gel method with TEOS as precursor, ethanol as solvent in the presence of ammonia. The effects of reaction temperature and the amount of ammonia and TEOS on the size and morphology of silica particles were investigated. The hydrolysis temperature , alkali and TEOS content does not affect the morphology of silica, the silica particles were spherical; With the increase of hydrolysis temperature, particle size of silica showed first increased and then decreased, when the hydrolysis temperature is 30 °C, the silica particle size up to 0.6 μm, when the hydrolysis temperature is 60 °C, the silica particle size is 0.15 μm; With the increase of the content of alkali, silica particle size showed first increased and then decreased, when the alkali content is 20 ml, the silica particle size up to 0.6 μm and when the alkali content is 10 ml, the silica particle size is 0.2 μm; With the increase of TEOS dosage, the amount of spherical silica increased and the particle size of silica spherical particles first increased and then decreased.

Synthesis of TEOS-Based Silica Spherical Particles by Sol-Gel Process

2013 ◽  
Vol 773 ◽  
pp. 606-610
Author(s):  
Jing Li ◽  
Hong Qi Zhang ◽  
Wei Xue
Keyword(s):  
Sol Gel ◽  
Silica Particles ◽  
Electron Cloud ◽  
Polymerization Rate ◽  
Spherical Particles ◽  
Condensation Polymerization ◽  
Spherical Silica ◽  
Sol Gel Process ◽  
Spherical Silica Particles

Spherical silica particles, with mean sizes about 1.2 μm, were prepared through TEOS sol-gel process catalyzed by ammonia. The silica particles have a smooth surface and a small specific surface area, 3.4 m2/g. The sol-gel process was monitored by React IRTMusing an in-situ technique. Based on the measurements, mechanism of TEOS hydrolyzation and succedent condensation polymerization was inferred. With the adding of ammonia, OH-anion attacks Si atomic nucleus directly and makes it showing negative electricity. Therefore the electron cloud shifts to the OR group on the other side. This weakens the Si-O bond and results in the removal of the OR group. Furthermore, silanol, generated from TEOS hydrolyzation, attracts Si-OR or other Si-OH around; thereby resulting rapid dehydration or dealcohol between molecular. So the condensation polymerization rate is elevated, and Si-O-Si bond comes into being. Lastly, cross-linking reaction among Si-O-Si bonds forms the particle.

Directive Effect of Chain Length in Modulating Peptide Nano-assemblies

2020 ◽  
Vol 27 (9) ◽  
pp. 923-929
Author(s):  
Gaurav Pandey ◽  
Prem Prakash Das ◽  
Vibin Ramakrishnan
Keyword(s):  
Electron Microscopy ◽  
Amino Acids ◽  
Light Scattering ◽  
Chain Length ◽  
Self Assembly ◽  
The Self ◽  
Ionic Charge ◽  
Self Assembling ◽  
Biophysical Techniques

Background: RADA-4 (Ac-RADARADARADARADA-NH2) is the most extensively studied and marketed self-assembling peptide, forming hydrogel, used to create defined threedimensional microenvironments for cell culture applications. Objectives: In this work, we use various biophysical techniques to investigate the length dependency of RADA aggregation and assembly. Methods: We synthesized a series of RADA-N peptides, N ranging from 1 to 4, resulting in four peptides having 4, 8, 12, and 16 amino acids in their sequence. Through a combination of various biophysical methods including thioflavin T fluorescence assay, static right angle light scattering assay, Dynamic Light Scattering (DLS), electron microscopy, CD, and IR spectroscopy, we have examined the role of chain-length on the self-assembly of RADA peptide. Results: Our observations show that the aggregation of ionic, charge-complementary RADA motifcontaining peptides is length-dependent, with N less than 3 are not forming spontaneous selfassemblies. Conclusion: The six biophysical experiments discussed in this paper validate the significance of chain-length on the epitaxial growth of RADA peptide self-assembly.

scholarly journals Design, synthesis, and catalytic performance of modified graphene oxide based on a cobalt complex as a heterogenous catalyst for the preparation of aminonaphthoquinone derivatives

RSC Advances ◽  
2021 ◽  
Vol 11 (28) ◽  
pp. 17108-17115
Author(s):  
Mahnaz Mirheidari ◽  
Javad Safaei-Ghomi
Keyword(s):  
Graphene Oxide ◽  
Cobalt Complex ◽  
Catalytic Performance ◽  
Silica Particles ◽  
Design Synthesis ◽  
Spherical Silica ◽  
Modified Graphene Oxide ◽  
Spherical Silica Particles ◽  
Heterogenous Catalyst ◽  
Modified Graphene

GO@f-SiO2@Co is a heterogenous catalyst composed of spherical silica particles grafted on the surface of graphene oxide with ethylenediamine ligands and coordination with Co(ii). We assessed the activity of the catalyst for the synthesis of aminonaphthoquinones.

scholarly journals Transcriptome Changes in Pseudomonas putida KT2440 during Medium-Chain-Length Polyhydroxyalkanoate Synthesis Induced by Nitrogen Limitation

2020 ◽  
Vol 22 (1) ◽  
pp. 152
Author(s):  
Dorota Dabrowska ◽  
Justyna Mozejko-Ciesielska ◽  
Tomasz Pokój ◽  
Slawomir Ciesielski
Keyword(s):  
Chain Length ◽  
Nitrogen Limitation ◽  
Stringent Response ◽  
Wild Type ◽  
Pseudomonas Putida Kt2440 ◽  
Medium Chain ◽  
Environmental Stimuli ◽  
Medium Chain Length ◽  
In The Wild

Pseudomonas putida’s versatility and metabolic flexibility make it an ideal biotechnological platform for producing valuable chemicals, such as medium-chain-length polyhydroxyalkanoates (mcl-PHAs), which are considered the next generation bioplastics. This bacterium responds to environmental stimuli by rearranging its metabolism to improve its fitness and increase its chances of survival in harsh environments. Mcl-PHAs play an important role in central metabolism, serving as a reservoir of carbon and energy. Due to the complexity of mcl-PHAs’ metabolism, the manner in which P. putida changes its transcriptome to favor mcl-PHA synthesis in response to environmental stimuli remains unclear. Therefore, our objective was to investigate how the P. putida KT2440 wild type and mutants adjust their transcriptomes to synthesize mcl-PHAs in response to nitrogen limitation when supplied with sodium gluconate as an external carbon source. We found that, under nitrogen limitation, mcl-PHA accumulation is significantly lower in the mutant deficient in the stringent response than in the wild type or the rpoN mutant. Transcriptome analysis revealed that, under N-limiting conditions, 24 genes were downregulated and 21 were upregulated that were common to all three strains. Additionally, potential regulators of these genes were identified: the global anaerobic regulator (Anr, consisting of FnrA, Fnrb, and FnrC), NorR, NasT, the sigma54-dependent transcriptional regulator, and the dual component NtrB/NtrC regulator all appear to play important roles in transcriptome rearrangement under N-limiting conditions. The role of these regulators in mcl-PHA synthesis is discussed.

scholarly journals Studies of Polymer Solvation by Dielectric Relaxation Spectroscopy III: Polyvinyl Pyrrolidone in N-Methyl-2-Pyrrolidone, Ethanediol, Methanol, and Water

1990 ◽  
Vol 45 (2) ◽  
pp. 126-134
Author(s):  
E. Dachwitz
Keyword(s):  
Dielectric Relaxation ◽  
Chain Length ◽  
Molar Mass ◽  
Polyvinyl Pyrrolidone ◽  
Dielectric Relaxation Spectroscopy ◽  
Length Effect ◽  
Repeat Units ◽  
Solvent Model ◽  
Spectral Components ◽  
High Concentrations

AbstractThe permittivity of the title solutions has been measured at frequencies between some MHz and 72 GHz at 20 °C. Polyvinyl pyrrolidone of relative molar mass ranging from 1200 to 360 000 has been used. Referring to the concentration of monomeric repeat units (x = 0.65 maximum) there is no significant chain length effect. The permittivity data are described in terms of discrete Debye type spectral components. Special attention is paid to the contributions ascribable to the solvents, which are discussed with respect to their solvation behaviour. This can be described by a three state solvent model as follows. Besides the "bulk" solvent a further contribution is found in any case which is due to loosely affected (slowed down) solvent. Moreover a part of the solvent appears to be tightly bound to the polymer at high concentrations. All the solvents considered show similar solvation properties, notwithstanding their different tendencies towards selfassociation.

Superlattice Formation in Fatty Acid Monolayers on a Divalent Ion Subphase: Role of Chain Length, Temperature, and Subphase Concentration

Langmuir ◽  
2003 ◽  
Vol 19 (26) ◽  
pp. 10808-10815 ◽  
Author(s):  
Vincent Dupres ◽  
Sophie Cantin ◽  
Fewzi Benhabib ◽  
Françoise Perrot ◽  
Philippe Fontaine ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Chain Length
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