scholarly journals The effect of the cross-linker ratio used in gellan gum biomaterial synthesis on biomineralization

2021 ◽  
Author(s):  
Serbülent TÜRK ◽  
Burak ÜNLÜ ◽  
Mahmut ÖZACAR
Keyword(s):  
Gellan Gum ◽  
Cross Linker ◽  
The Cross

scholarly journals Microencapsulation of Baker’s Yeast in Gellan Gum Beads Used in Repeated Cycles of Glucose Fermentation

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Camelia Elena Iurciuc (Tincu) ◽  
Catalina Peptu ◽  
Alexandru Savin ◽  
Leonard-Ionuț Atanase ◽  
Kaies Souidi ◽  
...  
Keyword(s):  
Immobilized Cells ◽  
Particle Morphology ◽  
Gellan Gum ◽  
Yeast Cells ◽  
Coagulation Bath ◽  
Yeast Fermentation ◽  
Immobilized Yeast ◽  
Cross Linker ◽  
The Cross ◽  
The Stability

The purpose of this work is to prepare ionically cross-linked (with CaCl2) gellan particles with immobilized yeast cells for their use in repeated fermentation cycles of glucose. The study investigates the influence of ionic cross-linker concentration on the stability and physical properties of the particles obtained before extrusion and during time in the coagulation bath (the cross-linker solution with different CaCl2 concentrations). It was found that by increasing the amount of the cross-linker the degree of cross-linking in the spherical gellan matrix increases, having a direct influence on the particle morphology and swelling degree in water. These characteristics were found to be very important for diffusion of substrate, that is, the glucose, into the yeast immobilized cells and for the biocatalytic activity of the yeast immobilized cells in gellan particles. These results highlight the potential of these bioreactors to be used in repeated fermentation cycles (minimum 10) without reducing their biocatalytic activity and maintaining their productivity at similar parameters to those obtained in the free yeast fermentation. Encapsulation of Saccharomyces cerevisiae into the gellan gum beads plays a role in the effective application of immobilized yeast for the fermentation process.

scholarly journals Effect of the Cross-Linking Density on the Swelling and Rheological Behavior of Ester-Bridged β-Cyclodextrin Nanosponges

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 478
Author(s):  
Gjylije Hoti ◽  
Fabrizio Caldera ◽  
Claudio Cecone ◽  
Alberto Rubin Pedrazzo ◽  
Anastasia Anceschi ◽  
...  
Keyword(s):  
Scale Up ◽  
Future Application ◽  
Cross Linking ◽  
Synthesis Reaction ◽  
Dependent Behavior ◽  
Cyclodextrin Nanosponges ◽  
Potential Applications ◽  
Cross Linker ◽  
The Cross ◽  
Shed Light

The cross-linking density influences the physicochemical properties of cyclodextrin-based nanosponges (CD-NSs). Although the effect of the cross-linker type and content on the NSs performance has been investigated, a detailed study of the cross-linking density has never been performed. In this contribution, nine ester-bridged NSs based on β-cyclodextrin (β-CD) and different quantities of pyromellitic dianhydride (PMDA), used as a cross-linking agent in stoichiometric proportions of 2, 3, 4, 5, 6, 7, 8, 9, and 10 moles of PMDA for each mole of CD, were synthesized and characterized in terms of swelling and rheological properties. The results, from the swelling experiments, exploiting Flory–Rehner theory, and rheology, strongly showed a cross-linker content-dependent behavior. The study of cross-linking density allowed to shed light on the efficiency of the synthesis reaction methods. Overall, our study demonstrates that by varying the amount of cross-linking agent, the cross-linked structure of the NSs matrix can be controlled effectively. As PMDA βCD-NSs have emerged over the years as a highly versatile class of materials with potential applications in various fields, this study represents the first step towards a full understanding of the correlation between their structure and properties, which is a key requirement to effectively tune their synthesis reaction in view of any specific future application or industrial scale-up.

scholarly journals Synthesis, Characterization of a New Polyacrylic Acid Superabsorbent, Some Heavy Metal Ion Sorption, the Adsorption Isotherms, and Quantum Chemical Investigation

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4390
Author(s):  
Sevil Savaskan Yilmaz ◽  
Nuri Yildirim ◽  
Murat Misir ◽  
Yasin Misirlioglu ◽  
Emre Celik
Keyword(s):  
Heavy Metal ◽  
Quantum Chemical ◽  
Metal Ion ◽  
Molecular Mechanic ◽  
Ion Concentration ◽  
Heavy Metal Ion ◽  
Competitive Sorption ◽  
Cross Linker ◽  
The Cross

Poly(acrylic acid/Kryptofix 23-Dimethacrylate) superabsorbent polymer [P (AA/Kry23-DM) SAP] was synthesized by solution polymerization to remove Co, Ni, Cu, Cd, Mn, Zn, Pb, Cr, and Fe ions in water and improve the quality of the water. Kry23-DM cross-linker (1,4,7,13,16-Pentaoxa-10,19 diazo cyclohexene icosane di methacrylate) was synthesized using Kry23 and methacryloyl chloride. The characterization of the molecules was done by FTIR, TGA, DSC, and SEM techniques. The effects of parameters such as pH, concentration, and the metal ion interaction on the heavy metal ions uptaking of SAP was investigated. It was observed that P (AA/Kry23-DM) SAP has maximum water absorption, and the absorption increases with the pH increase. Adsorption rates and sorption capacity, desorption ratios, competitive sorption (qcs), and distribution coefficient (log D) of P(AA/Kry23-DM) SAP were studied as a function of time and pH with the heavy metal ion concentration. Langmuir and Freundlich isotherms of the P (AA/Kry23-DM) SAP were investigated to verify the metal uptake. Molecular mechanic (MM2), Assisted Model Building with Energy Refinement (AMBER), and optimized potentials for liquid simulations (OPLS) methods. were used in quantum chemical calculations for the conformational analysis of the cross-linker and the SAP. ΔH0f calculations of the cross-linker and the superabsorbent were made using Austin Model 1(AM1) method.

scholarly journals Cross-linker system between neurofilaments, microtubules and membranous organelles in frog axons revealed by the quick-freeze, deep-etching method

1982 ◽  
Vol 94 (1) ◽  
pp. 129-142 ◽  
Author(s):  
N Hirokawa
Keyword(s):  
Chemical Extraction ◽  
Distilled Water ◽  
Deep Etching ◽  
Cross Links ◽  
Cross Linker ◽  
The Cross ◽  
Cross Bridges ◽  
20 Nm ◽  
Soluble Material ◽  
Soluble Components

The elaborate cross-connections among membranous organelles (MO), microtubules (MT), and neurofilaments (NF) were demonstrated in unifixed axons by the quick-freeze, deep-etch, and rotary-shadowing method. They were categorized into three groups: NF-associated cross-linker, MT-associated cross-bridges, and long cross-links in the subaxolemmal space. Other methods were also employed to make sure that the observed cross-connections in the unfixed axons were not a result of artifactual condensation or precipitation of soluble components or salt during deep-etching. Axolemma were permeablized either chemically (0.1% saponin) or physically (gentle homogenization), to allow egress of their soluble components from the axon; or else the axons were washed with distilled water after fixation. After physical rupture of the axolemma or saponin treatment, most of the MO remained intact. MT were stabilized by adding taxol in the incubation medium. Axons prepared by these methods contained many longitudinally oriented NF connected to each other by numerous fine cross-linkers (4-6 nm in diameter, 20-50 nm in length). Two specialized regions were apparent within the axons: one composed of fascicles of MT linked with each other by fine cross-bridges; the other was in the subaxolemmal space and consisted of actinlike filaments and a network of long cross-links (50-150 nm) which connected axolemma and actinlike filaments with NF and MT. F-actin was localized to the subaxolemmal space by the nitrobenzooxadiazol phallacidin method. MO were located mainly in these two specialized regions and were intimately associated with MT via fine short (10-20 nm in length) cross-bridges. Cross-links from NF to MO and MT were also common. All these cross-connections were observed after chemical extraction or physical rupture of the axon; however, these procedures removed granular materials which were attached to the filaments in the fresh unextracted axons. The cross-connections were also found in the axons washed with distilled water after fixation. I conclude that the cross- connections are real structures while the granular material is composed of soluble material, probably protein in nature.

scholarly journals Cross-linking of histones with dimethyl 3,3′-dithiobispropionimidate. Interference by a one-end reaction modifying histones at lysine amino groups

1984 ◽  
Vol 224 (3) ◽  
pp. 1019-1022
Author(s):  
E Kotthaus ◽  
W H Strätling
Keyword(s):  
Insoluble Fraction ◽  
Cross Linking ◽  
Amino Groups ◽  
Large Excess ◽  
Histone Dimers ◽  
Acid Solubility ◽  
Cross Linker ◽  
The Cross ◽  
Linker Molecules

We have studied the HClO4-solubility of histones H1 and H5 in hen erythrocyte nuclei after treatment with the cross-linker dimethyl 3,3′-dithiobispropionimidate (DTPI). The amount of acid-soluble, non-cross-linked, H1 and H5 histones was drastically decreased, and that of acid-soluble H1/H5 histone dimers went through an optimum as the DTPI concentration was raised. Incubation of the HClO4-insoluble fraction with 2-mercaptoethanol regenerated the acid-solubility of H1/H5 histones in this fraction. When purified H1/H5 histones were treated with increasing concentrations of DTPI under non-cross-linking conditions, the amount of HClO4-soluble histones also greatly decreased, but to a much lesser extent if the DTPI treatment was followed by reduction with 2-mercaptoethanol. This decrease was inversely correlated to the proportion of amino groups modified. It is concluded that, when the cross-linker was used in large excess, the cross-linking reaction competed with a one-end reaction modifying the histones at lysine amino groups by cross-linker molecules, of which the imidoester groups that had not reacted were hydrolysed. It is suggested that this modification produced the changes in acid-solubility.

Photodegradable cross-linked polymer derived from a vinylic rotaxane cross-linker possessing aromatic disulfide axle

2013 ◽  
Vol 85 (4) ◽  
pp. 835-842 ◽  
Author(s):  
Yasuhito Koyama ◽  
Takahiro Yoshii ◽  
Yasuhiro Kohsaka ◽  
Toshikazu Takata
Keyword(s):  
Crown Ether ◽  
Methyl Methacrylate ◽  
Radical Polymerization ◽  
Vinyl Monomer ◽  
Hydroxymethyl Group ◽  
Cross Links ◽  
Cross Linker ◽  
The Cross ◽  
Vinyl Group ◽  
Site Selective

A new concept for photodegradable cross-linked polymers utilizing characteristics of rotaxane cross-links and aromatic disulfides is proposed. The cross-linked polymer is obtained by the radical polymerization of a vinyl monomer in the presence of a [3]rotaxane-type cross-linker having two radically polymerizable groups. The [3]rotaxane-type cross-linker was prepared in 93 % yield by the typical rotaxane-forming reaction using a dumbbell-shaped aromatic disulfide possessing a bis(ammonium salt) moiety and a crown ether wheel tethered by a hydroxymethyl group (96 %) and the subsequent vinyl group-endowment (80 %). The radical polymerization of methyl methacrylate (MMA) in the presence of the cross-linker (0.1 mol %) at 60 °C afforded solvent-insoluble polymer in 90 % yield. When the polymer was swollen to a gel in dimethylformamide (DMF) and a small part of the gel was UV-irradiated, the gel was promptly solubilized, probably via the photochemical scission of the S–S linkage of the interlocked aromatic disulfide, causing the efficient decomposition of the rotaxane cross-links. The recovered poly(methyl methacrylate) bearing a small amount of crown ether moiety has a molecular weight of Mn 170 kg/mol (Mw/Mn 2.1) that indicated the occurrence of the site-selective photodegradation.

scholarly journals Influence of Cross-Linking Degree on Hydrodynamic Behavior and Stimulus-Sensitivity of Derivatives of Branched Polyethyleneimine

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1085
Author(s):  
Alina Amirova ◽  
Tatyana Kirila ◽  
Mikhail Kurlykin ◽  
Andrey Tenkovtsev ◽  
Alexander Filippov
Keyword(s):  
Aqueous Solutions ◽  
Mole Fraction ◽  
Solution Temperature ◽  
Linear Polymers ◽  
Intermolecular Hydrogen Bonds ◽  
Critical Solution Temperature ◽  
Cross Linker ◽  
The Cross ◽  
Derivatives Of ◽  
Constant Characteristics

Cross-linked derivatives of acylated branched polyethyleneimine containing 2-isopropyl-2-oxazoline units were investigated in chloroform and aqueous solutions using methods of molecular hydrodynamics, static and dynamic light scattering, and turbidity. The studied samples differed by the cross-linker content. The solubility of the polyethyleneimines studied worsened with the increasing mole fraction of the cross-linker. Cross-linked polyethyleneimines were characterized by small dimensions in comparison with linear analogs; the increase in the cross-linker content leads to a growth of intramolecular density. At low temperatures, the aqueous solutions of investigated samples were molecularly dispersed, and the large aggregates were formed due to the dehydration of oxazoline units and the formation of intermolecular hydrogen bonds. For the cross-linked polyethyleneimines, the phase separation temperatures were lower than that for linear and star-shaped poly-2-isopropyl-2-oxazolines. The low critical solution temperature of the solutions of studied polymers decreased with the increasing cross-linker mole fraction. The time of establishment of the constant characteristics of the studied solutions after the jump-like change in temperature reaches 3000 s, which is at least two times longer than for linear polymers.

Monodisperse highly cross-linked “living” microspheres prepared via photoinitiated RAFT dispersion polymerization

RSC Advances ◽  
2015 ◽  
Vol 5 (24) ◽  
pp. 18922-18931 ◽  
Author(s):  
Jianbo Tan ◽  
Xin Rao ◽  
Jianwen Yang ◽  
Zhaohua Zeng
Keyword(s):  
Dispersion Polymerization ◽  
Bifunctional Monomer ◽  
Cross Linker ◽  
The Cross

Monodisperse highly Cross-linked “Living” microspheres were synthesized via photoinitiated RAFT dispersion polymerization of MMA using a bifunctional monomer or a trifunctional monomer as the cross-linker.

Study on Cross-Linking Degree of Polyethylene

2013 ◽  
Vol 658 ◽  
pp. 56-60
Author(s):  
Li Qiu Zou ◽  
Guang Feng Wu
Keyword(s):  
Extraction Method ◽  
Low Density Polyethylene ◽  
Cross Linking ◽  
Low Density ◽  
Dicumyl Peroxide ◽  
Linear Low Density Polyethylene ◽  
Gel Content ◽  
Complete Decomposition ◽  
Cross Linker ◽  
The Cross

In this paper, the linear low density polyethylene (LLDPE) was melted and cross-linked by dicumyl peroxide (DCP) used to prepare cross-linked polyethylene (XPE). The gel content was determined by extraction method. The effect of content of cross-linker, cross- linked time, cross-linked temperature and other factors on the gel content were studied. It was found that the extraction time should be 18h for XPE. The gel content increased with the increasing of cross-linked time. When the cross-linked time was 10-15min, DCP was almost complete decomposition. The gel content was basically stable when the cross-linked temperature was 170-175 oC. The maximum of gel fraction was about 90%.

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