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The dynamics of phase partition. A study of parameters affecting rat liver organelle partitioning in aqueous two-polymer phase systems.

ABSTRACT: Separation of subcellular organelles by two-phase partition is thought to reflect differential partition of the organelles between the two phases or between one of the phases and the interface. Studies by Fisher and colleagues [Fisher & Walter (1984) Biochim. Biophys. Acta 801, 106-110] suggest that cell separation by phase partition is a dynamic process in which the partition changes with time. This is mainly due to association of the cells with sedimenting droplets of one phase in the bulk of the other. Rat liver organelle partition was studied to determine whether the same dynamic behaviour is observed. Partition was clearly time-dependent during 24 h at unit gravity, and was also affected by altering the volume ratio of the two phases and the duration of phase mixing. These results indicate that, as with cells, the partition of organelles between phases is a dynamic process, and is consistent with the demonstration that organelles adhere to the phase droplet surfaces. Optimization of the volume ratio between phases may lead to significant processing economies. Organelle sedimentation in the upper phase was significantly faster than in the isoosmotic sucrose. Theoretical modelling of apparent organelle sizes indicates that aggregation occurs in the poly(ethylene glycol)-rich upper phase. This phenomenon is likely to limit the use of this technique in organelle separations unless means can be found to decrease aggregation.

SUBMITTER: Heywood-Waddington D

PROVIDER: S-EPMC1146673 | biostudies-other | 1986 Apr

REPOSITORIES: biostudies-other

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Collagen Partition in Polymeric Aqueous Two-Phase Systems for Tissue Engineering.

Project description:Aqueous two-phase systems (ATPS) of polyethylene glycol (PEG) and dextran (DEX) are commonly used to partition proteins. Protein partition in ATPS is a complex phenomenon and depends on factors including molecular weight of polymers, and electrochemical and ionic properties of the phases. We studied the effect of polymer molecular weight on the partition of a natural protein, collagen, in several ATPS formulations made with non-ionic polymers polyethylene glycol (PEG) and dextran (DEX). We found that partitioning of collagen to an aqueous phase significantly increases when the molecular weight of the corresponding phase polymer decreases. Additionally, a large difference between the molecular weight of the phase-forming polymers was necessary to cause a significant uneven collagen distribution between the aqueous phases. We then employed one of the systems to create a three-dimensional breast cancer microtissue by entrapping a spheroid of breast cancer cells within the partitioned collagen. This convenient technique to generate 3D microtissues offers a convenient and promising approach for tissue engineering applications.

| S-EPMC6132203 | biostudies-literature

Linear Relationships between Partition Coefficients of Different Organic Compounds and Proteins in Aqueous Two-Phase Systems of Various Polymer and Ionic Compositions.

Project description:Analysis of the partition coefficients of small organic compounds and proteins in different aqueous two-phase systems under widely varied ionic compositions shows that logarithms of partition coefficients for any three compounds or proteins or two organic compounds and one protein are linearly interrelated, although for protein(s) there are ionic compositions when the linear fit does not hold. It is suggested that the established interrelationships are due to cooperativity of different types of solute-solvent interactions in aqueous media. This assumption is confirmed by analysis of distribution coefficients of various drugs in octanol-buffer systems with varied ionic compositions of the buffer. Analysis of the partition coefficients characterizing distribution of variety of drugs between blood and different tissues of rats in vivo reported in the literature showed that the above assumption is correct and enabled us to identify the tissues with the components of which the drug(s) may engage in presumably direct interactions. It shows that the suggested assumption is valid for even complex biological systems.

| S-EPMC7408505 | biostudies-literature

Aqueous Nanoclusters Govern Ion Partitioning in Dense Polymer Membranes.

Project description:The uptake and sorption of charged molecules by responsive polymer membranes and hydrogels in aqueous solutions is of key importance for the development of soft functional materials. Here, we investigate the partitioning of simple monatomic (Na+, K+, Cs+, Cl-, I-) and one molecular ion (4-nitrophenolate; NP-) within a dense, electroneutral poly(N-isopropylacrylamide) membrane using explicit-water molecular dynamics simulations. Inside the predominantly hydrophobic environment, water distributes in a network of polydisperse water nanoclusters. The average cluster size determines the mean electrostatic self-energy of the simple ions, which preferably reside deeply inside them; we therefore find substantially larger partition ratios K ?10-1 than expected from a simple Born picture using a uniform dielectric constant. Despite their irregular shapes, we observe that the water clusters possess a universal negative electrostatic potential with respect to their surroundings, as is known for aqueous liquid-vapor interfaces. This potential, which we find concealed in cases of symmetric monatomic salts, can dramatically impact the transfer free energies of larger charged molecules because of their weak hydration and increased affinity to interfaces. Consequently, and in stark contrast to the simple ions, the molecular ion NP- can have a partition ratio much larger than unity, K ?10-30 (depending on the cation type) or even 103 in excess of monovalent salt, which explains recent observations of enhanced reaction kinetics of NP- reduction catalyzed within dense polymer networks. These results also suggest that ionizing a molecule can even enhance the partitioning in a collapsed, rather hydrophobic gel, which strongly challenges the traditional simplistic reasoning.

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Distribution of free and antibody-bound peptide hormones in two-phase aqueous polymer systems.

Project description:Peptide hormones labelled with radioactive iodine were partitioned into the aqueous two-phase polymer systems developed by Albertsson (1960) and the conditions required for separation of free from antibody-bound hormone have been worked out. Hormones studied included insulin, growth hormone, parathyroid hormone and [arginine]-vasopressin. Free and antibody-bound hormones show different distribution coefficients in a number of systems tested; two systems, the dextran-polyethylene glycol and dextran sulphate-polyethylene glycol system, give optimum separation. Free hormones distribute readily into the upper phase of these systems, whereas hormone-antibody complexes, as well as uncombined antibody, are found almost completely in the lower phase. Various factors including the polymer concentration, the ionic composition of the system, the nature of the hormone and the nature of added serum protein differentially affect the distribution coefficients for free and antibody-bound hormone. These factors can be adequately controlled so as to improve separation. The two-phase partition method has been successfully applied to measure binding of labelled hormone to antibody under standard radioimmunoassay conditions. It exhibits several advantages over the method of equilibration dialysis and can be applied to the study of non-immunological interactions.

| S-EPMC1178431 | biostudies-other

Investigating and Optimizing Insulin Partitioning with Conjugated Au Nanoparticles in Aqueous Two-Phase Systems Using Response Surface Methodology

Project description: Not available

| S-EPMC10905728 | biostudies-literature

Characterization and optimization of polymer-polymer aqueous two-phase systems for the isolation and purification of CaCo2 cell-derived exosomes.

Project description:Exosomes are cell-derived vesicles that present attractive characteristics such as nano size and unique structure for their use as drug delivery systems for drug therapy, biomarkers for prognostic, diagnostic and personalized treatments. So far, one of the major challenges for therapeutic applications of exosomes is the development of optimized isolation methods. In this context, aqueous two-phase systems (ATPS) have been used as an alternative method to isolate biological molecules and particles with promising expectations for exosomes. In this work, fractionation of exosomes obtained from CaCo2 cell line and culture media contaminants were individually performed in 20 polymer-polymer ATPS. The effect of design parameters such as polymer composition, molecular weight, and tie-line length (TLL) on polyethylene glycol (PEG)-Dextran, Dextran-Ficoll and PEG-Ficoll systems was studied. After partition analysis, 4 of the 20 systems presented the best exosome fractionation from contaminants under initial conditions, which were optimized via salt addition (NaCl) to a final concentration of 25 mM, to improve collection efficiency. The PEG 10,000 gmol-1 -Dextran 10,000 gmol-1 system at TLL 25% w/w with NaCl, showed the best potential isolation efficiency. Following this proposed strategy, an exosome purification factor of 2 in the top PEG-rich phase can be expected furtherly demonstrating that ATPS have the potential for the selective recovery of these promising nanovesicles.

| S-EPMC9439200 | biostudies-literature

Effects of iodination on the distribution of peptide hormones in aqueous two-phase polymer systems.

Project description:1. The effect of iodination on the distribution of peptide hormones into the aqueous two-phase dextran-polyethylene glycol system and on the solubility of these hormones in aqueous polyethylene glycol and in water was assessed. Hormones that were studied included insulin, glucagon and parathyroid hormone. 2. The partition coefficient of native insulin in the dextran-polyethylene glycol system showed a minimum (about 1) near the isoelectric point of the hormone (pH 5). Partial iodination of insulin (one atom per molecule) caused little change in the distribution of the hormone. More extensive iodination markedly decreased the partition coefficient in the region of the isoelectric point and displaced the pH value at which the partition coefficient was a minimum towards lower values. 3. The solubility of native insulin in aqueous polyethylene glycol and in water showed a pH-dependence similar to that observed for the distribution in the dextran-polyethylene glycol system. Iodination of insulin decreased the solubility of the hormone in polyethylene glycol and in water in parallel, and decreased the pH value at which solubility was a minimum. The changes in solubility correlated with the degree of iodination and accounted for the changes in distribution observed at high concentrations of insulin. 4. Comparable effects of iodination on distribution and solubility were also observed with glucagon. 5. At concentrations of insulin below its maximum solubility, serum proteins caused a decrease in the partition coefficient of iodinated hormone, but not of native hormone. These effects correlated with the degree of iodination and resulted from a co-precipitation of iodinated insulin with serum proteins.

| S-EPMC1168355 | biostudies-other

Increase of vanillin partitioning using aqueous two phase system with promising nanoparticles.

Project description:The distinct features of ATPSs (aqueous two-phase systems) have made it possible to promote the extraction efficiency of biomolecules. The purpose of this study is to discover an appropriate nanoparticle to design an economical optimal separation process, and to understand the underlying molecular mechanism which allows the partitioning of vanillin as a phenolic compound using nanoparticle-based ATPSs. To this aim, the capabilities of several different nanoparticles were investigated as additives for boosting the partition coefficient of vanillin in two different ATPSs made up of polyethylene glycol and sodium sulfate/polyethylene glycol and dextran. Also, in an attempt to explain the salting-out effect, the NRTL (Non-random Two Liquid) thermodynamic model was applied. The impact of very small amounts of modified carbon nanotubes on the enhancement of the partition coefficient of vanillin in the ATPS consisting of the biocompatible polymer(s) and salt was quite remarkable. The results showed that the partition coefficient of vanillin grew by almost 127 percent compared to the system without nanoparticle. The molecular mechanism underlying the increase in the partition coefficient was interpreted by taking advantage of structural analyses.

| S-EPMC6927956 | biostudies-literature

Adaptive partitioning of a gene locus to the nuclear envelope in Saccharomyces cerevisiae is driven by polymer-polymer phase separation

Project description:Partitioning of active gene loci to the nuclear envelope is a key mechanism by which organisms can increase the speed of adaptation and metabolic robustness to fluctuating resources in the environment. In the budding yeast Saccharomyces cerevisiae, adaptation and transcriptional memory induced by nutrient depletion or other stresses, results from relocalization of active gene loci from nucleoplasm to the nuclear envelope, leading to increased transport of mRNAs to the cytosol and their translation. The mechanism by which this translocation occurs remains a mystery. We show here, that for the inositol depletion-responsive gene locus INO1 in yeast, translocation to the nuclear envelope is caused by a local phase transition of the mechanical stiffness of chromatin surrounding activated INO1 that favors phase separation of the active gene locus into low density regions of chromatin proximal to the nuclear envelope. Gene regulatory elements essential to translocation encode binding sites for histone acetyl transferases, which are necessary for chromatin decompaction. INO1 locus partitioning can be explained by a phenomenological model of chromatin decompaction, which reflects stiffening of chromatin and its partitioning into a dilute chromatin phase adjacent to the nuclear envelope, from the dense chromatin found in the nucleoplasmic phase. Recent evidence suggests that this demixing of chromatin could be due to the dissolution of multivalent chromatin interactions mediated by histone post-translational modifications.

2023-03-01 | PXD029913 | Pride

CTP and parS coordinate ParB partition complex dynamics and ParA-ATPase activation for ParABS-mediated DNA partitioning.

Project description:ParABS partition systems, comprising the centromere-like DNA sequence parS, the parS-binding ParB-CTPase, and the nucleoid-binding ParA-ATPase, ensure faithful segregation of bacterial chromosomes and low-copy-number plasmids. F-plasmid partition complexes containing ParBF and parSF move by generating and following a local concentration gradient of nucleoid-bound ParAF. However, the process through which ParBF activates ParAF-ATPase has not been defined. We studied CTP- and parSF-modulated ParAF-ParBF complex assembly, in which DNA-bound ParAF-ATP dimers are activated for ATP hydrolysis by interacting with two ParBF N-terminal domains. CTP or parSF enhances the ATPase rate without significantly accelerating ParAF-ParBF complex assembly. Together, parSF and CTP accelerate ParAF-ParBF assembly without further significant increase in ATPase rate. Magnetic-tweezers experiments showed that CTP promotes multiple ParBF loading onto parSF-containing DNA, generating condensed partition complex-like assemblies. We propose that ParBF in the partition complex adopts a conformation that enhances ParBF-ParBF and ParAF-ParBF interactions promoting efficient partitioning.

| S-EPMC8357417 | biostudies-literature

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