Complex Formation Of Poly Research Articles

Extrusion-Based 3D Printing of Photocrosslinkable Chitosan Inks.

Photocuring of chitosan has shown great promise in the extrusion-based 3D printing of scaffolds for advanced biomedical and tissue engineering applications. However, the poor mechanical stability of methacrylated chitosan photocuring ink restricts its applicability. The inclusion of co-networks by means of simultaneous polycomplex formation is an effective method by which to solve this drawback, but the formed hydrogel inks are not printable. This work aims to develop new photocurable chitosan inks based on the simultaneous photocrosslinking of methacrylated chitosan (CHIMe) with N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, and acrylic acid to be applied in extrusion 3D printing. Interestingly, the polycomplex co-network corresponding to the acrylic-acid-based ink could be successfully printed by the here-presented simultaneous photocuring strategy. Further, the conversion of photocrosslinking was studied via photo-DSC analyses that revealed a clear dependence on the chemical structure of the employed crosslinking agents (from 40 to ~100%). In addition, the mechanical and rheological properties of the photocured hydrogels were comparatively studied, as well as the printing quality of the extruded scaffolds. The newly developed chitosan photocurable inks demonstrated extrusion printability (squareness ~0.90; uniformity factor ~0.95) and tunable mechanical properties (Young modulus 14-1068 Pa) by means of different crosslinking approaches according to the chemical architecture of the reactive molecules employed. This work shows the great potential of photocrosslinkable chitosan inks.

Aggregation of chromosome axis proteins on the chromatin and in the nucleoplasm of Brassica oleracea meiocytes

Meiotic recombination is essential for the generation of genetic diversity in natural and breeding context. The chromosome axis comprises cohesin, HORMA-domain containing proteins and coiled coil proteins and is crucial for the establishment of meiotic recombination. These proteins form a complex during meiosis of Brassica oleracea but information about their respective localisation and dynamic on meiotic chromosomes remain sparse. Our study reveals that the HORMA-protein ASY1 aggregates on the chromatin and forms domains of high and low abundances. The regions enriched for ASY1 are also highly enriched for the axis proteins ASY3, SMC3 and SCC3, although to varying degrees between leptotene and pachytene stages. At later stages, when most DNA double strand breaks are repaired and the chromosome axis disassemble, ASY1, ASY3, SCC3 and SMC3 co-localise and form large aggregates on the discontinuous axis structures. As the axis structures reduce in length, we found that all four axis proteins relocalise in the nucleoplasm and further aggregates. Moreover, we found that ZYP1, the transverse filament of the synaptonemal complex, forms numerous chromosomic aggregates that are sometimes associated with MLH1 and can form ectopic synaptic interactions. Overall, our study indicates that axis proteins have a high propensity to aggregate. This property is important for assembling the chromosome axis but the association of axis proteins with the chromatin must be tightly regulated to limit polycomplex formation.

Polycomb group (PcG) proteins prevent the assembly of abnormal synaptonemal complex structures during meiosis

The synaptonemal complex (SC) is a proteinaceous scaffold that is assembled between paired homologous chromosomes during the onset of meiosis. Timely expression of SC coding genes is essential for SC assembly and successful meiosis. However, SC components have an intrinsic tendency to self-organize into abnormal repetitive structures, which are not assembled between the paired homologs and whose formation is potentially deleterious for meiosis and gametogenesis. This creates an interesting conundrum, where SC genes need to be robustly expressed during meiosis, but their expression must be carefully regulated to prevent the formation of anomalous SC structures. In this manuscript, we show that the Polycomb group protein Sfmbt, the Drosophila ortholog of human MBTD1 and L3MBTL2, is required to avoid excessive expression of SC genes during prophase I. Although SC assembly is normal after Sfmbt depletion, SC disassembly is abnormal with the formation of multiple synaptonemal complexes (polycomplexes) within the oocyte. Overexpression of the SC gene corona and depletion of other Polycomb group proteins are similarly associated with polycomplex formation during SC disassembly. These polycomplexes are highly dynamic and have a well-defined periodic structure. Further confirming the importance of Sfmbt, germ line depletion of this protein is associated with significant metaphase I defects and a reduction in female fertility. Since transcription of SC genes mostly occurs during early prophase I, our results suggest a role of Sfmbt and other Polycomb group proteins in downregulating the expression of these and other early prophase I genes during later stages of meiosis.

SYP-5 regulates meiotic thermotolerance in Caenorhabditis elegans.

Meiosis produces the haploid gametes required by all sexually reproducing organisms, occurring in specific temperature ranges in different organisms. However, how meiotic thermotolerance is regulated remains largely unknown. Using the model organism Caenorhabditis elegans, here, we identified the synaptonemal complex (SC) protein SYP-5 as a critical regulator of meiotic thermotolerance. syp-5-null mutants maintained a high percentage of viable progeny at 20°C but produced significantly fewer viable progeny at 25°C, a permissive temperature in wild-type worms. Cytological analysis of meiotic events in the mutants revealed that while SC assembly and disassembly, as well as DNA double-strand break repair kinetics, were not affected by the elevated temperature, crossover designation, and bivalent formation were significantly affected. More severe homolog segregation errors were also observed at elevated temperature. A temperature switching assay revealed that late meiotic prophase events were not temperature-sensitive and that meiotic defects during pachytene stage were responsible for the reduced viability of syp-5 mutants at the elevated temperature. Moreover, SC polycomplex formation and hexanediol sensitivity analysis suggested that SYP-5 was required for the normal properties of the SC, and charge-interacting elements in SC components were involved in regulating meiotic thermotolerance. Together, these findings provide a novel molecular mechanism for meiotic thermotolerance regulation.

Homozygous mutations in C14orf39/SIX6OS1 cause non-obstructive azoospermia and premature ovarian insufficiency in humans

SummaryHuman infertility is a multifactorial disease that affects 8%–12% of reproductive-aged couples worldwide. However, the genetic causes of human infertility are still poorly understood. Synaptonemal complex (SC) is a conserved tripartite structure that holds homologous chromosomes together and plays an indispensable role in the meiotic progression. Here, we identified three homozygous mutations in the SC coding gene C14orf39/SIX6OS1 in infertile individuals from different ethnic populations by whole-exome sequencing (WES). These mutations include a frameshift mutation (c.204_205del [p.His68Glnfs∗2]) from a consanguineous Pakistani family with two males suffering from non-obstructive azoospermia (NOA) and one female diagnosed with premature ovarian insufficiency (POI) as well as a nonsense mutation (c.958G>T [p.Glu320∗]) and a splicing mutation (c.1180−3C>G) in two unrelated Chinese men (individual P3907 and individual P6032, respectively) with meiotic arrest. Mutations in C14orf39 resulted in truncated proteins that retained SYCE1 binding but exhibited impaired polycomplex formation between C14ORF39 and SYCE1. Further cytological analyses of meiosis in germ cells revealed that the affected familial males with the C14orf39 frameshift mutation displayed complete asynapsis between homologous chromosomes, while the affected Chinese men carrying the nonsense or splicing mutation showed incomplete synapsis. The phenotypes of NOA and POI in affected individuals were well recapitulated by Six6os1 mutant mice carrying an analogous mutation. Collectively, our findings in humans and mice highlight the conserved role of C14ORF39/SIX6OS1 in SC assembly and indicate that the homozygous mutations in C14orf39/SIX6OS1 described here are responsible for infertility of these affected individuals, thus expanding our understanding of the genetic basis of human infertility.

A Study on the Complex Formation of Poly(Methyl Methacrylate), Poly(Vinyl Chloride) and Their Blend with Lithium Perchlorate Using FTIR Spectroscopy

AbstractFourier transform infrared spectrum of the polymer‐salt complexes of poly(methyl methacrylate), poly(vinyl chloride), and the salt lithium perchlorate is analyzed for different compositions. The functional group analysis reveals that polymers PMMA and PVC form stable complexes with LiClO4. A systematic analysis of the FTIR spectrum of the polymer blend‐salt complexes brings out the inference that the system with equal composition of PMMA and PVC, 37.5 wt% each, is found to show a better complex formation with 25 wt% of LiClO4. The peak positional change of C═O group of PMMA is analyzed critically to identify the complex‐forming behavior of polymer blend.

Regulating chromosomal movement by the cochaperone FKB-6 ensures timely pairing and synapsis.

In meiotic prophase I, homologous chromosome pairing is promoted through chromosome movement mediated by nuclear envelope proteins, microtubules, and dynein. After proper homologue pairing has been established, the synaptonemal complex (SC) assembles along the paired homologues, stabilizing their interaction and allowing for crossing over to occur. Previous studies have shown that perturbing chromosome movement leads to pairing defects and SC polycomplex formation. We show that FKB-6 plays a role in SC assembly and is required for timely pairing and proper double-strand break repair kinetics. FKB-6 localizes outside the nucleus, and in its absence, the microtubule network is altered. FKB-6 is required for proper movement of dynein, increasing resting time between movements. Attenuating chromosomal movement in fkb-6 mutants partially restores the defects in synapsis, in agreement with FKB-6 acting by decreasing chromosomal movement. Therefore, we suggest that FKB-6 plays a role in regulating dynein movement by preventing excess chromosome movement, which is essential for proper SC assembly and homologous chromosome pairing.

The Ecm11-Gmc2 Complex Promotes Synaptonemal Complex Formation through Assembly of Transverse Filaments in Budding Yeast

During meiosis, homologous chromosomes pair at close proximity to form the synaptonemal complex (SC). This association is mediated by transverse filament proteins that hold the axes of homologous chromosomes together along their entire length. Transverse filament proteins are highly aggregative and can form an aberrant aggregate called the polycomplex that is unassociated with chromosomes. Here, we show that the Ecm11-Gmc2 complex is a novel SC component, functioning to facilitate assembly of the yeast transverse filament protein, Zip1. Ecm11 and Gmc2 initially localize to the synapsis initiation sites, then throughout the synapsed regions of paired homologous chromosomes. The absence of either Ecm11 or Gmc2 substantially compromises the chromosomal assembly of Zip1 as well as polycomplex formation, indicating that the complex is required for extensive Zip1 polymerization. We also show that Ecm11 is SUMOylated in a Gmc2-dependent manner. Remarkably, in the unSUMOylatable ecm11 mutant, assembly of chromosomal Zip1 remained compromised while polycomplex formation became frequent. We propose that the Ecm11-Gmc2 complex facilitates the assembly of Zip1 and that SUMOylation of Ecm11 is critical for ensuring chromosomal assembly of Zip1, thus suppressing polycomplex formation.

Study of the multilayer assembly and complex formation of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(acrylic acid) (PAA) as a function of pH

The assembly of polyelectrolyte multilayers and the formation of complexes in a solution of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(acrylic acid) (PAA) have been studied as a function of pH. Quartz Crystal Microbalance with Dissipation (QCM-D) in combination with Ellipsometry shows that PAA–PDADMAC multilayers display a supralinear growth pattern at pH 3 with a corresponding change in the frequency response of more than 650 Hz for 17 polyelectrolyte layers. Atomic Force Microscopy (AFM) confirmed the formation of a 200 nm thick film. For pH values higher than 6, assembly is drastically reduced resulting in values below 150 Hz in the QCM-D for the same number of layers. Isothermal Titration Calorimetry (ITC) and Dynamic Light Scattering (DLS) were used to study complex formation. At pH 3, an exothermic heat of complex formation of −2.11 kcal mol−1 was measured. With increasing pH, the heat of complex formation has been seen to decrease. At pH 10, the heat of complex formation tends to be more endothermic and is approximately 0 at pH 13. The addition of urea to PAA at pH 13 resulted in an exothermic heat of complex formation of 1.41 kcal mol−1 during titration with PDADMAC, highlighting the role of hydrogen bonding with water of PAA in governing the interaction between PAA and PDADMAC.

Salt effect on microscopic structure and stability of colloidal complex obtained from neutral/polyelectrolyte block copolymer and oppositely charged surfactant

The salt effect on complex formation of poly(acrylamide)-block-poly(acrylic acid) (PAM-b-PAA) and dodecyltrimethylammonium bromide (DTAB) at different NaBr concentrations, CNaBr, was investigated by laser light scattering (LLS) and small angle neutron scattering (SANS). LLS and SANS clearly indicates that the aqueous solution of PAM-b-PAA and DTAB associate into colloidal complexes. For low surfactant-to-polymer charge ratio Z lower than the critical value ZC, the colloidal complexes are single DTAB micelles dressed by a few PAM-b-PAA. Above ZC, the colloidal complexes form a core–shell microstructure. The complex formation in the PAM-b-PAA/DTAB is enhanced by addition of salt: ZC decreases with increasing CNaBr. This is considered to similar to the cmc behavior for the pure surfactant system. The core of the complex consists of densely packed surfactant micelles (DTA+), and PAA block chains bind to these micelles, displace their counteranions (Br−) and bridge them. The corona of the complex is constituted from the PAM. Since the interaction between polyelectrolyte and oppositely charged surfactant is primarily electrostatic in nature, the core radius and the intermicellar distance of the DTA+ micelles inside the core depend on CNaBr. The addition of salt screens the electrostatic attraction between oppositely charged PAA block and DTAB, which weakens the interaction. With increasing CNaBr, therefore, the core of the colloidal complex is considered to swell, which leads to the increases in the core radius RC and the intermicellar distance of the DTA+ micelles inside the core. The aggregation number expressed in terms of DTA+ micelles per complex is also evaluated using the analogy with the homopolyelectrolyte/surfactant system.

Characterization of Water-Soluble Complexes of Polyacrylic Acid with α-Amylase from Aspergillus oryzae

Polycomplex formation of alpha-Amylase from Aspergillus oryzae (TAKA) with polyacrylic acid (PAA) was studied by pH titration, fluorescence, and high performance liquid chromatography (HPLC) methods in water solutions. According to the our results, the complex formation and its solubility were depended on nature of enzyme and the pH of solutions. Both of them correlates isoelectric points (PI). The stability of PAA-amylase complexes was negligibly weak at pH 7 [pH > pI (isoelectric pH)]. Stable water-soluble polycomplexes were formed at pH 5 (pI approximately 4.5) and coexisted with free protein molecules. Insoluble complexes has been observed at pH < 4.5. The frozen storage stabilities of the obtained complexes were also studied by measuring the activities at different pH.

Effect of ionic strength of the solution of some hydrogen - bonded interpolymer complexes on the stability and thermodynamic parameters

The effect of ionic strength of the solution on the complex formation of poly(acrylic acid) (PAA) with poly(vinyl pyrrolidone) (PVP) has been studied in aqueous solutions containing various inorganic salts (NaCl, KCl, NH 4 Cl). Stability constant (K s ), degree of linkage (θ) and related thermodynamic parameters (AG°, ΔH 0 and ΔS 0 ) have been compared for different complexation systems. The comparative study indicated considerable difference in the values of these parameters, which has been explained on the basis of relative strength of H-bond present in different systems.

Preparation of fluoride anion responsive poly(N-vinylcarbazole)-borane complexes

Abstract A series of novel fluoride anion responsive materials were facilely prepared by complex formation of poly( N -vinylcarbazole) with organoboron compounds in tetrahydrofuran. After addition of fluoride anion, visual color changes of fluorescence emission from green to blue were observed. The 11 B NMR spectra shown that poly( N -vinylcarbazole)-borane complexes were converted to poly( N -vinylcarbazole) and fluoroborate in the presence of fluoride anion. Among the obtained poly( N -vinylcarbazole)-borane complexes prepared, poly( N -vinylcarbazole)-triethylborane complex exhibited the most distinct visual changes in fluorescence emissions.

Salt Effect on Complex Formation of Neutral/Polyelectrolyte Block Copolymers and Oppositely Charged Surfactants

The salt effect on the complex formation of poly(acrylamide)- block-poly(sodium acrylate) (PAM- b-PAA) as a neutral-anionic block copolymer and dodecyltrimethylammonium bromide (DTAB) as a cationic surfactant at different NaBr concentrations, CNaBr, was investigated by turbidimetric titration, steady-state fluorescence spectroscopy, and dynamic light scattering. At C NaBr < 0.25 M, DTAB molecules may form micelle-like aggregates on PAM- b-PAA chains to form a PAM- b-PAA/DTAB complex above the critical surfactant concentration C critical for the onset of complex formation. In the region of relatively high turbidity, a larger complex is likely to form a core-shell structure, of which the core is a dense and disordered microphase made of surfactant micelles connected by the PAA blocks. The corona was a diffuse shell of PAM chains, and it ensured steric stability. At CNaBr = 0.25 M, a higher electrostatic intermicellar repulsion and intercomplex repulsion induced by a large amount of bound DTAB micelles may lead to a redissolution of large colloidal complexes into intrapolymer complexes. Moreover, a salt-enhancing effect on the complex formation was observed in the PAM- b-PAA/DTAB system; the critical surfactant concentration decreased with increasing salt concentration at CNaBr < 0.10 M. The salt-enhancing effect is due to the larger increase of interaction in comparison to the screening of the interaction.

The Formation of the Central Element of the Synaptonemal Complex May Occur by Multiple Mechanisms: The Roles of the N- and C-Terminal Domains of the Drosophila C(3)G Protein in Mediating Synapsis and Recombination

In Drosophila melanogaster oocytes, the C(3)G protein comprises the transverse filaments (TFs) of the synaptonemal complex (SC). Like other TF proteins, such as Zip1p in yeast and SCP1 in mammals, C(3)G is composed of a central coiled-coil-rich domain flanked by N- and C-terminal globular domains. Here, we analyze in-frame deletions within the N- and C-terminal regions of C(3)G in Drosophila oocytes. As is the case for Zip1p, a C-terminal deletion of C(3)G fails to attach to the lateral elements of the SC. Instead, this C-terminal deletion protein forms a large cylindrical polycomplex structure. EM analysis of this structure reveals a polycomplex of concentric rings alternating dark and light bands. However, unlike both yeast and mammals, all three proteins deleted for N-terminal regions completely abolished both SC and polycomplex formation. Both the N- and C-terminal deletions significantly reduce or abolish meiotic recombination similarly to c(3)G null homozygotes. To explain these data, we propose that in Drosophila the N terminus, but not the C-terminal globular domain, of C(3)G is critical for the formation of antiparallel pairs of C(3)G homodimers that span the central region and thus for assembly of complete TFs, while the C terminus is required to affix these homodimers to the lateral elements.

Optical and Electrochemical Detection of Saccharides with Poly(aniline-co-3-aminobenzeneboronic acid) Prepared from Enzymatic Polymerization

Boronic acid-based sensors for saccharides have been developed via biocatalysis. The self-doped copolymer of poly(aniline-co-3-aminobenzeneboronic acid) [poly(aniline-co-AB)], with various mole ratios of two components, was synthesized by oxidative enzymatic polymerization using a natural biocatalyst such as horseradish peroxidase together with an anionic polyelectrolyte template (sulfonated polystyrene) under mild conditions (pH 4.5). Poly(aniline-co-AB), having an aniline boronic acid-to-aniline ratio of 1:2 on average, gave rise to a green doped polymer with absorption maxima at 745 nm. The potentiometric detection of saccharides using poly(aniline-co-AB) is presented. Characteristics of both transient and steady-state response associated with the complex formation of poly(aniline-co-AB) with various saccharides were monitored by UV-vis spectroscopy and cyclic voltammetry (CV). The results obtained from UV-vis spectroscopy and CV show that the sensitivity of enzymatically synthesized water-soluble poly(aniline-co-AB) for various saccharides was improved significantly compared to the chemically synthesized counterpart. A possible mechanism for the sensitive detection of sugar molecules by boronic acid is proposed on the basis of UV-vis and IR spectrophotometry, and four-point probe conductivity measurements.

Static light scattering study of complex formation between protein and neutral water-soluble polymer

Complex formation of poly( N-isopropylacrylamide) (PNIPA) having a weight-average molecular weight of 1,720,000 g/mol with human serum albumin (HSA), ovalbumin (OVA) and lysozyme (LYZ) was studied in an aqueous medium containing 0.01 M NaCl and adjusted to pH 3. The polymer–protein mixtures at different molar ratios ( r m) were examined by static light scattering (SLS). The analysis of SLS data using our own approach [Kokufuta et al., Langmuir 15 (1999) 940; Biomacromolecules 4 (2003) 728] showed that the molecular weight of each resulting complex is smaller than that of the interpolymer complex composed of two polymer chains plus one protein. This indicates the formation of an intrapolymer complex in all the polymer–protein systems studied. Thus, at each r m we calculated the number of bound proteins per polymer, the value of which was OVA > HSA > LYZ in order. These results were compared with the hydropathy profiles of each protein which are a good tool for obtaining an information about distribution of hydrophobic and hydrophilic segments in a protein. It has become apparent that the hydrophobic interaction between polymer and protein plays an important role in the intrapolymer complex formation.

PH and salt effects on interpolymer complexation via hydrogen bonding in aqueous solutions

AbstractThe effect of inorganic salts addition on the complex formation of poly(acrylic acid) with various non‐ionic polymers such as poly(vinyl pyrrolidone), poly(acrylamide), poly(ethylene oxide), pol(vinyl methyl ether), poly(vinyl alcohol), poly(N‐isopropylacrylamide), poly(2‐hydroxyethyl vinyl ether), hydroxypropylcellulose and hydroxyethylcellulose has been studied in aqueous solutions. It was found that, depending on the nature of the polymers and pH medium, addition of inorganic salts could increase or decrease the critical pH values of complexation. A new classification of interpolymer complexes based on critical pH values and ionic strength effects is suggested. Copyright © 2004 Society of Chemical Industry

Complex formation of Poly(sodiumα-hydroxyacrylate) with fatty acid and its detergency performance

Complex formation of Poly(sodiumα-hydroxyacrylate) with fatty acid and its detergency performance

Thermodynamics of hydrogen bonding in polycomplexes of poly(4-vinylpyridine) with maleic acid- alt-ethylene copolymer

Hydrogen bonding formation in a polymer complex between poly(4-vinylpyridine) (P4VPy) and maleic acid- alt-ethylene (MA- alt-E) copolymer has been studied. Fourier transform infrared spectroscopic (FT-IR) studies have evidenced that the carboxylic groups of MA- alt-E interact with the pyridine ring of P4VPy. The existence of hydrogen bonding interactions in these systems is shown by the appearance of new bands at 1640 and 1503 cm −1 and a broadening of the –CC– band of the pyridinic ring. The thermodynamic analysis of the hydrogen bonding was performed through the estimation of the enthalpy of mixing in the polycomplex formation process. Δ H M was determined by means of an association model developed by Painter and co-workers and by flow calorimetric direct measurements. These results showed a high negative value for the enthalpy of mixing, which is consistent with the blend miscibility given that Δ H M is the main contribution to the change of the free energy of mixing, Δ G M.