Increment Of Molecular Weight Research Articles

NMR Study on Laccase Polymerization of Kraft Lignin Using Different Enzymes Source.

The usage of laccases is a sustainable and environmentally friendly approach to modifying the Kraft lignin structure for use in certain applications. However, the inherent structure of Kraft lignin, as well as that resulting from laccase modification, still presents challenges for fundamental comprehension and successful lignin valorization. In this study, bacterial and fungal laccases were employed to modify eucalypt Kraft lignin. To evaluate the type and range of the chemical and structural changes of laccase-treated lignins, different NMR techniques, including solution 1H and 2D NMR (heteronuclear single quantum correlation (HSQC)), and solid-state 13C NMR, were applied. Size exclusion chromatography and infrared spectroscopy were also used. Interestingly, HSQC analysis showed substantial changes in the oxygenated aliphatic region of lignins, showing an almost complete absence of signals corresponding to side-chains due to laccase depolymerization. Simultaneously, a significant loss of aromatic signals was observed by HSQC and 1H NMR, which was attributed to a deprotonation of the lignin benzenic rings due to polymerization/condensation by laccase reactions. Then, condensed structures, such as α-5', 5-5', and 4-O-5', were detected by HSQC and 13C NMR, supporting the increment in molecular weight, as well as the phenolic content reduction determined in lignins.

Laccase-catalyzed oxidative modification of lignosulfonates from acidic sulfite pulping of eucalyptus wood

Abstract Lignosulfonates (LS) from acidic magnesium-based sulfite cooking of Eucalyptus globulus wood were modified via laccase-catalyzed oxidative treatment with the aim to improve their performance as plasticizing additives in concrete formulations. The target parameters were the increment of molecular weight (Mw) and the amount of oxidized groups. The laccase-assisted oxidation under optimized conditions (40°C, pH 4.5, enzyme loads of 83–500 U g−1 for 90 min) allowed Mw increment up to 11-fold and almost doubled the amount of carbonyl and carboxyl groups without using any mediators. Modified LS maintained their solubility in water and possessed a zeta- potential close to that of initial LS. The characterization of modified LS has been carried out by ultraviolet-visible (UV-Vis), Fourier transform infrared-attenuated total reflectance (FTIR-ATR) and quantitative 13C nuclear magnetic resonance (NMR) spectroscopy, and the sulfonic and phenolic groups were assessed by conductometric titration. It was concluded that LS polymerization occurred mostly via the formation of new aryl ether bonds (two thirds of the modification) and biphenyl bonds (the remaining third). However, part of the newly formed bonds of unknown origin are temperature labile and cleaved during the concentration of LS at pH 4 and 80°C under vacuum, which led to the reduction of the Mw of the modified lignin to almost one third.

Increment in molecular weight of poly (dimethylamino-ethylmethacrylate) based polymers cause strong red blood cell aggregation but not hemolytic response

summary Polycations are frequently reported to tailor drug delivery systems, there is still a need to better correlate their macromolecular features with their biocompatibility, in particular with blood. In this view, we have analysed the RBC aggregation and hemolysis response caused by poly (dimethylamino-ethylmethacrylate) or poly(ethyleneimine) under a free form, i.e. without their preliminary association with polyanionic drug. Our results highlight that the molecular weight of PDMAEMA significantly affects the RBC aggregation without inducing any hemolysis.

Soluble neodymium chloride 2-ethylhexanol complex as a highly active catalyst for controlled isoprene polymerization

Soluble NdCl 3·3EHOH (2-ethyl hexanol) in hexane combined with AlEt 3 is highly active for isoprene polymerization in hexane. The NdCl 3·3EHOH/AlEt 3 has higher activity than the typical binary catalyst NdCl 3·3 i PrOH (isopropanol)/AlEt 3 and ternary catalyst NdV 3 (neodymium versatate)/AlEt 2Cl/Al( i-Bu) 2H. The molecular weight of polyisoprenes can be controlled by variation of [Nd], [Al]/[Nd] ratio and polymerization temperature and time. The NdCl 3·3EHOH/AlEt 3 catalyst polymerized isoprene to afford products featuring high cis-1,4 stereospecificity (ca. 96%), high molecular weight (ca. 10 5) and relatively narrow molecular weight distributions ( M w/ M n = 2.0–2.8) simultaneously. More importantly, some living polymerization characteristics were demonstrated: (a) absence of chain termination; (b) linear correlation between M n and polymer yield; (c) increment of molecular weight in the ‘seeding’ polymerization. Though some deviation from the typical living polymerization such as molecular weight distribution is not narrow enough and the line of M n and polymer yield does not extrapolate to zero, controlled polymerization with the current catalyst can still be concluded.

The effect of monomer molecular weight of acrylate on radiation grafting of polyethylene

A series of condensed ethylene glycol acrylate monomers with differentmolecular weight was grafted to polyethylene films by means of pre-irradiation.The effect of the molecular weight of monomer and co-solvent system on thegrafting reaction and the properties of the grafted sample were studied. Theexperimental results showed that the initial rate of grafting reaction decreasedand the molar degrees of grafting linearly decreased with the increment ofmolecular weight of the monomer. The grafting degree was increased with theswelling degree of the grafted film. The biocompatibility and blood compatibilityof the grafted PE films were evaluated by the determination of hydrophilicityand anti-thrombus.

Soluble Polyimides Based on Alkyldiaminobenzophenone

The synthesis and characterization of a novel series of soluble polyimides based on alkyldiaminobenzophenone (ADBP) having long chain linear alkyl groups with 9—14 carbon atoms are described. Polyimides containing tetracarboxylic dianhydrides such as 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and ADBP with even number carbon atoms were soluble in polar solvents such as N-methyl-2-pyrrolidone (NMP), while polyimides containing BTDA and ADBP with odd number carbon atoms (ADBP-9, 11, 13) were insoluble in NMP. These unique odd-even effects of solubility were assumed due to the conformational effects of long chain linear alkyl groups. Soluble copolyimides based on ADBP with conventional aromatic diamine, diaminodiphenylether (DDE) can be obtained. The incorporation of DDE resulted in increment of molecular weight and improve the thermal stability. Soluble polyimides and copolyimides based on ADBP were soluble in various polar solvents and exhibited high thermal stability in air and nitrogen.

Protein turnover in retina.

Rabbit retinas were exposed in vitro to 0.5-h pulses of [3H]leucine or [14C]leucine. Some retinas were harvested promptly after labeling to measure synthesis. These were combined, in double-labeling experiments, with retinas that had been returned to unlabeled medium for a subsequent 1 h or 3.75 h to measure degradation. All of the proteins were solubilized, and separated according to size by gel electrophoresis. The gels were cut into 95 slices, and each slice was differentially counted. The amount of protein in the slice was estimated from the Coomassie blue staining, and its molecular weight from the distribution of molecular weight (MW) standards. Turnover rates of the various sizes of proteins were calculated from these data using certain well-defined assumptions. Retinal protein contained about 32 X 10(3) nmol of polypeptide per g, with a median MW of 27,000. Total synthesis was at the rate of 103 nmol/g of protein/h, with the most rapid synthesis in the 33,000--43,000 MW range, at 2 nmol/g/h for every 1000 increment in MW. Protein renewal averaged 0.52%/h, but varied directly (p < 0.0001) with MW, so that proteins of 10,000 MW were being renewed at about 0.1%/h and proteins of 140,000 MW at about 1.4%/h. Taken together, the measurements of fractional renewal and the measurements of degradation of the newly synthesized proteins demonstrated that each slice contained proteins with markedly different breakdown coefficients, and provided enough information to characterize the proteins in the slice in terms of a fast and slow subgroup. This analysis indicated that: breakdown coefficients varied much more than rates of synthesis and were therefore the prime determinant of the amount of each protein that was present; as MW increased, breakdown coefficients of the long-lived proteins increased (p < 0.0001), accounting in major part for the correlation between size and turnover; most staining bands were due to proteins with peculiarly long lifespans; the proteins with the slowest turnover of all appeared to be histones; there was an unusually rapid synthesis of a 138,000 MW polypeptide with a moderately short half-life (about 3 h).

A unique IgG myeloma immunoglobulin molecular weight and other properties

Molecular weight and some other physicochemical properties of a unique myeloma immunoglobulin, designated IgG(Ud) are presented in the paper. The experiments were performed in a comparative way taking IgG as the standard protein. Molecular weight was determined by ultracentrifugation, Sephadex gel filtration and disc electrophoresis in sodium dodecyl sulphate solution. Molecular weight of IgG(Ud), and fragments F(ab′) 2 Ud and Fab Ud was found to be higher than that of IgG and its corresponding fragments, and for IgG(Ud) appeared to be approx. 176 000. The entire difference was accounted for solely by the Fab Ud fragment, which differs from Fab of IgG by about 8000. Both the light chain and Fd portion appeared to participate equally in the increment of molecular weight. Assuming correct interpretation of the experiments, the increment of molecular weight may be attributed to longer L chain and Fd portion. Amino acid analysis of IgG(Ud) showed higher content of tyrosine, lysine, glutamic acid and valine, and lower content of proline and phenylalanine. The elongation of polypeptide chain, as well as the difference in amino acid composition were supposed to result from unequal crossing-over.