scholarly journals Spruce milled wood lignin: linear, branched or cross-linked?

2020 ◽  
Vol 22 (13) ◽  
pp. 3985-4001 ◽  
Author(s):  
Mikhail Balakshin ◽  
Ewellyn Augsten Capanema ◽  
Xuhai Zhu ◽  
Irina Sulaeva ◽  
Antje Potthast ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Structural Model ◽  
Milled Wood Lignin ◽  
Weight Data

Plausible up-to-date structural model of spruce MWL in agreement with the current structural and molecular weight data.

scholarly journals Structural Changes in Milled Wood Lignin (MWL) of Chinese Quince (Chaenomeles sinensis) Fruit Subjected to Subcritical Water Treatment

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 398
Author(s):  
Wen-Yue Wang ◽  
Zhao Qin ◽  
Hua-Min Liu ◽  
Xue-De Wang ◽  
Jing-Hao Gao ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Water Treatment ◽  
Quantum Coherence ◽  
Structural Changes ◽  
31P Nmr ◽  
Subcritical Water ◽  
Water Extraction ◽  
Subcritical Water Extraction ◽  
Milled Wood Lignin ◽  
Chinese Quince

Subcritical water treatment has received considerable attention due to its cost effectiveness and environmentally friendly properties. In this investigation, Chinese quince fruits were submitted to subcritical water treatment (130, 150, and 170 °C), and the influence of treatments on the structure of milled wood lignin (MWL) was evaluated. Structural properties of these lignin samples (UL, L130, L150, and L170) were investigated by high-performance anion exchange chromatography (HPAEC), FT-IR, gel permeation chromatography (GPC), TGA, pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), 2D-Heteronculear Single Quantum Coherence (HSQC) -NMR, and 31P-NMR. The carbohydrate analysis showed that xylose in the samples increased significantly with higher temperature, and according to molecular weight and thermal analysis, the MWLs of the pretreated residues have higher thermal stability with increased molecular weight. The spectra of 2D-NMR and 31P-NMR demonstrated that the chemical linkages in the MWLs were mainly β-O-4′ ether bonds, β-5′ and β-β′, and the units were principally G- S- H- type with small amounts of ferulic acids; these results are consistent with the results of Py-GC/MS analysis. It is believed that understanding the structural changes in MWL caused by subcritical water treatment will contribute to understanding the mechanism of subcritical water extraction, which in turn will provide a theoretical basis for developing the technology of subcritical water extraction.

Organomercury compounds. XXIII. Organomercuric Quinolin-8-olates

1978 ◽  
Vol 31 (3) ◽  
pp. 527 ◽  
Author(s):  
RJ Bertino ◽  
GB Deacon ◽  
JM Miller
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Solid State ◽  
Carbon Tetrachloride ◽  
Crystal Structures ◽  
Supporting Evidence ◽  
Visible Spectroscopy ◽  
Organomercury Compounds ◽  
Weight Data

The complexes RHg(ox) (R = C6F5, p-HC6F4, or p-MeOC6F4; ox = quinolin-8- olate) have been prepared by reaction of thallous quinofin-8-olate with the appropriate organomercuric chlorides whilst PhHg(ox or meox), MeHg(ox),H2O, and MeHg(meox) (meox = 2-methylquinolin-8-olate) have been obtained from phenyl- or methyl-mercuric hydroxide and quinolin-8-ol or 2-methyl-quinolin-8-ol. Although MeHg(ox),H2O was readily dehydrated, the water could not be displaced by ligands (e.g. Ph3PO, Me2SO). Chelation of the quinolin-8-olate ligands (rather than unidentate O- bonding) was established for all complexes by ultraviolet/visible spectroscopy. Molecular weight data indicated that all complexes except MeHg(ox) and MeHg(ox),H2O are partly associated in benzene, chloroform and/or carbon tetrachloride [K(2 monomer ↔ dimer) in the range 1-40 mol-1 dm3]; this suggests an associated structure in the solid state. Some supporting evidence for associated structures was obtained by mass spectrometry. The structural conclusions are discussed in the light of crystal structures of PhHg(ox) and PhHg(meox) carried out in a concurrent investigation.

Studies in the stereochemistry of zinc(II). VII. Zinc complexes with dialkyldithiophosphates

1970 ◽  
Vol 23 (10) ◽  
pp. 1989 ◽  
Author(s):  
DR Dakternieks ◽  
DP Graddon
Keyword(s):  
Molecular Weight ◽  
Zinc Complexes ◽  
Weight Data ◽  
Infrared Data

A series of bis(O,O-dialkyldithiophosphato)zinc(11) complexes, ZnL2 (LH = (R0)2PS2H; R = Et, Pri, Bu, Bui, Bus, cyclohexyl), has been isolated. Pyridine adducts ZnL2(py)2 (R = Et, Pr, Pri, Bui) and ZnL2(py) (R = Pr, Pri, Bui) have also been obtained. Basic complexes ZnO,3ZnL2 (R = Et, Pr) have been isolated. Molecular weight data show that ZnL2 associates in benzene. When R = Pri 2ZnL2 ↔ Zn2L4 ΔG0c -6kJ mol-1 The adducts ZnL2(py) are stable. Adducts ZnL2(py)2 dissociate in benzene; when R = Pr ZnL2(py) + PY + ZnL2(py)2 ΔG0c-7kJmol-1 (ΔG0 calculated from molal concentrations). Infrared data cannot distinguish between chelate, bridging, and unidentate PS2 groups. Co-crystallization of ZnL2(py)2 and XiL2(py)2 could not be achieved, suggesting ZnL2(py)2 is cis-octahedral.

IV. The Micellar Theory of the Structure of Rubber

1942 ◽  
Vol 15 (3) ◽  
pp. 446-451
Author(s):  
G. Gee
Keyword(s):  
Molecular Weight ◽  
Physical Properties ◽  
Infinite Dilution ◽  
Mechanical Deformation ◽  
Point Of View ◽  
Pressure Measurements ◽  
Physical Behavior ◽  
Molecular Weights ◽  
Micelle Size ◽  
Weight Data

Abstract The molecular weight data reported in Part II depend on the assumption that the values obtained by extrapolating osmotic pressure measurements to infinite dilution represent true molecular weights. This point of view has been strongly criticized, particularly by Pummerer and his coworkers, according to whom rubber normally exists in solution in the form of micelles comprising more or less well-defined aggregates containing a considerable number of chemical molecules. The- osmotic “molecular weight” is then regarded as the weight of an average micelle. If they exist, these micelles may be important in determining both the chemical and physical behavior of rubber, for we should clearly expect the bonds by which the chemical molecules are bound into micelles to be weaker than those within the molecules. It may be noted that it has been shown elsewhere that the physical properties of a series of rubber fractions are closely related to their osmotic and viscosity molecular weights. Since, according to the micellar theory, these fractions can differ only in micelle size, their mechanical behavior must, from this viewpoint, be determined by the size of the micelles, which must therefore remain intact during mechanical deformation of the rubber. It is the object of the present paper to examine in more detail the basis of the micellar theory, and especially to offer an interpretation of the results of the East method, on which Pummerer's arguments are mainly based.

Coordination complexes of acetylene diphosphines. II. Diphosphine bridged palladium(II) and platinum(II) derivatives

1969 ◽  
Vol 47 (14) ◽  
pp. 2573-2578 ◽  
Author(s):  
A. J. Carty ◽  
A. Efraty
Keyword(s):  
Molecular Weight ◽  
Infrared Spectra ◽  
Coordination Complexes ◽  
Weight Data

Complexes of the type (MX2)2(DPPA)2 (M = Pd, Pt; X = Cl, Br, I, SCN; DPPA = bis(diphenylphosphino)acetylene) have been prepared and characterized. Raman, infrared, and molecular weight data have been used to show that the structures are binuclear with bridging bis(diphenylphosphino)acetylene groups. The infrared spectra of the compounds [M(SCN)2]2(DPPA)2 are suggestive of the presence of both N and S bonded thiocyanate within the same molecule.

Autohydrolysis of aspen milled wood lignin

1980 ◽  
Vol 58 (7) ◽  
pp. 669-676 ◽  
Author(s):  
Jairo H. Lora ◽  
Morris Wayman
Keyword(s):  
Molecular Weight ◽  
Populus Tremuloides ◽  
Soluble Fraction ◽  
Gel Permeation Chromatography ◽  
Insoluble Fraction ◽  
Low Molecular Weight ◽  
Milled Wood Lignin ◽  
Insoluble Material ◽  
Initial Generation ◽  
Insoluble Product

In order to obtain further understanding of the nature of lignin reactions during autocatalysed hydrolysis (autohydrolysis) of wood, milled wood lignin (MWL) was isolated from aspen (Populus tremuloides) and treated under autohydrolysis conditions. By this means reactions of the lignin itself could be distinguished from those taking place between lignin and the carbohydrate or other components of the wood. The material after the reaction was separated into a dioxane insoluble fraction (DI), a dioxane soluble but ether insoluble fraction (DSEI), and an ether soluble fraction (ES). Studies were carried out on the DI and DSEI fractions; no direct study was made of the small ES fraction.The formation of DI material increased linearly during the first 7.5 min at 170 °C and then levelled off. At the same time DSEI decreased and then levelled off. Gel permeation chromatography of the DSEI fraction suggested that during autohydrolysis there is an initial generation of low molecular weight fragments which recombine to form first a high molecular weight soluble fraction and from this the insoluble product. The DSEI fraction contained increased conjugated and unconjugated keto groups. Carboxylic acids were also detected; they have been attributed to the reincorporation of low molecular weight aromatic acids generated by the hydrolysis of the corresponding esters. The dioxane insoluble (DI) fraction had fewer unconjugated keto groups than the DSEI fraction, indicating that these groups participated in the condensation reactions leading to the formation of insoluble material. These probably involve position 6 of the aromatic ring.

scholarly journals Design and Expression of a Dimeric Form of Human Immunodeficiency Virus Type 1 Antibody 2G12 with Increased Neutralization Potency

2008 ◽  
Vol 83 (1) ◽  
pp. 98-104 ◽  
Author(s):  
Anthony P. West ◽  
Rachel P. Galimidi ◽  
Christopher P. Foglesong ◽  
Priyanthi N. P. Gnanapragasam ◽  
Kathryn E. Huey-Tubman ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Structural Model ◽  
Passive Immunization ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Antibody 2G12

ABSTRACT The antigen-binding fragment of the broadly neutralizing human immunodeficiency virus type 1 (HIV-1) antibody 2G12 has an unusual three-dimensional (3D) domain-swapped structure with two aligned combining sites that facilitates recognition of its carbohydrate epitope on gp120. When expressed as an intact immunoglobulin G (IgG), 2G12 formed typical IgG monomers containing two combining sites and a small fraction of a higher-molecular-weight species, which showed a significant increase in neutralization potency (50- to 80-fold compared to 2G12 monomer) across a range of clade A and B strains of HIV-1. Here we show that the higher-molecular-weight species corresponds to a 2G12 dimer containing four combining sites and present a model for how intermolecular 3D domain swapping could create a 2G12 dimer. Based on the structural model for a 3D domain-swapped 2G12 dimer, we designed and tested a series of 2G12 mutants predicted to increase the ratio of 2G12 dimer to monomer. We report a mutation that effectively increases the 2G12 dimer/monomer ratio without decreasing the expression yield. Increasing the proportion of 2G12 dimer compared to monomer could lead to a more potent reagent for gene therapy or passive immunization.

Characterization of autohydrolysis aspen (P. tremuloides) lignins. Part 2. Alkaline nitrobenzene oxidation studies of extracted autohydrolysis lignin

1979 ◽  
Vol 57 (19) ◽  
pp. 2599-2602 ◽  
Author(s):  
Morris Wayman ◽  
Miranda G. S. Chua
Keyword(s):  
Molecular Weight ◽  
Molar Ratio ◽  
Low Molecular Weight ◽  
Aspen Wood ◽  
Milled Wood Lignin ◽  
Wood Meal ◽  
Nitrobenzene Oxidation ◽  
Carbon Carbon Bonds ◽  
Degree Of Condensation

Alkaline nitrobenzene oxidation of the lignins extracted from extractive-free aspen wood meal after autohydrolysis at 195 °C for periods varying from 5 min to 2 h indicated that these lignins were structurally more condensed in terms of an increase in new carbon–carbon bonds than aspen milled wood lignin. The degree of condensation generally increased with longer autohydrolysis times. It is postulated that condensation involved materials from both the carbohydrate and lignin components of the wood which were generated during the autohydrolysis. The molar ratio of syringaldehyde to vanillin of extracted lignin on oxidation was observed to decrease with increasing autohydrolysis time. It is suggested that syringyl units are preferentially extracted as low molecular weight material.

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