scholarly journals Synthesis of Poly(N-fluoroalkyl benzamide) with Controlled Molecular Weight and Polydispersity Index

2007 ◽  
Vol 39 (8) ◽  
pp. 777-782 ◽  
Author(s):  
Kaoru Ohshimizu ◽  
Yuji Shibasaki ◽  
Mitsuru Ueda
Keyword(s):  
Molecular Weight ◽  
Polydispersity Index

scholarly journals A Water-Soluble Polysaccharide from the Fruit Bodies ofBulgaria inquinans(Fries) and Its Anti-Malarial Activity

2011 ◽  
Vol 2011 ◽  
pp. 1-12 ◽  
Author(s):  
Hongtao Bi ◽  
Han Han ◽  
Zonghong Li ◽  
Weihua Ni ◽  
Yan Chen ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Immune Function ◽  
Lymphocyte Proliferation ◽  
Water Soluble ◽  
Polydispersity Index ◽  
Immune Competence ◽  
Suppressive Activity ◽  
Macrophage Phagocytosis ◽  
Immunological Tests ◽  
Soluble Polysaccharide

A water-soluble polysaccharide (BIWS-4b) was purified from the fruit bodies ofBulgaria inquinans(Fries). It is composed of mannose (27.2%), glucose (15.5%) and galactose (57.3%). Its molecular weight was estimated to be 7.4 kDa (polydispersity index, Mw/Mn: 1.35). Structural analyses indicated that BIWS-4b mainly contains (1→6)-linked, (1→5)-linked and (1→5,6)-linkedβ-Galfunits; (1→4)-linked and non-reducing terminalβ-Glcpunits; and (1→2)-linked, (1→6)-linked, (1→2,6)-linked and non-reducing terminalα-Manpunits. When examined by the 4-day method and in a prophylactic assay in mice, BIWS-4b exhibited markedly suppressive activity against malaria while enhancing the activity of artesunate. Immunological tests indicated that BIWS-4b significantly enhanced macrophage phagocytosis and splenic lymphocyte proliferation in malaria-bearing mice and normal mice. The anti-malarial activity of BIWS-4b might be intermediated by enhancing immune competence and restoring artesunate-suppressed immune function. Thus, BIWS-4b is a potential adjuvant of anti-malaria drugs.

Evaluation of polydispersity index Mw/Mn by quasielastic light scattering

1987 ◽  
Vol 52 (5) ◽  
pp. 1235-1245 ◽  
Author(s):  
Petr Štěpánek ◽  
Zdeněk Tuzar ◽  
Čestmír Koňák
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Decay Time ◽  
Sampling Time ◽  
Polydispersity Index ◽  
New Method ◽  
Molecular Weights ◽  
Quasielastic Light Scattering ◽  
Good Agreement

The response of quasielastic light scattering to the polydispersity of scattering objects has been investigated. A new method of the polydispersity index determination has been suggested, suitable for the range 1.02 ⪬ Mw/Mn ⪬ 2.0 and consisting in the measurement of the dependence of the apparent decay time on the correlator sampling time. The polydispersity index can be determined by comparing these dependences with the theoretical ones obtained using correlation curves simulated for various values of the polydispersity index, assuming lognormal and Schulz-Zimm distributions of molecular weights. The test measurements on polystyrene standards having molecular weights in the range 9 103 – 20.6 106 give polydispersity index values Mw/Mn that are in a good agreement with those given by the manufacturer. The polydispersity index for polystyrene having the molecular weight Mw = 20.6 106 thus determined was Mw/Mn = 1.35.

Engineering of Stable Recombinant Bacteria for Production of Chiral Medium-Chain-Length Poly-3-Hydroxyalkanoates

1999 ◽  
Vol 65 (8) ◽  
pp. 3265-3271 ◽  
Author(s):  
Maria A. Prieto ◽  
Michele B. Kellerhals ◽  
Gian B. Bozzato ◽  
Dragan Radnovic ◽  
Bernard Witholt ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Chain Length ◽  
Expression System ◽  
Average Molecular Weight ◽  
Polydispersity Index ◽  
Recombinant Bacteria ◽  
E Coli ◽  
Medium Chain ◽  
Medium Chain Length ◽  
Pha Production

ABSTRACT In order to scale up medium-chain-length polyhydroxyalkanoate (mcl-PHA) production in recombinant microorganisms, we generated and investigated different recombinant bacteria containing a stable regulated expression system for phaC1, which encodes one of the mcl-PHA polymerases of Pseudomonas oleovorans. We used the mini-Tn5 system as a tool to constructEscherichia coli 193MC1 and P. oleovoransPOMC1, which had stable antibiotic resistance and PHA production phenotypes when they were cultured in a bioreactor in the absence of antibiotic selection. The molecular weight and the polydispersity index of the polymer varied, depending on the inducer level. E. coli 193MC1 produced considerably shorter polyesters thanP. oleovorans produced; the weight average molecular weight ranged from 67,000 to 70,000, and the polydispersity index was 2.7. Lower amounts of inducer added to the media shifted the molecular weight to a higher value and resulted in a broader molecular mass distribution. In addition, we found that E. coli 193MC1 incorporated exclusively the R configuration of the 3-hydroxyoctanoate monomer into the polymer, which corroborated the enantioselectivity of the PhaC1 polymerase enzyme.

scholarly journals Synthesis of Highcis-1,4-BR with Neodymium for the Manufacture of Tires

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Maria Leonor Méndez-Hernández ◽  
José Luis Rivera-Armenta ◽  
Ulises Páramo-García ◽  
Sergio Corona Galvan ◽  
Ricardo García-Alamilla ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Rheological Properties ◽  
Average Molecular Weight ◽  
Catalyst System ◽  
Polydispersity Index ◽  
Fatigue Properties ◽  
Number Average Molecular Weight ◽  
Weight Average Molecular Weight ◽  
Permanent Set ◽  
Reinforcing Filler

The salt of neodymium has been widely used in industrial polymerization of 1,3-butadiene. We used the ternary catalytic system neodymium versatate/diethylaluminum chloride/triisobutylaluminum (NdV3/DEAC/TIBA) with 0.5 mM NdV3/100 g Bd, NdV3 : DEAC = 1 : 9 mol : mol, and TIBA = 25, 50, 100, and 200 mM. The number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity index (PDI) were analyzed by GPC; the rheological properties were analyzed by DMA. The formulations were prepared with carbon black (IRB6) as reinforcing filler and the mechanical properties were compared to behavior of the different elastomeric compounds. The elastomeric compounds were characterized by their rheological properties, tensile strength, abrasion resistance, tear strength, permanent set, resilience, and fatigue properties. The highcis-1,4 polybutadiene (highcis-1,4-BR) was obtained with a percentage ofcis-1,4 ≥97%. The weight-average molecular weight (Mw) was from 150 × 103to 900 × 103 g/mol and polydispersity index (PDI) was from 3.1 to 5.1. This work is based on evaluation of the effect of the catalyst system on the final properties of the synthesized polybutadiene.

scholarly journals Dispersity in polymer science (IUPAC Recommendations 2009)

2009 ◽  
Vol 81 (2) ◽  
pp. 351-353 ◽  
Author(s):  
Robert F. T. Stepto
Keyword(s):  
Molecular Weight ◽  
Molecular Mass ◽  
Molar Mass ◽  
Polymeric Materials ◽  
Degree Of Polymerization ◽  
Polydispersity Index ◽  
Relative Molecular Mass ◽  
Polymer Science

This recommendation defines just three terms, viz., (1) molar-mass dispersity, relative-molecular-mass dispersity, or molecular-weight dispersity; (2) degree- of-polymerization dispersity; and (3) dispersity. "Dispersity" is a new word, coined to replace the misleading, but widely used term "polydispersity index" for Mw/Mn and Xw/Xn. The document, although brief, also has a broader significance in that it seeks to put the terminology describing dispersions of distributions of properties of polymeric (and non-polymeric) materials on an unambiguous and justifiable footing.

Carboxymethy Chitosan Grafted Ricinoleic Acid Group for Nanopesticide Carriers

2011 ◽  
Vol 236-238 ◽  
pp. 1783-1788 ◽  
Author(s):  
Bo Hua Feng ◽  
Zi Yong Zhang
Keyword(s):  
Molecular Weight ◽  
Surface Charge ◽  
Ricinoleic Acid ◽  
Spherical Shape ◽  
Acid Group ◽  
Polydispersity Index ◽  
Surface Shape ◽  
Botanical Insecticide ◽  
Negative Surface ◽  
Negative Surface Charge

A new chitosan derivate (CMC-g-RA) was prepared by grafting ricinoleic acid anhydride (RA) on carboxymethy chitosan (CMC) molecules. The reaction factors such as molecular weight, mole ratio of anhydride to amino, temperature and solvent were examined. Nanoparticles were obtained by blending botanical insecticide capsaicin (Cap) and CMC-g-RA. Surface shape, particle size, polydispersity index, surface charge, LE and stability of Cap/CMC-g-RA nanoparticles were characterized. The results showed that lower molecular weight was of advantage to higher degree of RA substitution. CMC-g-RA and Cap formed drug delivery nanoparticles with spherical shape and negative surface charge in water. The increased concentration of drug or carrier resulted in higher zeta potential and narrower polydispersity index (PDI) of Cap/CMC-g-RA. The loading efficiency (LE) of nanoparticles was up to 0.86, which provided efficiently protection for Cap, extended drug releasing period and dosage.

scholarly journals Recovery of Polyhydroxyalkanoates From Single and Mixed Microbial Cultures: A Review

2021 ◽  
Vol 9 ◽  
Author(s):  
Giorgia Pagliano ◽  
Paola Galletti ◽  
Chiara Samorì ◽  
Agnese Zaghini ◽  
Cristian Torri
Keyword(s):  
Molecular Weight ◽  
Physical Characteristics ◽  
Polydispersity Index ◽  
Bacterial Strains ◽  
Polymer Molecular Weight ◽  
Microbial Cultures ◽  
Halogenated Solvents ◽  
Mixed Microbial Cultures ◽  
Cellular Lysis ◽  
Recovery Methods

An overview of the main polyhydroxyalkanoates (PHA) recovery methods is here reported, by considering the kind of PHA-producing bacteria (single bacterial strains or mixed microbial cultures) and the chemico-physical characteristics of the extracted polymer (molecular weight and polydispersity index). Several recovery approaches are presented and categorized in two main strategies: PHA recovery with solvents (halogenated solvents, alkanes, alcohols, esters, carbonates and ketones) and PHA recovery by cellular lysis (with oxidants, acid and alkaline compounds, surfactants and enzymes). Comparative evaluations based on the recovery, purity and molecular weight of the recovered polymers as well as on the potential sustainability of the different approaches are here presented.

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