Chemical properties of a high molecular weight spleen extract with permeability activity

1974 ◽  
Vol 4 (2) ◽  
pp. 74-83 ◽  
Author(s):  
H. ff. S. Davies ◽  
Rose E. Hartley ◽  
H. O. Schild
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Chemical Properties

scholarly journals Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging

2019 ◽  
Vol 19 (1) ◽  
pp. 139-163 ◽  
Author(s):  
Chunlin Li ◽  
Quanfu He ◽  
Julian Schade ◽  
Johannes Passig ◽  
Ralf Zimmermann ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Light Absorption ◽  
Chemical Properties ◽  
Oh Radical ◽  
Dynamic Changes ◽  
Photochemical Process ◽  
Tar Balls ◽  
Photochemical Aging ◽  
And Chemical Properties

Abstract. Following wood pyrolysis, tar ball aerosols were laboratory generated from wood tar separated into polar and nonpolar phases. Chemical information of fresh tar balls was obtained from a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and single-particle laser desorption/resonance enhanced multiphoton ionization mass spectrometry (SP-LD-REMPI-MS). Their continuous refractive index (RI) between 365 and 425 nm was retrieved using a broadband cavity enhanced spectroscopy (BBCES). Dynamic changes in the optical and chemical properties for the nonpolar tar ball aerosols in NOx-dependent photochemical process were investigated in an oxidation flow reactor (OFR). Distinct differences in the chemical composition of the fresh polar and nonpolar tar aerosols were identified. Nonpolar tar aerosols contain predominantly high-molecular weight unsubstituted and alkyl-substituted polycylic aromatic hydrocarbons (PAHs), while polar tar aerosols consist of a high number of oxidized aromatic substances (e.g., methoxy-phenols, benzenediol) with higher O : C ratios and carbon oxidation states. Fresh tar balls have light absorption characteristics similar to atmospheric brown carbon (BrC) aerosol with higher absorption efficiency towards the UV wavelengths. The average retrieved RI is 1.661+0.020i and 1.635+0.003i for the nonpolar and polar tar aerosols, respectively, with an absorption Ångström exponent (AAE) between 5.7 and 7.8 in the detected wavelength range. The RI fits a volume mixing rule for internally mixed nonpolar/polar tar balls. The RI of the tar ball aerosols decreased with increasing wavelength under photochemical oxidation. Photolysis by UV light (254 nm), without strong oxidants in the system, slightly decreased the RI and increased the oxidation state of the tar balls. Oxidation under varying OH exposure levels and in the absence of NOx diminished the absorption (bleaching) and increased the O : C ratio of the tar balls. The photobleaching via OH radical initiated oxidation is mainly attributed to decomposition of chromophoric aromatics, nitrogen-containing organics, and high-molecular weight components in the aged particles. Photolysis of nitrous oxide (N2O) was used to simulate NOx-dependent photochemical aging of tar balls in the OFR. Under high-NOx conditions with similar OH exposure, photochemical aging led to the formation of organic nitrates, and increased both oxidation degree and light absorption for the aged tar ball aerosols. These observations suggest that secondary organic nitrate formation counteracts the bleaching by OH radical photooxidation to eventually regain some absorption of the aged tar ball aerosols. The atmospheric implication and climate effects from tar balls upon various oxidation processes are briefly discussed.

Stereocomplex electrospun fibers from high molecular weight of poly(L-lactic acid) and poly(D-lactic acid)

2020 ◽  
Vol 40 (2) ◽  
pp. 136-142 ◽  
Author(s):  
Homa Maleki ◽  
Hossein Barani
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Thermal Properties ◽  
High Molecular Weight ◽  
Chemical Properties ◽  
Electrospun Fibers ◽  
Scanning Calorimetry ◽  
Force Microscopy ◽  
Atomic Force ◽  
Electrospinning Method

AbstractThe stereocomplex formation is a promising method to improve the properties of poly(lactide) (PLA)-based products due to the strong interaction of the side-by-side arrangement of the molecular chains. Recently, electrospinning method has been applied to prepare PLA stereocomplex, which is more convenient. The objective of the current study is to make stereocomplexed PLA nanofibers using electrospinning method and compare their properties and structures with pure poly(l-lactide) (PLLA) fibers. The stereocomplexed fibers were electrospun from a blend solution of high molecular weight PLLA and poly(d-lactide) (1:1 ratio). The morphology of the obtained electrospun fibers was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Differential scanning calorimetry was applied to study their thermal properties and crystallinity. Fourier transform infrared spectroscopy (FTIR) test was conducted on the samples to characterize their chemical properties. The SEM and AFM images indicated that smooth uniform fibers with a cylindrical structure were produced. Besides, the FTIR results and thermal properties confirmed that only stereocomplex crystallites formed in the resulting fibers via the electrospinning method.

Isoprene and Rubber. XVII. The Fractionation of Balata

1930 ◽  
Vol 3 (3) ◽  
pp. 511-515
Author(s):  
H. Staudinger ◽  
H. F. Bondy
Keyword(s):  
Molecular Weight ◽  
Natural Products ◽  
High Molecular Weight ◽  
Homologous Series ◽  
Chemical Properties ◽  
Uniform Size ◽  
Gutta Percha ◽  
Synthetic Materials ◽  
The Individual ◽  
Physical And Chemical

Abstract On the basis of earlier experiments with synthetic materials, compounds of high molecular weight are not composed of a single substance, but consist of a mixture of homologous polymers. The individual members of a polymeric homologous series differ very little in physical and chemical properties, and therefore a mixture of polymeric homologous products such as is obtained in the polymerization of the monomer cannot as a rule be decomposed into simple compounds by means of solvents, but merely into mixtures of products of low and high molecular weight. Such separations have been carried out, for example, in the case of polyvinylace-tates, polystyrols, polyindenes, polyanetholes, and polyethyleneoxides. On the basis of these experiments it was assumed that natural products of high molecular weight likewise consist of a mixture of polymeric homologs. Thus purified rubber, for example, according to our views is not such a completely homogeneous hydrocarbon that all the molecules have the same length, but consists of a mixture of perhaps 100 or more polymeric homologs. Pummerer's decomposition of rubber into sol,- and gel-rubber, according to our experiments, is due to the fact that rubber consists of easily soluble polyprenes and difficultly soluble polyprenes, all belonging to the same polymeric homologous series. Of course there is the possibility that, in forming compounds of high molecular weight, nature produced primary molecules of uniform size, and that the mixture of polymeric homologs was formed only later through decomposition. In that case the natural products would differ in constitution from the synthetic material. They would not be polymerically uniform but completely uniform compounds in the sense of classical organic chemistry. The fact that in life processes methods are possible which we cannot realize in the laboratory is well known. Such a finding would not, of course, contradict our former view that natural products, such as rubber and balata, are of high molecular weight in the sense of classical structural chemistry. Our former work has indicated a similar structure for rubber and gutta-percha. Here it is simply a question whether or not the macromolecules of these natural products have a uniform length. In order to reach a decision, we first of all investigated balata, since it is prepared pure more easily than rubber. It was made from balata latex which was supplied to us through the courtesy of the management of the Norddeutsche Seekabelwerke, Nordenham." The balata thus obtained is a flocculent, cellulose-like mass, which looks like gutta-percha and crystallizes like it.

scholarly journals Chemical properties of a high molecular weight spleen extract with permeability activity

1974 ◽  
Vol 4 (3) ◽  
pp. 209-209
Author(s):  
H. ff. S. Davies ◽  
Rose E. Hartley ◽  
H. O. Schild
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Chemical Properties

Isolation and physico-chemical properties of a high molecular weight subfragment-2 of myosin

1978 ◽  
Vol 126 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Kazuo Sutoh ◽  
Keiko Sutoh ◽  
Trudy Karr ◽  
William F. Harrington
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Chemical Properties ◽  
Physico Chemical

scholarly journals Dynamic changes of optical and chemical properties of tar ball aerosols by atmospheric photochemical aging

2018 ◽  
Author(s):  
Chunlin Li ◽  
Quanfu He ◽  
Julian Schade ◽  
Johannes Passig ◽  
Ralf Zimmermann ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Refractive Index ◽  
High Molecular Weight ◽  
Oxidation State ◽  
Chemical Properties ◽  
Dynamic Changes ◽  
Photochemical Process ◽  
Tar Balls ◽  
Photochemical Aging ◽  
And Chemical Properties

Abstract. Following wood pyrolysis, tar ball aerosols were generated from wood tar separated into polar and nonpolar phases. Chemical information of fresh tar balls was obtained from the high-resolution time-of-flight aerosol mass spectrometer (HiRes-ToF-AMS) and laser desorption/resonance enhanced multiphoton ionization mass spectrometry (LD-REMPI-MS), and their refractive index between 365 and 425 nm were retrieved using a broadband cavity enhanced spectroscopy. Dynamic changes of the optical and chemical properties for the nonpolar tar ball aerosols in NOx-dependent photochemical process were investigated in an oxidation flow reactor (OFR). Distinct differences in the chemical composition of the polar and nonpolar tar aerosols were identified. Nonpolar tar aerosols contain predominantly high-molecular weight unsubstituted and alkyl-substituted polycylic aromatic hydrocarbons (PAHs), while polar tar aerosols consist of a high number of oxidized aromatic substances (e.g., methoxy-phenols, benzenediol) with higher O : C ratio and carbon oxidation state. Fresh tar aerosols have light absorption characteristics similar to atmospheric BrC with higher absorption efficiency towards the UV wavelengths. The average retrieved refractive index (RI) are 1.661 + 0.020i and 1.635 + 0.003i for the nonpolar and polar tar aerosols, respectively, with absorption Ångström exponent (AAE) between 5.7 and 7.8 in the wavelength region 365–425 nm. The RI fits a volume mixing rule for internally mixed nonpolar/polar tar aerosols. The RI of the tar aerosols decreased with increasing wavelength under photochemical oxidation. Photolysis by UV light (254 nm), without strong oxidants in the system, slightly decreased the RI and increased the oxidation state of the tar balls. Oxidation under varying OH exposure levels and in the absence of NOx diminished the absorption (bleaching), and increased the O : C ratio. The photobleaching of tar ball aerosols via photochemically induced OH-oxidation is mainly attributed to decomposition of chromophoric aromatics, nitrogen-containing organics, and high-molecular weight components. Photolysis of nitrous oxide (N2O) was used to simulate NOx-dependent photochemical aging of tar balls in the OFR. Under high NOx conditions, photochemical aging lead to the formation of organic-nitrates, increased oxidation degree and increased absorption for the tar ball aerosols. These observations suggest that secondary organic nitrate formation compensates the bleaching by photolysis and OH radical photooxidation to eventually regain some absorption of aged tar balls aerosols. The atmospheric implication and climatic effects from tar balls upon various oxidation processes are briefly discussed.

scholarly journals Biogels in Soils: Plant Mucilage as a Biofilm Matrix That Shapes the Rhizosphere Microbial Habitat

2022 ◽  
Vol 12 ◽  
Author(s):  
Meisam Nazari ◽  
Samuel Bickel ◽  
Pascal Benard ◽  
Kyle Mason-Jones ◽  
Andrea Carminati ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Extracellular Polymeric Substances ◽  
Chemical Properties ◽  
Nutrient Mobilization ◽  
Nutrient Sources ◽  
Moist Environment ◽  
Microbial Habitat ◽  
Almost All ◽  
Biofilm Matrix

Mucilage is a gelatinous high-molecular-weight substance produced by almost all plants, serving numerous functions for plant and soil. To date, research has mainly focused on hydraulic and physical functions of mucilage in the rhizosphere. Studies on the relevance of mucilage as a microbial habitat are scarce. Extracellular polymeric substances (EPS) are similarly gelatinous high-molecular-weight substances produced by microorganisms. EPS support the establishment of microbial assemblages in soils, mainly through providing a moist environment, a protective barrier, and serving as carbon and nutrient sources. We propose that mucilage shares physical and chemical properties with EPS, functioning similarly as a biofilm matrix covering a large extent of the rhizosphere. Our analyses found no evidence of consistent differences in viscosity and surface tension between EPS and mucilage, these being important physical properties. With regard to chemical composition, polysaccharide, protein, neutral monosaccharide, and uronic acid composition also showed no consistent differences between these biogels. Our analyses and literature review suggest that all major functions known for EPS and required for biofilm formation are also provided by mucilage, offering a protected habitat optimized for nutrient mobilization. Mucilage enables high rhizo-microbial abundance and activity by functioning as carbon and nutrient source. We suggest that the role of mucilage as a biofilm matrix has been underestimated, and should be considered in conceptual models of the rhizosphere.

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