scholarly journals The Molecular Weight At the Air-Water Interface of Some Keratin Derivatives Extracted From Wool

1955 ◽  
Vol 8 (1) ◽  
pp. 122 ◽  
Author(s):  
BS Harrap
Keyword(s):  
Molecular Weight ◽  
Cell Walls ◽  
Average Molecular Weight ◽  
Cortical Cell ◽  
Number Average Molecular Weight ◽  
Molecular Weights ◽  
Reversible Dissociation ◽  
Electrophoretic Patterns ◽  
Air Water Interface ◽  
Electrophoretic Component

Using the monolayer technique, number-average molecular weights have been determined for a series of extracts of wool prepared by successive treatments with alkaline sodium thioglycollate. The molecular weights of these extracts have been discussed in relation to their electrophoretic patterns. The change in the number-average molecular weight in the successive extracts has been correlated with the presence of certain electrophoretic components. The possibility of extraction of lipoidal or other non-protein material from the cortical cell walls is discussed. A reversible dissociation of the major electrophoretic component at high pH was observed.

scholarly journals Particle weights and protein composition of the ribosomal subunits of the extremely thermoacidophilic archaebacterium Caldariella acidophila

1983 ◽  
Vol 209 (2) ◽  
pp. 461-470 ◽  
Author(s):  
P Londei ◽  
A Teichner ◽  
P Cammarano ◽  
M De Rosa ◽  
A Gambacorta
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Buoyant Density ◽  
Protein Composition ◽  
Equilibrium Density ◽  
Number Average Molecular Weight ◽  
Ribosomal Subunits ◽  
Molecular Weights ◽  
Protein Components ◽  
Protein Number

1. The ribosomal subunits of one thermoacidophilic archaebacterium (Caldariella acidophila) and of two reference eubacterial species (Bacillus acidocaldarius, Escherichia coli) were compared with respect to ribosome mass and protein composition by (i) equilibrium-density sedimentation of the particles in CsCl and (ii) gel-electrophoretic estimations of the molecular weights of the protein and the rRNA. 2. By either procedure, it is estimated that synthetically active archaebacterial 30S subunits (52% protein by wt.) are appreciably richer in protein than the corresponding eubacterial particles (31% protein by wt.) 3. The greater protein content of the archaebacterial 30S subunits is accounted for by both a larger number and a greater average molecular weight of the subunit proteins; specifically, C. acidophila 30S subunits yield 28 proteins whose combined mass is 0.6×10(6) Da, compared with 20 proteins totalling 0.35×10(6) Da mass for eubacterial 30S subunits. 4. No differences in protein number are detected among the large subunits, but C. acidophila 50S subunits exhibit a greater number-average molecular weight of their protein components than do eubacterial 50S particles. 5. Particle weights estimated by either buoyant-density data, or molecular weights of rRNA plus protein, agree to within less than 2%. By either procedure C. acidophila 30S subunits 1.15×10(6) Da mass) are estimated to be about 300 000 Da heavier than their eubacterial counterparts (0.87×10(6) Da mass); a smaller difference. 0.15×10(6) Da, exists between the archaebacterial and the eubacterial 50S subunits (respectively 1.8×10(6) and 1.65×10(6) Da). It is concluded that the heavier-than-eubacterial mass of the C. acidophila ribosomes resides principally in their smaller subunits.

EBULLIOMETRY AND THE DETERMINATION OF THE MOLECULAR WEIGHTS OF POLYMERS: PART I. THE SMALL EBULLIOMETER

1959 ◽  
Vol 37 (9) ◽  
pp. 1508-1516 ◽  
Author(s):  
W. R. Blackmore
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Molecular Weights

An ebulliometer that has been in routine use for the determination of the number average molecular weight of polymers is described. The results obtained with two different series of polythenes (which were also measured elsewhere) are given. These results show this ebulliometer to be subject to experimental difficulties which limit it to number average molecular weights of perhaps 20,000 depending on the precision required.

Chemistry and Properties of Imide Oligomers from Phenylethynyl-Containing Diamines

2000 ◽  
Vol 12 (1) ◽  
pp. 213-223 ◽  
Author(s):  
J G Smith ◽  
J W Connell
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Research Effort ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Similar Composition ◽  
Imide Oligomers ◽  
Calculated Number

As an extension of work on pendent phenylethynyl-containing imide oligomers, three new diamines containing pendent phenylethynyl groups were prepared and characterized. These diamines were used to prepare pendent and pendent and terminal phenylethynyl imide oligomers via the amide acid route in N-methyl-2-pyrrolidinone at a calculated number average molecular weight of 5000 g mol−1. The pendent phenylethynyl groups were randomly distributed along the oligomer backbone and provided a means of controlling the distance between reactive sites. The imide oligomers were characterized and thermally cured, and the cured polymers evaluated as thin films and compared with materials of similar composition prepared from 3,5-diamino-4′-phenylethynylbenzophenone. This work was performed as part of a continuing research effort to develop structural resins for potential aeronautical applications.

Probing the molecular weights of sweetgum and pine kraft lignin fractions

TAPPI Journal ◽  
2021 ◽  
Vol 20 (6) ◽  
pp. 381-391
Author(s):  
JULIANA M. JARDIM ◽  
PETER W. HART ◽  
LUCIAN LUCIA ◽  
HASAN JAMEEL
Keyword(s):  
Molecular Weight ◽  
Black Liquor ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Systematic Investigation ◽  
Kraft Pulping ◽  
Molecular Weights ◽  
Lignin Recovery ◽  
Lignin Reactivity ◽  
Kinetics Of

The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physicochemical properties. Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30–150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to deter- mine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weightlignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.

Alternating poly(ester amide)s from glutaric anhydride and α,ω-aminoalcohols: synthesis and thermal properties

e-Polymers ◽  
2003 ◽  
Vol 3 (1) ◽  
Author(s):  
Thomas Fey ◽  
Helmut Keul ◽  
Hartwig Höcker
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Homologous Series ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Melting Points ◽  
Glutaric Anhydride ◽  
H Nmr ◽  
Activating Agent ◽  
Dimethylformamide Solution

Abstract Alternating poly(ester amide)s 6a - e were prepared by polycondensation of α-carboxyl-ω-hydroxyamides 3a - e which were obtained by aminolysis of glutaric anhydride (1) and α,ω-aminoalcohols, H2N-(CH2)x-OH (x = 2 - 6) 2a - e. The polycondensation was performed in dimethylformamide solution using a carbodiimide as activating agent, or in bulk with Bu2Sn(OMe)2, Ti(OBu)4 and Sn(octoate)2 as a catalyst. For the polycondensation in bulk, the influence of catalyst and of temperature on the number-average molecular weight was studied. 1H NMR analyses of the poly(ester amide)s clearly show the alternating microstructure. The poly(ester amide)s from glutaric anhydride and the homologous series of α,ω-aminoalcohols are semicrystalline materials; their melting points show the odd/even effect observed for other poly(ester amide)s.

Isoprene and Rubber. Part 29. High Molecular Hydrorubbers

1932 ◽  
Vol 5 (2) ◽  
pp. 136-140
Author(s):  
H. Staudinger ◽  
W. Feisst
Keyword(s):  
Molecular Weight ◽  
Catalytic Reduction ◽  
Molecular Form ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Decomposition Products ◽  
Molecular Weights ◽  
Rubber Part ◽  
Derivatives Of ◽  
Suitable Process

Abstract The molecular concept in organic chemistry is based upon the fact that the molecules, whose existence is proved by vapor density determinations, enter into chemical reactions as the smallest particles. If now it is assumed that organic molecular colloids like rubber are dissolved in dilute solution in molecular form then it must be proved that in the chemical transposition of macromolecules as well no change in the size of the macromolecules occurs. In the case of hemicolloids, therefore for molecular colloids with an average molecular weight of 1000 to 10,000, this has been proved by the reduction of polyindenes, especially of polysterenes, to hydroproducts with the same average molecular weight, and also by the fact that cyclorubbers do not change their molecular weight upon autoöxidation. The molecular weights of hemi-colloidal hydrocarbons are therefore invariable. This is much more difficult to prove in the case of rubber, although there are many more ways in which unsaturated rubber can be transposed than the stable polysterenes, polyindenes, and poly cyclorubbers. In most of the reactions with rubber, as in its action with nitrosobenzene, oxidizing agents, hydrogen halides, and halogens, an extensive decomposition takes place as a result of the instability of the molecule, which is referred to in another work. Therefore derivatives of rubber are not formed, but derivatives of hemi-colloidal decomposition products. The catalytic reduction of rubber in the cold appears to be the most suitable process of making it react without changing its molecular size in order to prove that in a chemical transposition its molecular weight remains the same.

SIZE, STABILITY, AND HETEROGENEITY OF APURINIC ACID

1956 ◽  
Vol 34 (6) ◽  
pp. 1107-1117 ◽  
Author(s):  
G. C. Wood ◽  
David B. Smith
Keyword(s):  
Molecular Weight ◽  
Nucleic Acid ◽  
Acid Treatment ◽  
Average Molecular Weight ◽  
Weight Average Molecular Weight ◽  
Molecular Weights ◽  
Size Stability ◽  
Mild Acid

Apurinic acid prepared by mild acid treatment of sodium desoxyribonucleate and of fractions of sodium desoxyribonucleate was sufficiently stable to permit estimations of molecular weight and polydispersity. Apurinic acid from unfractionated desoxyribonucleate had a weight-average molecular weight of 25,000 and was very polydisperse. Preparations from fractionated desoxyribonucleate representing about half the original nucleic acid were much less polydisperse and had molecular weights of about 10,000.

Relative Efficacy of Separation of "Free" and "Bound" [3',5'-3H]Pteroylglutamate by Charcoal Coated with Various Materials

1975 ◽  
Vol 21 (13) ◽  
pp. 1927-1931 ◽  
Author(s):  
Alfred Zettner ◽  
Peggy E Duly
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Relative Efficacy ◽  
Molecular Weights

Abstract We studied the effectiveness with which various charcoal preparations separate free [3H]pteroylglutamate from that complexed with milk folate binder. We tested, in various concentrations, uncoated charcoals and charcoals coated with dextrans of various molecular weights, or with albumin, hemoglobin, or polyvinylpyrrolidone with an average molecular weight of 40 000. Although there was some distinction between the "bound" and "free" fractions with all charcoals, those treated with dextrans of average molecular weights of 43 500 or 70 000, or with polyvinylpyrrolidone gave the best separation over a greater range of charcoal concentration. Uncoated charcoal and charcoals coated with albumin, hemoglobin, or dextran T10 (average molecular weight, 10 500) were least effective.

Molecular Weights and Intrinsic Viscosities of Polyisobutylenes

1943 ◽  
Vol 16 (3) ◽  
pp. 493-508
Author(s):  
Paul J. Flory
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Average Molecular Weight ◽  
Chain Structure ◽  
Molecular Weight Range ◽  
Molecular Weights ◽  
Satisfactory Precision ◽  
Heterogeneous Polymers ◽  
Definition Of

Abstract Experimental methods for fractionating polyisobutylene and for determining osmotic pressures have been described. The ratio π/c of osmotic pressure to concentration has been found in the case of cyclohexane solutions of polyisobutylene to vary nonlinearly with concentration, contrary to recent theories advanced by Huggins and the writer. The slope of this relationship appears to be independent of molecular weight. Reliable methods for extrapolating π/c to c=0 have been established, enabling the determination of absolute molecular weights with satisfactory precision up to values of about 1,000,000. Molecular weights of polyisobutylenes calculated from Staudinger's equation are too low; the discrepancy is more than ten-fold at high molecular weights. On the basis of data for carefully fractionated samples covering a two-hundred-fold molecular weight range, the intrinsic viscosity is found to be proportional to the 0.64 power of the molecular weight. This decided deviation from Staudinger's “law”cannot in this instance be attributed to nonlinear chain structure, as Staudinger has sought to do in other cases. This dependence of molecular weight on intrinsic viscosity leads to the definition of a “viscosity average”molecular weight which is obtained when the relationship is applied to heterogeneous polymers. The viscosity average is less than the weight average molecular weight, which would be obtained if Staudinger's equation were applicable, and greater than the number average obtained by osmotic or cryoscopic methods.

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