scholarly journals The molecular weight of, and evidence for two types of subunits in, the molybdenum-iron protein of Azotobacter vinelandii nitrogenase

1977 ◽  
Vol 163 (3) ◽  
pp. 427-432 ◽  
Author(s):  
R H Swisher ◽  
M L Landt ◽  
F J Reithel
Keyword(s):  
Molecular Weight ◽  
Azotobacter Vinelandii ◽  
Average Molecular Weight ◽  
Amino Acid Content ◽  
Sedimentation Equilibrium ◽  
Weight Average Molecular Weight ◽  
Molybdenum Iron Protein ◽  
Iron Protein ◽  
Molecular Weights ◽  
Fe Protein

The weight-average molecular weight of the Mo-Fe protein isolated from Azotobacter vinelandii has been determined by sedimentation-equilibrium techniques. In buffer, the value is 245000+/-5000; in 8M-urea, the value is 61000+/-1000. The protein was separated into two components by chromatography on CM-cellulose in 7M-urea, pH 4.5. These components have similar molecular weights but were shown to differ in charge, amino acid content and arginine-containing peptides. It is proposed that the tetramer has the subunit composition (nalpha2nbeta2).

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.

SIZE, STABILITY, AND HETEROGENEITY OF APURINIC ACID

1956 ◽  
Vol 34 (1) ◽  
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.

scholarly journals Use of Rubber Process Analyzer for Characterizing the Molecular Weight Parameters of Natural Rubber

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Tianming Gao ◽  
Ruihong Xie ◽  
Linghong Zhang ◽  
Hongxing Gui ◽  
Maofang Huang
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Milling Time ◽  
Laser Light ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Sweep Frequency ◽  
Weight Average Molecular Weight ◽  
Molecular Weights ◽  
Strain Sweep

The aim of this work is to introduce a simple and rapid method for characterizing the molecular weight parameters and other molecular structure parameters of natural rubber (NR) using a rubber process analyzer (RPA). In this work, NR of different molecular weights was prepared by milling. Molecular weight parameters were measured by gel permeation chromatography coupled with laser light scattering (GPC-LLS) for comparison with RPA results. It was verified that increasing of milling time leads to a decrease of the number-average molecular weight (M-n), weight-average molecular weight (M-w), and molecular weight distribution (MWD). The dynamic and rheological properties were evaluated on RPA by tests of strain sweep, frequency sweep, and stress relaxation. These results were used to characterize the average molecular weight, MWD, and viscosity of NR and were found to agree with those from GPC-LLS. This convenient and rapid technology for characterizing NR molecular weight parameters would be especially useful in the elastomer industry.

scholarly journals Molecular weight of Escherichia coli β-galactosidase in concentrated solutions of guanidine hydrochloride

1970 ◽  
Vol 120 (2) ◽  
pp. 255-261 ◽  
Author(s):  
Robert P. Erickson
Keyword(s):  
Escherichia Coli ◽  
Molecular Weight ◽  
Guanidine Hydrochloride ◽  
Average Molecular Weight ◽  
Sedimentation Velocity ◽  
Sedimentation Equilibrium ◽  
Weight Average Molecular Weight ◽  
Random Coils ◽  
Equilibrium Sedimentation ◽  
Apparent Weight

The molecular weight of Escherichia coli β-galactosidase was determined in 6m- and 8m-guanidine hydrochloride by meniscus-depletion sedimentation equilibrium, sedimentation velocity and viscosity. Sedimentation equilibrium revealed heterogeneity with the smallest component having a molecular weight of about 50000. At lower speeds, the apparent weight-average molecular weight is about 80000. By use of a calculation based on an empirical correlation for proteins that are random coils in 6m-guanidine hydrochloride, sedimentation velocity gave a molecular weight of 91000, and the intrinsic viscosity indicated a viscosity-average molecular weight of 84000. Heating in 6m-guanidine hydrochloride lowered the viscosity of β-galactosidase in a variable manner.

INFLUENCE OF METHANOL ON VISCOSITY AND LIGHT SCATTERING PROPERTIES OF DEXTRAN SOLUTIONS

1956 ◽  
Vol 34 (4) ◽  
pp. 445-450 ◽  
Author(s):  
W. Donald Graham ◽  
Odette Patry ◽  
E. Helen Jackman
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Intrinsic Viscosity ◽  
Marked Effect ◽  
Average Molecular Weight ◽  
Alcohol Concentration ◽  
Methanol Concentration ◽  
Weight Average Molecular Weight ◽  
Molecular Weights ◽  
Apparent Weight

Failure to consider the presence of up to 16% by volume of methanol in solutions of dextran fractions had a very marked effect on apparent intrinsic viscosity determinations (the term apparent signifies that measurements were made assuming that the solvent was water only). Unless methanol were removed or otherwise taken into account, high erroneous results were obtained. Apparent weight average molecular weights determined by light scattering were not significantly affected at these alcohol concentrations. The relations found over the range 0 to 16% methanol for dextran samples with weight average molecular weights of 265,000, 155,000, and 72,000 held for the latter sample up to 44% methanol. In the higher range of alcohol concentration the apparent weight average molecular weight was depressed. The true intrinsic viscosity of dextran solutions decreased as methanol concentration was increased.

Metathesis Polymerization of Phenylacetylene by Tungsten Aryloxo Complexes

1995 ◽  
Vol 60 (3) ◽  
pp. 489-497 ◽  
Author(s):  
Hynek Balcar ◽  
Jan Sedláček ◽  
Marta Pacovská ◽  
Vratislav Blechta
Keyword(s):  
Molecular Weight ◽  
Catalytic Activity ◽  
Induction Period ◽  
Average Molecular Weight ◽  
Molar Fraction ◽  
Molar Ratio ◽  
Weight Average Molecular Weight ◽  
Polymer Yield ◽  
Positive Effect ◽  
Ligand Addition

Catalytic activity of the tungsten aryloxo complexes WCl5(OAr) and WOCl3(OAr), where Ar = 4-t-C4H9C6H4, 2,6-(t-C4H9)2C6H3, 2,6-Cl2C6H3, 2,4,6-Cl3C6H2, and 2,4,6-Br3C6H2 in polymerization of phenylacetylene (20 °C, monomer to catalyst molar ratio = 1 000) was studied. The activity of WCl5(OAr) as unicomponent catalysts increases with increasing electron withdrawing character of the -OAr ligand. Addition of two equivalents of organotin cocatalysts (Me4Sn, Bu4Sn, Ph4Sn, Bu3SnH) to WCl5(O-C6H2Cl3-2,4 ,6) has only slight positive effect (slightly higher polymer yield and/or molecular weight of poly(phenylacetylene)s was achieved). However, in the case of WOCl3(O-C6H3Cl2-2, 6) catalyst, it enhances the activity considerably by eliminating the induction period. Poly(phenylacetylene)s prepared with the catalysts studied have weight-average molecular weight ranging from 100 000 to 200 000. They are trans-prevailing and have relatively low molar fraction of monomer units comprised in cyclohexadiene sequences (about 6%).

ULTRACENTRIFUGE AND DIFFUSION STUDIES ON GLUTEN

1942 ◽  
Vol 20c (3) ◽  
pp. 130-159 ◽  
Author(s):  
A. G. McCalla ◽  
Nils Gralén
Keyword(s):  
Sodium Salicylate ◽  
Minimum Weight ◽  
Average Molecular Weight ◽  
Sedimentation Equilibrium ◽  
Velocity Sedimentation ◽  
Molecular Characteristics ◽  
Weight Average Molecular Weight ◽  
Diffusion Constants ◽  
Diffusion Studies ◽  
And Diffusion

The molecular characteristics of gluten in sodium salicylate solutions were studied by means of sedimentation velocity, sedimentation equilibrium, and diffusion measurements. The proportion of total gluten protein molecularly dispersed increased with increase in concentration of sodium salicylate up to 12%, but the dispersed portions had essentially the same sedimentation constant (2.5 ± 0.15) regardless of the concentration of the dispersing medium.The most soluble 25 per cent of the gluten was all molecularly dispersed, but was definitely inhomogeneous. The weight-average molecular weight of this fraction was 44,000, but there is reason to believe the minimum weight may be about 35,000. None of the other fractions was entirely molecularly dispersed, the proportion decreasing with decreasing solubility of the fractions. Aggregates of many sizes existed in all of these fractions, but only the most insoluble contained aggregates large enough to cause opacity. Sedimentation constants of the molecularly dispersed portions increased slightly with decreasing solubility, while diffusion constants decreased markedly. None of the fractions yielded normal curves (diffusion diagrams) but the more soluble the fraction, the more nearly normal the curve. The inhomogeneity responsible for the varying rates of diffusion was due partly to differences in proportion and properties of the molecularly dispersed gluten and partly to aggregates.All properties showed progressive changes both within and between the arbitrarily produced fractions. These results, therefore, support the hypothesis that gluten is a protein system showing progressive and regular changes in properties with change in solubility.

scholarly journals The molybdenum–iron protein of Klebsiella pneumoniae nitrogenase. Evidence for non-identical subunits from peptide ‘mapping’

1976 ◽  
Vol 155 (2) ◽  
pp. 383-389 ◽  
Author(s):  
C Kennedy ◽  
R R. Eady ◽  
E Kondorosi ◽  
D K Rekosh
Keyword(s):  
Amino Acid ◽  
Klebsiella Pneumoniae ◽  
Sodium Dodecyl Sulphate ◽  
Azotobacter Vinelandii ◽  
Peptide Mapping ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Amino Acid Content ◽  
Rhizobium Japonicum ◽  
Fe Protein

The molybdenum- and iron-containing protein components of nitrogenase purified from Klebsiella pneumoniae, Azotobacter vinelandii, Azotobacter chroococcum and Rhizobium japonicum bacteroids all gave either one or two protein-staining bands after sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, depending on the commercial brand of sodium dodecyl sulphate used. The single band obtained with K. pneumoniae Mo-Fe protein when some commercial brands of sodium dodecyl sulphate were used in the preparation of the electrode buffer was resolved into two bands by the addition of 0.01% (v/v) dodecanol to the buffer. Protein extracted from the two bands obtained after electrophoresis of K. pneumoniae Mo-Fe protein gave unique and distinct peptide ‘maps’ after tryptic digestion. Undissociated Mo-Fe protein contained both sets of tryptic peptides. These data are consistent with Mo-Fe protein from K. pneumoniae being composed of non-identical subunits. Amino acid analyses of the subunit proteins revealed some clear differences in amino acid content, but the two subunits showed close compositional relatedness, with a different index [Metzer, H., Shapiro, M.B., Mosiman, J.E. & Vinton, J.G. (1968) Nature (London) 219, 1166-1168] of 4.7.

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