Use of Combined Schlieren and Interference Optics for Determination of Molecular Weights from Sedimentation Equilibrium Data.

SUMMARYMultiple regression analysis was applied to sedimentation equilibrium data for determination of the molecular weight distribution (MWD) of model systems consisting of up to 3 components. Negative weight fractions which were frequently encountered during multiple regression analysis were forced to zero by sequentially eliminating from the regression matrix the corresponding molecular weights in order of the magnitude of negative t-values. The simplex optimization of Morgan & Deming (1974), modified by incorporating a prohibit–range– trespassing routine, was used to search for the best fit values for weight average molecular weights and relative concentrations of the components. This method almost quantitatively reproduced the molecular weights and concentrations of the original model systems. This quantitative information supplemented the multiple regression matrix to improve the resolution of MWD.A direct comparison using model systems revealed that the multiple regression method in conjunction with the simplex optimization routine was more quantitative than the linear programming method of Scholte (1969). When applied to mixtures of standard proteins (ribonuclease A; ovalbumin; γ-globulin and ovalbumin; γ-globulin; apoferritin), the simplex optimization routine yielded values for average molecular weights and relative concentrations of the component proteins which were in good agreement with the known values in the original mixtures.The MWD of αs1-k-casein mixtures at an ionic strength of 0.1 suggested that k-casein was readily dissociated to the monomer (or the dimer) and interacted with the monomer (or the dimer) of αs1-casein forming a complex of approximately 400000.

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The scattering of light in protein solutions. I—Gelatin solutions and gels

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1930.0170 ◽

1930 ◽

Vol 129 (811) ◽

pp. 490-508 ◽

Cited By ~ 11

Keyword(s):

Analytical Data ◽

Sedimentation Velocity ◽

Sedimentation Equilibrium ◽

Protein Solutions ◽

Scattering Of Light ◽

Molecular Weights ◽

Protein Molecules ◽

Long Time ◽

And Diffusion

In a previous paper, the investigation of the scattering of light in agar sols and gels was described and a view regarding the changes taking place in the system during gelation was developed. In a series of paper, of which this is the first, the author proposes to publish investigations of the scattering of light in protein solutions. The various physical properties of the different proteins have been studied for a long time past. Several workers have tried to evaluate the molecular weights of the proteins from the osmotic pressure of their solutions and also from analytical data. Recently a very precise and definite method for the determination of the molecular weights of the proteins, based upon the sedimentation of these heavy molecules in the ultra-centrifuge, has been successfully developed by Svedberg. The molecular weight can be determined in two ways:—(I) by the measurement of the sedimentation equilibrium reached in the cell as a result of the centrifugal and diffusion forces; (II) by measuring the sedimentation velocity of the protein molecules in high centrifugal fields.

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Determination of Membrane Protein Molecular Weights and Association Equilibrium Constants Using Sedimentation Equilibrium and Sedimentation Velocity

Biophysical Tools for Biologists, Volume One: In Vitro Techniques - Methods in Cell Biology ◽

10.1016/s0091-679x(07)84007-6 ◽

2008 ◽

pp. 181-211 ◽

Cited By ~ 17

Author(s):

Nancy K. Burgess ◽

Ann Marie Stanley ◽

Karen G. Fleming

Keyword(s):

Membrane Protein ◽

Equilibrium Constants ◽

Sedimentation Velocity ◽

Sedimentation Equilibrium ◽

Molecular Weights ◽

Association Equilibrium

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Transmission Electron Microscopy of Protein Macromolecules

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066176 ◽

1971 ◽

Vol 29 ◽

pp. 424-425

Author(s):

Henry S. Slayter

Keyword(s):

Biological Systems ◽

Metal Vapor ◽

Resolving Power ◽

Electron Microscopic ◽

Chemical Methods ◽

Molecular Weights ◽

The Past ◽

Physical Chemical ◽

Transmission Electron

Electron microscopic methods have been applied increasingly during the past fifteen years, to problems in structural molecular biology. Used in conjunction with physical chemical methods and/or Fourier methods of analysis, they constitute powerful tools for determining sizes, shapes and modes of aggregation of biopolymers with molecular weights greater than 50, 000. However, the application of the e.m. to the determination of very fine structure approaching the limit of instrumental resolving power in biological systems has not been productive, due to various difficulties such as the destructive effects of dehydration, damage to the specimen by the electron beam, and lack of adequate and specific contrast. One of the most satisfactory methods for contrasting individual macromolecules involves the deposition of heavy metal vapor upon the specimen. We have investigated this process, and present here what we believe to be the more important considerations for optimizing it. Results of the application of these methods to several biological systems including muscle proteins, fibrinogen, ribosomes and chromatin will be discussed.

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