841. High-polymer solutions. Part II. The determination of number-average molecular weights from measurements of osmotic pressure

1952 ◽  
pp. 4390 ◽  
Author(s):  
Esm� Ducker ◽  
E. C. Fieller ◽  
H. T. Hookway ◽  
R. Townsend
Keyword(s):  
Osmotic Pressure ◽  
Polymer Solutions ◽  
High Polymer ◽  
Molecular Weights

EBULLIOMETRY AND THE DETERMINATION OF THE MOLECULAR WEIGHTS OF POLYMERS: PART II. BACKGROUND NOISE IN THE SMALL EBULLIOMETER

1959 ◽  
Vol 37 (9) ◽  
pp. 1517-1526 ◽  
Author(s):  
W. R. Blackmore
Keyword(s):  
Boiling Point ◽  
Background Noise ◽  
Polymer Solutions ◽  
Liquid Surface ◽  
Pressure Fluctuations ◽  
High Polymer ◽  
Molecular Weights ◽  
Usual Form ◽  
Lower Background

It is shown that the usual form of ebulliometer is subject to at least three sources of noise. Those discussed here are (1) pressure fluctuations over the boiling liquid surface, (2) the Cottrell pump, and (3) the foam which appears on many polymer solutions when maintained at the boiling point. Background noise in this, and other ebulliometers commonly employed, may be large compared to the size of the signals expected for dilute high polymer solutions. Consequently further progress in ebulliometry is dependent on the development of a new ebulliometer with a much lower background noise.

Transmission Electron Microscopy of Protein Macromolecules

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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