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.

EBULLIOMETRY AND THE DETERMINATION OF THE MOLECULAR WEIGHTS OF POLYMERS: PART III. CONSIDERATIONS ON THERMISTOR WHEATSTONE BRIDGES

1959 ◽  
Vol 37 (12) ◽  
pp. 1365-1373 ◽  
Author(s):  
W. R. Blackmore
Keyword(s):  
Atmospheric Pressure ◽  
Background Noise ◽  
Wheatstone Bridge ◽  
Thermistor Bridge ◽  
Molecular Weights ◽  
Boiling Points ◽  
Pure Solvent ◽  
Unbalance Voltage

It is shown that a d-c. thermistor Wheatstone bridge may be used in ebulliometry to measure the small temperature differences which are observed between the boiling points of polymer solutions and the pure solvent. A relationship is derived between the thermistor bridge unbalance voltage and the solute molecular weight, which it is desired to measure. It is shown that a bridge composed of suitably matched thermistors may be made independent of the gross changes in boiling point of both solution and solvent produced by changes in atmospheric pressure. The possibility of the current flowing through the thermistors disturbing the measurements is discussed and in situ measurements of thermistor dissipation and time constants are given. The sensitivity attainable with various thermistor bridges and modern amplifiers at full gain is calculated and shown to be much greater than may be employed with the usual type of ebulliometer. The reason for this is the relatively large background noise (random temperature fluctuations) produced in the ebulliometer by the boiling process itself.

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.

Preparation of graft copolymers by the reaction of polymeric acyl chlorides with monohydroxy-terminated polymers: An introductory study

1988 ◽  
Vol 53 (8) ◽  
pp. 1735-1744 ◽  
Author(s):  
Jitka Horská ◽  
Jaroslav Stejskal ◽  
Pavel Kratochvíl ◽  
Aubrey D. Jenkins ◽  
Eugenia Tsartolia ◽  
...  
Keyword(s):  
Light Scattering ◽  
Chemical Composition ◽  
Statistical Model ◽  
Graft Copolymers ◽  
Coupling Reaction ◽  
Molecular Characteristics ◽  
Gel Formation ◽  
Acyl Chlorides ◽  
Molecular Weights

An attempt was made to prepare well-defined graft copolymers by the coupling reaction between acyl chloride groups located along the backbone chain and monohydroxy-terminated grafts prepared separately. The molecular weights and the parameters of heterogeneity in chemical composition of the products were determined by light scattering and osmometry. The determination of molecular characteristics revealed that the degree of grafting was low. The results therefore could not be confronted with a statistical model at this stage. The problems encountered in the synthesis, e.g., gel formation, and the data relating to the soluble products are discussed.

Determination of molecular weights by the archibald method using absorption optics

1969 ◽  
Vol 30 (2) ◽  
pp. 212-216 ◽  
Author(s):  
K. de Groot ◽  
J.C.M. Reijnen ◽  
H.J. Hoenders
Keyword(s):  
Molecular Weights
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