An Isothermal Distillation Method for Determining Molecular Weights

1954 ◽  
Vol 26 (12) ◽  
pp. 1963-1964 ◽  
Author(s):  
C. E. Childs
Keyword(s):  
Distillation Method ◽  
Molecular Weights ◽  
Isothermal Distillation

CUPRIETHYLENEDIAMINE AS A REAGENT FOR HEMICELLULOSE SEPARATION FROM WHEAT STRAW HOLOCELLULOSE

1951 ◽  
Vol 29 (11) ◽  
pp. 974-985
Author(s):  
V. D. Harwood
Keyword(s):  
Molecular Weight ◽  
Vapor Pressure ◽  
Petroleum Ether ◽  
Wheat Straw ◽  
Periodate Oxidation ◽  
Chloroform Solution ◽  
Chemical Compositions ◽  
Distillation Method ◽  
Molecular Weights ◽  
Isothermal Distillation

Wheat straw and wheat straw holocellulose were dispersed in aqueous cupriethylenediamine solutions and fractionated by graded precipitation with acid and alcohol. From the holocellulose a 25.4% recovery of a hemicellulose containing negligible quantities of hexoses was achieved. The corresponding product from wheat straw was contaminated with both lignin and cellulose but a comparison of the chemical compositions of the two hemicelluloses showed that the acid chlorite used for delignification had caused very little hydrolytic action. The acetate of the hemicellulose from holocellulose was fractionated from chloroform solution by the addition of petroleum ether into a series of fractions and subfractions. Analysis of representative fractions from this series led to the conclusion that the hexoses present were not chemically combined with pentosan. Molecular weights were determined by periodate oxidation, the Signer isothermal distillation method, and from the lowering of the vapor pressure of their chloroform solutions and showed that the hemicellulose molecules were relatively small (mol. wt. < 10,000). The decreasing ratio of xylose to arabinose in the fractions of lower molecular weight indicated increasing chain branching.

scholarly journals The mechanism of isothermal distillation in the porous-disk osmometer

1948 ◽  
Vol 195 (1040) ◽  
pp. 97-115 ◽  
Keyword(s):  
Thermal Conduction ◽  
Theoretical Study ◽  
Quantitative Relationship ◽  
Porous Disk ◽  
Molecular Weights ◽  
Experimental Apparatus ◽  
Theoretical Investigations ◽  
Isothermal Distillation ◽  
Thermostat Temperature ◽  
Made In

This paper describes the theoretical investigations which have been made in an effort to clarify several well-established but unexplained observations by previous workers who have carried out experiments by the unusual osmotic-pressure technique known as isothermal distillation. The treatment is essentially thermodynamic, and leads to the derivation of equations which agree with the accumulated experimental evidence while showing how substantial improvements in performance can be achieved by designing the apparatus in accordance with the guidance given by the theoretical study. One of the derived equations stresses the importance of good thermal conduction between the solvent and solution inside the stillhead, while another gives a quantitative relationship between thermostat temperature fluctuations and osmoticpressure errors. A description is then given of the essential features of the experimental apparatus which has been built for the application of these theoretical advances to the measurement of the molecular weights of high polymers.

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.

Characterization of microtubules by dark-field STEM and replication

1991 ◽  
Vol 49 ◽  
pp. 152-153
Author(s):  
S.B. Andrews ◽  
R.D. Leapman ◽  
P.E. Gallant ◽  
T.S. Reese
Keyword(s):  
Protein Interactions ◽  
Low Dose ◽  
Unit Length ◽  
Dark Field ◽  
Carbon Films ◽  
Microtubule Associated Proteins ◽  
Molecular Weights ◽  
Freeze Dried ◽  
Protein Motors ◽  
Associated Proteins

As part of a study on protein interactions involved in microtubule (MT)-based transport, we used the VG HB501 field-emission STEM to obtain low-dose dark-field mass maps of isolated, taxol-stabilized MTs and correlated these micrographs with detailed stereo images from replicas of the same MTs. This approach promises to be useful for determining how protein motors interact with MTs. MTs prepared from bovine and squid brain tubulin were purified and free from microtubule-associated proteins (MAPs). These MTs (0.1-1 mg/ml tubulin) were adsorbed to 3-nm evaporated carbon films supported over Formvar nets on 600-m copper grids. Following adsorption, the grids were washed twice in buffer and then in either distilled water or in isotonic or hypotonic ammonium acetate, blotted, and plunge-frozen in ethane/propane cryogen (ca. -185 C). After cryotransfer into the STEM, specimens were freeze-dried and recooled to ca.-160 C for low-dose (<3000 e/nm2) dark-field mapping. The molecular weights per unit length of MT were determined relative to tobacco mosaic virus standards from elastic scattering intensities. Parallel grids were freeze-dried and rotary shadowed with Pt/C at 14°.

Electron Microscope Study of RNA's of Paramyxoviruses

1972 ◽  
Vol 30 ◽  
pp. 196-197
Author(s):  
Ruchama Baum ◽  
J.T. Seto
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Electron Microscope Study ◽  
Sendai Virus ◽  
Sodium Dodecyl ◽  
Rna Molecules ◽  
Virus Particles ◽  
Molecular Weights ◽  
Length Measurements

The ribonucleic acid (RNA) of paramyxoviruses has been characterized by biochemical and physiochemical methods. However, paramyxovirus RNA molecules have not been studied by electron microscopy. The molecular weights of these single-stranded viral RNA molecules are not known as yet. Since electron microscopy has been found to be useful for the characterization of single-stranded RNA, this investigation was initiated to examine the morphology and length measurements of paramyxovirus RNA's.Sendai virus Z strain and Newcastle disease virus (NDV), Milano strain, were used. For these studies it was necessary to develop a method of extracting RNA molecules from purified virus particles. Highly purified Sendai virus was treated with pronase (300 μg/ml) at 37°C for 30 minutes and the RNA extracted by the sodium dodecyl sulfate (SDS)-phenol procedure.

Nucleic Acid Molecules Prepared by Monolayer Techniques

1972 ◽  
Vol 30 ◽  
pp. 178-179
Author(s):  
Dimitrij Lang
Keyword(s):  
Electron Microscopy ◽  
Standard Deviation ◽  
Nucleic Acid ◽  
Cytochrome C ◽  
Nucleic Acids ◽  
Contour Length ◽  
Sample Standard Deviation ◽  
Molecular Weights ◽  
Length Measurements ◽  
Protein Monolayer

The success of the protein monolayer technique for electron microscopy of individual DNA molecules is based on the prevention of aggregation and orientation of the molecules during drying on specimen grids. DNA adsorbs first to a surface-denatured, insoluble cytochrome c monolayer which is then transferred to grids, without major distortion, by touching. Fig. 1 shows three basic procedures which, modified or not, permit the study of various important properties of nucleic acids, either in concert with other methods or exclusively:1) Molecular weights relative to DNA standards as well as number distributions of molecular weights can be obtained from contour length measurements with a sample standard deviation between 1 and 4%.

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