Determination of molecular weights of humic substances by analytical (UV scanning) ultracentrifugation

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

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19881735 ◽

1988 ◽

Vol 53 (8) ◽

pp. 1735-1744 ◽

Cited By ~ 1

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.

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Determination of Organic Compounds, Fulvic Acid, Humic Acid, and Humin in Peat and Sapropel Alkaline Extracts

Molecules ◽

10.3390/molecules26102995 ◽

2021 ◽

Vol 26 (10) ◽

pp. 2995

Author(s):

Laurynas Jarukas ◽

Liudas Ivanauskas ◽

Giedre Kasparaviciene ◽

Juste Baranauskaite ◽

Mindaugas Marksa ◽

...

Keyword(s):

Humic Acid ◽

Fulvic Acid ◽

Humic Substances ◽

Organic Compounds ◽

Chemical Constituents ◽

Acid Amide ◽

Extraction Methods ◽

Ultrasound Extraction ◽

Different Origins

Black, brown, and light peat and sapropel were analyzed as natural sources of organic and humic substances. These specific substances are applicable in industry, agriculture, the environment, and biomedicine with well-known and novel approaches. Analysis of the organic compounds fulvic acid, humic acid, and humin in different peat and sapropel extracts from Lithuania was performed in this study. The dominant organic compound was bis(tert-butyldimethylsilyl) carbonate, which varied from 6.90% to 25.68% in peat extracts. The highest mass fraction of malonic acid amide was in the sapropel extract; it varied from 12.44% to 26.84%. Significant amounts of acetohydroxamic, lactic, and glycolic acid derivatives were identified in peat and sapropel extracts. Comparing the two extraction methods, it was concluded that active maceration was more efficient than ultrasound extraction in yielding higher amounts of organic compounds. The highest amounts of fulvic acid (1%) and humic acid and humin (15.3%) were determined in pure brown peat samples. This research on humic substances is useful to characterize the peat of different origins, to develop possible aspects of standardization, and to describe potential of the chemical constituents.

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