DEFECTS AND TEXTURES IN CHOLESTERIC ANALOGUES GIVEN BY SOME BIOLOGICAL SYSTEMS

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.

Download Full-text

Freeze-fracture cytochemistry: A goal set by Russell Steere in 1957

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010014614x ◽

1993 ◽

Vol 51 ◽

pp. 60-61

Author(s):

Nicholas J Severs

Keyword(s):

Chemical Nature ◽

Biological Systems ◽

Freeze Fracture ◽

Structural Components ◽

Major Goal ◽

Membrane Biology ◽

Routine Application ◽

The Future ◽

Freeze Etching

In his pioneering demonstration of the potential of freeze-etching in biological systems, Russell Steere assessed the future promise and limitations of the technique with remarkable foresight. Item 2 in his list of inherent difficulties as they then stood stated “The chemical nature of the objects seen in the replica cannot be determined”. This defined a major goal for practitioners of freeze-fracture which, for more than a decade, seemed unattainable. It was not until the introduction of the label-fracture-etch technique in the early 1970s that the mould was broken, and not until the following decade that the full scope of modern freeze-fracture cytochemistry took shape. The culmination of these developments in the 1990s now equips the researcher with a set of effective techniques for routine application in cell and membrane biology.Freeze-fracture cytochemical techniques are all designed to provide information on the chemical nature of structural components revealed by freeze-fracture, but differ in how this is achieved, in precisely what type of information is obtained, and in which types of specimen can be studied.

Download Full-text

Seeking to uncover biology's chemical roots

Emerging Topics in Life Sciences ◽

10.1042/etls20190012 ◽

2019 ◽

Vol 3 (5) ◽

pp. 435-443 ◽

Cited By ~ 3

Author(s):

Addy Pross

Keyword(s):

Environmental Changes ◽

Biological Systems ◽

Significant Development ◽

The Road ◽

Physical Chemical ◽

Systems Chemistry ◽

Biological World ◽

Inanimate Matter ◽

The Origin Of Life ◽

Opening Up

Despite the considerable advances in molecular biology over the past several decades, the nature of the physical–chemical process by which inanimate matter become transformed into simplest life remains elusive. In this review, we describe recent advances in a relatively new area of chemistry, systems chemistry, which attempts to uncover the physical–chemical principles underlying that remarkable transformation. A significant development has been the discovery that within the space of chemical potentiality there exists a largely unexplored kinetic domain which could be termed dynamic kinetic chemistry. Our analysis suggests that all biological systems and associated sub-systems belong to this distinct domain, thereby facilitating the placement of biological systems within a coherent physical/chemical framework. That discovery offers new insights into the origin of life process, as well as opening the door toward the preparation of active materials able to self-heal, adapt to environmental changes, even communicate, mimicking what transpires routinely in the biological world. The road to simplest proto-life appears to be opening up.

Download Full-text