Solvent Effects on the Molecular Organization and Properties of Biological Systems

1994 ◽  
pp. 79-91
Author(s):  
R. Bartucci ◽  
R. Guzzi ◽  
P. Sapia ◽  
L. Sportelli
Keyword(s):  
Solvent Effects ◽  
Biological Systems ◽  
Molecular Organization

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.

Bimolecular and Monomolecular Lipid Films: Selected Area Electron Diffraction

1969 ◽  
Vol 27 ◽  
pp. 338-339
Author(s):  
Robert M. Glaeser ◽  
David W. Deamer
Keyword(s):  
Electron Diffraction ◽  
Membrane Structure ◽  
Molecular Organization ◽  
Membrane Material ◽  
X Ray Diffraction ◽  
Membrane Systems ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Lipid Films ◽  
Ultimate Objective

In the investigation of the molecular organization of cell membranes it is often supposed that lipid molecules are arranged in a bimolecular film. X-ray diffraction data obtained in a direction perpendicular to the plane of suitably layered membrane systems have generally been interpreted in accord with such a model of the membrane structure. The present studies were begun in order to determine whether selected area electron diffraction would provide a tool of sufficient sensitivity to permit investigation of the degree of intermolecular order within lipid films. The ultimate objective would then be to apply the method to single fragments of cell membrane material in order to obtain data complementary to the transverse data obtainable by x-ray diffraction.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

On the structural organization of biological pumps and channels

1984 ◽  
Vol 42 ◽  
pp. 138-141
Author(s):  
G. Zampighi ◽  
M. Kreman
Keyword(s):  
Active Transport ◽  
Transport System ◽  
Plasma Membranes ◽  
Transport Proteins ◽  
Molecular Organization ◽  
Passive Transport ◽  
Concentration Gradients ◽  
Cell Functions ◽  
Natural Concentration ◽  
Active Transport System

The plasma membranes of most animal cells contain transport proteins which function to provide passageways for the transported species across essentially impermeable lipid bilayers. The channel is a passive transport system which allows the movement of ions and low molecular weight molecules along their concentration gradients. The pump is an active transport system and can translocate cations against their natural concentration gradients. The actions and interplay of these two kinds of transport proteins control crucial cell functions such as active transport, excitability and cell communication. In this paper, we will describe and compare several features of the molecular organization of pumps and channels. As an example of an active transport system, we will discuss the structure of the sodium and potassium ion-activated triphosphatase [(Na+ +K+)-ATPase] and as an example of a passive transport system, the communicating channel of gap junctions and lens junctions.

High-resolution measurement of birefringent fine structure in living cells using a new polarized light microscope

1995 ◽  
Vol 53 ◽  
pp. 54-55
Author(s):  
Rudolf Oldenbourg
Keyword(s):  
Light Microscope ◽  
Fluorescent Dyes ◽  
Polarized Light ◽  
Processing System ◽  
Video Camera ◽  
Molecular Organization ◽  
Computer Assisted ◽  
Image Recording ◽  
Birefringent Crystal ◽  
Technological Advances

The recent renaissance of the light microsope is fueled in part by technological advances in components on the periphery of the microscope, such as the laser as illumination source, electronic image recording (video), computer assisted image analysis and the biochemistry of fluorescent dyes for labeling specimens. After great progress in these peripheral parts, it seems timely to examine the optics itself and ask how progress in the periphery facilitates the use of new optical components and of new optical designs inside the microscope. Some results of this fruitful reflection are presented in this symposium.We have considered the polarized light microscope, and developed a design that replaces the traditional compensator, typically a birefringent crystal plate, with a precision universal compensator made of two liquid crystal variable retarders. A video camera and digital image processing system provide fast measurements of specimen anisotropy (retardance magnitude and azimuth) at ALL POINTS of the image forming the field of view. The images document fine structural and molecular organization within a thin optical section of the specimen.

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

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.

Seeking to uncover biology's chemical roots

2019 ◽  
Vol 3 (5) ◽  
pp. 435-443 ◽  
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.

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