Biological particles measuring system

National Institute of Standards and Technology (NIST). The NIST is the source of many of the standards used in chemical and physical analyses in the United States and throughout the world. The standards prepared and distributed by the NIST are used to caUbrate measurement systems and to provide a central basis for uniformity and accuracy of measurement. At present, over 1200 Standard Reference Materials (SRMs) are available and are described by the NIST (15). Included are many steels, nonferrous alloys, high purity metals, primary standards for use in volumetric analysis, microchemical standards, clinical laboratory standards, biological material certified for trace elements, environmental standards, trace element standards, ion-activity standards (for pH and ion-selective electrodes), freezing and melting point standards, colorimetry standards, optical standards, radioactivity standards, particle-size standards, and density standards. Certificates are issued with the standard reference materials showing values for the parameters that have been determined. 

Journal of Aerosol Science (0021-8502) (1879-1964). Covering all aspects of basic and applied aerosol research, the original papers in this journal describe recent theoretical and experimental research relating to the basic physical, chemical, and biological properties of systems of airborne particles of all types their measurement, formation, transport, deposition and effects and industrial, medical, and environmental applications. 

The special needs of size characterization methods for the biological and pharmaceutical systems that are now so important in the medical sciences today are reviewed. Submicrometre and subcolloidal particulate systems are more frequently encountered that do not have the sharply defined interfaces familiar to the analyst of 25 years ago. Philosophically it is pointed out that many particles with indeterminate interfaces will move under the application of external forces as if they were inside a sphere of influence and it is, in fact, the dimensions of this sphere that are measured. Under these conditions it is valid to measure the particle size characteristics of particles down to the molecular dimensions, at least, of some of the larger protein molecules, and some methods will certain reach down into these size regions without excessive difficulty. 

Other methods that detect a sphere of influence include those based on the Coulter principle which will also be reviewed at this conference. Here the data is reported in terms of a sphere of equivalent volume, irrespective of the shape or, in some situations, the state of the particulate interface. The method depends, essentially, on measuring the increase in resistance experienced between two electrodes as a particle passes between them and an essential requirement, therefore, is the presence of electrolyte in the measurement system. The method is realistically limited to particles down to about 1/jm in diameter, and there is no practical upper limit to the principle. The presence of electrolyte in the environment is an advantage in some situations since the effect is to suppress charge effects at the particle interface and this simplifies the measurement of the size of colloidal dispersions. Submicrometre dispersions can be measured but it should be noted that interference effects become more pronounced and there is less certainty about the magnitude of coincidence effects, quite apart from the intrinsic experimental difficulties of keeping orifices with diameters of less than 50um clean and operationally effective. Nevertheless, the Coulter principle has proved to be an invaluable technique for the detailed characterization of biological systems such as blood cells and, in some instances, bacterial suspensions. 

Electroultrafiltration (EUF) combines forced-flow electrophoresis (see Electroseparations,electrophoresis) with ultrafiltration to control or eliminate the gel-polarization layer (45—47). Suspended colloidal particles have electrophoretic mobilities measured by a zeta potential (see Colloids Elotation). Most naturally occurring suspensoids (eg, clay, PVC latex, and biological systems), emulsions, and protein solutes are negatively charged. Placing an electric field across an ultrafiltration membrane faciUtates transport of retained species away from the membrane surface. Thus, the retention of partially rejected solutes can be dramatically improved (see Electrodialysis). 

For reactors with free turbulent flow without dominant boundary layer flows or gas/hquid interfaces (due to rising gas bubbles) such as stirred reactors with bafQes, all used model particle systems and also many biological systems produce similar results, and it may therefore be assumed that these results are also applicable to other particle systems. For stirred tanks in particular, the stress produced by impellers of various types can be predicted with the aid of a geometrical function (Eq. (20)) derived from the results of the measurements. Impellers with a large blade area in relation to the tank dimensions produce less shear, because of their uniform power input, in contrast to small and especially axial-flow impellers, such as propellers, and all kinds of inclined-blade impellers. 

This strnctnring of liqnids into discrete layers when confined by a solid surface has been more readily observable in liquid systems other than water [1,55]. In fact, such solvation forces in water, also known as hydration forces, have been notoriously difficult to measure due to the small size of the water molecule and the ease with which trace amounts of contamination can affect the ordering. However, hydration forces are thought to be influential in many adhesive processes. In colloidal and biological systems, the idea that the hydration layer mnst be overcome before two molecules, colloidal particles, or membranes can adhere to each other is prevalent. This implies that factors affecting the water structure, such as the presence of salts, can also control adhesive processes. 

There is great interest in the electrical and optical properties of materials confined within small particles known as nanoparticles. These are materials made up of clusters (of atoms or molecules) that are small enough to have material properties very different from the bulk. Most of the atoms or molecules are near the surface and have different environments from those in the interior—indeed, the properties vary with the nanoparticle s actual size. These are key players in what is hoped to be the nanoscience revolution. There is still very active work to learn how to make nanoscale particles of defined size and composition, to measure their properties, and to understand how their special properties depend on particle size. One vision of this revolution includes the possibility of making tiny machines that can imitate many of the processes we see in single-cell organisms, that possess much of the information content of biological systems, and that have the ability to form tiny computer components and enable the design of much faster computers. However, like truisms of the past, nanoparticles are such an unknown area of chemical materials that predictions of their possible uses will evolve and expand rapidly in the future. 

Several derivatives of Eosin have been prepared and employed to study biological systems. Their main applications are as singlet energy acceptors and as triplet probes [93-97] to measure the rotational mobility of virus particles [98] and proteins in membranes and in solution. Examples of proteins studied using Eosin derivatives include myosin [99,100], band 3 protein [101,102], pyruvate dehydrogenase [103,104], and Sarcoplasmic... 

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