Biological physical characteristics

Biological reactors play a valuable role in tlie conversion of substrates by microorganisms and mammalian cells into a wide range of products such as antibiotics, insulin, and polymers. Figures 11-12, 11-13, and 11-14 illustrate various types of biological reactor, and Figure 11-15 shows the physical characteristics of a typical coimuercial fermentation vessel. 

The perceived sensitivity of plant cells to the hydrodynamic stress associated with aeration and agitation conditions is typically attributed to the physical characteristics of the suspended cells, namely their size, the presence of a cell wall, the existence of a large vacuole, and their tendency to aggregate. Table 1 illustrates some of the differences between plant cells and other biological systems. Chalmers [19] attributed shear sensitivity in mammalian cultures at least in part to the fact that these cells occur naturally as part of a tissue, surrounded by other cells. The same is true for plant cells. The more robust microbial systems, on the other hand, exist in nature as single organisms or mycelial structures, very close to the forms they assume in submerged culture. 

Purification of biopharmaceuticals often involves the removal of materials with physical characteristics very similar to the desired product, such as failure sequences from DNA synthesis or misfolded proteins from bacterial fermentations. The contaminants, however, may have biological characteristics very different from the desired product, including different antigenicities, bioactivities, and specificities. There are even systems in which the... 

As briefly mentioned, the occurrence of sediments in sewers is closely related to the hydraulics and physical process characteristics and the properties of the solids. This text does not include a quantitative description of the physical processes in sewers, such as sedimentation, deposition and erosion, and the corresponding physical characteristics of sewer solids. A great number of publications and textbooks address these subjects. A comprehensive description with a broad range of literature references can be found in Ashley and Verbanck (1998). Other important publications in this respect are found in Ashley (1996), Hvitved-Jacobsen et al. (1995) and Hvitved-Jacobsen (1998). Perspectives and relations to the chemical and biological sewer processes are outlined in Ashley etal. (1999). 

The physical characteristics of sewer deposits can be described in terms of individual particle and bulk properties. The hydraulic and structural conditions in the sewer, together with the nature of the inputs, will control the type of material that deposits at a given location. Crabtree (1989) has proposed a sewer sediment taxonomy that is relevant mainly in terms of physical properties but also to chemical and biological processes (Table 3.5). The taxonomy is based on four primary classes with a fifth class B comprising agglutinated or cemented class A material. 

The sequence of amino acids in a polypeptide chain is known as the primary structure. This feature is genetically determined and is responsible not only for the final shape of the protein but also for its physical characteristics and, ultimately, for its biological function. Proteins are made up of about 22 amino acids, which are linked by the peptide bond (Figure 11.1), an amide linkage involving the amino group of one amind acid and the carboxyl group of another. 

The chemical, biological, and physical characteristics of the drug substance can be manipulated and hence optimized by conversion to a salt form. Every compound that exhibits acid or base characteristics can participate in salt formation. Various salts of the same compound often behave quite differently because of the physical, chemical, and thermodynamic properties they impart to the parent compound. Table 1 lists the top ten FDA approved commercially marketed final drug forms and Table 2... 

Kikuchi E, Kurihara Y. 1977. In vitro studies on the effects of tubificids on the biological, chemical, and physical characteristics of submerged ricefield soil and overlying floodwater. Oikos 29 348-356. 

It should be noted that no additional aspects were taken into consideration in this compilation other than the influence on runoff characteristics. Any evaluation of morphological, biological, physical, or chemical parameters would produce a very different pattern. 

Figure 28 Schematic presentation of the relative situation of the different types of radiations used in therapy. Two criteria are considered the physical selectivity and the LET (or radiobiological properties). For the low-LET radiations, the physical selectivity was improved from the historical 200-kV x-rays to cobalt-60 gamma rays and the modern linacs. Even with the linacs today, significant improvement is continuously achieved (IMRT, etc.). Among the low-LET radiation, the proton beams have the best physical characteristics, but one of the issues is the proportion of patients who will benefit from proton irradiation. A similar scale can be drawn for high-LET radiation the heavy-ion beams have a physical selectivity similar to protons. Selection between low- and high-LET radiation is a biological/medical problem it depends on the tumor characteristics, and reliable criteria still need to be established (see text). (From Ref 54.)...

Often, stability of a drug has been referred to as the time from the date of manufacture and packaging until its chemical or biological activity is not less than a predetermined level of labeled potency without the physical characteristics changing appreciably. For most drugs, 90% of labeled potency is generally recognized as the minimum acceptable potency. 

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