Biological experimental conditions

An atom-economical reaction should be selected as the conversion reaction to avoid a side effect derived from coreleased products in biologic experimental conditions. 

The cultivation of viruses from material taken from lesions is an important step in the diagnosis of many viral diseases. Studies of the basic biology and multiplication processes of human viruses also require that they are grown in the laboratory under experimental conditions. Human pathogenic viruses can be propagated in three types of cell systems. 

Various types of cell-based in vitro studies have shown that carotenoids can exert prooxidant effects under certain conditions. Most of these studies show in fact decreases in antioxidant efficacy of carotenoids with increasing carotenoid concentration examples of true prooxidant effects are rarer. It is also important to pay attention to the experimental conditions and their biological relevance. Indeed, carotenoids have sometimes been proven to (I) exert prooxidant activity in an atmosphere of pure oxygen, (2) never occur in vivo, or (3) appear in concentrations that they would never reach in vivo. 

An important technique for the qualitative and quantitative analysis of different macromolecular materiafs is based on the efectrophoretic separation of particfes having different transport vefocities (e.g., because they have different zeta potentiafs). This technique is used for the anafysis of proteins, pofysaccharides, and other naturally occurring substances whose molecular size approaches that of colloidal particles (for more details, see Section 30.3.4). It is an advantage of the electrophoretic method that mild experimental conditions can be used—dilute solutions with pH values around 7, room temperature, and so on—which are not destructive to the biological macromolecules. 

A number of autoxidation reactions exhibit exotic kinetic phenomena under specific experimental conditions. One of the most widely studied systems is the peroxidase-oxidase (PO) oscillator which is the only enzyme reaction showing oscillation in vitro in homogeneous stirred solution. The net reaction is the oxidation of nicotinamide adenine dinucleotide (NADH), a biologically vital coenzyme, by dioxygen in a horseradish peroxidase enzyme (HRP) catalyzed process ... 

Cultured nasal cells are reliable models for drug transport and metabolism studies, since they are known to express important biological features (e.g. tight junctions, mucin secretion, cilia, and various transporters), resembling those found in vivo systems. Moreover, easy control of experimental conditions as well as separation of the permeation step from the subsequent absorption cascade is also possible. A relatively simple primary culture condition using human nasal epithelial cells for in vitro drug transport studies has been established and applied in transport and metabolism studies of drugs. It is known that the culture condition and/or selection of culture media are critical in the recapitulation of well-differentiation features of in vivo nasal mucosal epithelium [46],... 

We wish to stress that comparison of the isotopic effects in biologic and abiologic systems will be most meaningful if experimental conditions are identical, where the only difference is the presence or absence of bacteria. The wide variety of buffers, growth media, and others conditions that are involved in biological experiments raise the possibihty that spurious results may be obtained if these factors are not carefully controlled. Because speciation may exert a strong control on Fe isotope fractionations (Schauble et al. 2001), even small differences across experimental studies may be significant. 

ISEs are well suited for flow measurements because the instrumentation and signal handling are simple, the measurement is almost independent of the liquid flow-rate, the linear dynamic range is broad, the temperature dependence is not very pronounced and the measurement is selective (the selectivity is, however, a drawback in applications to chromatography). The experimental conditions are readily adjusted and often only consist of ionic strength and pH maintenance. ISEs with solid membranes usually exhibit better performance than liquid membrane electrodes and gas probes, because their response is faster and they are mechanically stronger. The most difficult problem is passivation of the electrodes in some media, for example, biological fluids or surface and waste waters. 

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