Chemical-biological processes

Weathering and transportation is followed by the sedimentation of material. The depositional environment can be defined as an area with a typical set of physical, chemical and biological processes which result in a specific type of rock. The characteristics of the resulting sediment package are dependent on the intensity and duration of these processes. The physical, chemical, biological and geomorphic variables... 

Sample Preservation Once removed from its target population, a liquid sample s chemical composition may change as a result of chemical, biological, or physical processes. Following its collection, samples are preserved by controlling the solu-... 

Care should be exercised when attempting to interpret in vivo pharmacological data in terms of specific chemical—biological interactions for a series of asymmetric compounds, particularly when this interaction is the only parameter considered in the analysis (10). It is important to recognize that the observed difference in activity between optical antipodes is not simply a result of the association of the compound with an enzyme or receptor target. Enantiomers differ in absorption rates across membranes, especially where active transport mechanisms are involved (11). They bind with different affinities to plasma proteins (12) and undergo alternative metaboHc and detoxification processes (13). This ultimately leads to one enantiomer being more available to produce a therapeutic effect. 

The treatment of waste is the third element of the hierarchy and should be utilized only in the absence of feasible source reduction or recychng opportunities. Waste treatment involves the use of chemical, biological, or physical processes to reduce or eliminate waste material. The incineration of wastes is included in this categoiy and is considered preferable to other treatment methods (i.e., chemical, biological, and physical) because incineration can permanently destroy the hazardous components in waste materials (Ref. 4). It can also be employed to reduce the volume of waste to be treated. 

Almost all cooling water system deposits are waterborne. It would be impossible to list each deposit specifically, but general categorization is possible. Deposits are precipitates, transported particulate, biological materials, and a variety of contaminants such as grease, oil, process chemicals, and silt. Associated corrosion is fundamentally related to whether deposits are innately aggressive or simply serve as an occluding medium beneath which concentration cells develop. An American... 

Most treatment options for detoxifying the hazardous constituents from RCRA facilities must have a uniform feed to the process. However, the media in which hazardous constituents are located are not generally homogeneous. Thus, some form of pretreatment of the waste or waste medium will probably be required to prepare the waste for further treatment by chemical, biological or thermal means. 

End-of-pipe treatment refers to the application of chemical, biological, and physical processes to reduce the toxicity or volume of downstream waste. Treatment options include biological systems, chemical precipitation, flocculation, coagulation, and incineration as well as boilers and industrial furnaces (BIFs). 

To control water pollution, a waste stream can be subjected to at least one, or perhaps a combination, of chemical, biological, and physical treatments. Some of these processes are discussed below. 

Cycle Process (chemical transformation) Biological group responsible... 

Even if organocatalysis is a common activation process in biological transformations, this concept has only recently been developed for chemical applications. During the last decade, achiral ureas and thioureas have been used in allylation reactions [146], the Bayhs-Hillman reaction [147] and the Claisen rearrangement [148]. Chiral organocatalysis can be achieved with optically active ureas and thioureas for asymmetric C - C bond-forming reactions such as the Strecker reaction (Sect. 5.1), Mannich reactions (Sect. 5.2), phosphorylation reactions (Sect. 5.3), Michael reactions (Sect. 5.4) and Diels-Alder cyclisations (Sect. 5.6). Finally, deprotonated chiral thioureas were used as chiral bases (Sect. 5.7). 

Many years have passed since the early days of AFM, when adhesion was seen as a hindrance, and it is now regarded as a useful parameter for identification of material as well as a key to understanding many important processes in biological function. In this area, the ability of AFM to map spatial variations of adhesion has not yet been fully exploited but in future could prove to be particularly useful. At present, the chemical nature and interaction area of the AFM probe are still rarely characterized to a desirable level. This may be improved dramatically by the use of nanotubes, carbon or otherwise, with functionalized end groups. However, reliance on other measurement techniques, such as transmission electron microscopy and field ion microscopy, will probably be essential in order to fully evaluate the tip-sample systems under investigation. 

Phillips of the BHR Group, UK, provides a compact definition of process intensification, saying it is ... a design philosophy whereby the fluid dynamics in a process are matched to its chemical, biological and/or physical requirements,. .. [27]. In this way, significant benefits are gained, those listed above. 

Hannington, M.D., Jonasson, I.R., Herzig, P.M. and Petersen, S. (1995) Physical and chemical processes of seafloor mineralization at midocean ridges. In Seafloor Hydrothermal Systems Physical, Chemical, Biological, and Geological Interactions. Geophysical Monograph, 91, 115-157. 

The power of the pooled GST fusion protein approach will increase as new biochemical reagents and assays become available. The development of chemical probes for biological processes, termed chemical biology, is a rapidly advancing field. For example, the chemical synthesis of an active site directed probe for identification of members of the serine hydrolase enzyme family has recently been described (Liu et al., 1999). The activity of the probe is based on the potent and irreversible inhibition of serine hydrolases by fluorophosphate (FP) derivatives such as diisopropyl fluorophosphate. The probe consists of a biotinylated long-chain fluorophosphonate, called FP-biotin (Liu et al., 1999). The FP-biotin was tested on crude tissue extracts from various organs of the rat. These experiments showed that the reagent can react with numerous serine hydrolases in crude extracts and can detect enzymes at subnanomolar... 

The authors are grateful for financial support from the Swiss National Science Foundation, National Centre of Competence in Research Chemical Biology—Visualisation and Control of Biological Processes Using Chemistry (to PJD) and Dr. J. Jacobi Trust (to PNS). The authors thank Tse Wong for technical assistance, Maxime Dubois for the help in the synthesis of the compounds and Dr. Lucienne Juillerat-Jeanneret (Institute of Pathology, CHUV, Lausanne, Switzerland) for providing the MDA-MB-231 cells. 

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