Physical methods supporting

Enzymes are immobilized by a variety of methods. Two general types of immobilization procedures are used. The first-type procedures are based on weak interactions between the support and the enzyme and are classified as physical methods. The second-type procedures rest upon the formation of covalent bonds between the enzyme and the support and are classified as chemical methods. 

When the chemical-imbalance theory was introduced more than 40 years ago, the main evidence in favour of it was the contention that antidepressants, which were thought to increase the availability of serotonin and/or other neurotransmitters in the brain, seemed to be effective in the treatment of depression. As Alec Coppen wrote in 1967, one of the most cogent reasons for believing that there is a biochemical basis for depression or mania is the astonishing success of physical methods of treatment of these conditions. 26 The situation has not changed very much since then. People still cite the supposed effectiveness of antidepressants as fundamental support for the chemical-imbalance hypothesis. This theory, they say, is supported by the indisputable therapeutic efficacy of these drugs .27... 

Micro- (and even nano-) electrode arrays are commonly produced with photolithography and electronic beam techniques by insulating of macro-electrode surface with subsequent drilling micro-holes in an insulating layer [136, 137], Physical methods are, however, expensive and, besides that, unsuitable for sensor development in certain cases (for instance, for modification of the lateral surface of needle electrodes). That s why an increasing interest is being applied to chemical approaches of material nanostructuring on solid supports [140, 141],... 

Immobilization of the bilayer membranes as thin solid films is required when the bilayer membranes are used as novel functional materials. Casting method is a simple way to immobilize the bilayer membrane on a solid support from an aqueous solution by drying. Polymer film is easily prepared when the cast film of polymerizable bilayer membrane is polymerized. A free standing polymer film prepared by photo polymerization of the cast film of diacetylene amphiphiles was reported by O Brien and co-workers [34]. Composition with macromolecular materials is another way of polymer film preparation. Bilayer membranes are immobilized as polymer composites by the following physical methods ... 

The concept of superelectrophilic activation was first proposed 30 years ago.20 Since these early publications from the Olah group, superelectrophilic activation has been recognized in many organic, inorganic, and biochemical reactions.22 Due to the unusual reactivities observed of superelectrophiles, they have been exploited in varied synthetic reactions and in mechanistic studies. Superelectrophiles have also been the subject of numerous theoretical investigations and some have been directly observed by physical methods (spectroscopic, gas-phase methods, etc.). The results of kinetic studies also support the role of superelectrophilic activation. Because of the importance of electrophilic chemistry in general and super-acidic catalysis in particular, there continues to be substantial interest in the chemistry of these reactive species. It is thus timely to review their chemistry. 

Physical methods that involve the supporting of a biological element in any way that is not depending on covalent bond formation (e.g., adsorption, entrapment, microencapsulation). These procedures are simple and in most cases the biocatalyst remains unchanged. 

An alternative to this physical method of preparing structurally uniform metal clusters on supports involves chemistry by which molecular metal carbonyl clusters (e.g., [Rh6(CO)i6]) serve as precursors on the support. These precursors are decarbonylated with maintenance of the metal frame to give supported nanoclusters (e.g., Rh6). Advantages of this chemical preparation method are its applicability to many porous supports, such as zeolites (and not just planar surfaces) and the opportunities to use spectroscopic methods to follow the chemistry of synthesis of the precursor on the support and its subsequent decarbonylation. Zeolites, because their molecular-scale cages are part of a regular (crystalline) structure, offer the prospect of regular three-dimensional arrays of nanoclusters. 

Now that a theoretical order of partial covalence has been established it is as well to examine physical methods to see if they confirm these covalence orders. Table 9 gives some evidence in support of the general theoretical analysis. 

PFAS were obtained with 2 moles of water, for each mole of acid and they could not be dehydrated with physical methods. Hydrated acids, both as such and supported on silica using water as solvent, were not active in isobutane alkylation. Therefore the effect of different dehydrating solvent was studied, in order to remove residual water. The catalysts obtained by supporting perfluoroethanedisulphonic acid on Si02 (PFES-Si02) after dissolution in various dehydrating solvents were tested in the reaction and resulted active with high butene conversion (Table 1). 

Full support for that hypothesis came with information concerning the position of atoms in enzymes, their complexes with substrates and inhibitors, and the values of so called B-factors that relate to the average amplitude of atoms displacement. Structural investigations with the use of such physical methods as NMR and Raman resonance spectroscopy, theoretical calculations, in particular, also produce evidence in favour of this concept. 

A number of physical methods have found support in molecular orbital theory, or have provided evidence that the deductions of molecular orbital theory have some experimental basis. Electron affinities correlate moderately well with the calculated energies of the LUMO, ionisation potentials correlate moderately well with the calculated energies of the HOMO, and spectroscopic methods reveal features that support molecular orbital theory. 

Other methods of calculation yield figures supporting those of Morley. They utilize the densities and other physical constants of hydrogen and oxygen, and are based on the purely physical methods... 

The structural problem was finally cleared up by physical methods, including molar refraction,255-252 and ultraviolet263 and Raman254 spectroscopy. The 3-benzoyl derivative has also been submitted to X-ray analysis.233-235 All the evidence supports a planar fused system of six- and five-membered rings, although some of the earlier work was interpreted in terms of other structures. The proton NMR spectrum of anthranil has been analyzed 265 the parameters are listed in Table A. 

---