Types of Binding Forces

Unless a drug comes into contact with intrinsic structures of the body, it cannot affect body function. 

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This identification of the chemical and the physical bond at once led to the association with the chemist s ionic and covalent bonds of two other types of binding force not previously regarded as chemical in nature at all, namely, the metallic bond responsible for the cohesion of a metal, and the very much weaker van der Waals or residual bond responsible for the crystallization of the inert gases at very low temperatures. These metallic and van der Waals forces, however, did not lend themselves as readily as did the ionic and covalent to any simple explanation in terms of the Bohr theory, and it is only in recent years that the development of quantum mechanics has enabled a qualitative and even quantitative description of these bonds to be given. At the same time quantum theory has furnished a more exact description of the properties of the ionic and covalent bonds, which were previously so successfully described qualitatively in terms of older ideas, so that it is now possible to give a satisfactory theoretical explanation of many of the physical and chemical properties of simple structures. 

Most proteins contain more than one polypeptide chain. The manner in which these chains associate determines quaternary structure. Binding involves the same types of noncovalent forces mentioned for tertiary structure van der Waals forces, hydrophobic and hydrophilic attractions, and hydrogen bonding. However, the interactions are now interchain rather than infrachain (tertiary structure determination). The quaternary structure of hemoglobin (four almost identical subunits) will be discussed in Chapter 4, that of superoxide dismutase (two identical subunits) will be discussed in Chapter 5, and that of nitrogenase (multiple dissimilar subunits) will be discussed in Chapter 6. 

In addition, if the spheres are in water, there will be a repulsive electrostatic force between them. Under usual conditions of stability, this force is quite strong and its range is on the order of the sphere s radii. It is easy to see that the location of this repulsive wall with respect to the thickness 5 of the adsorbed layers will determine the type of binding which will be possible. If the wall is within the adsorbed layer ((7. 5)> unsaturated spheres will experience a short range attraction and... 

The solutions initially separated because of a difference in intermol-ecular attraction, a type of intermolecular force. These attractions occur between molecules, as distinguished from intramolecular forces—chemical bonds—which bind the nuclei within a molecule. 

Typically, the attraction between the molecules of the enzyme and its substrate molecules is noncovalent binding. Physical forces used in this type of binding include hydrogen bonding, electrostatic and hydrophobic interactions, and van der Waals forces. 

On a molecular level the adsorption process is the formation of binding forces between the surface of the adsorbent and the molecules of the fluid phase. The binding forces can be different in nature and strength. Basically, two different types of binding can be distinguished (Atkins, 1990 lUPAC, 1972) ... 

There are two types of nuclear forces strong and weak. The strong force is an interaction that binds protons and neutrons together in atomic nuclei. 

Liquids and solids are quite a different story. The principal difference between the condensed states (liquids and solids) and the gaseous state is the distance between molecules. In a liquid, the molecules are so close together that there is very little empty space. Thus, liquids are much more difficult to compress than gases, and they are alBpmiali serptT piori g t ( itip iyi dPtecules in a liquid are held together by oncOT mWe types of attractive forces, which were discussed in Section 4.6. A liquid also has a definite volume because molecules in a liquid cannot overcome the attractive forces that bind them to one another. The molecules can, however, move past one another freely, and so a liquid can flow, can be poured, and will assume the shape of its container. 

Sorption is a complex process, which is controlled by dye-substrate interactions involving various types of intermolecular forces, such as electrostatic (ionic), van der Waals (London)," "" polar (hydrogen bonding)" " and hydrophobic (cooperative binding) interactions.The interaction forces involved in a sorption system depend on the physical and chemical properties of dyes and substrates. In general the adsorption of dye into the fibres can be represented by the following mechanism ... 

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