Consequently the charging energy is then‭ (‬±e/2‭)‬2/C,‭ ‬for either case.  This effect can be seen in metal and semiconductor‭ ‬dots. In the latter,‭ ‬the‭ ‬quantum-mechanical energy levels of the electrons are also important,‭ ‬as their wavelength is comparable to the size of the‭ ‬dot.

Note:‭  ‬The term tunneling should not be confused with a particle actually traveling through a substance. It is a term that references the quantum mechanical concept of the statistical likelihood of the particle existing in a particular location.  If one uses the analogy of a quantum dot being a box,‭ “‬Over enough measurements,‭ ‬that means that eventually an electron will be found outside of the box. We say that the electron has‭ "‬tunneled‭" ‬out of the box,‭ ‬but it never really existed inside the box. It only had a probability that it could be inside the box,‭ ‬and this particular electron,‭ ‬when measured,‭ ‬was one of the few that were outside the box.‭”‬

Nanotechnology and quantum dots can have significant applications outside the physical sciences.  In biology,‭ ‬the uses can be varied,‭ ‬reactivity of enzymes,‭ ‬flow of ions in channels,‭ ‬aiding in immunity,‭ ‬imaging and detection developments with tags and DNA,‭ ‬as well as working with the electron transport chain in photosynthesis.  To fully understand the role this development has,‭ ‬it is important to understand some biological functions.

An enzyme is an organic molecule that facilitates biochemical reactions,‭ ‬i.e. a catalyst. A‭ ‬catalyst cannot make a thermodynamically unfavorable reaction proceed. Rather,‭ ‬it can only speed up a reaction that is already thermodynamically favorable. Such a reaction in the absence of a catalyst would proceed,‭ ‬even without the catalyst,‭ ‬although perhaps too slowly to be observed or of use in a given context.

Catalysts accelerate the chemical reaction by providing a lower energy pathway between the reactants and the products. This usually involves the formation of an intermediate,‭ ‬which cannot be formed without the catalyst. The formation of this intermediate and subsequent reaction generally has a much lower activation energy barrier than is required for the direct reaction of reactants to products.

Enzymes share three properties that are common to all catalysts,‭ ‬whether the catalyst be organic or inorganic. First,‭ ‬the rate of reaction is increased through the lowering of the activation energy requirement. Therefore,‭ ‬the reaction is thermodynamically feasible without thermal activation.  Second,‭ ‬catalysts form a transient complex with the substrate that assists in the reaction process. Lastly,‭ ‬catalysts affect the rate of reaction but do not alter the position of the equilibrium constant‭ (‬Keq‭)‬.

Typically,‭ ‬most enzymes are proteins that contain an active site within the polypeptide. The active site is usually a collection of amino acids that form a specific three-dimensional structure where a specific substrate can bind. The access or availability of the active site is altered through the conformational‭ (‬shape‭) ‬changes of the enzyme. Some enzymes have cofactors that increase or decrease the affinity of the enzyme to the substrate. Some cofactors can directly effect the conformation of the enzyme.