Amino bases are proton acceptors. Amines have two options,

Amino acids consist of carboxylic acids (acidic) and amines (basic). Acids are protons donors because a hydrogen atom is a proton with one electron, technically an H ion is just a proton. So an acid is just a proton donor. Also, bases are proton acceptors. Amines have two options, they can either be neutral (NH2) or gain a proton (NH3+). Carboxylic acids can either be neutral (COOH) or lose a proton. (COO-). The proton count on each will be determined by the acidity of the solution and that amino acids can only be neutral or zwitterion (overall neutral but have formal charges across the molecule).

http://study.com/academy/lesson/zwitterion-structure-function.html

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A zwitterion is sometimes called dipolar ions. This is due to having a negative end (anion) and a positive end (cation). At a neutral PH, amino acids exist in their zwitterion form (dipolar form). This means that the amino acids contain a positive charge and a negative charge.

a)     At the low PH of 0/1 the carboxylic group is protonated. At this acidic PH, amino acids are positively charged species.

b)     As the PH increased, the carboxylic acid group loses its hydrogen to form a zwitterion.

c)      The zwitterion form usually persists until around a PH of 9. At this basic PH, the low H+ causes the amino acids to lose its hydrogen therefore forming a negatively charged species.

 

 

Ion exchange chromatography:  Ion exchange chromatography is a separation technique based on the electrostatic interaction of charged surfaces based on what PH they are. . The types of ion exchange chromatography based on the ion exchange, the ion exchange chromatography can be classified into two types. Cation exchange chromatography and anion exchange chromatography. Also, ion exchange chromatography is based on the reversible electrostatic interaction of proteins with the separation matrix. Mechanism of protein separation in ion exchange chromatography have two types, PH based binding and salt based binding. The PH based binding depends on the differences between the net surface charges on the solute molecules. Proteins, for instance contain numerous groups which can ionize to varying ways depending on the PH of the solution. The ionic state of these groups is highly dependent on the PH and because of this the net surface charge of protein will go through a change as the PH of their environment varies at the isoelectric point of the protein. So, the protein will have little to no tendency to bind to a cationic stationary phase or to anionic stationary phase.

 

 

 

 

 

 

 

 

At PH value below the pi, the protein will have a net positive charge and will tend to bind reversibly to the width of the surface of a cation exchange resin that is one that has negatively charged groups at the PH. Note that a cation exchange resin is anionic having negatively charged groups while an anion exchange resin in cationic since it has positively charged groups. Binding to the matrix requires buffer ions that are bound to the matrix during equilibration process.

Gel electrophoresis:

Electrophoresis is the migration of charged particles in an electric field.The buffers function to maintain the PH. The proteins net charge is dependent on the PH of the solution they are placed in. As the protein is placed into the buffer with specific PH, the difference in the buffer PH relative to the isoelectric point of the protein determines the magnitude and type of charge on the protein 
acid pH (pHpI), negative charge (migrates toward anode) OR: subtract the pH of the buffer from the pI of the protein: if the resulting number is pos, pos charge and vise versa eg: pI 5.6 in PH 8.6 = -3 greater the difference between pI and PH the greater the charge typically use PH of 8.6, therefore proteins are anions (negative charge) and migrate toward the anode (1) What happens if the buffer solution you use has a low pH? In the presence of a low acidic solution, all the -COOH groups present will exist as -COOH groups, and not as ions. All the -NH2 groups will have picked up hydrogen ions to form -NH3+.That means that all of the amino acids will carry a positive charge, and all of them will move towards the negative electrode. On the other hand, if the buffer solution has a higher PH then all the -COOH groups present will exist as -COO- ions. All the -NH2 groups will exist as simple -NH2 groups – not ions. That means that all of the amino acids will carry a negative charge, and all of them will move towards the positive electrode. However, due to mass and shape, they will move in different rates. 2)

1)       https://quizlet.com/19762196/electrophoresis-flash-cards/

2)       http://www.chemguideforcie.co.uk/section112/learninga.html

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