How do you find the isoelectric point?

The isoelectric point (IEP) is the pH value where the zeta potential is zero. The IEP can be determined using the Nicomp Z3000 system by titrating the sample and recording zeta potential as a function of pH. Coffee mate creamer was prepared by mixing 0.1 g in 200 mL of DI water.

What is the effect of side chains on their pI?

The pI of amino acids with acidic side chains In case the side chain is basic, the pI is at a higher pH because the acidic side chain will result in an additional +1 charge. Subsequently, the neutral form arises under conditions of basicity, when the additional -1 charge has been neutralized.

What does the side chain of an amino acid determine?

In proteins, which are composed of amino acid residues, the side chains are attached to the alpha-carbon atoms of the amide backbone. The side chain connected to the alpha-carbon is specific for each amino acid and is responsible for determining charge and polarity of the amino acid.

How can you tell if an amino acid side chain is acidic or basic?

Since an amino acid has both an amine and acid group which have been neutralized in the zwitterion, the amino acid is neutral unless there is an extra acid or base on the side chain. If neither is present then then the whole amino acid is neutral.

What is the isoelectric point of amino acid?

The isoelectric point of an amino acid is the point at which the amino acid has no net electrical charge. It is an important characteristic for any amino acid, because every amino acid has at least two acid–base (titratable) groups.

How do you find the isoelectric point on a titration curve?

For a simple diprotic amino acid, the pI falls halfway between the two pK values. For acidic amino acids, the pI is given by ½(pK1 + pK2) and for basic amino acids it’s given by ½(pK2 + pK3).

What are the R side chains in each?

Each of the 20 amino acids has a specific side chain, known as an R group, that is also attached to the α carbon. The R groups have a variety of shapes, sizes, charges, and reactivities. This allows amino acids to be grouped according to the chemical properties of their side chains.

How do you determine the structure of an amino acid?

Generally, amino acids have the following structural properties:

1. A carbon (the alpha carbon)
2. A hydrogen atom (H)
3. A Carboxyl group (-COOH)
4. An Amino group (-NH2)
5. A “variable” group or “R” group.

How can you determine whether an amino acid is acidic quizlet?

If there are a lot of amino acids that have a low pKa (D or E) then the pI will be low or acidic. If the amino acids have a basic pKa (R) then the pI will be high or basic.

What is the isoelectric point formula for amino acids with neutral side chains?

The isoelectric point formula for an amino acid having a neutral side chain will be as follows: For amino acids having a neutral side chain, the pI value is calculated by taking a mean of the pKa of the carboxylate and the pKa of the aminonium group.

How do you find the isoelectric point of lysine?

Lysine has a basic group in its side chain. To calculate the isoelectric point of Lysine, the pKa of the similarly ionizable groups will be considered which are the ammonium group (pKa = 8.95) and the basic side chain (pKa = 10.53). The isoelectric point of amino acids differs based on the following factors:

How do you find the isoelectric point of aspartic acid?

Aspartic acid is an amino acid having an acidic side chain CH2COOH. To calculate the isoelectric point for this amino acid, the pKa of the similarly ionizable groups will be considered which in this case are the carboxylic acid group (pKa = 1.88) and the acidic side chain (pKa = 3.65). pI=1.88 +3.652=2.77. Calculate the isoelectric point of Lysine

What is the isoelectric point of a tripeptide?

Isoelectric point will be near pH 7, because the amino acid residues present in this tripeptide are all neutral amino acids. Ser-Val-Asp The pI for this tripeptide will be less than 7, due to the presence of an acidic amino acid (Asp) in this tripeptide.