What are the pKa values of arginine?
| Amino Acid | Abbreviation | pKa (25 °C) |
|---|---|---|
| Arginine | Arg | 8.99 |
| Asparagine | Asn | 8.72 |
| Aspartic Acid | Asp | 9.90 |
| Cysteine | Cys | 10.70 |
Why does arginine have high pKa?
Sometimes the amino acid side chain contains a basic group. Examples are histidine, lysine and arginine. The higher the pKa of the conjugate acid, the more tightly the proton is held, and so the more basic the nitrogen atom. Arginine is by far the most basic and histidine is the least basic.
What is the functional group of arginine?
Like all of the amino acids, arginine has two functional groups, a carboxyl group (COOH) and an amine group (NH2). It has one of the most complex side chains (CH2-CH2-CH2-NH-CNH-NH2). Arginine is the most basic of the amino acids that in turn form the building blocks of proteins.
Is arginine acidic or basic?
Amino acid poperties
| Amino-acid name | 3-letter code | Properties |
|---|---|---|
| Arginine | Arg | Positively charged (basic amino acids; non-acidic amino acids); Polar; Hydrophilic; pK=12.5 |
| Asparagine | Asn | Polar, non-charged |
| Aspartate | Asp | Negatively charged (acidic amino acids); Polar; Hydrophilic; pK=3.9 |
| Cysteine | Cys | Polar, non-charged |
How many ionizable groups are in arginine?
two ionisable groups
It has only two ionisable groups, a carboxyl group and amino group. When titrated with a strong base (NaOH), the titration curve so obtained is as shown in Fig. 2. Two steps are involved corresponding to the deprotonation of the two groups with NaOH.
Is arginine charged at pH 7?
At pH 7, Arg has a fully protonated side chain and is capable of being only a hydrogen bond donor (see Stryer, p. 33). Any amino acid side chain capable of accepting a hydrogen bond can hydrogen bond with Arg at pH = 7….
| Amino Acid | Arginine |
|---|---|
| charge at pH 2 | +1 |
| charge at pH 7 | +1 |
| charge at pH 12 | +1 (50%) |
At what pH is arginine neutral?
12.5
The two nitrogens of the histidine side chain have a relatively weak affinity for an H+ and are only partly positive at neutral pH….Charged side chains.
| Amino acid | pK of the side chain group |
|---|---|
| Aspartic acid | 3.9 |
| Glutamic acid | 4.2 |
| Lysine | 10.5 |
| Arginine | 12.5 |
What is the pH of arginine?
Table 2: Charge of the amino acid side chains. Only the side chains are shown. At pH=7, side chains of the 5 amino acids are charged….Charged side chains.
| Amino acid | pK of the side chain group |
|---|---|
| Aspartic acid | 3.9 |
| Glutamic acid | 4.2 |
| Lysine | 10.5 |
| Arginine | 12.5 |
Why is arginine more basic?
Why is arginine more basic than histidine? The arginine side chain is very basic because its positive charge is stabilized by resonance. The two nitrogens of the histidine side chain have a relatively weak affinity for an H+ and are only partly positive at neutral pH.
Why is arginine positively charged?
These are arginine (Arg), lysine (Lys), and histidine (His). Their side chains contain nitrogen and resemble ammonia, which is a base. Their pKa’s are high enough that they tend to bind protons, gaining a positive charge in the process.
