Amino Acid Properties
| Amino Acid Name | 3-Letter Code | Side Chain Acidity / Basicity |
|---|
| Serine | Ser | Neutral |
| Threonine | Thr | Neutral |
| Tryptophan | Trp | Neutral |
| Tyrosine | Tyr | Neutral |
Sources. Foods high in threonine include cottage cheese, poultry, fish, meat, lentils, black turtle bean and sesame seeds. Racemic threonine can be prepared from crotonic acid by alpha-functionalization using mercury(II) acetate.
Amino Acid Properties
| Amino Acid Name | 3-Letter Code | Side Chain Polarity |
|---|
| Threonine | Thr | Polar |
| Tryptophan | Trp | Nonpolar, aromatic |
| Tyrosine | Tyr | Polar, aromatic |
| Valine | Val | Nonpolar |
Since proteins have nonpolar side chains their reaction in a watery environment is similar to that of oil in water. The nonpolar side chains are pushed to the interior of the protein allowing them to avoid water molecule and giving the protein a globular shape.
For basic side chains, the amino acids are: Lysine (K), Arginine (R) and Histidine (H). For non-polar side chains, the amino acids are: Alanine (A), Valine (V), Leucine (L), Isoleucine (I), Proline (P), Phenylalanine (F), Methionine (M), Tryptophan (W), Glycine (G) and Cysteine (C).
Threonine is both ketogenic and glucogenic because of acetaldehyde/acetyl CoA formation.
Among the 20 common amino acids, five have a side chain which can be charged. At pH=7, two are negative charged: aspartic acid (Asp, D) and glutamic acid (Glu, E) (acidic side chains), and three are positive charged: lysine (Lys, K), arginine (Arg, R) and histidine (His, H) (basic side chains).
Serine (Ser) and threonine (Thr) are polar since both carry a hydroxyl group, asparagine (Asn) and glutamine (Gln) carry a polar amide group. When both groups are protonated, the side chain has a charge of +1.
Both serine and threonine have side chains with -OH groups. As alcohol groups they are certainly ionizable at HIGH enough pH. Although the side chain on tyrosine can be ionized, the pKa is around 10.5.
four possible stereoisomers
Phosphorylation usually occurs on serine, threonine, tyrosine and histidine residues in eukaryotic proteins. The addition of a phosphate (PO4) molecule to a non-polar R group of an amino acid residue can turn a hydrophobic portion of a protein into a polar and extremely hydrophilic portion of a molecule.
Amino Acid Properties
| Amino Acid Name | 3-Letter Code | Side Chain Acidity / Basicity |
|---|
| Alanine | Ala | Neutral |
| Arginine | Arg | Basic (strongly) |
| Asparagine | Asn | Neutral |
| Aspartic acid | Asp | Acidic |
There are three amino acids that have basic side chains at neutral pH. 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.
Charged side chains
When an amino acid (AA) is incorporated into a polypeptide, the charges on the amino and carboxyl groups disappear. Among the 20 common amino acids, five have a side chain which can be charged.Examples include valine, alanine, leucine, isoleucine, phenylalanine. The number of alkyl groups also influences the polarity. The more alkyl groups present, the more non-polar the amino acid will be. This effect makes valine more non-polar than alanine; leucine is more non-polar than valine.
At pH=7, two are negative charged: aspartic acid (Asp, D) and glutamic acid (Glu, E) (acidic side chains), and three are positive charged: lysine (Lys, K), arginine (Arg, R) and histidine (His, H) (basic side chains).
There are three amino acids that have basic side chains at neutral pH. 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.
An isoelectric point is the pH at which an amino acid exists as its zwitterion. If the pH is higher (in alkaline conditions) than the isoelectric point then the amino acid acts as an acid and donates a proton from its carboxyl group. This gives it a negative charge.
The Twenty Amino Acids
- alanine - ala - A (gif, interactive)
- arginine - arg - R (gif, interactive)
- asparagine - asn - N (gif, interactive)
- aspartic acid - asp - D (gif, interactive)
- cysteine - cys - C (gif, interactive)
- glutamine - gln - Q (gif, interactive)
- glutamic acid - glu - E (gif, interactive)
- glycine - gly - G (gif, interactive)
The nine amino acids that have hydrophobic side chains are glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), isoleucine (Ile), proline (Pro), phenylalanine (Phe), methionine (Met), and tryptophan (Trp). Shown at the right is the structure of valine.
Threonine, an essential amino acid, is a hydrophilic molecule. Threonine is an other hydroxyl-containing amino acid. It differs from serine by having a methyl substituent in place of one of the hydrogens on the β carbon and it differs from valine by replacement of a methyl substituent with a hydroxyl group.
Your body needs 20 different amino acids to grow and function properly. Though all 20 of these are important for your health, only nine amino acids are classified as essential ( 1 ). These are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
L-tryptophan is an essential amino acid that helps the body make proteins and certain brain-signaling chemicals. Your body changes L-tryptophan into a brain chemical called serotonin. Serotonin helps control your mood and sleep.
It also creates niacin, which is essential in creating the neurotransmitter serotonin. There are two types of tryptophan: L-tryptophan and D-tryptophan. The only difference between the two types is the orientation of the molecule. You can get tryptophan through certain foods or a supplement in powder form.
L-tryptophan is used for insomnia, sleep apnea, depression, anxiety, facial pain, a severe form of premenstrual syndrome called premenstrual dysphoric disorder (PMDD), smoking cessation, grinding teeth during sleep (bruxism), attention deficit-hyperactivity disorder (ADHD), Tourette's syndrome, and to improve athletic
Tyrosine is a popular dietary supplement used to improve alertness, attention and focus. It produces important brain chemicals that help nerve cells communicate and may even regulate mood ( 1 ). Despite these benefits, supplementing with tyrosine can have side effects and interact with medications.
Phenylalanine is an amino acid found in many foods and used by your body to produce proteins and other important molecules. It has been studied for its effects on depression, pain and skin disorders.
Threonine, an essential amino acid, is a hydrophilic molecule. Threonine is an other hydroxyl-containing amino acid. It differs from serine by having a methyl substituent in place of one of the hydrogens on the β carbon and it differs from valine by replacement of a methyl substituent with a hydroxyl group.
The sequence of amino acids in the chain determines how the chain will fold up to make the protein, so different proteins have different three-dimensional shapes. This is because proteins form attachments and interact with many other molecules and structures inside organisms.
Lysine is an amino acid (building block of protein). People use it to make medicine. Lysine is used for preventing and treating cold sores (caused by the virus called herpes simplex labialis). It is taken by mouth or applied directly to the skin for this use.
Essential amino acids cannot be made by the body. As a result, they must come from food. The 9 essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
