Amino acids hydroxyl containing

Cysteine is derived from serine by replacing the hydroxyl group with the sulfhydryl group. It is the second protein amino acid that contains sulfur. 

Immobilization of enzymes. Enzymes consist of amino acids which contain reactive groups such as amino(lysine, c-terminus), thiol (cysteine), carbonyl (aspartate, glutamate and c-terminus), aromatic hydroxyl (tyrosine) and aliphatic hydroxyl (serine and threonine). Chemical, ionic or chelation reactions with such groups can enable us to attach the amino acids and hence proteins to insoluble, inert supports. Immobilization is one of the best ways of stabilizing enzymes. There is a vast literature on this subject and the reader is directed to Barker (9) and Goughian et al (10) for further reading on specific systems, techniques and applications of immobilization. 

The other major protein in the extracellular matrix is elastin, which is the main component of elastic fibers found in ligaments, large arteries, and lungs. After synthesis and partial hydroxylation of proline residues, a 72 kDa molecule of tropoelastin is secreted into the matrix. This protein is rich in nonpolar amino acids and contains repeating sequences, such as (Val-Pro-Gly-Val-Gly). These sections form an amorphous, random-coiled structure with frequent reverse turns. Other recurrent sequences are rich in alanine with paired lysine residues, e.g., -Ala-Ala-Ala-Ala-Lys-Ala-Ala-Lys-... 

HU-211 is highly liposoluble, which makes it readily accessible to the central nervous system since it readily crosses the blood brain barrier. However, its poor solubility in water hampers development of formulations suitable for i.v. administration. In order to overcome this drawback, Popp et al. have prepared a series of water-soluble salts of glycinate esters (attached to the allylic hydroxyl) and salts of amino acid esters containing tertiary and quaternary nitrogen heterocyclics (attached to the phenolic hydroxyl) (see Figure 5.5) [201, 202]. Most of the new compounds were relatively soluble in water or 10% aqueous ethanol, and showed neuroprotective properties, attributed to the parent compound, formed on hydrolysis of the esters in vivo. 

Table II summarizes those amino acids that contain more than an un-reactive aliphatic chain, namely a reactive site which may be a functional group in the traditional sense such as sulfhydryl, thiomethyl, hydroxyl, carboxyl, carbamide, amino, or guanido, or may be an activated aromatic ring or heterocycle such as the phenolic part of tyrosine, the pyrrole unit in troptophan, and the imidazole part in histidine. Phenylalanine would only be considered in this connection as the reactive di- or tetrahydro derivative ring. iV-Peptides derived from proline and hydroxyproline are in a separate class because they are tertiary amides carrying no proton at the nitrogen atom. It may be possible to utilize this special feature for a preferential cleavage under proper conditions.

Protein kinases phosphorylate proteins only at certain hydroxyl groups on amino acid side chains. Which of the following groups of amino acids all contain side chain hydroxyl groups ... 

Somewhat similar results were observed for poly(amino acids) which contain the hydroxyl (Ser) 4 (139) and phenoxyl (Tyr) 9 (138) groups in addition to tiie carboxyl group. 

Amino acids can be classified according to their substituent R groups (Fig. 1.2 to Fig. 1.8) in basic amino acids, R contains a further amino group, whereas in acidic amino acids, R contains a further carboxyl group. In addition, there are aliphatic, aromatic, hydroxyl containing and sulfur containing amino acids according to the nature of the substituent, as well as a secondary amino acid. 

Of the three aromatic amino acids phenylalanine, tyrosine and tryptophan, phenylalanine has been classified with the hydrophobic amino acids which have a non-polar side chain and tyrosine with those containing a hydroxyl group. This leaves tryptophan, the largest and rarest of the amino acids which contains the heterocyclic indole nucleus as its bulky R group. Trytophan is the parent compound for the neurotransmitter serotonin which is 5-hydroxytryptamine. 

A condensation reaction is one in which two moiecuies or parts of the same moiecuie combine. A small molecule, such as water, is usually removed during the reaction. An example is the reaction between two amino acids, which contain both amine and carboxyl groups. One hydrogen from the amine group of one amino acid combines with the hydroxyl from the carboxyl group of the other amino acid to form a molecule of water. When repeated many times, this reaction forms a protein molecule. 

Me3SiNEt2- Trimethylsilyldiethylamine selectively silylates equatorial hydroxyl groups in quantitative yield (4-10 h, 25°). The report indicated no reaction at axial hydroxyl groups. In the prostaglandin series the order of reactivity of trimethylsilyldiethylamine is Cii > Ci5 C9 (no reaction). These trimethylsilyl ethers are readily hydrolyzed in aqueous methanol containing a trace of acetic acid. The reagent is also useful for the silylation of amino-acids. ... 

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