Carboxylic acid residues

Marsden BJ, Nguyen TM-D, Schiller PW. Spontaneous degradation via diketopiperazine formation of peptides containing a tetrahydroisoquinoline-3-carboxylic acid residue in the 2-position of the peptide sequence. Int J Peptide Protein Res 1993 41 313-316. 

K. Yeowell O Connell, W. Pauwels, M. Seven, Z. L. Jin, M. R. Walker, S. M. Rappa-port, H. Veulemans, Comparison of Styrene-7,8-oxide Adducts Formed via Reaction with Cysteine, N-Terminal Valine and Carboxylic Acid Residues in Human, Mouse and Rat Hemoglobin , Chem.-Biol. Interact. 1997, 106, 67 - 85. 

The basis of the separation of amino acids by AAA lies in the interaction between acids - present in the elution buffer - and the stationary phase. This resin is made up of small sulfonated polystyrene particles. The negative charge of the sulfonic acid residues is counterbalanced by the Li+ -cations of the elution buffer. As the whole separation process takes place at a weakly acidic pH, the carboxylic acid residues are protonated and the interaction with the stationary phase of the column is achieved by the protonated (and thus positively charged) amino group(s) of the amino acids. The more basic the amino acid is, the stronger the interaction with the stationary phase and - consequently - the longer the retention time. So it is easily understood... 

The enniatins and beauveracin are cyclic hexadepsipeptides and so are 18-membered macrocycles built up of alternating amino acid and carboxylic acid residues. They exhibit lower selectivity than (137) and consequently are more broad spectrum ionophores. The structure of (138)KI has been solved544 but it was not possible to conclude, with certainty, whether the metal is entrapped in the central cavity, as in related cyclic polyether structures (Figure 14a), or whether it occupi.es a site between two adjacent ligand molecules to give an infinite sandwich (147) as has been found in the RbNCS complex of a synthetic ldlldl isomer of (138).545 Adducts of 1 2 sandwich and 2 3 club sandwich stoichiometry have been proposed for Cs+ complexes of (138),546a and the 1 2 K+ sandwich complex of (138) has been proposed as the species which transports K+ across lipid layers as it shields the metal effectively from solvent interactions.5461 ... 

Cl-, SO42-, citrate(3-), oxalate(2-), and other carboxylic acid residues. 

Separate signals for N-alkyl groups syn or (Z) and anti or ( ) to the carbonyl oxygen are observed for N-N-dialkylamides (Table 4.35) [313-315] due to the amide resonance. But the rotational barrier of the CN partial double bond decreases with increasing size of the carboxylic acid residue R [315]. 

Recently, the reduction of an N-terminal pyrrolidone carboxylic acid residue of proteins with diborane in tetrahydrofuran or tetramethyl urea was attempted with some success the N-terminal pyrrolidone carboxylic acid residue may thus be identified by its conversion to proline... 

Special procedures (44) are required for the demonstration of N-terminal pyrrolidone carboxylic acid residues in peptides and proteins frequently, pyrrolidone carboxylyl-peptides can be detected by the procedure of Rydon and Smith (SO). Discovery of enzymes capable of cleaving pyrrolidone carboxylic acid from the N-terminus of peptide chains should facilitate studies of this type (45, 46) (see below). 

The ligands X, usually anions, should consist of groups that have intermediate binding strength to Pt(II), or that are - for other reasons - easily leaving (i.e. by enzymatic activation). Examples are Cl-, SO4- citrate(3-), oxalate(2-) and other carboxylic acid residues. 

Calcium ions, which are essential for catalytic activity [3e], are believed [143] to be linked by a carboxylic acid residue to the Mn aggregate [144], either 3.3 A [128,145] or at least 3.6 A [146] from a Mn. Ca2+ ions are also required in the assembly of the Mn aggregate, at Mn,vMn,v oxidation level [147], Ca2+ depletion or replacement by Sr2+ alters the magnetic interactions within the Mn aggregate as evidenced by variations in the S2 multiline EPR signal, which loses its hyperhne structure (g = 4.1 signal) [142a,148]. 

Seven carboxylic acid residues to be studied were constructed in the cloned A. saitoi 1,2-a-D-mannosidase gene (msdS) by site-directed mutagenesis. The roles of six conserved active... 

There is also a shorthand notation to show the number of carbon atoms and the position of any double bonds in the structure. A fatty acid with 18 carbons and no double bonds is designated 18 0, while one with 18 carbons and two double bonds is 18 2. The carbon atoms in fatty acids are numbered from the carboxylic acid residue, and so the position of double bonds can be described using the number of the first carbon involved in the bond (e.g. A9 shows a... 

The first peptides with an incorporated 4-amino-l,2-dithiolane-4-carboxylic acid residue (Adt), represented by structures 319 <2000BMCL1585>, 320 <2002BMCL147>, and 321 <2005PES104>, were synthesized in order to restrict their conformational mobility and stabilize defined secondary structures, thus making them chemically more stable and biochemically active. 

---