Covalent amidation

FIGURE 4.2 The a-COOH and groups of two amino acids can react with the resulting loss of a water molecule to form a covalent amide bond. (Irving Geis.)... 

NH2 (Lysine, arginine) -COOH active ester epoxy electrostatic covalent -> amide... 

The first report of surface-immobilized dendrimers was in 1994 [54]. Subsequently, our research group showed that the amine-terminated PAMAM and PPl dendrimers could be attached to an activated mercaptoimdecanoic acid (MUA) self-assembled monolayer (SAM) via covalent amide linkages [55, 56]. Others developed alternative surface immobilization strategies involving metal com-plexation [10] and electrostatic binding [57]. These surface-confined dendrimer monolayers and multilayers have found use as chemical sensors, stationary phases in chromatography, and catalytic interfaces [41,56,58,59]. Additional applications for surface-confined dendrimers are inevitable, and are dependent only on the synthesis of new materials and the development of clever, new immobilization strategies. 

Hybrid MIPs. More recently, hybrid imprinting strategies have been developed that combine the advantages of both the covalent and noncovalent imprinting strategies (Whitcombe et al. 1995 Lubke et al. 2000). A recent example by Whitcombe s group is presented in Scheme 15.4 (Klein et al. 1999). The monomer-template prepolymerization complex is formed via a combination of covalent amide bonds and... 

Physical and Chemical Integrity of Proteins. The primary sequence of proteins and peptides is comprised of L-amino acids linked together by covalent amide bonds. Substituent group polarity and/or charge is a critical determinant of secondary and tertiary structure and stability. Secondary structures (a-helices and P-sheets) arise from hydrophobic, ionic, and Van der Waals interactions that fold the primary amino acid chain upon itself. Most therapeutic proteins exhibit tertiary structure vital to functionality and are held together by covalent and noncovalent bonding of secondary structures (Figure 5.2). 

While Tetrahymena must have lipoic acid in its diet, we humans can make our own, and it is not considered a vitamin. Lipoic acid is present in tissues in extraordinarily small amounts. Its major function is to participate in the oxidative decarboxylation of a-oxoacids but it also plays an essential role in glycine catabolism in the human body as well as in plants.295 296 The structure is simple, and the functional group is clearly the cyclic disulfide which swings on the end of a long arm. Like biotin, which is also present in tissues in very small amounts, lipoic acid is bound in covalent amide linkage to lysine side chains in active sites of enzymes 2963... 

Peptide. An organic molecule in which a covalent amide bond is formed between the a-amino group of one amino acid and the a-carboxyl group of another amino acid, with the elimination of a water molecule. 

Scheme 6.2). For some functional groups such as amines, the covalent amidation functionalization is likely accompanied by significant noncovalent interactions or strong adsorption of the functional groups on the nanotube surface, thus substantially improving some properties of the functionalized nanotube samples (such as excellent water solubility for a hydrophilic functionalization agent16).

The development of newer separation techniques, in particular preparative gas and liquid chromatography, has broadened the scope of resolution in recent years. An alternative to the acid-base salt separation by crystallization, for example, would be formation of the covalent amide linkage, chromatographic separation of the diastereomers, and then chemical hydrolysis. 

Amino acid polymerization requires elimination of a water molecule as the carboxyl group of one amino acid reacts with the amino group of another amino acid to form a covalent amide bond. The repetition of this process with many amino acids yields a polymer, known as a polypeptide. The amide bonds linking amino acids to each other are known as peptide bonds. Each amino acid unit within the polypeptide is referred to as a residue. The sequence of amino acids in a protein is dictated by the sequence of nucleotides in a segment of the DNA in the chromosomes and the uniqueness of each living organism is due to its endowment of specific proteins. 

This compound is the product of oxidation of the enamine by any one of the following oxidizing agents on enzymes most commonly by the dithiolane ring of lipoic acid covalently amidated to a lysine side chain in the 2-oxoacid dehydrogenase multienzyme complexes less frequently by FAD in the pyruvate oxidases — these come in two flavors, forming acetate in Escherichia coli and forming acetylphosphate in L. plantarum, finally by NAD. ... 

Which groups on amino acids react to form a peptide bond Peptides are formed by linking the carboxyl group of one amino acid to the amino group of another amino acid in a covalent (amide) bond. Proteins consist of polypeptide chains the number of amino acids in a protein is usually 100 or more. The peptide group is planar this stereochemical constraint plays an important role in determining the three-dimensional structures of peptides and proteins. 

First, the KE2 antibody is thiolated using iV-succinimidyl-S-acetyl thioacetate in dimethyl strlfoxide. The succinimide group is coupled to the primary amines on the protein (antibody) which leads to the formation of covalent amide bonds with the loss of hydroxy succinimide. The sulfhydryl group is thus protected. The deprotection, through deacetylation, is carried out using EDTA and hydroxyl... 

In the specific case of nanotubes, biofunetionalization for enhanced compatibility has been an area of rapid growth during recent years (154). Several studies have focused on the binding of proteins to SWNT via noncovalent and covalent functionalization schemes. For example, Dai et al. (155) have adsorbed pyrene onto the side-walls of SWNT and then have made the succinimidyl ester group react with the amine groups in the lysine residues of the proteins to form covalent amide linkages. Similarly, MWNT have been functionalized with 4-hydroxynonenal to induce adsorption of the 4-hydroxynonenal antibody (156). 

The prodrug, acyl methyl phosphate benzylpenicillin (96), can release ben-zylpenicillin by hydrolysis of the acyl phosphate (half-life 90 h at pH 7.5 and 25°C). Moreover, (96) can also interact with yff-lactamase by two mechanisms it can either be a substrate, with the hydroxyl group of serine-70 of )8-lactamase cleaving the lactam ring or can act as an irreversible inhibitor. The amino side-chain of Lys-234, which normally stabilizes the carboxylate group of the antibiotic, can react at the acyl group to form a covalent amide bond to the protein, with methyl phosphate as the by-product [108]. 

Self-organization processes proceeding in IPECs are not timited by the nanometer scale, pronouncedly manifesting themselves on the scale corresponding to mesostructures and in bulk. The self-organization can lead to the selective formation of highly ordered structures. An example of such a stracture is stoichiometric IPEC formed by PA anions and protonated linear poly(ethylene imine) (PEI) cations. The study of chemical transformatirais in such macromolecular co-assemblies provided evidence that more than about 80% (mol) of interpolymer salt bonds can be converted to covalent amide braids, as illustrated by Scheme (11) ... 

NO. Non-covalent, biotin-streptavidin link between the aptamer CS and the chromatographic support C covalent, amide bond for the aptamer CS immobilization to the chromatographic support AMP, ADP, ATP adenosine mono, di, tri-phosphate nd Not determined... 

Denaturation of a protein occurs when there is a change that disrupts the interactions that stabilize the secondary, tertiary, or quaternary structure. However, the covalent amide bonds of the primary structure are not affected. 

Covalent amide bonds can be formed between polymer chains during to the presence of-COOH and -NH groups, which is not common in synthetic polymer fibers. 

---