Amino acids containing

In a typical experiment 105 mg (0.50 mmol) of 3.8c, dissolved in a minimal amount of ethanol, and 100 mg (1.50 mmol) of 3.9 were added to a solution of 1.21g (5 mmol) of Cu(N03)2 BH20 and 5 mmol of ligand in 500 ml of water in a 500 ml flask. -Amino-acid containing solutions required addition of one equivalent of sodium hydroxide. When necessary, the pH was adjusted to a value of 5 ( -amino acids) and 7.5 (amines). The flask was sealed carefully and the solution was stirred for 2A hours, followed by extraction with ether. After drying over sodium sulfate the ether was evaporated. Tire endo-exo ratios were determined from the H-NMR spectra of the product mixtures as described in Chapter 2. 

The key enzyme in this sequence, isopenicillin N synthase (IPNS), has been purified from E. coli (59) and the recombinant enzyme shown to be a single polypeptide of 336 amino acids containing two cysteines, numbers 106 and 255 from the /V-teiminus, and probably a ferrous ion in a nonheme environment. The enzyme has been crystallized and studies undertaken to obtain suitably sized crystals for diffraction studies. 

From a chemical point of view, the common amino acids are all weak polyprotic acids. The ionizable groups are not strongly dissociating ones, and the degree of dissociation thus depends on the pH of the medium. All the amino acids contain at least two dissociable hydrogens. 

Wade, D., et al., 1990. All-o amino acid-containing channel-forming and-biodc peptides. Proceedings of the National Academy of Sciences U.S.A. 87 4761-4765. 

Histidine, one of the 20 natural amino acids, contains an imidazole ring. 

Arginine, the most basic of the 20 common amino acids, contains a guanidino functional group in its side chain. Explain, using resonance structures to show how the protonated guanidino group is stabilized. 

As noted in Section 23.2, molecules containing NH2 and COOH groups can undergo condensation polymerization. Amino acids contain both groups in the same molecule. Hence, two amino add molecules can combine by the reaction of the COOH group in one molecule with die NH2 group of the other molecule. If the adds involved are different, two different structural isomers are possible ... 

A modified 1,4 diketone 17 was employed for the microwave-assisted preparation of amino acids containing the pyrrole ring (Scheme 6). The products were further employed for the introduction of this original moiety into a peptide sequence [33]. 

Two ferredoxins were isolated and purified from D. vulgaris Miyazaki. Fdl, the major form, contains two redox centers with distinct behavior and a high sequence homology to D. africanus Fdlll (73). The protein is a dimer of a polypeptide chain of 61 amino acids with 7 cysteines. D. vulgaris Miyazaki Fdll is a dimer of 63 amino acids, containing 7 cysteines but only one [4Fe-4S] cluster (73-75). 

Amino acids belong to the first category. As its name implies, an amino acid contains an amine and a carboxyl group. Amino acids join through amide linkages ... 

Coupling constants are routinely used to determine the side-chain conformation of amino acids in peptides and proteins. Whereas proteins nowadays are almost exclusively studied as C- and N-labeled isotopomers, peptides usually have these isotopes in natural abundance, i.e. the magnetically active heteronuclei are highly diluted. Most amino acids contain a methylene group at the ji-position for which the X angle is determined by the conformation of the Ca—Cp bond. Two vicinal Jhh coupling constants can be measured Ha to and H to Usually... 

Cyclic citrullinated peptide A circular peptide (a ring of amino acids) containing the amino acid citrulline. Autoantibodies directed against cyclic citrullinated peptide provide the basis for a test of importance in rheumatoid arthritis. 

Amino acids containing nucleobases like uracil and adenine, as well as imidazole, such as / -(uraciM-yl)-a-alanine, j5-(adenin-9-yl)-a-alanine, and j8-(imidazol-l-yl)-a-alanine, can also be polycondensed by CDI in aqueous imidazole buffer solution at pH 6.8 at 0 °C. The polycondensation leads to low conversion (yields of polymer 1% after four days), but pure polypeptides resulted from the reaction. Thus, compared to other alternative procedures for polycondensation, that using CDI proved to be the most effective 503... 

Amino acids containing nucleobases were polycondensed by means of CDI as indicated in the following examples [52]... 

Phenylthiocarbamoyl derivatives of 18 chiral amino acids were separated on a C8 column connected in series to a phenylcarbamoylated (3-cyclodextrin column (Iida et al., 1997). The Cg column separated the derivatized amino acids from one another entering the chiral column. Under this configuration several enantiomers of adjacent amino acids coeluted resulting in poor resolution. However, this configuration was successful in determining the amino acid sequence and chirality of the amino acids in a D-amino acid containing peptide. 

The molar ellipticity of these dendrimers was found to increase proportional to the number of chiral end groups. This is to be expected, in the absence of interactions between the terminal tryptophane moieties. No higher-generation dendrimers of this type have been reported. Other amino-acid-containing chiral dendrimers have been described by Meijer et al. who attached various amino acid derivatives to the periphery of poly(propylene imine) dendrimers (see Sect. 3) and more recently by Liskamp et al. (modification of polyamide dendra) [22] and Ritter et al. (synthesis of grafted polymerizable dendrimers containing L-aspartic acid components) [23]. 

An amino acid contains both an amine group and a carboxyl group. 

The amino acid contains a small amount of ammonium chloride, which can be removed by dissolving the product in 21 times its weight of water and precipitating it by the addition of 42 times its weight of absolute ethyl alcohol (Note 5). The mixture is allowed to stand overnight in a refrigerator. The amino acid... 

Dixon, D. A., and W. N. Kipscomb. 1976. Electronic Structure and Bonding of the Amino Acids Containing First Row Atoms. J. Biol. Chem. 251, 5992-6000. 

Enhancements in the sensitivity with which amino acids containing a primary amine group can be determined have been achieved by derivatization. Chen and Sato [37] reported derivatization with divinyl-sulfone-reduced limits of detection by several orders of magnitude, while Lee and Nieman [38] reported derivatization with dansyl-chloride-reduced limits of detection by a factor of three. 

Two protected 3-amino acids, containing indolizidine and quinolizidine skeletons (607a,b), have been synthesized by using 1,3-dipolar cycloaddition of nitrones (551) and (552) to methyl ( )-5-mesyloxy-2-pentenoate. The key steps of this approach is demonstrated by novel syntheses of indolizidinone and quino-lizidinone derivatives (606a,b) and by the ring opening of the tricyclic 1,3-dipolar cycloaddition products (605a,b) (Scheme 2.268) (779). 

---