Leucine chemical structure

B 10. In your biochemistry research project, you have isolated a new protein from spinach leaves. You wish to do a Western blot experiment with the protein to help determine its chemical structure and/or biological function. An amino acid analysis of the protein showed a great abundance of phenylalanine, leucine, and valine. What would be your choice of membrane for the blotting experiments ... 

Table 1.2. CHEMICAL STRUCTURES OF CYCLOSPORINS A-Z Bmt = (2S, 3R, 4R, 6 -2-amino-3-hydroxy-4-methyl-6-octenoic acid (= (4R)-4-(( )-2-butenyl)-4-methyI-L-threonine) Abu = L-a-aminobuty-ric acid Nva = L-norvaline MeVal = V-methyl-L-valine MeLeu = A -methyl-L-leucine. 

Isoenzymes or isozymes are enzymes from a single species that have the same kind of enzymatic activity but differ in chemical structure. In addition, they may differ in quantitative characteristics such as possessing different Km s with the same substrate and may differ in response to temperature and effectors. Isozymes of more than 100 enzymes have been demonstrated in humans. The most important of these for diagnostic purposes are the isozymes of LDH, CK, alkaline phosphatase, leucine aminopeptidase, acid phosphatase, and aldolase. These have been exploited for differential organ diagnosis. 

Leucine aminopeptidase is an enzyme for which the most systematic and detailed computational studies regarding enzyme-inhibitor interactions have been performed.54,56-73,74 This results both from the availability of the crystal structure of LAP with bound inhibitors, including phosphonic acid analogue of leucine -LeuP (structure encoded as llcp in PDB, Figure 8-4), and from the existence of binding data for many LAP inhibitors. Such a set of experimental results enabled to evaluate the effectiveness of theoretical methods both empirical and quantum chemical in designing and activity prediction of LAP inhibitors. 

Scheme 4 Chemical structures of poly(y-benzyl-L-glutamate)-b-poly(ethylene glycol)-b-poly(y-benzyl-L-glutamate) (PBLG-PEG-PBLG), poly(y-benzyl-L-asparate)-b-poly(ethylene glycol)-b-poly(y-benzyl-L-asparate) (PBLA-PEG-PBLA), poly(ethylene glycol)-b-poly(L-alanine) (PEG-PLA) and poly(ethylene glycol)-b-poly(DL-valine-co-DL-leucine) (PEG-poly( valine-co-leucine))...

Although leucine and isoleucine have different chemical structures (see below), they have the same atomic composition so their mass is the same and the mass spectrometer sees them as the same. 

Application of Global Sequence Similarity to Find an Inhibitor of Acetolactate Synthase. Acetolactate synthase (ALS) Is the site of action of sulfonylurea, Imldazollnone, and trlazolo pyrimidine herbicides (10-14). Their mode of Inhibition and binding sites on ALS were ambiguous, because (1) these herbicides bear no obvious similarity In their chemical structures to those of ALS substrates (pyruvate and acetolactate), cofactors (thiamine pyrophosphate, FAD, and Mg ) and effectors (valine, Isoleuclne, and leucine) and (2) they Inhibit ALS In a mode too complex to be analyzed. 

FIGURE 8.21 Chemical structure of the copoly(ester amide) based on L-lysine and L-leucine amino adds that has been developed to prepare microspheres for oral insulin delivery. 

Frequently dimethylallyl residues are attached to compounds with other chemical structures (see above). They may form additional rings as in ageratochro-mene, a compound isolated from the plant Ageratum haustoniatum with anti-juvenile hormone activity in insects (E 5.5.3). Isovaleric acid and 3,3-dimethyl-acrylic acid, which have been found in higher plants, are thought to be products of leucine metabolism (D 14). 

Surfactin is a cyclic lipopeptide produced by B. subtilis.The chemical structure consists of several variants differing in their fatty acid chain and their peptide moiety.They comprise a peptide loop of seven amino acids (t-asparagine, L-leucine, glutamic acid, L-leucine, L-valine and two D-leucines), and a a, -hydroxy C13-C15 fatty acid chain (Figure 14.7). 

Figure 7 Peptide sequences and chemical structures of amino acids and fluorophores. Shown are the sequences for peptides TBQ, TH2, TFl, and TF2 and structures of y3-alanine (single amino acid code B), the fluorescence donor NBD, and acceptor TAMRA. Leucine residues replaced by hexafluoroleucine in the peptide sequences are indicated in green.

Figure 4.7 Chemical structures of the amino acids L- //o-isoleucine (L-aiLe), D-leucine (D-Leu), L-norvaline (L-Nva), D-methionine (D-Met), L-2-aminobutyric acid (L-Abu) and D-norleucine (D-Nle).

The chemical structures of these peptides were established in the usual way by quantitative amino-acid analysis and sequence analysis by a combination of chemical and enzymic methods, including dinitrophenylation, dansylation, Edman degradation, hydrazinolysis and digestion with leucine aminopeptidase and carboxypeptidases A and B. The Neutral Protease peptides of the salmine and iridine components or derivatives thus identified are listed in Table VIII-6 with their recovery values. Differences in the amino-acid sequences and amounts of the peptides obtained from iridine I aroused the suspicion that two molecular species (a and b) were present in the iridine I component. This result, as already described, was supported by observations on the thermolysin peptides of iridine I. 

The stability of peptides is generally increased when natural amino acids are substituted by fluorinated analogs (e.g., tri- or hexafluoroleucine, hexafluorova-line). Such stabilization augments with the number of hexafluoroleucine residues introduced [77]. Native-like structure was preserved, but the peptides had a more structured backbone and less fluid hydrophobic core. Substitution of four leucine residues by trifluoroleucines in the leucine zipper peptide GCN4-p1d led to a substantial gain in thermal stability and resistance to chemical denaturation of the... 

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