Amides 2,4-disulfide

The efficacy of MS to characterize effectors of Drosophila immunity and Phormia (also referred in the literature as Protophormia) terranovae is illustrated by several examples. This will not follow a chronological order but is in accordance with the complexity of the MS analyses. MS allowed (i) to define precise molecular masses, to identify post-translational modifications (N-terminal cyclisation, C-terminal amidation, disulfide bonds array, glycosylation), (ii) to determine primary structures of immune peptides (sequencing by MS/MS), (iii) to have mass fingerprints and to identify peptide effectors that are part of Drosophila immunity (molecular mass differential display by MALDI-MS),... 

Figure 28 A tetra-amide-disulfide porph)Tin synthesized by Beer and coworkers for attachment to gold nanoparticles throngh ligand substitution.

Thiocyanates can often be utilized as intermediates in the Reparation of other sulfur-containing compounds, alkylthiocarbonic acid amides, disulfides, mercaptans, sulfides, and sulfonic acids. Typical reactions are as follows ... 

Phosphoms trichloride and pentachloride form sodium chloride and sodium phosphide, respectively, in the presence of sodium. Phosphoms oxychloride, POCl, when heated with sodium, explodes. Carbon disulfide reacts violendy, forming sodium sulfide. Sodium amide (sodamide), NaNH2, is formed by the reaction of ammonia gas with Hquid sodium. SoHd sodium reacts only superficially with Hquid sulfur dioxide but molten sodium and gaseous... 

Thermal Stability. Dimethyl sulfoxide decomposes slowly at 189°C to a mixture of products that includes methanethiol, formaldehyde, water, bis(methylthio)methane, dimethyl disulfide, dimethyl sulfone, and dimethyl sulfide. The decomposition is accelerated by acids, glycols, or amides (30). This product mixture suggests a sequence in which DMSO initially undergoes a Pummerer reaction to give (methylthio)methano1, which is labile and reacts according to equations 1—3. Disproportionation (eq. 4) also occurs to a small extent ... 

Lipoic acid exists as a mixture of two structures a closed-ring disulfide form and an open-chain reduced form (Figure 18.33). Oxidation-reduction cycles interconvert these two species. As is the case for biotin, lipoic acid does not often occur free in nature, but rather is covalently attached in amide linkage with lysine residues on enzymes. The enzyme that catalyzes the formation of the lipoamide nk.2Lg c requires ATP and produces lipoamide-enzyme conjugates, AMP, and pyrophosphate as products of the reaction. 

In these papers, the carboxylic acid to be protected was a stable, unsubstituted compound. Harsh conditions were acceptable for both formation and cleavage of the amide. Typically, a simple secondary amide is very difficult to cleave. As the pKa of the conjugate acid of an amide decreases, the rate of hydrolysis of amides derived from these amines increases. The dimethylamide of a cephalosporin was prepared as follows using 2,2 -dipyridyl disulfide. ... 

A disulfide bond between cysteine residues in different peptide chains links the otherwise separate chains together, while a disulfide bond between cysteine residues in the same chain forms a loop. Such is the case, for instance, with vasopressin, an antidiuretic hormone found in the pituitary gland. Note that the C-terminal end of vasopressin occurs as the primary amide, -CONHz, rather than as the free acid. 

The carbanion 5, formed from V,V-diethyl-5-phenyl-3//-azepin-2-amine (4) with potassium amide in liquid ammonia, or with lithium 2,2,6,6-tetramethylpiperidide in tetrahydrofuran, is thiolated by dialkyl or diaryl disulfides to yield 3-(alkylsulfanyl)-3//-azepines, e.g. 6.38... 

Sea snake short-chain toxins have a molecular weight of only 6,800. The small size with four disulfide bonds makes these toxins very compact and stable molecules. Therefore, when the Pelamis platurus toxin is subjected to heat treatment at 100 C and subsequent cooling, it does not change its conformation substantially. Amide I and ni bands and S-S stretching vibration did not change by heat treatment. 

Carbodi-imides are used to mediate the formation of amide linkage betwen a carboxylate and an amine or phosphoramidate linkages between a phosphate and an amine [12]. The following is essentially the method of Rockwood [13] and is modified to give a phospho-diester link between the terminal monophosphate of the oligonucleotide and the hydroxyl group of 2-hydroxyethyl disulfide (HEDS) [14]. 

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