Disulfides oligomers

Cyclic 1,2-diketones, 24 594 Cyclic acrolein acetals, 2 271 Cyclic amidine curing agents, 10 410 Cyclic amidines, 10 412 Cyclic (aromatic disulfide) oligomers, 23 712... 

Fig. 27 Synthesis of cyclic aromatic disulfide oligomers by copper catalytic oxidation reaction...

In the synthesis of a series of cyclic aromatic disulfide oligomers using oxidative coupling of dithiols with oxygen catalyzed by copper salts and an amine, an effective, easy, and rapid method for the synthesis of macrocyclic aromatic disulfide oligomer from 4,4/-oxybis(benzenethiol) by cyclodepoly-... 

Ding, Y. and Hay, A. S., Cyclic Aromatic Disulfide Oligomers S3mthesis and Characterization, Macromolecules, 29, 6386, 1996. 

Chem. Descrip. Nonylphenol disulfide oligomer Uses Antioxidant tor disproportionation and bleaching rosins and rosin ester, enabling prod, of lighter colored resins for use as adhesive tackitiers and clear coatings (varnishes) decreases tendency of rosins to crystallize improves stability and lightens color of rosin esters Properties Dk. brn. vise, liq. mild sulfur odor sol. in common org. soivs. (methanol, heptane, toluene) sol. < 1% in water sp.gr. 1.03 (15.6 C) vise. 24-34 cSt (100 C) 9.4-10.6% sulfur Ethazate [Uniroyal]... 

Chen and co-workers [13] have carried out studies on the thermal decomposition of aromatic disulfide oligomers using a variety of techniques. 

A simple procedure for strengthening oligomercaptanes uses oxygen. The mechanism of the process is based on formation of thiolanons (RS—), which subsequently yield electrons and transform into the radical RS, which following recombination forms disulfide oligomers [55]. 

Tg measurements have been performed on many other polymers and copolymers including phenol bark resins [71], PS [72-74], p-nitrobenzene substituted polymethacrylates [75], PC [76], polyimines [77], polyurethanes (PU) [78], Novolac resins [71], polyisoprene, polybutadiene, polychloroprene, nitrile rubber, ethylene-propylene-diene terpolymer and butyl rubber [79], bisphenol-A epoxy diacrylate-trimethylolpropane triacrylate [80], mono and dipolyphosphazenes [81], polyethylene glycol-polylactic acid entrapment polymers [82], polyether nitrile copolymers [83], polyacrylate-polyoxyethylene grafts [84], Novolak type thermosets [71], polyester carbonates [85], polyethylene naphthalene, 2,6, dicarboxylate [86], PET-polyethylene 2,6-naphthalone carboxylate blends [87], a-phenyl substituted aromatic-aliphatic polyamides [88], sodium acrylate-methyl methacrylate multiblock copolymers [89], telechelic sulfonate polyester ionomers [90], aromatic polyamides [91], polyimides [91], 4,4"-bis(4-oxyphenoxy)benzophenone diglycidyl ether - 3,4 epoxycyclohexyl methyl 3,4 epoxy cyclohexane carboxylate blends [92], PET [93], polyhydroxybutyrate [94], polyetherimides [95], macrocyclic aromatic disulfide oligomers [96], acrylics [97], PU urea elastomers [97], glass reinforced epoxy resin composites [98], PVOH [99], polymethyl methacrylate-N-phenyl maleimide, styrene copolymers [100], chiral... 

Ding and Hay [664] recently described a new synthesis of P(PS) from 4-bromo-benzenethiol using a free radical initiator, as shown schematically in Eg. 14.11 below The product was found to almost exclusively possess the 1,4-linkage only. Diaryl sulfide initiators used included bis(4-Br-phenyl) disulfide, 2,2 -dithiobis(benz-othiazole) and a cyclic disulfide oligomer (Eg. 14.111. 

Meng Y Z, Tjong S C, Hay A S (2001) S5mthesis of cocyclic(arylene disulfide) oligomers and their adhesion properties as heating-melt adhesive . Polymer, 42(12), 5215-5224. 

Size Isomers. In solution, hGH is a mixture of monomer, dimer, and higher molecular weight oligomers. Furthermore, there are aggregated forms of hGH found in both the pituitary and in the circulation (16,17). The dimeric forms of hGH have been the most carefully studied and there appear to be at least three distinct types of dimer a disulfide dimer connected through interchain disulfide bonds (8) a covalent or irreversible dimer that is detected on sodium dodecylsulfate- (SDS-)polyacrylamide gels (see Electroseparations, Electrophoresis) and is not a disulfide dimer (19,20) and a noncovalent dimer which is easily dissociated into monomeric hGH by treatment with agents that dismpt hydrophobic interactions in proteins (21). In addition, hGH forms a dimeric complex with ( 2). Scatchard analysis has revealed that two ions associate per hGH dimer in a cooperative... 

Potl inhibitors differ from other protease inhibitors, and from all other defense peptides mentioned thus far, in their relative lack of disulfide bonds. This means that the loop with the reactive site is not fixed, as it is in the Bowman-Birk inhibitors, yet they still form a stable fold, as shown in Figure 11. An interesting feature of some Potl inhibitors is their tendency to form stable, noncovalently bound oligomers. This has, for example, been shown for chymotrypsin inhibitor I from tomato. This peptide has a monomer weight of 8300 Da under dissociating sodium dodecyl sulfate (SDS) gel conditions. Gel filtration and ultracentrifugal analysis revealed a... 

I -Disulfide makes cyclic dimers, and linear oligomers via DDAA H-bonding array... 

Oxidation of mono-cysteine peptides to the dimer is a straightforward reaction that can produce only the desired product. In the case of bis-cysteine peptides statistically the oxidation leads to the homodimers in parallel and antiparallel orientation as well as to the disulfide-bridged monomer and oligomers. When the two cysteine residues are placed in the adjacent position formation of homodimers is highly favored over the cyclic monomer (Section 6.1.5.1) and the product distribution depends strongly on the peptide concentration. Such a type of intermolecular disulfide bridging is present in bovine seminal ribonuclease, where an antiparallel alignment occurs at the interface of the dimer. 97 ... 

Fig. 5.2. Structural principles of transmembrane receptors, a) Representation of the most important functional domains of transmembrane receptors, b) Examples of subunit structures. Transmembrane receptors can exist in a monomeric form (1), dimeric form (2) and as higher oligomers (3,4). Further subunits may associate at the extracellular and cytosohc domains, via disulfide bridges (3) or via non-covalent interactions (4). c) Examples of structures of the transmembrane domains of receptors. The transmembrane domain may be composed of an a-hehx (1) or several a-helices linked by loops at the cytosolic and extracellular side (2). The 7-helix transmembrane receptors are a frequently occurring receptor type (see 5.3). Several subunits of a transmembrane protein may associate into an ohgomeric structure (3), as is the case for voltage-controUed ion channels (e.g., K channel) or for receptors with intrinsic ion channel function (see Chapter 17).

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