Thiol amphiphile

Glycosidic thiol groups can be introduced into glycosyl bromides by successive reactions with thiourea and aqueous sodium disulfite (D. Horton, 1963 M. Cemy, 1961, 1963). Such thiols are excellent nucleophiles in weakly basic media and add to electrophilic double bonds, e.g., of maleic esters, to give Michael adducts in high yields. Several chiral amphiphiles have thus been prepared without any need for chromatography (J.-H. Fuhrhop, 1986 A). 

Self-assembled monolayers of amphiphilic molecules have been deposited at surfaces since Langmuir and Blodgett developed their dip coating deposition method in 1937.4 These were briefly discussed in Chapter 10 in relation to thiol... 

These possibilities rectify the proposed subsequent appearance and amplification of chiral autocatalytic molecules and hypercydes. [190] Any autocatalytic systems would propagate [191] throughout an extensive adjoining hydrated porous network already rich in layered amphiphiles, lipids, polymeric materials, amino acids, thiols, and so forth. In addition, amphiphiles are known to be organized into lipid membranes by interaction with the inner surfaces of porous minerals. [136] It is a small organizational jump from these membranes to frilly formed lipid vesides. 

Maleimide-functionalized peptides react quantitatively with thiols and thus with di-fatty acid substituted thioglycerol, a fact which facilitates purification of the amphiphilic lipopeptide derivatives by simple precipitation as required for separation of the excess lipid building block (Scheme 16).t163 164 167l... 

Electron-poor thiols such as amphiphilic perfluorinated thiols with a perfluori-nated chain in a-position to the thiol group are not able to reduce Aum and to form the Au -SR polymer. On the other hand, when thiols like HS-F8-PEG (Fig. 4.7), are used in the thiolate form, water-soluble AuNPs protected by a monolayer that... 

Figure 4.7 Structure of the amphiphilic fluorinated thiol used for the synthesis of water-soluble AuNPs.169...

Figure 4.8 Functional thiols used to form mixed monolayers in combination with the amphiphilic thiol HS-C8-TEGME.197...

Experimental studies reported by Lucarini et al.216 are in agreement with the hypothesis of the existence of an increasingly available space between thiols upon reduction of the diameter of the NPs. In this investigation, ESR spectroscopy has been used to study the interaction of an amphiphilic nitroxide radical with the mono-layer of water-soluble protected gold clusters having a core diameter between 1.6 and... 

Figure fO.2 compares the optical properties and hydrodynamic sizes of CdTe quantum dots (2.5 nm) coated with a traditional amphiphilic pol3mier (octylamine-modihed polyacrylic acid) or the mixed thiol/amine multidentate ligand. Although the amphiphilic pol3mier and the multidenate ligand were prepared from the same molecular-weight polyacrylic acid backbone, the... 

Thus, the toxicity of DMM is mediated by its dealkylation. Cleavage of the carbon-mercury bond generates MMM metabolites, which can form covalent bonds with cellular ligands with amphiphilic properties. The mercury center reacts with sulfur and sulfur-containing thiol groups of enzymes and thereby inhibits them. The metal center of DMM acts as a soft acid, and binds tightly to polarizable donor atoms in soft bases. Within cells, mercury may interact with a variety of proteins, particularly microsomal and mitochondrial enzymes. This can severely impair cell function. 

The extension and wide application of this work has come from the work of Chatgilialoglu and co-workers on the use of (Me3Si)3SiH as a hydrogen donor suitable for water-soluble and water-insoluble precursors, in systems comprising substrate, silane and initiator (ACCN) mixed at 100 °C. This system was proposed as it worked well for both hydrophilic and hydrophobic substrates, with the only variation that an amphiphilic thiol was also needed in the case of water-soluble compounds (Scheme 4.10).25... 

The molar fractions of oxo (thiono) and hydroxy (thiol) tautomers for a series of monohydroxy- and monomercapto-substituted pyridines, quinolines, and acridines were calculated from the acid-base constants of these compounds at the isoelectric points in an amphiphilic medium (80ZOR1499). 

The isomer trends of the models were very useful for helping the identification of isomers. Cell cultures of human leukemia cell lines (THP-1) were incubated in the absence and presence of thiol compounds, ensuring that no trans compounds could come from the medium [45]. In parallel experiments, some millimolar levels of thiol compounds were added to the cell cultures during incubation, and the comparison of isomeric trends was carried out. A basic content of trans lipids in THP-1 cell membranes could be found during their growth without thiol, and after the addition of the amphiphilic 2-mercaptoethanol, it increased to 5.6% of the main fatty acid residues. Moreover, when a radical stress by y-irradiation is artificially produced in the cell cultures added with thiol, a larger isomerization effect could be seen, with trans lipid formation up to 15.5% in membrane phospholipids. The fatty acid residues most involved in this transformation were arachidonate moieties, as expected. 

Particles of the enzymatically synthesized phenolic polymers were also formed by reverse micellar polymerization. A thiol-containing polymer was synthesized by peroxidase-catalyzed copolymerization of p-hydroxythiophenol and p-ethylphenol in reverse micelles [70], CdS nanoparticles were attached to the copolymer to give polymer-CdS nanocomposites. The reverse micellar system was also effective for the enzymatic synthesis of poly(2-naphthol) consisting of qui-nonoid structure [71], which showed a fluorescence characteristic of the naphthol chromophore. Amphiphilic higher alkyl ester derivatives were enzymatically polymerized in a micellar solution to give surface-active polymers at the air-water interface [72, 73]. 

Stabilization of a lipid membrane onto a solid support by covalent attachment also provides the physical stability necessary for the development of practical sensors. An oriented membrane can be prepared by allowing self-assembly of individual amphiphilic molecules onto a solid surface through either the reaction of terminal silane moieties with a hydroxylated surface to form a silyl ether [33,34], or by the reaction of sulfur-terminated compounds (alkylthiols or disulfides) with gold surfaces [35,36]. A variety of species, both with and without polar head groups, have been deposited onto surfaces such as glass, quartz, silicon, and gold [37-39]. These include phospholipids, fatty acids, and fatty amines which were synthetically altered so as to contain either a silyl chloride or a thiol moiety at the terminus of the acyl chain [40]. Both monolayers... 

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