Amines, monolayers

The schematic model of the film deposited by the technique is shown in Figure 45. A single-stranded DNA layer is sandwiched between two aliphatic amine monolayers. Thus, the technique can be useful for our objectives, for it allows depisition of single-stranded DNA on practically any substrate and does not demand a large quantity of DNA, since only one monolayer will be deposited. Nevertheless, there is a question of whether DNA in such a structure will hybridize. In fact, the film contains a single-stfanded DNA monolayer between two amine monolayers, and it is questionable whether the upper amine monolayer will prevent hybridization with complementary DNA stfands. 

XPS has been of use in revealing the oxidation of MC species in LB films. For example with films containing CdS, constructed from a mixed BeH/octadecyl amine monolayer on a subphase of stabilized CdS particles, only one oxygen state was found (79). By contrast, three oxygen states were found for the colloid in solution, indicating that the CdS in the film is protected from oxidation. This result correlated well with an observation that copper sulfide made in an LB film is resistant to oxidation when compared to copper sulfide prepared analogously in solution (9). The decomposition, via oxidation, of PbS made in films of StH has been followed by XPS (68,70). One study found that the decomposition rate of PbS was much slower for films deposited at faster rate (70). It was suggested that films deposited at the faster deposition rate were more ordered and this presented a barrier to PbS decomposition via oxidation. 

The change from calcite to vaterite nucleation on stearate films at low [Ca] suggests that the extent of Ca binding is important for polymorph selection. The nucleation of calcite is favored by the formation of a well-defined Ca-carboxylate layer that mimics the first layer of the (110) face of the unit cell. By contrast, the structural requirements for vaterite formation are less precise. This is consistent with vaterite being the dominant phase on amine monolayers where no Ca binding is present, and suggests that kinetic factors of charge accumulation... 

Cottington, R. L., Levine, O., Zisman, W. A., "Effects of Adsorbed Water and Surface Roughness of Glasses of Various Compositions on the Friction and Wear Properties of Adsorbed Fatty Acid and Amine Monolayers," 134th Meeting, ACS, Chicago, III., September 1958. 

Forced peptide synthesis, formation of an amide bond by physically pushing the reactants together. A plasma-oxidized flat PDMS stamp inked with an N-Boc-L-amino acid was pressed into contact with an amine monolayer on gold to form an amide bond. Following this approach, an RGD peptide ( Arg-Gly-Asp ) was synthesized and shown to support cell adhesion, and a 20-mer peptide nucleic acid ( PNA) strand was synthesized step-by-step on the surface and proven to hybridize with a 16-mer dsDNA [T. P. Sullivan et al., Angew. Chem. Int. Ed. 2004, 43, 4190]. 

Because of the charged nature of many Langmuir films, fairly marked effects of changing the pH of the substrate phase are often observed. An obvious case is that of the fatty-acid monolayers these will be ionized on alkaline substrates, and as a result of the repulsion between the charged polar groups, the film reverts to a gaseous or liquid expanded state at a much lower temperature than does the acid form [121]. Also, the surface potential drops since, as illustrated in Fig. XV-13, the presence of nearby counterions introduces a dipole opposite in orientation to that previously present. A similar situation is found with long-chain amines on acid substrates [122]. 

Deposited monolayers of such RX-type compounds as fatty acids and amines can be extremely tenaciously held, as evident for example, in frictional wear experiments (see Section XII-7) and in their stability against evaporation under... 

Most LB-forming amphiphiles have hydrophobic tails, leaving a very hydrophobic surface. In order to introduce polarity to the final surface, one needs to incorporate bipolar components that would not normally form LB films on their own. Berg and co-workers have partly surmounted this problem with two- and three-component mixtures of fatty acids, amines, and bipolar alcohols [175, 176]. Interestingly, the type of deposition depends on the contact angle of the substrate, and, thus, when relatively polar monolayers are formed, they are deposited as Z-type multilayers. Phase-separated LB films of hydrocarbon-fluorocarbon mixtures provide selective adsorption sites for macromolecules, due to the formation of a step site at the domain boundary [177]. 

From what you know about wetting, contact angles, and spread monolayers, explain why a Langmuir-Blodgett layer will deposit as a F type if there are nonpolar fatty acids, yet will switch to a Z-type deposition if bipolar alcohols or amines are added (see Refs. 175, 176). What defines the critical contact angle for the deposition change ... 

A monolayer of the pyridine-substituted alkyl merocyanine (12) was prepared in the 1970s (67), and a noncentro symmetric multilayer stmcture of merocyanine amphiphiles was later prepared (68) using derivatives, but introducing long-chain amines as the counter layer in an ABABAB system (69,70). 

Alternate-layer LB films (Y-type, ABAB) of long-chain amines and fatty acids maybe used for pyrroelectric appHcations (Fig. 5). Stearylamine, C gH2yNH2, and a series of straight-chain fatty acids, yield a thick film (several hundreds of monolayers) which gave a pyrroelectric coefficient of - 0.05 nC/(cm -K) (72). A coefficient of 0.3 nC/(cm -K) for an 11-monolayer sample of CO-tricosenoic acid and docosylamine C22H4 NH2 has been reported (73). 

Direct measurements on metals such as iron, nickel and stainless steel have shown that adsorption occurs from acid solutions of inhibitors such as iodide ions, carbon monoxide and organic compounds such as amines , thioureas , sulphoxides , sulphidesand mer-captans. These studies have shown that the efficiency of inhibition (expressed as the relative reduction in corrosion rate) can be qualitatively related to the amount of adsorbed inhibitor on the metal surface. However, no detailed quantitative correlation has yet been achieved between these parameters. There is some evidence that adsorption of inhibitor species at low surface coverage d (for complete surface coverage 0=1) may be more effective in producing inhibition than adsorption at high surface coverage. In particular, the adsorption of polyvinyl pyridine on iron in hydrochloric acid at 0 < 0 -1 monolayer has been found to produce an 80% reduction in corrosion rate . 

In this method DNA was attached to a preliminarily formed monolayer of octade-cylamine (or hexadecylamine). The technique is based on the fact that at neutral pH, DNA is charged negatively while amine groups are positive (Frommer et al. 1970). Analysis of the film suggests that DNA in such a film is in a single-stranded form (Sukhorukov et al. 

DNA solution (25 mg/mL) was used as a subphase. Octadecylamine monolayer was spread at the subphase surface and compressed to the surface-pressnre valne of 15 mN/m. The adsorption of DNA at the amine head groups was performed for 1 hour. Then the layer was compressed to 30 mN/m and the film was transferred onto solid snbstrates. 

The surface shear viscosity of a monolayer is a valuable tool in that it reflects the intermolecular associations within the film at a given thermodynamic state as defined by the surface pressure and average molecular area. These data may be Used in conjunction with II/A isotherms and thermodynamic analyses of equilibrium spreading to determine the phase of a monolayer at a given surface pressure. This has been demonstrated in the shear viscosities of long-chain fatty acids, esters, amides, and amines (Jarvis, 1965). In addition,... 

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