Amide functionalized networks

Figure 28 Stabilization of the phosphonateTSAforthe hydrolysis of esters, by a network of H bonds involving H35 histidine and amide functions of the principal chain of antibody CNJ206.

We realized, however, that if the polyesteramides merely acted as multi 2-hy-droxypropyl-amide functional polymers, they could never provide good flow and optical appearance of the coatings. From the mathematical theory of network formation [24] it is known that a binder formulation with a 2-functional resin and a crosslinker bearing many (> 5) functional groups reaches its gel-point at low chemical conversion, as shown in Fig. 21. 

In a recent NMR study, Derenne et al.(77) obtained evidence for non hydrolyzable amide structures in refractory fractions of the algae Scenedesmus quadricauda. The solid-state NMR spectra showed a major peak around -260 ppm for amides accompanied by a peak around -195 ppm for substituted pyrroles and a shoulder at -235 ppm assigned to unsubstituted pyrroles of the insoluble residue. The authors suggest, that the amides are protected by association with long polymethylenic chains within a macromolecular network. Knicker and Hatcher offer an alternative explanation,- that protection of amide functional groups as part of proteinaceous material are affected by encapsulation within the macromolecular matrix forming sedimentaryhumic material(7.. ... 

Amide functional groups are ubiquitous in nature due to their abundant presence in small or complex synthetic, natural or biological molecules [1], They also play a very important role in structural chemistry due to their ability to form complementary supramolecu-lar synthons [2, 3]. The importance of N-H- -O hydrogen bonds is well established in protein folding and conformations of nucleic acids. Some examples of hydrogen bonded networks which are formed in the secondary structure of proteins are depicted in Scheme 7.1 [4]. They also play an important role in synthetic polymers such as nylon 6,6, nylon 6 and Kevlar (Scheme 7.2). 

Post-synthetic modification of CMPs opens up a wide range of new functionality that can be incorporated. A strategy recently adopted by Ratvijitvech et al. is to design in functionality specifically for post-synthetic modification. A CMP building block with a pendant amine group was synthesised, which was subsequently used for reaction with anhydrides to produce a series of amide-functionalised networks. ... 

Figure 13 NMR and structural data supporting a hydrogen bonding network in cyclotides linking a conserved Glu residue in loop 1 (Glu7) with backbone amides of loop 3. (a) pH titration of selected residues in kalata Bl. Proton chemical shifts for the amide protons of Asnl5 and Thrl6 are plottted as a function of pH. These residues display a marked pH dependence as a result of the protonation of Glu7. (b) The hydrogen bond network is highlighted in the NMR structure of kalata Bl.

Nguyen et al. have recently examined the structure-directing properties of the hydroxyl group, which would appear to be a useful supramolecular functionality capable of forming strong, predictable O-H O networks such as that illustrated in synthon IV [34]. The structures of a number of new urea and oxal-amide derivatives (8-10) were found, however, to exhibit considerable variation... 

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