Carbodiimide, comparison with

Dolinnaya, N.G. Sokolova, N.I. Ashirbekova, D.T. Shabarova, Z.A. The use of Bren for assembling modified DNA duplexes and DNA-RNA hybrids—Comparison with water-soluble carbodiimide. Nucl. Acids Res. 1991, 19 (11), 3067-3072. 

Polymers with intramolecular cross-links have organized spatial structures, and are good models for the tertiary structure of proteins (26,27,1 ). In the studies discussed here poly Glu52Lys33Tyr15 (No. 3) was internally cross-linked with Woodward s reagent K or ionic carbodiimide and fractionated on Sephadex G-100. The number of cross-links in each fraction was determined by amino acid analysis. In addition, the parent polymer was fractionated in the same way to provide standards for comparison with the cross-linked polypeptides. 

Active esters commonly used in solution (e.g., o-nitrophenyl and iV-hydroxy-succinimide) [148] have limited applicability in the solid phase, primarily because of their low reactivity in comparison with carbodiimide-based methods. Thus, coupling reactions typically require a reaction time of 8-18 h... 

Since the result of the saponification of the methyl ester of immobilized 4-iso-cyanatomethyl butanoate was not proven directly by XPS the free acid group was reacted with 4-amino-TEMPO using the carbodiimide method. The immobilized 4-amino-TEMPO leads to an ESR signal characterized by reduced molecular motion in comparison with an uncoupled spin probe as a control sample [133], Consequently, the modified PCU/PVA surface is suitable for the immobilization of the fibronectin fragment GRGDS via the M-terminus [147]. A pepide content of 8 to 15 nmol cm on the PVC/PVA surface immobilized with GRGDS was verified by means of amino acid analysis. 

Hirano et al. [150, 151] immobilized several peptides, RGDS, on ethylene-acrylic acid copolymer (EAA, acrylic acid content 20 wt%) film by reacting the amino-terminal of the peptide with the carboxylic acid of the copolymer with the aid of a water-soluble carbodiimide, to form EAA-co-NH-RGDX. Their objective was to examine effect of the fourth residue, X, on the cell-attachment activity of the tetrapeptide, RGDX, where X is S, V and T. They also examined the activity of RGD, YIGSR and YIGSR-NH2 for comparison. The cell lines used were ovary CHO-K1 cell (Chinese hamster), kidney NRK cell... 

Cyclic carbodiimide 48 theoretically exists as two conformational isomers. Comparison of the coupling constant values, calculated using AMI Hamiltonian and Karplus relationship, with the experimental vicinal coupling constants of 8.33 and 1.05 Hz, undoubtedly prove its methyl-out structure 48 <1996JOC4289>. 

Poly(isoimide)s received interest as intermediates for Pis, because the ring closure of the poly(amic acid) runs faster with carbodiimides, e.g., di-cyclohexylcarbodiimide, in comparison to acetic anhydride. " However, the use of a carbodiimide yields the isoimide moiety exclusively, whereas acetic anhydride yields the ordinary imide. However, by the treatment with suitable isomerizing agents, such as 1-hydroxyhenzotriazole, or 3-hydroxy-l,2,3-benzotriazin-4-one, the isoimide can he converted to the imide. This technique is suitable for the synthesis of Uquid thermosetting maleimide resins. 

A comparison of mechanosynthesis with other synthetic methods showed the superiority of microwave-assisted method and solution conditions over mechanoehemical and ultrasound reactions for the less-reactive carbodiimides. More-reactive carbodi-imides provide full conversion under aU conditions, while best yields were obtained in MW and solution reactions (entries 6 and 7). 

The experimental dipole moments of carbodiimides, such as 55 and 56, have been of interest primarily in connection with the question of their molecular structures (1(>). Comparisons between experimental and calculated dipole moments confirmed that the carbodiimides have no planar structures, but have their substituents in perpendicular planes (16). 

In a somewhat similar work, Hoare and Koshland investigated the kinetics of the reaction between glycine methyl ester, N-benzyl-N -3-di-methylamino-propyl carbodiimide, and various enz3nnes in l.OM acetate buffer at pH 4.75 (29). A comparison of the present results with their data is given in Table IV. It can be seen that their results tend to confirm the present findings. 

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