Alanine grafting

Fig. 6 Reaction scheme of covalent alanine grafting onto polypropylene surfaces...

The obtained L-a-alanine grafted polymer 49 was further reacted with p-nitrophenyl ester-containing bases, according to the procedure mentioned earlier. From the NMR and UV spectra, the polymers obtained were found to contain about 98% adenine units 50 (A-Ala-PEI) and about 100% thymine units for polymer 51 (T-Ala-PEI). 

When poly(L-alanine)-grafted silica is applied for separation of PAHs in a reversed phase mode, we can encounter various specific selectivities. For example, 0=10.4 was obtained for a mixture of p- and o-terphenyls, while a= 1.5 in ODS. Both p- and o-terphenyls possess the same numbers in carbon atoms and rr-electrons, but the molecular planarity is entirely different. As indicated in the Corey-Pauling-Koltun (CPK) models of Fig. 7A,p-terphe-nyl is a little twisted (almost planar), but more slender (linear) than o-terphenyl. No similar enhancement of the selectivity is observed in poly(L-leucine)- and poly(L-phenylalanine)-grafted silica. These polypeptides show, rather, similarity to ODS e.g., 0=1.7 in poly(L-leucine)-grafted silica. 

Similar results were obtained when polyethylene was modified by grafting acrylamide and cholesterol ester of N-methacryloyl-[3-alanine to get 0.3 + 0.1 mg UChD/ cm2. The efficiency of UChD bound to polymer was close to that of UChD immobilized in a polyacrylamide gel the graft copolymers sorbed from the plasma solution the amount of 0.9 mg heparin/mg of immobilized UChD. The clotting time of blood contacting the modified (but not heparinized) polyethylene was 6 min, whereas on its heparinization the time increased to 30 minutes. The latter figure was actually unaltered after sixfold repetition of the heparin sorption, subsequent washing heparin off the polymer and its repeated sorption. 

Alanine or Cysteine Grafting. The PP surface modified with y-aminopropyltrimethoxysilane and glutaraldehyde was incubated in a solution consisting of 1.0 g of alanine or cysteine dissolved in 10 ml of doubly distilled water for a period of 3 hours. The, the film was washed with water and methanol and dried. 

The 2-carboxyethyl derivatives of nucleic acid bases were further grafted onto the monomeric graft polymers of L-a-amino acids on linear polyethylenimine (Table 18). The synthetic route to the graft polymers containing L-o-alanine and nucleic add bases is shown in Scheme 14. 

N-Carbobenzyloxy-L-a-alanine was condensed with linear polyethylenimine in the presence of DCC to give polymer 48, Cbz-Ala-PEI. The protective group of polymer 48 was removed by HBr in acetic acid to yield the grafted polymer 49, HBr-Ala-PEI. This polymer was found to be grafted almost quantitatively as determined by elemental analysis and the NMR spectrum. The IR spectrum suggested the presence of an amide bond. 

Jin L, Wells JA (1994) Dissecting the energetics of an antibody-antigen interface by alanine shaving and molecular grafting. Protein Sci 3(12) 2351-2357... 

L. Jin and J.A. Wells, (1994). Dissecting the Energetics of an Antibody-Antigen Interface by Alanine Shaving and Molecular Grafting. Protein Sci. 3, 2351-2357. 

Both in the case of gastrin (53,97) and CCK (64,102) it was known that N-terminal modifications do not affect their bioactivity profile. Correspondingly, the N-terminus of gastrin and CCK was used for grafting the lipid moiety via the thiol/maleimide approach. For this purpose p-alanine was chosen as spacer of the maleimide group since the methylene moiety allows for sufficient flexibility without displacing too much the peptide chain from the double-tailed lipid. This fact was expected to allow more appropriate mimicry of natural lipids and thus, a better interdigitation with lipid bilayers. 

These polymers consist of a synthetic polymer backbone onto which amino acids or peptides are grafted as side chains. Examples of materials with amino acids as side chains have been found to exhibit polyelectrolytic and metal complexation behaviour. Such systems include polymethacrylamides with glycylglycine and phenylalanine (Methenitis, 1994), as well as alanine, aspartic acid, asparagine, glutamic acid, and lysine (Morcellet-Sauvage, 1981 Morcellet, 1982 Lekchiri, 1987). 

---