Peptide as attractants

Since the first report of the nonequivalence phenomenon, approximately 40 chiral substances have been reported to induce enantiomeric nonequivalence in the NMR spectra of a host of solutes. These CSAs are encountered in subsequent discussions. Two qualities considered to be essential in the design of the first reported experiment (3) are evident in nearly all CSA-solute combinations. In all cases, the CSA and the solute have the common feature of complementary functionality, which permits their interaction. Both are in general hydrogen bond donors or acceptors the CSAs are acids, amines, alcohols, sulfoxides, or cyclic compounds such as cyclodextiins, crown ethers, or peptides, which attractively interact with appropriate enantiomeric solutes, engendering different spatial environments for their nuclei. In nearly every case the CSA contains a group of high diamagnetic anisotropy near its asymmetric center, a feature... 

As mentioned above, the rectal route is very attractive for systemic delivery of peptide and protein drugs, but rectal administration of peptides often results in very low bioavailability due to not only poor membrane penetration characteristics (transport barrier) but also due to hydrolysis of peptides by digestive enzymes of the GI tract (enzymatic barrier). Of these two barriers, the latter is of greater importance for certain unstable small peptides, as these peptides, unless they have been degraded by various proteases, can be transported across the intestinal membrane. Therefore, the use of protease inhibitors is one of the most promising approaches to overcome the delivery problems of these peptides and proteins. Many compounds have been used as protease inhibitors for improving the stability of various peptides and proteins. These include aprotinin, trypsin inhibitors, bacitracin, puromycin, bestatin, and bile salts such as NaCC and are frequently used with absorption enhancers for improvement in rectal absorption. 

An asymmetric version of a Michael addition with nitrogen nucleophiles can be also realized with simple short-chain peptides as catalysts. This has been demonstrated by Miller et al. for the addition of an azide to a,/(-unsaturated carbonyl compounds [16]. In the presence of the tripeptide 9 as a catalyst (2.5 mol-%) the products 10 have been formed in excellent yields and with up to 85% ee (Scheme 7). In addition, this reaction represents an attractive access to /(-amino acids. 

The stereo- and regiospecificity of proteases and the possibility of reversing the proteolysis into peptide bond formation between essentially unprotected amino acids or peptides has attracted the attention of peptide chemists since the early days of this field of research.f l Thus, a search was launched for enzymes suitable as biocatalysts for peptide bond formation in a manner independent of the nature of the individual amino acids, and for media in which proteolysis is optimally reversed into ligase activity. This led to a state of the art for this particular methodology that can be competitive with chemical methods for short peptides and in selected cases may even be superior in terms of economical industrial-scale preparations (for details see Section However, to overcome the intrinsic problem of... 

Anticancer peptides have attracted concern recently due to their characteristics features such as multifunction, high sensitivity, and stability. There are number of publications on anticancer peptides from food protein, such as fish sauce (Lee et ah, 2004), soy protein (Kim et ah, 2000),... 

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