Peptides construction

The conformational preferences of mixed /9-peptides containing both /9 - and /9 -amino acid residues in their sequence differ markedly from that of the corresponding homopolymers consisting exclusively of /9 - or /9 -amino acid residues. Several types of mixed /9-peptides have been investigated including block peptides constructed with triads of /9 -amino acid residues and triads of /9 -amino acid residues (e.g. 93) [104,161], as well as alternating peptides of jf lff type (e.g., 72,... 

Scheme 13. Conjugate addition of cysteine thiol group to the maleiimido functionality for the synthesis of protein-peptide constructs...

Besides drug delivery, liposomes have also gained wide acceptance in other fields such as diagnostic imaging (4,5) and vaccines. In this chapter we will focus our attention specifically on the conjugation of peptides to liposomes. We will outline the major techniques involved, present some applications of liposomes-peptides constructs, and mainly discuss their use as vaccines. 

TAT liposomes remain intact within one hour of translocation and slowly migrate through the cell, bypassing the endocytic pathway, to the perinuclear zone where they disintegrate (95). The mechanism utilized by TAT to migrate across the membrane was thought to be energy independent because it operates at similar rates at both 4°C and 37°C (95,96). Cell entry by TAT is also unhindered by metabolic inhibitors such as sodium azide or iodoacetamide (97). Peptides constructed of both the d and l amino acids of Antp can be detected intracellularly, the inference of which is that no specific receptor was required because both isomers had equal potential (98,99). 

Synthesis of (Aminomethyl)benzoic Acid Peptides Construction and Protection of (Aminomethyl)benzoic Acid... 

The frequently observed difficulties in the activation of u,p-didehydropeptides, especially in the case of AAla, can be avoided by peptide construction using the corresponding (1-sub-stituted amino acids and subsequent p-elimination in the peptide)158-161 A further possibility is the phosphonate condensation, where the corresponding, modified phosphorylglycine esters can react with aldehydes to yield u,p-didehydropeptidesII5l l62 IM (Scheme 26). 

Kragol, G. and Otvos, LJ. (2001) Orthogonal solid-phase synthesis of tetraman-nosylated peptide constructs carrying three independent branched epitopes. Tetrahedron 57, 957-966. 

Oonk, H.B., Turkstra, J.A., Schaaper, W.M., et al. (1998) New GnRH-like peptide construct to optimize efficient immunocastration of male pigs by immunoneutral-ization of GnRH. Vaccine 16(11-12), 1074-1082. 

The main goal of this chapter is to describe the synthesis details of complex, orthogonally protected peptide constructs. Thus, major emphasis is placed on the peptide chain assembly design and practice and the alterations from the solid-phase synthesis of simple, nonmodified peptides. The technology for peptide purification and quality control is not significantly different from that of other peptides, and these methods will be just briefly described. Many chapters of this book focus on the optimization of HPLC and MALDI-MS procedures for peptide separation and analysis and illustrate the expected and/or acceptable quality control parameters. 

After purification, lyophilize the peptide constructs and check their purity on analytical HPLC and MALDI-TOF mass spectroscopy. The conventional matrix for peptide mass spectroscopy, a-cyano-4-hydroxycinnamic acid, appears to work properly for the vaccine constructs. While it is less frequently used in standard peptide chemistry (and thus not detailed here), the size of these multiple peptide antigens allows quality control by SDS-PAGE as shown in Fig. 2. For this purpose we recommend the use of 16.5% precast peptide gels. These gels tend to break easily, so be careful during gel handling. 

Kragol, G., Otvos, L Jr., Feng, J., Gerhard, W and Wade, J.D. (2001) Synthesis of a disulfide-linked octameric peptide construct carrying three different antigenic determinants. Bioorg. Med. Chem. Lett. 11,1417-1420. 

Olive C, Batzloff MR, Horvath A, Wong A, Clair T, Yarwood P, Toth I, Good MF (2002) A lipid core peptide construct containing a conserved region determinant of the group A streptococcal M protein elicits heterologous opsonic antibodies. Infect Immun 70(5) 2734-2738... 

Zeng W, Jackson DC, Murray J, Rose K, Brown LE (2000) Totally synthetic lipid-containing polyoxime peptide constructs are potent immunogens. Vaccine 18(11-12) 1031-1039... 

Chimeras synthesized by tandem linkage (see Subheading 3.1.1.) is the quantitatively dominant form of construct studied to date. The relative ease of synthesis using conventional methodologies (see Chapter 1) is one explanation for the relative abundance of tandem constructs. A brief discussion of homo- and hetero-dimeric peptides constructed by the covalent crosslinking of monomers is also provided, in Subheading 3.1.2. 

The phrase chimeric peptide is widely used in the literature for unnatural peptide constructs consisting of bioactive compounds from at least two different peptides and/or proteins or two sequences from different parts of the same protein. Such multifunctional peptide combinations are prepared to enhance the biological activity or selectivity of their components. New biological effects can also be achieved with chimeric constructs. A chimeric peptide composed of... 

In this chimeric peptide construct the aim was to combine the carrier function and immunstimulatory activity of tuftsin derivatives with an epitope derived from HSV gD to achieve an increased antibody response. Tuftsin is a well-known natural tetrapeptide (TKPR) that has a pronounced effect on the immune system (28,29). Polymerized tuftsin (polytuftsin) is also considered as a carrier molecule that increased antibody levels against attached epitopes in mice (30,31). New, sequential oligopeptides based on repeated tuftsin derivatives (H-[Thr-Lys-Pro-Lys-Gly]n-NH2, where n = 2,4,6,8) were developed in our laboratory to eliminate the drawbacks of tuftsin derivatives produced by polymerization. These new, nontoxic, nonimmunogenic compounds have immunostimulatory activity and a minor chemoattractant effect on monocytes (32). An oligotuftsin derivative was used in this study for the synthesis of a peptide chimera containing an HSV peptide epitope. 

If PNA effects are measured a long time after the first treatment, additional quantities of PNA-peptide construct can be exogenously added to maintain intracellular PNA concentration. This is the case when the target mRNA of the PNA sequence encodes a protein with a long half-life. 

Fig. 2.1. a. Basic chemical structure and stereochemistry of L-amino acids, b. Polymeric structure of proteins and peptides constructed from monomeric units. 

The DNA strands were first reported by Brenner and co-workers to define the sequence of a peptide constructed on a solid support. Upon completion of the synthesis, an on-bead assay was performed. Whereas each bioactive peptide was defined by a unique DNA sequence, the decoding process simply involved amplification of the code by the polymerase chain reaction followed by sequencing. This technique marked the beginning of the tagging method for encoded split synthesis. Sequenceable peptide strands are an alternative to DNA encoding. The code is read by HPLC of the Edmon degradation phenylthiohydantoin amino acid derivatives, a well-developed microsequencing method. 

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