Polypeptide solids

So far, mainly OM has been used to directly observe in real time the nucleation and growth of ordered polypeptide solid ellipsoidal structures in thin solution films. Detailed characterization of these ellipsoidal structures will be given in this section. In particular, more information will be presented on how these structures form at the molecular level, and about the forces that lead to formation of ellipsoidal ordered structures with an aspect ratio of about 2. It will also be explained how two different populations of ordered structures can be generated in a single film. 

Fig. 111. Absorption spectra of oriented films of some synthetic polypeptides. Solid line electric vector of radiation perpendicular to direction of rolling dashed line electric vector parallel to direction of rolling (Ambrose and Elliott, 1951a).

The major disadvantage of solid-phase peptide synthesis is the fact that ail the by-products attached to the resin can only be removed at the final stages of synthesis. Another problem is the relatively low local concentration of peptide which can be obtained on the polymer, and this limits the turnover of all other educts. Preparation of large quantities (> 1 g) is therefore difficult. Thirdly, the racemization-safe methods for acid activation, e.g. with azides, are too mild (= slow) for solid-phase synthesis. For these reasons the convenient Menifield procedures are quite generally used for syntheses of small peptides, whereas for larger polypeptides many research groups adhere to classic solution methods and purification after each condensation step (F.M. Finn, 1976). 

Section 27 18 In the Memfield method the carboxyl group of an ammo acid is anchored to a solid support and the chain extended one ammo acid at a time When all the ammo acid residues have been added the polypeptide is removed from the solid support... 

Solid phase peptide synthesis (Section 27 18) Method for peptide synthesis m which the C terminal ammo acid is co valently attached to an inert solid support and successive ammo acids are attached via peptide bond formation At the completion of the synthesis the polypeptide is removed from the support... 

One widely used method involving protected compounds is solid-phase synthesis (polymer-supponed reagents). This method has the advantage of requiring only a simple workup by filtration such as in automated syntheses, especially of polypeptides, oligonucleotides, and oligosaccharides. 

Kubota S, Easman GD (1975) Beta-conformation of polypeptides of valine, isoleucine, and threonine in solution and solid-state - optical and infrared studies. Biopolymers 14 605-631... 

Schlaad H, Smarsly B, Losik M (2004) The role of chain-length distribution in the formation of solid-state structures of polypeptide-based rod-coil block copolymers. Macromolecules 37 2210-2214... 

ELPs can be produced via chemical synthesis and biosynthetically. For chemical synthesis via solid phase peptide synthesis, the attainable polymer length is limited, and if long polymers with a defined length are required then the biosynthetic approach is more appropriate. An advantage of chemical synthesis is, however, that it enables the facile introduction of functional residues in the polypeptide [27]. 

Pardaxin, a marine neurotoxic polypeptide isolated from the secretion of the flatfish Pardachirus marmoratus or synthesized by the solid phase method, is a single chain, acidic, amphipathic polypeptide with... 

The techniques for automated solid phase synthesis were first highly developed for polypeptides and the method is abbreviated as SPPS. Polypeptide synthesis requires the sequential coupling of the individual amino acids. After each unit is added, it must be deprotected for use in the next coupling step. 

Over the past decade the techniques of combinatorial synthesis have received much attention. Solid phase synthesis of polypeptides and oligonucleotides are especially adaptable to combinatorial synthesis, but the method is not limited to these fields. The goal of combinatorial synthesis is to prepare a large number of related... 

---