Polypeptide systems

Fortunately, it was found that in polypeptide systems the effective dimensionality of conformational spaces is significantly smaller than the dimensionality of the full space, with only a few principal axes contributing to the projection [38-41]. In fact, in many cases a projection quality of 70-90% can be achieved in as few as tliree dimensions [42], opening the way for real 3D visualization of molecular conformational space. Figure 8... 

The polymer may behave as a weak acid ion exchange resin. Branched copolymers have also been proposed as an approach to achieving "smoother" release patterns for polypeptide systems (40). 

Historically, after the development of oligopeptide-based vesicles, several groups developed and characterized vesicles using polypeptide hybrid systems consisting of polypeptide and synthetic polymer blocks [17-19]. Soon thereafter, vesicles formed entirely from polypeptides, such as poly(L-lysine)-h-poly(L-leucine) and poly(L-lysine)-h-poly(L-glutamate), were developed [20, 21]. This review will focus on recent developments in the formation of vesicles composed of polypeptide hybrid or polypeptide systems, as well as the potential promise of these systems as effective dmg delivery vehicles. A specific example of a polypeptide-based vesicle is shown in Fig. 1, where the hydrophobic segment is a-helical and the hydrophilic segment is a random coil. 

For comparison with these data, the types of salt effects that have been observed for model protein and polypeptide systems that achieve true thermodynamic equilibrium in solution can be summarized into three classes ... 

Other photochromic polypeptide systems have been described, in which the ability to photocontrol the specific conformation of polypeptides is an essential feature in the design of biomaterials for devices that can be photo switched. 

If amyloid fibrils and other self-assembling polypeptide systems are to be developed as new materials and components for nanotechnology and biomedicine, it is important that we understand the pathways and kinetics of their assembly. It will also be desirable to be able to control this assembly and any subsequent disassembly. 

Surfaces can do more than stimulate the growth of amyloid fibrils the presence of a surface during assembly can also influence fibril morphology. Fibril diameter has been observed to be smaller on surfaces than in the bulk for some polypeptide systems (Zhu et al., 2002). This may be due to the constraints imposed by the surface or could result from a different mechanism of fibril growth. The shape of fibrils formed on surfaces can also differ to the shape of fibrils formed in the bulk solution. 

Chirality Induced Through Association with Polypeptide Systems... 

Horton, J. C., and Donald, A. M. (1991). Gelation in a synthetic polypeptide system. In Food Polymers, Gels and Colloids, Dickinson, E. (Ed.), pp. 508-512. Royal Chem. Soc., London. 

Vitamin B6 enzyme models that can catalyze five types of reactions - transamination, racemization, decarboxylation, P-elimination and replacement, and aldolase-type reactions - have been reviewed. There are also five approaches to construct the vitamin B6 enzyme models (i) vitamin B6 augmented with basic or chiral auxiliary functional groups (ii) vitamin B6 having an artificial binding site (iii) vitamin B6-surfactant systems (iv) vitamin B6-polypeptide systems (v) polymeric and dendrimeric vitamin B6 systems. These model systems show rate enhancement and some selectivity in vitamin B6-dependent reactions, but they are still primitive compared with the real enzymes. We expect to see improved reaction rates and selectivities in future generations of vitamin B6 enzyme models. An additional goal, which has not received ade-... 

In these relatively simple polypeptide systems, therefore, the experimental studies so far performed suggest at least a crude correlation between the capacity of a solvent to disrupt polypeptide helices and the capacity of a solvent to form strong hydrogen bonds, although in special cases electrostatic and lyophobic interactions also appear to be involved. There is little apparent correlation whth any other independent property of the solvents. 

Crystalline ribonuclease (Fig. 19) was chosen as a model for the selective cleavage of tyrosine peptide bonds in more complex polypeptide systems (Cohen and Wilson, 1961). Although on addition of NBS the ultraviolet spectral intensities at 260 m/i reached 80 % of theory, cleavage of the six... 

Fig. 11. Comparison of theoretical curves, which describe the thermal helix-coil transition of a polypeptide system as a function of chain length, with experimental points obtained for poly-->-benzyl-i,-glutamate polymers of varying degrees of polymerization, n. In this solvent mixture, ethylene dichloride and dichloroacetic acid, the helical form, characterized by the more positive rotations, is stable at higher temperatures. The manner in which increased length sharpens the transition, both in theory and in actuality, is here clearly illustrated. For comparative purposes, Tc is defined as the temperature at the mid-point of the transition for the sample of highest molecular weight. (Zimm et al., 1959.)...

Influence of Water. Even in desiccated corneum there is a weak, broad endotherm centering at about 120°-130°C as well as the higher temperature doublet melts at 194 °C and 210 °C. Both melts appear to be somewhat lower in temperature for corneum than for wool, which is consistent with the accepted higher degree of orientation and helical content of wool. The 130°C transition has been reported in other polypeptide systems by DSC, IR, and x-ray diffraction where it was found to be highly moisture sensitive (67). It has been suggested that this endothermic process which occurs between 110° and 150 °C in a number of polypeptide systems is a partial conversion from the alpha-... 

Detailed analyses of the vibrational spectra of raacromolecules, however, have provided a deeper understanding of structure and interactions in these systems (Krimm, 1960). An important advance in this direction for proteins came with the determination of the normal modes of vibration of the peptide group in A -methylacetamide (Miyazawa et al., 1958), and the characterization of several specific amide vibrations in polypeptide systems (Miyazawa, 1962, 1967). Extensive use has been made of spectra-structure correlations based on some of these amide modes, including attempts to determine secondary structure composition in proteins (see, for example, Pezolet et al., 1976 Lippert et al., 1976 Williams and Dunker, 1981 Williams, 1983). 

Since Av and A are measurable quantities, and the dfi/dr can be calculated by quantum-mechanical methods (Cheam and Krimm, 1985) (see Section V11,B,3), it is possible to evaluate from experiment the internal consistency of the TDC hypothesis for explaining band splittings in polypeptide systems. For (Gly) I, Moore and Krimm (1976a) found that amide 1 splittings could be accounted for by TDC using ) Afxl = 0.348 D oriented at 20° to the CO bond. From Eq. (77) we hnd that, for vq = 1672 cm (Moore and Krimm, 1976a), this corresponds to... 

Analogous photoresponsive peptide and polypeptide systems are being developed the photochemical properties of poly[W -p-(phenyl-azo)benzoyl-L-a,/8-diaminopropionic acid] have been examined, and the first example of photoregulation of permeability across a membrane has been achieved by the use of a new polyvinyl/poly-peptide graft copolymer composed of a photoresponsive copolypeptide branch from /3-p-phenylazobenzyl L-asparate and /3-benzyl L-asparate attached to a poly(Bu methacrylate) backbone.Papain activity has similarly been regulated by anchoring a photo-responsive azo group to the enzyme backbone. ... 

As described above, the C. purpurea LPS complex is unique among eukaryotes in having its activities divided between two different polypeptides. In its two-polypeptide nature, LPS resembles some prokaryotic peptide synthetases such as tyrocidine synthetase and gramicidin synthetase. However, unlike the prokaryotic peptide synthetases consisting of two polypeptides, the available DNA sequence of cppl (Tudzynski et al., 1999) indicates that its product does not begin with a recognizable condensation domain, as would be typical of the receiving synthetase of a dual-polypeptide system (Marahiel et al., 1997 von Dohren et al., 1997). 

Although palladium on polypeptide systems mentioned above are heterogeneous, homogeneous system may be realized by the complexadon of ruthenium(HI) ion to poly(S-glutamic acid), which was found effective as catalyst for the asymmetric hydrogenation of methyl acetoacetate (Hirai, Aikawa, Furuta (7)). 

C Nmr investigations of proteins and/or polypeptide systems can be classified into three general categories (1) 1 3C chemical shifts and spin lattice relaxation times of native and specifically labelled or 13C-enriched proteins and subunits (2) helix-coil transitions of polypeptides and (3) binding studies, protein-substrate interactions and complex formation. 

We have been studying model polypeptide systems with an a-helical main chain in which a variety of nonnatural aromatic amino acids are incorporated [27-32]. Similar studies on polypeptides carrying aromatic amino acids have been reported from other laboratories [33-42]. The polypeptide systems have the following unique characteristics ... 

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