Polypeptide coating

Since the uptake of particles in nasal epithelial tissue is known to be mostly mediated by M cells, nasal administration has been investigated as a noninva-sive delivery of vaccines [37], However, since the uptake of naked DNA by endocytocis is limited, use of either nanoparticles as mucosal delivery systems [37] or hypotonic shock [38] is reported for the efficient transfection of gene and vaccine into the nasal epithelium. It was also reported that polypeptides and polypeptide-coated nanospheres (diameter about 500 nm) are transported through endocytic process in rat M cells [39],... 

Very high optical yields of up to 93% have been reported for the oxidation of re/t-butyl phenyl sulfide with a polypeptide-coated Pt electrode (Scheme 21) (47). 

FIG U RE 6.10 ATR FT-IR spectra of polypeptide-coated P(NiPAM-co-MAA) microgels. Adapted from Ref [18], copyright 2012, with permission from the American Chemical Society. 

The asymmetric unit contains one copy each of the subunits VPl, VP2, VP3, and VP4. VP4 is buried inside the shell and does not reach the surface. The arrangement of VPl, VP2, and VP3 on the surface of the capsid is shown in Figure 16.12a. These three different polypeptide chains build up the virus shell in a way that is analogous to that of the three different conformations A, C, and B of the same polypeptide chain in tomato bushy stunt virus. The viral coat assembles from 12 compact aggregates, or pen tamers, which contain five of each of the coat proteins. The contours of the outward-facing surfaces of the subunits give to each pentamer the shape of a molecular mountain the VPl subunits, which correspond to the A subunits in T = 3 plant viruses, cluster at the peak of the mountain VP2 and VP3 alternate around the foot and VP4 provides the foundation. The amino termini of the five VP3 subunits of the pentamer intertwine around the fivefold axis in the interior of the virion to form a p stmcture that stabilizes the pentamer and in addition interacts with VP4. 

In all jelly roll barrels the polypeptide chain enters and leaves the barrel at the same end, the base of the barrel. In the viral coat proteins a fairly large number of amino acids at the termini of the polypeptide chain usually lie outside the actual barrel structure. These regions vary considerably both in size and conformation between different coat proteins. In addition, there are three loop regions at this end of the barrel that usually are quite long and that also show considerable variation in size in the plant viruses and the... 

Figure 16.17 The subunit structure of the bacteriophage MS2 coat protein is different from those of other sphericai viruses. The 129 amino acid polypeptide chain is folded into an up-and-down antiparallei P sheet of five strands, P3-P7, with a hairpin at the amino end and two C-terminai a helices. (Adapted from a diagram provided by L. Liijas.)...

A SEC material should be hydrophilic if it is to be used for biological applications. One such material, introduced by PolyLC in 1990 (8), is silica with a covalently attached coating of poly(2-hydroxyethyl aspartamide) the trade name is PolyHYDROXYETHYL Aspartamide (PolyHEA). This material was evaluated for SEC of polypeptides by P.C. Andrews (University of Michigan) and worked well for the purpose (Fig. 8.1). Because formic acid is a good solvent for polypeptides, Dr. Andrews tried a mobile phase of 50 mM formic acid. The result was a dramatic shift to a lower fractionation range for both Vq and V, (Fig. 8.2) to the point that V, was defined by the elution position of water. 

It should be noted that in forming this dimeric channel structure all the hydrogen bonds are parallel to the channel axis and that the inner surface is lined with the polar polypeptide groups. In addition the various lipophilic side chains coat the outer wall of the structure and are thus in contact with the lipid hydrocarbon chains. The resulting gramicidin A channel is a most efficient means of ion transport with approximately 107 sodium ions traversing the channel per second, under conditions of 1 M NaCl, 100 mV applied potential and a temperature of 25 °C 225). The detailed mechanism by which this can be achieved is under active study 226). 

Clathrin-coated vesicles mediate transport from the Golgi apparatus to endosomes, and from the plasma membrane to endosomes. A multi-subunit protein, clath-rin, constitutes the major protein of this vesicle type (see Ch. 2). Clathrin is composed of three large and three small polypeptide chains, which assemble to form a triskelion (Fig. 9-2). Regulatory mechanisms control the assembly and formation of a convex, polyhexa-pentagonal basketlike structure by these triskelions [5], This structure is responsible for the formation of coated pits on the cytosolic face of plasma membranes. 

C. Porta, S. Dossena, V. Rossi, M. Pinza, and D. Cremaschi. Rabbit nasal mucosa Nanosphere coated polypeptides bound to specific anti-polypeptide IgG are better... 

Kamande, M. W., Zhu, X., Kapnissi-Christodoulou, C., and Warner, 1. M. (2004). Chiral separations using a polypeptide and polymeric dipeptide surfactant polyelectrolyte multilayer coating in open-tubular capillary electrochromatography. Anal. Chem. 76, 6681—6692. 

Ferritin, found in plants, animals, and some bacteria, serves as a reserve of iron for iron-proteins, such as those of respiration, photosynthesis, and DNA synthesis, as well as providing a safe site for detoxification of excess iron. The structure of ferritin, unique among proteins, is a protein coat of multiple, highly conserved polypeptides around a core of hydrous ferric oxide with variable amounts of phosphate. 

The Protein Coat. Twenty-four polypeptides assemble into a hollow sphere, of ca. 100-120 X in outer diameter, to form the protein coat of ferritin. The diameter of the interior, which becomes filled with hydrous ferric oxide, is ca. 70-80 A. Subunit assembly appears to be spontaneous the coat remains assembled even without the iron core. Subunit biosynthesis is actually controlled by the amount of iron to be stored by a cell the subunit templates (mRNAs) are stored in the cytoplasm of a cell in a repressed form and are recruited for biosynthesis when the concentration of iron increases (3). 

---