Polypeptide chemical structures

The question whether silk fibroin filaments are resorbable or permanent is open to interpretation. Having a polypeptide chemical structure, silk fibroin, like any other protein, is susceptible to proteolytic degradation, and will become weaker and eventually over a period of 2 years will be totally resorbed in vzvo. However, given the definition for an absorbable suture in the United States Pharmacopeia as a material that loses most of its tensile strength within 60 days post-implantation silk can therefore be classified as a permanent biomaterial. 

Fig. 2 PICsomes formed from oppositely charged building blocks, (a) Chemical structures of the hybrid polypeptides for PICsomes and scheme of the PICsome preparation, (b) Cryo-TEM image of 100-nm-sized PICsomes (scale bar 50 run). Arrows indicate vesicle walls. Adapted from [70] with permission. Copyright 2010 American Chemical Society...

Fig. 5 Polypeptide vesicles demonstrate the ability to utilize the EPR effect, (a) Chemical structure of the amphiphilic block polypeptide PSar-b-PMLG. (b) Fluorescence image using fluorescently labeled PEG. Fluorescence is not observed in the cancer site although accumulation is observed in the bladder, (c) Fluorescence image using ICG-labeled vesicles, showing evidence of vesicle accumulation due to the EPR effect. Adapted from [41] with permission. Copyright 2008 American Chemical Society...

Polyamides are macromolecules with acidamide units —CONH—, where the chemical structure of the other parts of the monomers can be aliphatic and/or aromatic. Similar structures are found in nature, for example, polypeptides. Although in principle a large number of potential polyamide structures can be produced, only a few polyamides are produced in industrial scale. 

Figure 2.1 Chemical structure of polypeptides. The R, and R2 J group possibilities are shown in Fig. 2.2, and n is the number of...

Polypeptides and poly(a-amino acid)s are polymers of a-amino acids, with the chemical structure I ... 

Scheme 2 Chemical structure of polypeptides containing p-phenylazo-L-phenylalanine and y-benzyl-L-glutamate residues (II).

Scheme 5 Chemical structure of azo-modified polypeptide analogs of poly(L-lysine), VIII (n = 1, 2, 3, and 4) and IX.

SchemelO Chemical structure ofthe polypeptide obtained after introducing spiropyran units into the side chains of succinylated poly(L-lysine) (XVII). 70 ...

Scheme 12 Chemical structure of the polypeptide XXI, consisting of two a-helical chains of poly(y-methyl-L-glutamate)...

Figure 2.6. Chemical structure of proline. The structure of proline differs from that of other amino acids because a ring is part of the polypeptide backbone. The chain backbone includes the amide nitrogen (N), Coe, and the carbonyl carbon (C02H).

Chemists have devoted much effort to exploring this natural world of chemistry as well as to determining structures the natural world has stimulated the extension of the chemical world into models and analogs of the natural chemicals. The field of organic chemistry was influenced heavily by the types of chemical structures found in natural products many medicinal compounds are still invented by using natural products as models for analogs. Chemists have also invented important polymers once nature showed us the natural polymeric carbohydrates, polypeptides, nucleic acids, and the polymers such as rubber that are produced from natural materials. 

The surface glycoprotein of Halobacterium salinarium was the first glycosylated protein detected in prokaryotes [109]. More recent work on the chemical structure of glycopeptides [110-113] and the primary structure of the polypeptide moiety of the surface glycoprotein of Halobacterium halobium - an organism related to Hb. salinarium at the species level - has led to a detailed picture (Fig. 15A) of this molecule. Its main features are ... 

Unfortunately, there is no report on the detailed physical characterization of these polymers. Such information as unidirectional twist angle and form optical rotation, as well as their dependence on chemical structures and temperature, can be very useful in further understanding the molecular orientations of the polymers in the cholesteric phase. In contrast, a number of studies have been made on the physical-chemical properties of cholesteric lyotropic polymer systems, especially polypeptides. 

Residue The portion of a chemical structure (hat cun be idcnii-tled us coming from a porticuiar building block,. such as the alanine residue in a polypeptide. In u generic structure, (he residues arc (he. substituents that correspond to the R-gniup.s in the structure. 

In contrast to polypeptides that have many possible conformations, poly(hexyl isocynate) is known to have a stiff rodlike helical conformation in the solid state and in a wide range of solvents, which is responsible for the formation of a nematic liquid crystalline phase.45-47 The inherent chain stiffness of this polymer is primarily determined by chemical structure rather than by intramolecular hydrogen bonding. This results in a greater stability in the stiff rodlike characteristics in the solution as compared to polypeptides. The lyotropic liquid crystalline behavior in a number of different solvents was extensively studied by Aharoni et al.48-50 In contrast to homopolymers, interesting new supramolecular structures can be expected if a flexible block is connected to the rigid polyisocyanate block (rod—coil copolymers) because the molecule imparts both microphase separation characteristics of the blocks and a tendency of rod segments to form anisotropic order. 

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