Molecule folded-chain

Transfer RNA (tRNA) serves as a carrier of amino acid residues for protein synthesis. Transfer RNA molecules also fold into a characteristic secondary structure (marginal figure). The amino acid is attached as an aminoacyl ester to the 3 -terminus of the tRNA. Aminoacyl-tRNAs are the substrates for protein biosynthesis. The tRNAs are the smallest RNAs (size range—23 to 30 kD) and contain 73 to 94 residues, a substantial number of which are methylated or otherwise unusually modified. Transfer RNA derives its name from its role as the carrier of amino acids during the process of protein synthesis (see Chapters 32 and 33). Each of the 20 amino acids of proteins has at least one unique tRNA species dedicated to chauffeuring its delivery to ribosomes for insertion into growing polypeptide chains, and some amino acids are served by several tRNAs. For example, five different tRNAs act in the transfer of leucine into... 

Crystallites occurring in PET fibers can assume two kinds of morphological forms. The first form represents the crystallite formed by molecules of folded conformation, while the other is formed from molecules of extended-chain conformation. The first form is sometimes called a flexural morphological form, whereas the other is called a straightened morphological form. The flexural form is the typical and prevailing morphological form in PET fibers. However, it should be stressed that no... 

The mesomorphous phase, also called an intermediate phase or a mesophase, is formed by molecules occurring in surface layers of the crystallites. It can be assumed that the mesophase is made up largely by regularly adjacent reentry folds. However, it cannot be excluded that the mesophase is also composed of some irregular chain folds, which are characterized by a long length and run near the crystal face in the direction perpendicular to the microfibril axis. 

It should be noted that the concept extended-chain crystal (ECC) does not mean a crystal, in which not a single molecule can form a told. ECC can contain some molecules with folded conformation but the folds play a role of defects... 

For density values g > 0.92 g/cm3 the deformation modes of the crystals predominate. The hard elements are the lamellae. The mechanical properties are primarily determined by the large anisotropy of molecular forces. The mosaic structure of blocks introduces a specific weakness element which permits chain slip to proceed faster at the block boundaries than inside the blocks. The weakest element of the solid is the surface layer between adjacent lamellae, containing chain folds, free chain ends, tie molecules, etc. 

A small number of proteins, and again insulin is an example, are synthesized as pro-proteins with an additional amino acid sequence which dictates the final three-dimensional structure. In the case of proinsulin, proteolytic attack cleaves out a stretch of 35 amino acids in the middle of the molecule to generate insulin. The peptide that is removed is known as the C chain. The other chains, A and B, remain crosslinked and thus locked in a stable tertiary stiucture by the disulphide bridges formed when the molecule originally folded as proinsulin. Bacteria have no mechanism for specifically cutting out the folding sequences from pro-hormones and the way of solving this problem is described in a later section. 

Then we extended the 2D-model to a 3D one [21]. We considered crystallization of a single polymer chain C500 from a vapor phase onto a solid substrate, taking into account detailed interactions between the chain and the substrate. Though the polymer molecule in a vacuum was collapsed, like in a very poor solvent, under the influence of bare van der Waals interactions between atoms, the molecule was found to show quick adsorption and crystallization into a rather neat chain folded lamella. 

Molecular processes at the growth surface of the crystal are one of our greatest concerns. By melting a chain-folded lamella at 600 K for 200 ps, we prepared a 2D random-coil of the molecule. The random-coil was then instanta-... 

During crystallization, the molecules change their conformation from the random coil to chain folded. The chain conformation in the crystalline state has been the subject of great discussion, since it reflects the path that molecules have followed during crystallization. In the case of sufficiently long... 

Fluorescent molecule (1) (Figure 6.5) acts as a host for Ca2+ ions. On addition of Ca2+ ions, the flexible polyether chain folds, leading to stacking of the anthracene fluorophores, and monomer emission is replaced by excimer emission. 

The irreversible loss of a protein s native molecular shape is familiar to anyone who has boiled an egg. The white of an egg is largely a single protein called albumin. In a fresh egg, each albumin molecule is folded in a particular way that is its natural shape. This arrangement of each protein chain is stable at room temperature, but heat disrupts the interactions holding it together. At the temperature of boiling water the albumin unfolds, becoming a jumble... 

Elenga el al. [78] observed a drastic loss of drawability, together with a significant increase in strength at yield, for PET annealed for long periods of time. They attributed this to ester interchange reactions, which turn chain folds into intercrystalline tie molecules between neighbouring lamellae. 

Such a polypeptide chain folding into two distinct domains could be correlated with the amino add sequence. The N-terminus of the polypeptide chain is located at an as yet unknown site of the head part and starts with the sequence Pyr.Glu-Ser-Ala-Cys-Thr-, the C-terminal region is located at the end of the tail and has the sequence -Pro-Tyr-TVr-Ser-Gln-Cys-Leu. From the total of 497 amino acids about 430 are located in the head part, where the chain is partially ordered in jS-structures. Ten disulfide bridges give stability and rigidity to this part of the molecule 24. The bridges interconnect the cysteine residues 4-50, 19-25, 61-71(7), 67-72(7), 138-397, 172-209(7), 176-210(7), 230-256, 238-243, and 261-331. The exact position of some... 

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