Linear macromolecules, structural

Many complex systems have been spread on liquid interfaces for a variety of reasons. We begin this chapter with a discussion of the behavior of synthetic polymers at the liquid-air interface. Most of these systems are linear macromolecules however, rigid-rod polymers and more complex structures are of interest for potential optoelectronic applications. Biological macromolecules are spread at the liquid-vapor interface to fabricate sensors and other biomedical devices. In addition, the study of proteins at the air-water interface yields important information on enzymatic recognition, and membrane protein behavior. We touch on other biological systems, namely, phospholipids and cholesterol monolayers. These systems are so widely and routinely studied these days that they were also mentioned in some detail in Chapter IV. The closely related matter of bilayers and vesicles is also briefly addressed. 

Transcriptases - catalyzing the translation of information from one linear macromolecule into the structure of the nascent linear macromole. 

Macromolecules differ from small molecules in a number of critical properties. First, the linear chain structure confers elasticity, toughness, and strength on the solid state system. This is a consequence of the reorientational freedom of the skeletal bonds and of their ability to absorb impact or undergo elastic deformation by means of conformational changes rather than bond cleavage. 

When amino acids are linked together by acid-amide bonds, linear macromolecules (peptides) are produced. Those containing more than ca. 100 amino acid residues are described as proteins (polypeptides). Every organism contains thousands of different proteins, which have a variety of functions. At a magnification of ca. 1.5 million, the semischematic illustration shows the structures of a few intra and extracellular proteins, giving an impression of their variety. The functions of proteins can be classified as follows. 

For non-linear macromolecules, the skeletal structure should be reflected in the name. Non-linear macromolecular structures and molecular assemblies are classified using the following terms ... 

The topology of the structure of the non-linear macromolecule or modes of combination of the constituent species of macromolecules are ascertained. 

The following italicized qualifiers can be used as both prefixes (e.g. blend-, net-) and connectives (e.g. -blend-, -net-), separated by (a) hyphen(s) from the constituent name(s), to designate the skeletal structure of non-linear macromolecules or macromolecular assemblies ... 

An interesting polymer constrained to a relatively compact conformation is polyethylenimine (PEI), which can be prepared by suitable polymerization of ethylenimine (Fig. 2) to give a highly branched rather than a linear macromolecule.19 The structure of a segment of this polymer is shown in Fig. 2. Approximately 25% of its nitrogens are primary amines, 50% secondary, and 25% tertiary.19 The branching of the polymer may be represented schematically as shown in Fig. 3. 

The kinetics of transition from the liquid crystal to the fully ordered crystal of flexible, linear macromolecules was studied by Warner and Jaffe 38) on copolyesters of hydroxybenzoic acid, naphthalene dicarboxylic acid, isophthalic acid, and hydro-quinone. The analytical techniques were optical microscopy, calorimetry and wide angle X-ray diffraction. Despite the fact that massive structural rearrangements did not occur on crystallization, nucleation and growth followed the Avrami expression with an exponent of 2. The authors suggested a rod-like crystal growth. 

Paul W, Smith GD (2004) Structure and dynamics of amorphous polymers computer simulations compared to experiment and theory. Rep Prog Phys 67 1117-1185 Peterlin A (1967) Frequency dependence of intrinsic viscosity of macromolecules with finite internal viscosity. J Polym Sci A - 2 5(1) 179-193 Peterlin A (1972) Origin of internal viscosity in linear macromolecules. Polym Lett 10 101— 105... 

In previous sections of this chapter, as well as in chapter 6, we have discussed several reasons why liquid water is so critical for life. To briefly review the salient points (1) Water is essential for driving the formation of the three-dimensional structures of macromolecules. These structures, on which macromolecular function depends, are encoded in a latent form in the linear primary structures of proteins and nucleic acids, but can be manifested only when liquid water is present to foster hydrophobic interactions. (2) The assembly of bilayer membranes from lipids and proteins likewise is driven in large measure by hydrophobic effects. (3) Water in the liquid state is a requirement for most types of transport of materials between organism and environment and between compartments within the organism. (4) Lastly, the... 

The radical chain mechanism shown in Section 24.1 implies that polyethylene and polystyrene are composed of linear macromolecules—that is, that the carbons of the vinyl groups of the monomers are connected in a straight chain. In fact, two processes can cause individual macromolecules to have branched structures. The first of these occurs when a growing radical chain abstracts a hydrogen from a random position in the interior of another macromolecule. This process, called chain transfer, occurs when the radical does not find another monomer unit to which to add nor another radical... 

TABLE 5.4 Relationships between liquid Cp and temperature T for different structure groups in linear macromolecules... 

---