Macromolecular fields

Examination of models easily convinces one that, even for simple molecules such as linear hydrocarbons, there exists a strong correlation among the rotations about two adjacent C—C bonds and that the energy cannot always be considered the sum of the contributions corresponding to each rotation. For this reason simple diagrams of E vs. 0, like that often seen for butane, are not used in the macromolecular field. It is preferable to represent the state of the system by square maps in which the values of the variables 0 and 02 are placed on the axes and the energy is represented by a series of contour lines. 

As an example chosen in the macromolecular field the C NMR spectrum of syndiotactic polypropylene might be mentioned In solution (averaged random coil conformation, molecular model corresponding to 7) it presents three signals in the crystal state, where a chiral rigid conformation exists [(2/1)2 helix], it shows four signals (Figure 17). 

From the preceding sections it is clear that isomorphism of monomeric units in synthetic copolymeric systems is a quite general phenomenon. We wish to recall here that the requirements for the isomorphous substitution in the macromolecular field are similar to those holding for solid solutions in ionic or metallic crystals however, the degree of... 

In the macromolecular field the amount of literature is extremely large. Nevertheless the researcher is often confronted with the problem that neither directly measured properties, nor reliable methods to calculate them, can be found. This is the justification of the present book. The value of estimation and correlation methods largely depends, however, on their simplicity. Complicated methods have to be rejected. This has been one of our guiding principles. 

Hence, if the quantity n/c, termed the "reduced osmotic pressure is plotted against c, a horizontal line should result. In the macromolecular field, and particularly if chain molecules are concerned, deviations from this simple law are usually met with even at great dilution (See Chapter III section 8, p. 84). 

The OPLS force field is described in twtt papers, one discussing parameters for proteins W. L. Jorgensen and J. Tirado-Rives,/. Amer. (. hem. Soc., 110, 1557 (iy8K) and on e discii ssin g param eters for n iicleotide bases [J. Pranata, S. Wiersch ke, and W. L. Jorgen sen. , /.. Amer. Chem. Soc.. 117, 281(1 ( 1991)1. The force field uses the united atom concept ftir many, but not all. hydrttgens attached to carbons to allow faster calculation s on macromolecular systems. The amino and nucleic acid residue templates in HyperChein automatically switch to a united atom representation where appropriate when th e OPLS option is selected. 

Chemistry at Harvard macromolecular mechanics (CHARMM) is the name of both a force field and a program incorporating that force field. The academic version of this program is designated CHARMM and the commercial version is called CHARMm. It was originally devised for proteins and nucleic acids. It has... 

CHARMM (chemistry at Harvard macromolecular mechanics) a molecular mechanics force field... 

Note The BIO+ force field is an implementation of the CHARMM (Chemistry at HARvard Macromolecular Mechanics) force field developed in the group of Martin Karplus at Harvard University. Like AMBER and OPLS, it is primarily designed to explore macromolecules. 

H. Staudinger (Freiburg) discoveries in the field of macromolecular chemistry. 

From the various autocorrelation times which characterized macromolecular fluctuations, those associated with the fluctuation of the electrostatic field from the protein on its reacting fragments are probably the most important (see Ref. 8). These autocorrelation times define the dielectric relaxation times for different protein sites and can be used to estimate dynamical effects on biological reactions (see Chapter 9 for more details). 

It is now a common feeling that our world cannot survive as it is without plastics [1]. Starting from 1930, when the macromolecular concept started to gain acceptance in the scientific community [2], the advances in polymer science have been so striking that plastics have invaded almost every aspect of modern human life, both as daily materials and as sophisticated substrates able to cover high-tech applications [3]. A very easy and simple way to check this assertion is to visit the The Macrogalleria web site (1st floor) [4] where an extensive exemplification of the most common and important plastic applications in different fields is provided in a really immediate and impressive way. 

The rapid advances In electronic structure applications are causing the field to be discussed under many new names, such as computer-aided molecular design or computer-aided materials design (both abbreviated CAMD as a rather obvious variation on CAD/CAM). One especially promising subfield concerns the design of bloactlve molecular agents (computer-aided macromolecular design). 

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